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University of British Columbia
Cpsc 527Advanced Computer Networks
Instructor Dr Son T Vuong
Email vuongcsubcca
The World Connected
Spring 2010 ndash Dr Son Vuong Cpsc 527 2
Information and Organization Instructor Dr Son Vuong
Email vuongcsubcca or stvuonggmailcom
Office Hours M W 2-3 pm
References
Research reportspapers and protocol standard documents
Computer Networks A Tanenbaum ndash 4th Ed Prentice Hall (2003)
Data and Computer Communications W Stallings - 8th Ed (2006)
Computer Networks and Internets (5th Edition) D Comer Prentice Hall (2008)
ldquoComputer Networking A Top Down Approach Featuring the Internetrdquo Jim Kurose amp Keith Ross 5th Ed Addison Wesley 2009
2
Spring 2010 ndash Dr Son Vuong Cpsc 527 3
Text and Workload Tentative Course Load and Evaluation
1 Project (50)
1 Presentation (15)
Short Quizzes (25)
1 Assignment (10)
Class Participation (Bonus 4)
Use of BlueCT (on Laptop) for interactive participation and learning
Use of Peerwise for prereading and peerwiselearning (CourseID=3109)
httppeerwisecsaucklandacnzatubc_ca
Spring 2010 ndash Dr Son Vuong Cpsc 527 4
Cpsc 527 Outline
The Internet and TCPIP (including IPv6 Muticasting
ATM congestion control) () Intro to the Internet of Things (IOT)
ext-Generation Internet QoS Scheduling MPLS IntServ DiffServ RSVP
Distributed multimedia systems Compression RTPRTSP VoIP
P2P etworks and Grid Computing
P2P Video-on-demand streaming (BitVampire)
etwork security (Intrusions VPN IPSec VoIP security)
Other hot topics (if time permits)
- Mobile (wireless) communications (Mobile-IP 80211abg
Cellular PAN - Bluetooth Satellites)
- Mobile intelligent agents (WaveNEMO)
- etwork management SNMPv2 RMON2 etc
() Review
3
Spring 2010 ndash Dr Son Vuong Cpsc 527 5
Review
Overview - Protocol and Service
Internet Protocol Architecture
IPv4IPv6 TCP
Other Internet Protocols
Spring 2010 ndash Dr Son Vuong Cpsc 527 6
Convergence
Eniac 1947
Telephone1876
Computer+ Modem1957
Early WirelessPhones 1978
First Color TVBroadcast 1953
HBO Launched 1972
Interactive TV 1990
Handheld PortablePhones 1990
First PCAltair1974
IBMPC1981
AppleMac1984
ApplePowerbook
1990
IBMThinkpad
1992
HPPalmtop1991
AppleNewton1993
PentiumPC 1993
Red Herring 1099
4
Spring 2010 ndash Dr Son Vuong Cpsc 527 7
Game ConsolesPersonal Digital Assistants
Digital VCRs (TiVo ReplayTV)Communicators
Smart TelephonesE-Toys (Furby Aibo)
Divergence
PentiumPC 1993
Atari HomePong 1972
Apple
iMac 1998
Pentium IIPC 1997
Palm VIIPDA 1999
NetworkComputer1996
FreePC 1999
SegaDreamcast
1999
Internet-enabledSmart Phones
1999
Red Herring 1099
Proliferation of diverseend devices and access networks
Spring 2010 ndash Dr Son Vuong Cpsc 527 8
The Shape of Things to Come
Toyota Pod Concept Car
Co-designed with Sony
Detects driverrsquos skill level and adjust suspension
Detects driverrsquos mood (pulse rate perspiration)
compensates for road rage and incorporates a mood
meter (happy vs angry face)
Inter-pod wireless LAN to communicate intentions
between vehicles such as passing
Individual entertainment stations for each passenger
5
Spring 2010 ndash Dr Son Vuong Cpsc 527 9
Automobiles663 Million
Telephones15 Billion
Electronic Chips30 Billion
X-Internet
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
93Million
407 Million
Internet Computers
Internet Users
Todayrsquos Internet
Spring 2010 ndash Dr Son Vuong Cpsc 527 10
0
5000
10000
15000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
Millions
Year
XInternet
PCInternet
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
2
Spring 2010 ndash Dr Son Vuong Cpsc 527 3
Text and Workload Tentative Course Load and Evaluation
1 Project (50)
1 Presentation (15)
Short Quizzes (25)
1 Assignment (10)
Class Participation (Bonus 4)
Use of BlueCT (on Laptop) for interactive participation and learning
Use of Peerwise for prereading and peerwiselearning (CourseID=3109)
httppeerwisecsaucklandacnzatubc_ca
Spring 2010 ndash Dr Son Vuong Cpsc 527 4
Cpsc 527 Outline
The Internet and TCPIP (including IPv6 Muticasting
ATM congestion control) () Intro to the Internet of Things (IOT)
ext-Generation Internet QoS Scheduling MPLS IntServ DiffServ RSVP
Distributed multimedia systems Compression RTPRTSP VoIP
P2P etworks and Grid Computing
P2P Video-on-demand streaming (BitVampire)
etwork security (Intrusions VPN IPSec VoIP security)
Other hot topics (if time permits)
- Mobile (wireless) communications (Mobile-IP 80211abg
Cellular PAN - Bluetooth Satellites)
- Mobile intelligent agents (WaveNEMO)
- etwork management SNMPv2 RMON2 etc
() Review
3
Spring 2010 ndash Dr Son Vuong Cpsc 527 5
Review
Overview - Protocol and Service
Internet Protocol Architecture
IPv4IPv6 TCP
Other Internet Protocols
Spring 2010 ndash Dr Son Vuong Cpsc 527 6
Convergence
Eniac 1947
Telephone1876
Computer+ Modem1957
Early WirelessPhones 1978
First Color TVBroadcast 1953
HBO Launched 1972
Interactive TV 1990
Handheld PortablePhones 1990
First PCAltair1974
IBMPC1981
AppleMac1984
ApplePowerbook
1990
IBMThinkpad
1992
HPPalmtop1991
AppleNewton1993
PentiumPC 1993
Red Herring 1099
4
Spring 2010 ndash Dr Son Vuong Cpsc 527 7
Game ConsolesPersonal Digital Assistants
Digital VCRs (TiVo ReplayTV)Communicators
Smart TelephonesE-Toys (Furby Aibo)
Divergence
PentiumPC 1993
Atari HomePong 1972
Apple
iMac 1998
Pentium IIPC 1997
Palm VIIPDA 1999
NetworkComputer1996
FreePC 1999
SegaDreamcast
1999
Internet-enabledSmart Phones
1999
Red Herring 1099
Proliferation of diverseend devices and access networks
Spring 2010 ndash Dr Son Vuong Cpsc 527 8
The Shape of Things to Come
Toyota Pod Concept Car
Co-designed with Sony
Detects driverrsquos skill level and adjust suspension
Detects driverrsquos mood (pulse rate perspiration)
compensates for road rage and incorporates a mood
meter (happy vs angry face)
Inter-pod wireless LAN to communicate intentions
between vehicles such as passing
Individual entertainment stations for each passenger
5
Spring 2010 ndash Dr Son Vuong Cpsc 527 9
Automobiles663 Million
Telephones15 Billion
Electronic Chips30 Billion
X-Internet
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
93Million
407 Million
Internet Computers
Internet Users
Todayrsquos Internet
Spring 2010 ndash Dr Son Vuong Cpsc 527 10
0
5000
10000
15000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
Millions
Year
XInternet
PCInternet
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
3
Spring 2010 ndash Dr Son Vuong Cpsc 527 5
Review
Overview - Protocol and Service
Internet Protocol Architecture
IPv4IPv6 TCP
Other Internet Protocols
Spring 2010 ndash Dr Son Vuong Cpsc 527 6
Convergence
Eniac 1947
Telephone1876
Computer+ Modem1957
Early WirelessPhones 1978
First Color TVBroadcast 1953
HBO Launched 1972
Interactive TV 1990
Handheld PortablePhones 1990
First PCAltair1974
IBMPC1981
AppleMac1984
ApplePowerbook
1990
IBMThinkpad
1992
HPPalmtop1991
AppleNewton1993
PentiumPC 1993
Red Herring 1099
4
Spring 2010 ndash Dr Son Vuong Cpsc 527 7
Game ConsolesPersonal Digital Assistants
Digital VCRs (TiVo ReplayTV)Communicators
Smart TelephonesE-Toys (Furby Aibo)
Divergence
PentiumPC 1993
Atari HomePong 1972
Apple
iMac 1998
Pentium IIPC 1997
Palm VIIPDA 1999
NetworkComputer1996
FreePC 1999
SegaDreamcast
1999
Internet-enabledSmart Phones
1999
Red Herring 1099
Proliferation of diverseend devices and access networks
Spring 2010 ndash Dr Son Vuong Cpsc 527 8
The Shape of Things to Come
Toyota Pod Concept Car
Co-designed with Sony
Detects driverrsquos skill level and adjust suspension
Detects driverrsquos mood (pulse rate perspiration)
compensates for road rage and incorporates a mood
meter (happy vs angry face)
Inter-pod wireless LAN to communicate intentions
between vehicles such as passing
Individual entertainment stations for each passenger
5
Spring 2010 ndash Dr Son Vuong Cpsc 527 9
Automobiles663 Million
Telephones15 Billion
Electronic Chips30 Billion
X-Internet
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
93Million
407 Million
Internet Computers
Internet Users
Todayrsquos Internet
Spring 2010 ndash Dr Son Vuong Cpsc 527 10
0
5000
10000
15000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
Millions
Year
XInternet
PCInternet
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
4
Spring 2010 ndash Dr Son Vuong Cpsc 527 7
Game ConsolesPersonal Digital Assistants
Digital VCRs (TiVo ReplayTV)Communicators
Smart TelephonesE-Toys (Furby Aibo)
Divergence
PentiumPC 1993
Atari HomePong 1972
Apple
iMac 1998
Pentium IIPC 1997
Palm VIIPDA 1999
NetworkComputer1996
FreePC 1999
SegaDreamcast
1999
Internet-enabledSmart Phones
1999
Red Herring 1099
Proliferation of diverseend devices and access networks
Spring 2010 ndash Dr Son Vuong Cpsc 527 8
The Shape of Things to Come
Toyota Pod Concept Car
Co-designed with Sony
Detects driverrsquos skill level and adjust suspension
Detects driverrsquos mood (pulse rate perspiration)
compensates for road rage and incorporates a mood
meter (happy vs angry face)
Inter-pod wireless LAN to communicate intentions
between vehicles such as passing
Individual entertainment stations for each passenger
5
Spring 2010 ndash Dr Son Vuong Cpsc 527 9
Automobiles663 Million
Telephones15 Billion
Electronic Chips30 Billion
X-Internet
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
93Million
407 Million
Internet Computers
Internet Users
Todayrsquos Internet
Spring 2010 ndash Dr Son Vuong Cpsc 527 10
0
5000
10000
15000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
Millions
Year
XInternet
PCInternet
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
5
Spring 2010 ndash Dr Son Vuong Cpsc 527 9
Automobiles663 Million
Telephones15 Billion
Electronic Chips30 Billion
X-Internet
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
93Million
407 Million
Internet Computers
Internet Users
Todayrsquos Internet
Spring 2010 ndash Dr Son Vuong Cpsc 527 10
0
5000
10000
15000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
ldquoX-Internetrdquo Beyond the PC
Forrester Research May 2001
Millions
Year
XInternet
PCInternet
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
6
Spring 2010 ndash Dr Son Vuong Cpsc 527 11
Uses of Computer Networks
bull Business Applications
bull Home Applications
bull Mobile Users
bull Social Issues
Spring 2010 ndash Dr Son Vuong Cpsc 527 12
Business Applications of Networks
A network with two clients and one server
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
7
Spring 2010 ndash Dr Son Vuong Cpsc 527 13
Business Applications of Networks (2)
The client-server model involves requests
and replies
Spring 2010 ndash Dr Son Vuong Cpsc 527 14
Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
Home Gateway Initiative (HGI)
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
8
Spring 2010 ndash Dr Son Vuong Cpsc 527 15
Home Network Applications (2)
In peer-to-peer system there are no fixed clients
and servers
Spring 2010 ndash Dr Son Vuong Cpsc 527 16
Home Network Applications (3)
Some forms of e-commerce
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
9
Spring 2010 ndash Dr Son Vuong Cpsc 527 17
Home environment
Ho
me
Ne
two
rks
WiFi
Bluetooth
Ethernet
PLT
Coax
Audiovisual
Telephony
Portable
Domotics
Gateway
Internet
High Speed Access
Service
platform
Service
platformxDSL
CATV
Wireless
FTTH
Spring 2010 ndash Dr Son Vuong Cpsc 527 18
Internet
Home Gateway
PC
Voice services
Security
Entertainment
Personal content
Gaming
What will HGI enablehellip
End to end service delivery
Security
ServicesQoS control
Service integration
Device Management
Home
Network
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
10
Spring 2010 ndash Dr Son Vuong Cpsc 527 19
Mobile Network Users
Combinations of wireless networks and mobile
computing
Spring 2010 ndash Dr Son Vuong Cpsc 527 20
Classification of Networks
Classification of interconnected processors by scale
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
11
Spring 2010 ndash Dr Son Vuong Cpsc 527 21
Network Perspective
Network users services that their applications need eg guarantee that each message it sends will be delivered without error within a certain amount of time
Network designers cost-effective design eg that network resources are efficiently utilized and fairly allocated to different users
Network providers system that is easy to administer and manage eg that faults can be easily isolated and it is easy to account for usage
Spring 2010 ndash Dr Son Vuong Cpsc 527 22
Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication
Fill gap between what applications expect and what the underlying technology provides
Host Host
Application
Host
Application
Host Host
Channel
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
12
Spring 2010 ndash Dr Son Vuong Cpsc 527 23
IPC Abstractions
RequestReply (responsive traffic)
distributed file systems
digital libraries (web)
Stream-Based (non-responsive traffic)
video sequence of frames
14 NTSC = 352x240 pixels (CIFSIF)
(352 x 240 x 24)8=2475KB = 2 Mbits
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Spring 2010 ndash Dr Son Vuong Cpsc 527 24
Host 1
Protocol
Host 2
Protocol
High-level
object
High-level
object
SERVICEinterface
Peer-to-peer
Interface
Interfaces (Protocol and Service)
PROTOCOL
SERVICEinterface
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
13
Spring 2010 ndash Dr Son Vuong Cpsc 527 25
IP
TCP
send(IP message) deliver(TCP message)
IP
TCP
Spring 2010 ndash Dr Son Vuong Cpsc 527 26
ISO Architecture
Application
Presentation
Session
Transport
End host
One or more nodes
within the network
Network
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
End host
Network
Data link
Physical
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
14
Spring 2010 ndash Dr Son Vuong Cpsc 527 27
Spring 2010 ndash Dr Son Vuong Cpsc 527 28
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
15
Spring 2010 ndash Dr Son Vuong Cpsc 527 29
The Mail System
Nick Dave
Stanford MIT
Admin Admin
Spring 2010 ndash Dr Son Vuong Cpsc 527 30
The Mail System (Cont)
Nick Dave
Stanford MIT
Admin Admin
Application Layer
Transport Layer
Network Layer
Link Layer
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
16
Spring 2010 ndash Dr Son Vuong Cpsc 527 31
The Internet
Nick Dave
LelandStanfordedu AthenaMITedu
Network Layer
Link Layer
Application Layer
Transport Layer
OS OSHdrData HdrData
HD
HD
HD
HD HD
HD
Spring 2010 ndash Dr Son Vuong Cpsc 527 32
Where is the next ldquonarrow waistrdquo
What is the InternetldquoItrsquos the TCPIP Protocol Stackrdquo
ApplicationsWeb
VideoAudio
TCPIP Access Technologies
Ethernet (LAN)
Wireless (LMDS WLAN Cellular)
Cable
ADSL
Satellite
TCPIP
Applications
AccessTechnologies
ldquoNarrowWaistrdquo
Transport Services andRepresentrsquon Standards
Open Data NetworkBearer Service
MiddlewareServices
NetworkTechnologySubstrate
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
17
Spring 2010 ndash Dr Son Vuong Cpsc 527 33
Lect 1 Peer Instruction Question 10 ndashCharacteristics of Current Internet
What are the characteristics of current Internet
A No time guarantee for delivery
B No guarantee of delivery in sequence or at all
C Each packet is individually routed
D Best effort service
E All of the above
F None of the above
Spring 2010 ndash Dr Son Vuong Cpsc 527 34
Characteristics of the Internet Each packet is individually routed
No time guarantee for delivery
No guarantee of delivery in sequence or at all
Things get lost
Acknowledgements
Retransmission
How to determine when to retransmit Timeout
Need local copies of contents of each packet
How long to keep each copy
What if an acknowledgement is lost
No guarantee of integrity of data
Packets can be fragmented
Packets may be duplicated
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
18
Spring 2010 ndash Dr Son Vuong Cpsc 527 35
Layering in the Internet
Transport Layer
Provides reliable in-sequence delivery of data
from end-to-end on behalf of application
Network Layer
Provides ldquobest-effortrdquo but unreliable delivery
of datagrams
Link Layer
Carries data over (usually) point-to-point links
between hosts and routers or between routers
and routers
Spring 2010 ndash Dr Son Vuong Cpsc 527 36
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
19
Spring 2010 ndash Dr Son Vuong Cpsc 527 37
Spring 2010 ndash Dr Son Vuong Cpsc 527 38
Lect 1 Peer Instruction Question 11 ndash Hub and Switch
What are the differences between a hub and a
switch
A Layer physical layer (repeater) link layer
B Buffering yesno
C Intelligence without CSMACD
D Collision domain single vs multiple
E Forwarding flooding vs self-learning
F Plug-and-play yesno
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
20
Spring 2010 ndash Dr Son Vuong Cpsc 527 39
Switch example
Suppose C sends frame to D
Switch receives frame from C
notes in bridge table that C is on interface 1
because D is not in table switch forwards frame into
interfaces 2 and 3
frame received by D
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEG C
11231
12 3
Spring 2010 ndash Dr Son Vuong Cpsc 527 40
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
21
Spring 2010 ndash Dr Son Vuong Cpsc 527 41
Lect 1 Peer Instruction Question 12 ndashSwitch Self-Learning
How many copies of the frame from C must be
made for this frame to reach D
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 42
Switch example
Suppose D replies back with frame to C
Switch receives frame from D
notes in bridge table that D is on interface 2
because C is in table switch forwards frame only to
interface 1
frame received by C
hub hub hub
switch
A
B C DE
FG H
I
address interface
ABEGCD
112312
1
2 3
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
22
Spring 2010 ndash Dr Son Vuong Cpsc 527 43
Lect 1 Peer Instruction Question 13 ndashSwitch Self-Learning
Now how many copies of the frame from D
must be made for this frame to reach C
Answer
A 3 B 4 C8 D12 E none of those
Spring 2010 ndash Dr Son Vuong Cpsc 527 44
Summary
ISOOSI reference model has seven layers
TCPIP Protocol suite has four layers
Interconnection devices Gateway Router
SwitchBridge HubRepeater
Next lecture IPv4-v6
Then TCP
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
23
Spring 2010 ndash Dr Son Vuong Cpsc 527 45
Example TCPIP Internet
R1
ETH FDDI
IPIP
ETH
TCP R2
FDDI PPP
IP
R3
PPP ETH
H1
IP
ETH
TCP
H8
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4
(point-to-point)
H7 R3 H8
Spring 2010 ndash Dr Son Vuong Cpsc 527 46
Ethernet CSMACD algorithm
1 Adaptor receives datagram
from net layer amp creates
frame
2 If adapter senses channel
idle it starts to transmit
frame If it senses channel
busy waits until channel
idle and then transmits
3 If adapter transmits entire
frame without detecting
another transmission the
adapter is done with frame
4 If adapter detects another
transmission while
transmitting aborts and
sends jam signal
5 After aborting adapter
enters exponential
backoff after the mth
collision adapter chooses a
K at random from
0122m-1 Adapter
waits K512 bit times and
returns to Step 2
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
24
Spring 2010 ndash Dr Son Vuong Cpsc 527 47
Ethernetrsquos CSMACD (more)
Jam Signal make sure all other
transmitters are aware of
collision 48 bits
Bit time 1 microsec for 10
Mbps Ethernet
for K=1023 wait time is
about 50 msec
Exponential Backoff
Goal adapt retransmission
attempts to estimated current
load
heavy load random wait
will be longer
first collision choose K from
01 delay is K 512 bit
transmission times
after second collision
choose K from 0123U
after ten collisions choose K
from 01234U1023
Seeinteract with Javaapplet on AWL Web sitehighly recommended
Spring 2010 ndash Dr Son Vuong Cpsc 527 48
Lect 7 (Ch 5) Peer Instruction Question 71 ndash Bin Exp Backoff
In CSMACD after the 5th collision what is the
probability that a node chooses K=4
Answer
A18 B116 C132 D164 E none
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=
25
Spring 2010 ndash Dr Son Vuong Cpsc 527 49
Efficiency of Ethernet (CSMACD)
Efficiency = ____1_____
(1 + 54 αααα)where αααα = tprop ttrans = (Lc) (FR) = LRcF
(L cable length c prop speed R rate F frame size)
Derivation
Efficiency = _____ ttrans _____
(ttrans + tcontention)
Tcontention = tslot Nslots = (2 tprop) (e) = 2e T = 54 T
Nslots= 1Prob (some station acquires channel in the slot) = e
Spring 2010 ndash Dr Son Vuong Cpsc 527 50
CSMACD efficiency
Tprop = max prop between 2 nodes in LAN
ttrans = time to transmit max-size frame
Efficiency goes to 1 as tprop goes to 0
Goes to 1 as ttrans goes to infinity
Much better than ALOHA but still decentralized
simple and cheap
transprop tt 51
1Efficiency+
=