advanced computer network - tsinghua university
TRANSCRIPT
Lecture 1 Introduction Green networking
The name you like to be called
Make sure about your registration for the
course
Edition, Larry L. Peterson and Bruce S. Davie
Reading list of papers
2014/2/25 5
What are the Internet’s design principles and
architectures?
Where is the future Internet architecture heading to?
2014/2/25 6
Real and important problem
2014/2/25 7
Course Format
13 lectures Please read at least 1 paper for every lecture topic
after the lecture
Week 3: Data center network
Week 4: Internetworking & IPv6
Week 5: Intra-domain routing
Week 6: Inter-domain routing
2014/2/25 9
Week 10: P2P and overlay network
Week 11: Mobile & wireless network
Week 12: Network security
Week 13: Future Internet
Week 15: Course project report
Week 16: Examination
Background, motivation, solution, evaluation,
10-minte discussion
2014/2/25 11
Course Project
Two options
Problem, existing solutions, comparison
Problem definition, solution design, evaluation
Report two times
Second time: solution, evaluation, documentation
Try to publish
Do not need to take notes
Ask questions
2014/2/25 13
than the grade
Project 1 20%
Project 2 25%
2014/2/25 15
Networking Review
nodes
computer network
moves information
every other node in the network
Problem: coordinate the access of all nodes to the
shared communication medium (Multiple Access
Problem)
Broadcast vs. Switched (Cont.)
designated nodes
Example: WAN
node(s)
Conversation 1: A->B
Conversation 2: C->D
2014/2/25 20
to the destination
Then the connection is torn down
Example: telephony network
2014/2/25 22
propagation delay
2014/2/25 23
Circuit Switching
incoming links outgoing links Node
2014/2/25 24
A more practical approach is to multiplex
multiple circuits over a single “fast” wire
2014/2/25 25
Circuit Switching:
Time divided in frames and frames divided in slots
Relative slot position inside a frame determines which conversation the data belongs to
Needs synchronization between sender and receiver
In case of non-permanent conversations
Needs to dynamically bind a slot to a conservation
2014/2/25 26
At each node the entire packet is received, stored,
and then forwarded to the next node
Store-and-Forward Networks
Memory
transmitted at any given time
How to tell them apart?
Use meta-data (header) to describe packet
2014/2/25 29
Efficient bandwidth usage
More complex routers
Harder to provide good network services (e.g., delay and bandwidth guarantees)
In practice they are combined
IP over SONET, IP over Frame Relay
2014/2/25 30
Outgoing link of the packet is determined by the
switching node in per-packet granularity
No pre-allocated (reserved) path in advance
The paths for packets from the same
conversation can be different
propagation
Virtual-Circuit Packet Switching
Hybrid of circuit switching and packet switching Data is transmitted as packets
All packets from one conversation are sent along a pre-established path (=virtual circuit)
Guarantees in-sequence delivery of packets within a virtual circuit
However: Packets from different virtual circuits may be interleaved
Example: ATM networks
place in three phases
Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
propagation delay
Guarantee in-sequence packet delivery
cannot be used by other circuits
But no slot reservation in virtual-circuit packet
switching
2014/2/25 39
Scalability?
(IETF) as standard body ( http://www.ietf.org )
Technical basis for other types of networks
Intranet: enterprise IP network
2014/2/25 45
ARPANET 1969, built by DARPA
Started as a research project for the military, < 100 computers , 56 kbps
Mid of 70’s, using TCP/IP
1983, ARPANET and MILNET split
NSFNET NSF builds NSFNET in 1986
Links 6 Supercomputer centers
1.5 Mbps, 10,000 computers
2014/2/25 46
1990 NSFNET moves to 45 Mbps, 16 mid-level networks
1994 NSF backbone dismantled, multiple private backbones
1994 Birth of WWW
>300 millions users from allover the world
2011 Backbone speed reaches 100s Gbps
>2 billion users in the world, among which 0.48 billion from China
2014/2/25 47
Shared access to computing resources Telnet (1970’s)
Shared access to data/files FTP, NFS (1980’s)
Communication medium over which people interact Email (1980’s), on-line chat rooms (1990’s) Instant messaging, IP Telephony (2000’s)
A medium for information dissemination WWW (1990’s) Audio, video (2000’s): peer-to-peer systems
2014/2/25 48
2014/2/25 50
Layering is a particular form of modularization
The system is broken into a vertical hierarchy of logically distinct entities (layers)
The service provided by one layer is based solely on the service provided by the layer below
Rigid structure
2014/2/25 51
Why Layering?
Without layering Each new application has to be re-implemented for
every network technology
High cost
2014/2/25 52
Why layering? (Cont.)
Solution: introduce an intermediate layer that provides a unique abstraction for various network technologies
2014/2/25 53
Modularity – protocols easier to manage and maintain
Abstract functionality – lower layers can be changed without affecting the upper layers
Reuse – upper layers can reuse the functionality provided by lower layers
Disadvantages
ISO/OSI Reference Models
– Next four layers are implemented only at hosts
2014/2/25 56
Logical Communication
peer
Application
Presentation
Session
Transport
Network
Datalink
Physical
Application
Presentation
Session
Transport
Network
Datalink
Physical
Network
Datalink
Physical
network, then to peer, then up to relevant
layer
Application
Presentation
Session
Transport
Network
Datalink
Physical
Application
Presentation
Session
Transport
Network
Datalink
Physical
Network
Datalink
Physical
Encapsulation
• A layer can use only the service provided by the layer
immediate below it
• Each layer may change and add a header to data packet
data
data
data
data
data
data
data
data
data
data
data
data
data
data
Interface –says how to access the service
Protocol –says how is the service implemented
A set of rules and formats that govern the communication between two peers
Term “protocol” is overloaded
specification of peer-to-peer interface
2014/2/25 60
Layer k+1
Protocol
Service
Move the information between two systems connected by a physical link
Interface
Protocol
Make sure the correct transmission
Coding scheme used to represent a bit, voltage levels, duration of a bit
Examples
2014/2/25 62
Service Transform a raw transmission facility into a line appearing
free of undetected transmission erros to the upper layer Framing, i.e., attach frames separator
Others (optional) Arbitrate the access to common physical media
Ensure reliable transmission
Provide flow control
connected to the same physical media
Protocol Layer addresses, mechanisms for Medium Access Control
(MAC) (e.g., CSMA/CD)…
InfiniBand
Features: QoS, failover, Scalable
Gigabit-speed network technology
Network Layer
Perform segmentation/reassemble (fragmentation/ defragmentation)
Protocol Define global unique addresses
Construct routing tables
Best effort delivery
Characterized as unreliable
Data corruption, data packet loss, duplicate arrival, out-of-order packet delivery
2014/2/25 66
Many fields are useless 2014/2/25 67
Ver IHL ToS Total Length
Identifier Fragment
the addresses
2014/2/25 68
Examine header to determine intended destination
Look up in table to determine next hop in path
Send packet out appropriate port
2014/2/25 69
Direct link between routers represented by edge
Edge “cost” c(x,y) denotes measure of difficulty
of using link
connection
Interface How to send/receive a segment by user’s requirements
Protocol Implement reliability, flow control and congestion control
Examples TCP and UDP
Delivered out of order to app
Connectionless No handshaking between UDP sender and receiver
Each UDP segment handled independently of others
Unreliable No flow control, no error control, no retransmission
Applications Streaming multimedia apps:
Loss tolerant Rate sensitive
2014/2/25 73
TCP adds…
Application layer
Interface
Data link – sends frames, handles access control to shared media
Network – delivers packets, using routing
Transport – demultiplexes, provides reliability & flow control
Session & Presentation – seldom used
2014/2/25 76
• Internet: provide a successful implementation
2014/2/25 77
data link layers
•Minor protocols deeply
Idea
applications over many different networks
Technology
Applications
The “Curse of the Narrow Waist”
IP over anything, anything over IP
Has allowed for much innovation both above and below the IP layer of the stack
An IP stack gets a device on the Internet
Drawbacks:
But…people are trying (GENI)
Only a small amount of information available about lower levels (wireless)
2014/2/25 80
2014/2/25 81
Important issues
model
other clients
Applications
Users share computers and data In the cloud
Elasticity and Multiplexing Cost saving
Technologies Data center
The core of cloud computing
Interconnect hundreds of thousands of computers and provide the routing service
A new environment of networking
Quite different from Internet
The name you like to be called
Make sure about your registration for the
course
Edition, Larry L. Peterson and Bruce S. Davie
Reading list of papers
2014/2/25 5
What are the Internet’s design principles and
architectures?
Where is the future Internet architecture heading to?
2014/2/25 6
Real and important problem
2014/2/25 7
Course Format
13 lectures Please read at least 1 paper for every lecture topic
after the lecture
Week 3: Data center network
Week 4: Internetworking & IPv6
Week 5: Intra-domain routing
Week 6: Inter-domain routing
2014/2/25 9
Week 10: P2P and overlay network
Week 11: Mobile & wireless network
Week 12: Network security
Week 13: Future Internet
Week 15: Course project report
Week 16: Examination
Background, motivation, solution, evaluation,
10-minte discussion
2014/2/25 11
Course Project
Two options
Problem, existing solutions, comparison
Problem definition, solution design, evaluation
Report two times
Second time: solution, evaluation, documentation
Try to publish
Do not need to take notes
Ask questions
2014/2/25 13
than the grade
Project 1 20%
Project 2 25%
2014/2/25 15
Networking Review
nodes
computer network
moves information
every other node in the network
Problem: coordinate the access of all nodes to the
shared communication medium (Multiple Access
Problem)
Broadcast vs. Switched (Cont.)
designated nodes
Example: WAN
node(s)
Conversation 1: A->B
Conversation 2: C->D
2014/2/25 20
to the destination
Then the connection is torn down
Example: telephony network
2014/2/25 22
propagation delay
2014/2/25 23
Circuit Switching
incoming links outgoing links Node
2014/2/25 24
A more practical approach is to multiplex
multiple circuits over a single “fast” wire
2014/2/25 25
Circuit Switching:
Time divided in frames and frames divided in slots
Relative slot position inside a frame determines which conversation the data belongs to
Needs synchronization between sender and receiver
In case of non-permanent conversations
Needs to dynamically bind a slot to a conservation
2014/2/25 26
At each node the entire packet is received, stored,
and then forwarded to the next node
Store-and-Forward Networks
Memory
transmitted at any given time
How to tell them apart?
Use meta-data (header) to describe packet
2014/2/25 29
Efficient bandwidth usage
More complex routers
Harder to provide good network services (e.g., delay and bandwidth guarantees)
In practice they are combined
IP over SONET, IP over Frame Relay
2014/2/25 30
Outgoing link of the packet is determined by the
switching node in per-packet granularity
No pre-allocated (reserved) path in advance
The paths for packets from the same
conversation can be different
propagation
Virtual-Circuit Packet Switching
Hybrid of circuit switching and packet switching Data is transmitted as packets
All packets from one conversation are sent along a pre-established path (=virtual circuit)
Guarantees in-sequence delivery of packets within a virtual circuit
However: Packets from different virtual circuits may be interleaved
Example: ATM networks
place in three phases
Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
propagation delay
Guarantee in-sequence packet delivery
cannot be used by other circuits
But no slot reservation in virtual-circuit packet
switching
2014/2/25 39
Scalability?
(IETF) as standard body ( http://www.ietf.org )
Technical basis for other types of networks
Intranet: enterprise IP network
2014/2/25 45
ARPANET 1969, built by DARPA
Started as a research project for the military, < 100 computers , 56 kbps
Mid of 70’s, using TCP/IP
1983, ARPANET and MILNET split
NSFNET NSF builds NSFNET in 1986
Links 6 Supercomputer centers
1.5 Mbps, 10,000 computers
2014/2/25 46
1990 NSFNET moves to 45 Mbps, 16 mid-level networks
1994 NSF backbone dismantled, multiple private backbones
1994 Birth of WWW
>300 millions users from allover the world
2011 Backbone speed reaches 100s Gbps
>2 billion users in the world, among which 0.48 billion from China
2014/2/25 47
Shared access to computing resources Telnet (1970’s)
Shared access to data/files FTP, NFS (1980’s)
Communication medium over which people interact Email (1980’s), on-line chat rooms (1990’s) Instant messaging, IP Telephony (2000’s)
A medium for information dissemination WWW (1990’s) Audio, video (2000’s): peer-to-peer systems
2014/2/25 48
2014/2/25 50
Layering is a particular form of modularization
The system is broken into a vertical hierarchy of logically distinct entities (layers)
The service provided by one layer is based solely on the service provided by the layer below
Rigid structure
2014/2/25 51
Why Layering?
Without layering Each new application has to be re-implemented for
every network technology
High cost
2014/2/25 52
Why layering? (Cont.)
Solution: introduce an intermediate layer that provides a unique abstraction for various network technologies
2014/2/25 53
Modularity – protocols easier to manage and maintain
Abstract functionality – lower layers can be changed without affecting the upper layers
Reuse – upper layers can reuse the functionality provided by lower layers
Disadvantages
ISO/OSI Reference Models
– Next four layers are implemented only at hosts
2014/2/25 56
Logical Communication
peer
Application
Presentation
Session
Transport
Network
Datalink
Physical
Application
Presentation
Session
Transport
Network
Datalink
Physical
Network
Datalink
Physical
network, then to peer, then up to relevant
layer
Application
Presentation
Session
Transport
Network
Datalink
Physical
Application
Presentation
Session
Transport
Network
Datalink
Physical
Network
Datalink
Physical
Encapsulation
• A layer can use only the service provided by the layer
immediate below it
• Each layer may change and add a header to data packet
data
data
data
data
data
data
data
data
data
data
data
data
data
data
Interface –says how to access the service
Protocol –says how is the service implemented
A set of rules and formats that govern the communication between two peers
Term “protocol” is overloaded
specification of peer-to-peer interface
2014/2/25 60
Layer k+1
Protocol
Service
Move the information between two systems connected by a physical link
Interface
Protocol
Make sure the correct transmission
Coding scheme used to represent a bit, voltage levels, duration of a bit
Examples
2014/2/25 62
Service Transform a raw transmission facility into a line appearing
free of undetected transmission erros to the upper layer Framing, i.e., attach frames separator
Others (optional) Arbitrate the access to common physical media
Ensure reliable transmission
Provide flow control
connected to the same physical media
Protocol Layer addresses, mechanisms for Medium Access Control
(MAC) (e.g., CSMA/CD)…
InfiniBand
Features: QoS, failover, Scalable
Gigabit-speed network technology
Network Layer
Perform segmentation/reassemble (fragmentation/ defragmentation)
Protocol Define global unique addresses
Construct routing tables
Best effort delivery
Characterized as unreliable
Data corruption, data packet loss, duplicate arrival, out-of-order packet delivery
2014/2/25 66
Many fields are useless 2014/2/25 67
Ver IHL ToS Total Length
Identifier Fragment
the addresses
2014/2/25 68
Examine header to determine intended destination
Look up in table to determine next hop in path
Send packet out appropriate port
2014/2/25 69
Direct link between routers represented by edge
Edge “cost” c(x,y) denotes measure of difficulty
of using link
connection
Interface How to send/receive a segment by user’s requirements
Protocol Implement reliability, flow control and congestion control
Examples TCP and UDP
Delivered out of order to app
Connectionless No handshaking between UDP sender and receiver
Each UDP segment handled independently of others
Unreliable No flow control, no error control, no retransmission
Applications Streaming multimedia apps:
Loss tolerant Rate sensitive
2014/2/25 73
TCP adds…
Application layer
Interface
Data link – sends frames, handles access control to shared media
Network – delivers packets, using routing
Transport – demultiplexes, provides reliability & flow control
Session & Presentation – seldom used
2014/2/25 76
• Internet: provide a successful implementation
2014/2/25 77
data link layers
•Minor protocols deeply
Idea
applications over many different networks
Technology
Applications
The “Curse of the Narrow Waist”
IP over anything, anything over IP
Has allowed for much innovation both above and below the IP layer of the stack
An IP stack gets a device on the Internet
Drawbacks:
But…people are trying (GENI)
Only a small amount of information available about lower levels (wireless)
2014/2/25 80
2014/2/25 81
Important issues
model
other clients
Applications
Users share computers and data In the cloud
Elasticity and Multiplexing Cost saving
Technologies Data center
The core of cloud computing
Interconnect hundreds of thousands of computers and provide the routing service
A new environment of networking
Quite different from Internet