Network Layer 4-1

Summary TCP Congestion Control

When CongWin is below Threshold sender in slow-start phase window grows exponentially

When CongWin is above Threshold sender is in congestion-avoidance phase window grows linearly

When a triple duplicate ACK occurs Threshold set to CongWin2 and CongWin set to Threshold

When timeout occurs Threshold set to CongWin2 and CongWin is set to 1 MSS

Network Layer 4-2

TCP sender congestion control

State Event TCP Sender Action Commentary

Slow Start (SS)

ACK receipt for previously unacked data

CongWin = CongWin + MSS If (CongWin gt Threshold) set state to ldquoCongestion Avoidancerdquo

Resulting in a doubling of CongWin every RTT

CongestionAvoidance (CA)

ACK receipt for previously unacked data

CongWin = CongWin+MSS (MSSCongWin)

Additive increase resulting in increase of CongWin by 1 MSS every RTT

SS or CA Loss event detected by triple duplicate ACK

Threshold = CongWin2 CongWin = ThresholdSet state to ldquoCongestion Avoidancerdquo

Fast recovery implementing multiplicative decrease CongWin will not drop below 1 MSS

SS or CA Timeout Threshold = CongWin2 CongWin = 1 MSSSet state to ldquoSlow Startrdquo

Enter slow start

SS or CA Duplicate ACK

Increment duplicate ACK count for segment being acked

CongWin and Threshold not changed

Network Layer 4-3

TCP Throughput

Whatrsquos the average throughout of TCP as a function of window size and RTT

Ignore slow start

Let W be the window size when loss occursWhen window is W throughput is WRTTJust after loss window drops to W2 throughput to W2RTT Average throughout 75 WRTT

Network Layer 4-4

TCP Futures

Example 1500 byte segments 100ms RTT want 10 Gbps throughputRequires window size W = 83333 in-flight segmentsThroughput in terms of loss rate

L = 210-10 WowNew versions of TCP for high-speed needed

Network Layer 4-5

Fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-2

TCP sender congestion control

State Event TCP Sender Action Commentary

Slow Start (SS)

ACK receipt for previously unacked data

CongWin = CongWin + MSS If (CongWin gt Threshold) set state to ldquoCongestion Avoidancerdquo

Resulting in a doubling of CongWin every RTT

CongestionAvoidance (CA)

ACK receipt for previously unacked data

CongWin = CongWin+MSS (MSSCongWin)

Additive increase resulting in increase of CongWin by 1 MSS every RTT

SS or CA Loss event detected by triple duplicate ACK

Threshold = CongWin2 CongWin = ThresholdSet state to ldquoCongestion Avoidancerdquo

Fast recovery implementing multiplicative decrease CongWin will not drop below 1 MSS

SS or CA Timeout Threshold = CongWin2 CongWin = 1 MSSSet state to ldquoSlow Startrdquo

Enter slow start

SS or CA Duplicate ACK

Increment duplicate ACK count for segment being acked

CongWin and Threshold not changed

Network Layer 4-3

TCP Throughput

Whatrsquos the average throughout of TCP as a function of window size and RTT

Ignore slow start

Let W be the window size when loss occursWhen window is W throughput is WRTTJust after loss window drops to W2 throughput to W2RTT Average throughout 75 WRTT

Network Layer 4-4

TCP Futures

Example 1500 byte segments 100ms RTT want 10 Gbps throughputRequires window size W = 83333 in-flight segmentsThroughput in terms of loss rate

L = 210-10 WowNew versions of TCP for high-speed needed

Network Layer 4-5

Fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-3

TCP Throughput

Whatrsquos the average throughout of TCP as a function of window size and RTT

Ignore slow start

Let W be the window size when loss occursWhen window is W throughput is WRTTJust after loss window drops to W2 throughput to W2RTT Average throughout 75 WRTT

Network Layer 4-4

TCP Futures

Example 1500 byte segments 100ms RTT want 10 Gbps throughputRequires window size W = 83333 in-flight segmentsThroughput in terms of loss rate

L = 210-10 WowNew versions of TCP for high-speed needed

Network Layer 4-5

Fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-4

TCP Futures

Example 1500 byte segments 100ms RTT want 10 Gbps throughputRequires window size W = 83333 in-flight segmentsThroughput in terms of loss rate

L = 210-10 WowNew versions of TCP for high-speed needed

Network Layer 4-5

Fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-5

Fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-6

Why is TCP fair

Two competing sessionsAdditive increase gives slope of 1 as throughput increasesMultiplicative decrease decreases throughput proportionally R

R

equal bandwidth share

Connection 1 throughputConnection 2 throughput

congestion avoidance additive increase

loss decrease window by factor of 2congestion avoidance additive

increase

loss decrease window by factor of 2

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-7

Fairness

Fairness and UDPMultimedia apps often do not use TCP

Do not want rate throttled by congestion control

Instead use UDPPump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsNothing prevents app from opening parallel connections between 2 hostsWeb browsers do thisExample link of rate R supporting 9 connections New app asks for 1 TCP

gets rate R10New app asks for 11 TCPs

gets R2

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-8

Chapter 4Network Layer

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004

Modified by Jelena Mirkovic

All material copyright 1996-2005JF Kurose and KW Ross All Rights Reserved

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-9

Network layerTransport segment from sending to receiving host Sending side encapsulates segments into datagramsReceiving side delivers segments to transport layerNetwork layer protocols in every host routerRouter examines header fields in all IP datagrams passing through it

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

networkdata link

physical

application

transport

networkdata link

physical

application

transport

networkdata link

physical

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-10

Key Network-Layer Functionsforwarding move packets from routerrsquos input to appropriate router outputrouting determine route taken by packets from source to dest

Routing algorithms

analogyrouting process of planning trip from source to destforwarding process of getting through single interchange

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-11

1

23

0111

value in arrivingpacketrsquos header

routing algorithm

local forwarding tableheader value output link

0100010101111001

3221

Interplay between routing and forwarding

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-12

Connection setup

3rd important function in some network architectures

ATM frame relay X25

Before datagrams flow two hosts and intervening routers establish virtual connection

Routers get involved

Network and transport layer service

Network between two hostsTransport between two processes

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-13

Network service model

Q What service model for ldquochannelrdquo transporting datagrams from sender to rcvrExample services for individual datagramsGuaranteed deliveryGuaranteed delivery with less than 40 msec delay

Example services for a flow of datagramsIn-order datagram deliveryGuaranteed minimum bandwidth to flowRestrictions on changes in inter-packet spacing

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-14

Network layer service models

NetworkArchitecture

Internet

ATM

ATM

ATM

ATM

ServiceModel

best effort

CBR

VBR

ABR

UBR

Bandwidth

none

constantrateguaranteedrateguaranteed minimumnone

Loss

no

yes

yes

no

no

Order

no

yes

yes

yes

yes

Timing

no

yes

yes

no

no

Congestionfeedback

no (inferredvia loss)nocongestionnocongestionyes

no

Guarantees

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-15

Network layer connection and connection-less service

Datagram network provides network-layer connectionless serviceVC network provides network-layer connection serviceAnalogous to the transport-layer services but

Service host-to-hostHost has no choice network provides one or the otherImplementation in the core

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-16

Virtual circuits

Call setup teardown for each call before data can flowEach packet carries VC identifier (not destination host address)Every router on source-dest path maintains ldquostaterdquo for each passing connectionLink router resources (bandwidth buffers) may be allocated to VC

ldquosource-to-dest path behaves much like telephone circuitrdquo

performance-wisenetwork actions along source-to-dest path

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-17

VC implementation

A VC consists of1 Path from source to destination2 VC numbers one number for each link

along path3 Entries in forwarding tables in

routers along path

Packet belonging to VC carries a VC numberVC number must be changed on each link

New VC number comes from forwarding table

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-18

Forwarding table

12 22 32

1 23

VC number

interfacenumber

Incoming interface Incoming VC Outgoing interface Outgoing VC

1 12 3 222 63 1 18 3 7 2 171 97 3 87hellip hellip hellip hellip

Forwarding table innorthwest router

Routers maintain connection state information

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-19

Virtual circuits signaling protocols

Used to setup maintain teardown VCUsed in ATM frame-relay X25Not used in todayrsquos Internet

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Initiate call 2 incoming call

3 Accept call4 Call connected5 Data flow begins 6 Receive data

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-20

Datagram networksNo call setup at network layerRouters no state about end-to-end connections

No network-level concept of ldquoconnectionrdquo

Packets forwarded using destination host addres

Packets between same source-dest pair may take different paths

application

transportnetwork

data linkphysical

application

transportnetwork

data linkphysical

1 Send data 2 Receive data

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-21

Forwarding table

Destination Address Range Link Interface

11001000 00010111 00010000 00000000 through 0 11001000 00010111 00010111 11111111

11001000 00010111 00011000 00000000 through 1 11001000 00010111 00011000 11111111

11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111

otherwise 3

4 billion possible entries

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-22

Longest prefix matching

Prefix Match Link Interface 11001000 00010111 00010 0 11001000 00010111 00011000 1 11001000 00010111 00011 2 otherwise 3

DA 11001000 00010111 00011000 10101010

Examples

DA 11001000 00010111 00010110 10100001 Which interface

Which interface

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network

Network Layer 4-23

Datagram or VC network

InternetData exchange among computers

No strict timing req

ldquosmartrdquo end systems (computers) simple coremany link types

different characteristicsuniform service difficult

ATMEvolved from telephonyHuman conversation

strict timing reliability requirements

ldquodumbrdquo end systems complexity inside network

• Summary TCP Congestion Control
• TCP sender congestion control
• TCP Throughput
• TCP Futures
• TCP Fairness
• Why is TCP fair
• Fairness
• PowerPoint Presentation
• Network layer
• Key Network-Layer Functions
• Slide 11
• Connection setup
• Network service model
• Network layer service models
• Network layer connection and connection-less service
• Virtual circuits
• VC implementation
• Forwarding table
• Virtual circuits signaling protocols
• Datagram networks
• Slide 21
• Longest prefix matching
• Datagram or VC network