lecture 9

Introduction 1-1

Lecture 9

Computer Networking A Top Down Approach 6th edition Jim Kurose Keith RossAddison-WesleyMarch 2012

CS3516

These slides are generated from those made available by the authors of our text

Transport Layer 3-2

Lecture 9 outline35 connection-

oriented transport TCP segment structure reliable data

transfer flow control connection

management36 principles of

congestion control37 TCP congestion

control

Transport Layer 3-3

TCP flow controlapplicationprocess

TCP socketreceiver buffers

TCPcode

IPcode

applicationOS

receiver protocol stack

application may remove data from

TCP socket buffers hellip

hellip slower than TCP receiver is delivering(sender is sending)

from sender

receiver controls sender so sender wonrsquot overflow receiverrsquos buffer by transmitting too much too fast

flow control

Transport Layer 3-4

TCP flow controlbuffered data

free buffer spacerwnd

RcvBuffer

TCP segment payloads

to application process

receiver ldquoadvertisesrdquo free buffer space by including rwnd value in TCP header of receiver-to-sender segments RcvBuffer size set via

socket options (typical default is 4096 bytes)

many operating systems autoadjust RcvBuffer

sender limits amount of unacked (ldquoin-flightrdquo) data to receiverrsquos rwnd value

guarantees receive buffer will not overflow

receiver-side buffering

Transport Layer 3-5






control

Transport Layer 3-6

Connection Managementbefore exchanging data senderreceiver

ldquohandshakerdquo agree to establish connection (each knowing the

other willing to establish connection) agree on connection parameters

connection state ESTABconnection variables

seq client-to-server server-to-clientrcvBuffer size at serverclient

application

network

connection state ESTABconnection Variables


application

network

Socket clientSocket = newSocket(hostnameport

number)

Socket connectionSocket = welcomeSocketaccept()

CS118 2-742605

Blue army

Red army

the well-known ldquotwo-army problemrdquo

Q how can the 2 red armies agree on an attack time

Fact the one who sends a message does not know whether the message is delivered

Basic rule one cannot send an ACK to acknowledge an ACK ndash it goes on forever

Red army

The red armies together can defeat the blue army but separately the blue army wins

Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x

choose init seq num xsend TCP SYN msg

ESTAB

SYNbit=1 Seq=yACKbit=1 ACKnum=x+1

choose init seq num ysend TCP SYNACKmsg acking SYN

ACKbit=1 ACKnum=y+1

received SYNACK(x) indicates server is livesend ACK for SYNACK

this segment may contain client-to-server data received ACK(y)

indicates client is live

SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9

TCP closing a connection client server each close their side of

connection send TCP segment with FIN bit = 1

respond to received FIN with ACK on receiving FIN ACK can be combined with

own FIN simultaneous FIN exchanges can be

handled

Transport Layer 3-10

FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1

ACKbit=1 ACKnum=x+1 wait for server

closecan stillsend data

can no longersend data

LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED

TCP closing a connection

FIN_WAIT_1 FINbit=1 seq=xcan no longersend but can receive data

clientSocketclose()

client state server state

ESTABESTAB

Fin

Ack







control


congestion informally ldquotoo many sources sending

too much data too fast for network to handlerdquo

different from flow control manifestations

lost packets (buffer overflow at routers)

long delays (queueing in router buffers)

a top-10 problem

Principles of congestion control


Causescosts of congestion scenario 1 two senders two

receivers one router infinite

buffers output link capacity

R no retransmission

maximum per-connection throughput R2

unlimited shared output link buffers

Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay

lin large delays as arrival

rate lin approaches capacity


one router finite buffers sender retransmission of timed-out

packet application-layer input = application-layer

output lin = lout transport-layer input includes retransmissions

lin lin

finite shared output link buffers

Host A

lin original data

Host B

loutlin original data plus retransmitted data

lsquo

Causescosts of congestion scenario 2


idealization perfect knowledge

sender sends only when router buffers available


lin original dataloutlin original data plus

retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space

Idealization known loss packets can be lost dropped at router due to full buffers

sender only resends if packet known to be lost


A

Host B



retransmitted data

free buffer space




R2

R2lin

l out

when sending at R2 some packets are retransmissions but asymptotic goodput is still R2 (why)

A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out

when sending at R2 some packets are retransmissions including duplicated that are delivered

Host B

Realistic duplicates packets can be lost

dropped at router due to full buffers

sender times out prematurely sending two copies both of which are delivered



R2

l out


ldquocostsrdquo of congestion more work (retrans) for given ldquogoodputrdquo unneeded retransmissions link carries multiple

copies of pkt decreasing goodput

R2lin

Causescosts of congestion scenario 2 Realistic duplicates packets can be lost




four senders multihop paths timeoutretransmit

Q what happens as lin and lin

rsquo increase


Host A lout


Host B

Host CHost D

lin original data

lin original data plus retransmitted data

A as red linrsquo increases all

arriving blue pkts at upper queue are dropped blue throughput g 0


another ldquocostrdquo of congestion when packet dropped any ldquoupstream

transmission capacity used for that packet was wasted


C2

C2

l out

linrsquo


Approaches towards congestion controltwo broad approaches towards congestion

controlend-end

congestion control

no explicit feedback from network

congestion inferred from end-system observed loss delay

approach taken by TCP

network-assisted congestion control

routers provide feedback to end systemssingle bit indicating congestion (SNA DECbit TCPIP ECN ATM)

explicit rate for sender to send at







control

45 routing algorithms link state distance vector hierarchical routing


TCP congestion control additive increase multiplicative decrease

approach sender increases transmission rate (window size) probing for usable bandwidth until loss occurs additive increase increase cwnd by 1

MSS every RTT until loss detectedmultiplicative decrease cut cwnd in half

after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize

AIMD saw toothbehavior probing

for bandwidth

additively increase window size helliphellip until loss occurs (then cut window in half)

time


TCP Congestion Control details

sender limits transmission

cwnd is dynamic function of perceived network congestion

TCP sending rate roughly send

cwnd bytes wait RTT for ACKS then send more bytes

last byteACKed sent not-

yet ACKed(ldquoin-flightrdquo)

last byte sent

cwnd

LastByteSent-LastByteAcked

lt cwnd

sender sequence number space

rate ~~cwndRTT bytessec


TCP Slow Start when connection

begins increase rate exponentially until first loss event initially cwnd = 1

MSS double cwnd every

RTT done by

incrementing cwnd for every ACK received

summary initial rate is slow but ramps up exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


TCP detecting reacting to loss

loss indicated by timeout cwnd set to 1 MSS window then grows exponentially (as in

slow start) to threshold then grows linearly

loss indicated by 3 duplicate ACKs TCP RENO dup ACKs indicate network capable of

delivering some segments cwnd is cut in half window then grows

linearly TCP Tahoe always sets cwnd to 1

(timeout or 3 duplicate acks)


Q when should the exponential increase switch to linear

A when cwnd gets to 12 of its value before timeout

Implementation variable ssthresh on loss event ssthresh is set to 12 of cwnd just before loss event

TCP switching from slow start to CA


Summary TCP Congestion Control

timeoutssthresh = cwnd2cwnd = 1 MSSdupACKcount = 0retransmit missing segment

Lcwnd gt ssthresh

congestionavoidance

cwnd = cwnd + MSS (MSScwnd)dupACKcount = 0transmit new segment(s) as allowed

new ACK

dupACKcount++duplicate ACK

fastrecovery

cwnd = cwnd + MSStransmit new segment(s) as allowed

duplicate ACK

ssthresh= cwnd2cwnd = ssthresh + 3

retransmit missing segment

dupACKcount == 3

timeoutssthresh = cwnd2cwnd = 1 dupACKcount = 0retransmit missing segment

ssthresh= cwnd2cwnd = ssthresh + 3retransmit missing segment

dupACKcount == 3cwnd = ssthreshdupACKcount = 0

New ACK

slow start

timeoutssthresh = cwnd2 cwnd = 1 MSSdupACKcount = 0retransmit missing segment

cwnd = cwnd+MSSdupACKcount = 0transmit new segment(s) as allowed

new ACKdupACKcount++duplicate ACK

Lcwnd = 1 MSSssthresh = 64 KBdupACKcount = 0

NewACK

NewACK

NewACK


TCP throughput avg TCP thruput as function of window

size RTT ignore slow start assume always data to send

W window size (measured in bytes) where loss occurs avg window size ( in-flight bytes) is frac34 W avg thruput is 34W per RTT

W

W2

avg TCP thruput = 34WRTTbytessec


TCP Futures TCP over ldquolong fat pipesrdquo example 1500 byte segments 100ms

RTT want 10 Gbps throughput requires W = 83333 in-flight segments throughput in terms of segment loss

probability L [Mathis 1997]

to achieve 10 Gbps throughput need a loss rate of L = 210-10 ndash a very small loss rate

new versions of TCP for high-speed

TCP throughput = 122 MSSRTT L







control


Network Layer 4-33

123

IP destination address in arriving packetrsquos header

routing algorithm

local forwarding tabledest address output

linkaddress-range 1address-range 2address-range 3address-range 4

3221

Interplay between routing forwarding

routing algorithm determinesend-end-path through networkforwarding table determineslocal forwarding at this router

Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)

N = set of routers = u v w x y z

E = set of links = (uv) (ux) (vx) (vw) (xw) (xy) (wy) (wz) (yz)

Graph abstraction

aside graph abstraction is useful in other network contexts eg P2P where N is set of peers and E is set of TCP connections

Network Layer 4-35

Graph abstraction costs

u

yx

wv

z2

21 3

1

12

53

5 c(xxrsquo) = cost of link (xxrsquo) eg c(wz) = 5

cost could always be 1 or inversely related to bandwidthor inversely related to congestion

cost of path (x1 x2 x3hellip xp) = c(x1x2) + c(x2x3) + hellip + c(xp-1xp)

key question what is the least-cost path between u and z routing algorithm algorithm that finds that least cost path

Network Layer 4-36

Routing algorithm classificationQ global or decentralized

informationglobal all routers have

complete topology link cost info

ldquolink staterdquo algorithmsdecentralized router knows

physically-connected neighbors link costs to neighbors

iterative process of computation exchange of info with neighbors

ldquodistance vectorrdquo algorithms

Q static or dynamic

static routes change slowly

over timedynamic routes change more

quickly periodic update in response to link

cost changes







control


Network Layer 4-38

A Link-State Routing AlgorithmDijkstrarsquos algorithm net topology link

costs known to all nodes accomplished via ldquolink

state broadcastrdquo all nodes have same

info computes least cost

paths from one node (lsquosourcerdquo) to all other nodes gives forwarding table

for that node iterative after k

iterations know least cost path to k destrsquos

notation c(xy) link cost from node x to y = infin if not

direct neighbors D(v) current value of cost of path from source

to dest v p(v) predecessor node along path from source

to v N set of nodes whose least cost path

definitively known

Network Layer 4-39

Dijsktrarsquos Algorithm1 Initialization 2 N = u 3 for all nodes v 4 if v adjacent to u 5 then D(v) = c(uv) 6 else D(v) = infin 7 8 Loop 9 find w not in N such that D(w) is a minimum 10 add w to N 11 update D(v) for all v adjacent to w and not in N 12 D(v) = min( D(v) D(w) + c(wv) ) 13 new cost to v is either old cost to v or known 14 shortest path cost to w plus cost from w to v 15 until all nodes in N

Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9

Dijkstrarsquos algorithm exampleStep N

D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)

u infin infin 7u 3u 5uuw infin 11w 6w 5u

14x 11w 6wuwxuwxv 14x 10v

uwxvy 12y

notes construct shortest path

tree by tracing predecessor nodes

ties can exist (can be broken arbitrarily)

uwxvyz

Network Layer 4-41

Dijkstrarsquos algorithm another example

Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x

D(z)p(z)infin infin 4y4y4y

u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42

Dijkstrarsquos algorithm example (2)

u

yx

wv

z

resulting shortest-path tree from u

vxywz

(uv)(ux)(ux)(ux)(ux)

destination link

resulting forwarding table in u

Network Layer 4-43

Dijkstrarsquos algorithm discussionalgorithm complexity n nodes each iteration need to check all nodes w

not in N n(n+1)2 comparisons O(n2) more efficient implementations possible

O(nlogn)oscillations possible eg support link cost equals amount of

carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B

given these costsfind new routinghellip

resulting in new costs

2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control

TCP flow control (2)

Lecture 9 outline (2)

Connection Management


TCP 3-way handshake


TCP closing a connection (2)





Causescosts of congestion scenario 2 (2)







Approaches towards congestion control


TCP congestion control additive increase multiplicative decrea


TCP Slow Start




TCP throughput

TCP Futures TCP over ldquolong fat pipesrdquo



Graph abstraction


Routing algorithm classification


A Link-State Routing Algorithm

Dijsktrarsquos Algorithm

Slide 40



Dijkstrarsquos algorithm discussion

The End is Near

Transport Layer 3-2






control

Transport Layer 3-3



TCPcode

IPcode

applicationOS





from sender


flow control

Transport Layer 3-4



RcvBuffer









Transport Layer 3-5






control

Transport Layer 3-6






application

network



application

network


number)


CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-3



TCPcode

IPcode

applicationOS





from sender


flow control

Transport Layer 3-4



RcvBuffer









Transport Layer 3-5






control

Transport Layer 3-6






application

network



application

network


number)


CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-4



RcvBuffer









Transport Layer 3-5






control

Transport Layer 3-6






application

network



application

network


number)


CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-5






control

Transport Layer 3-6






application

network



application

network


number)


CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-6






application

network



application

network


number)


CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

CS118 2-742605

Blue army

Red army





Red army


Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-8

TCP 3-way handshake

SYNbit=1 Seq=x


ESTAB



ACKbit=1 ACKnum=y+1




SYNSENT

ESTAB

SYN RCVD

client state

LISTENserver state

LISTEN

Syn

Ack

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Transport Layer 3-9





handled


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near


FIN_WAIT_2

CLOSE_WAIT

FINbit=1 seq=y

ACKbit=1 ACKnum=y+1




LAST_ACK

CLOSED

TIMED_WAIT

timed wait for 2max

segment lifetime

CLOSED



clientSocketclose()


ESTABESTAB

Fin

Ack







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near







control







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near







a top-10 problem






R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

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lay







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Host A

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Host B

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R2

R2lin

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Host A lout


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congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

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ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2de

lay







lin lin


Host A

lin original data

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lsquo







retransmitted data

copy

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R2

R2

l out

lin


Host B

A



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copy

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A

Host B



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free buffer space




R2

R2lin

l out


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lin loutlincopy

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timeout

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l out


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Host A lout


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Host CHost D

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controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

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ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





lin lin


Host A

lin original data

Host B


lsquo







retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



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copy

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A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








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C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near






retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


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R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near



retransmitted data

copy

no buffer space




A

Host B



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near



retransmitted data

free buffer space




R2

R2lin

l out


A

Host B


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near


A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin







rsquo increase


Host A lout


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Host CHost D

lin original data








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C2

l out

linrsquo



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congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near


R2

l out




R2lin







rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near




rsquo increase


Host A lout


Host B

Host CHost D

lin original data








C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





C2

C2

l out

linrsquo



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near



controlend-end

congestion control













control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near







control






after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





after loss

cwnd

TCP

sen

der

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near









last byte sent

cwnd


lt cwnd







RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





RTT done by



Host A

one segment

RTT

Host B

time

two segments

four segments

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

















Lcwnd gt ssthresh

congestionavoidance


new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start





NewACK

NewACK

NewACK





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near





W

W2















control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near














control


Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-33

123


routing algorithm



3221



Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-34

u

yx

wv

z2

21 3

1

12

53

5

graph G = (NE)



Graph abstraction


Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-35


u

yx

wv

z2

21 3

1

12

53





Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-36








Q static or dynamic




cost changes







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near







control


Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-38












definitively known

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-39


Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-40

w3

4

v

x

u

5

37 4

y8

z2

7

9


D(v)p(v)

012345

D(w)p(w)

D(x)p(x)

D(y)p(y)

D(z)p(z)



uwxvy 12y




uwxvyz

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-41


Step012345

Nu

uxuxy

uxyvuxyvw

uxyvwz

D(v)p(v)2u2u2u

D(w)p(w)5u4x3y3y

D(x)p(x)1u

D(y)p(y)infin

2x


u

yx

wv

z2

21 3

1

12

53

5

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-42


u

yx

wv

z


vxywz


destination link


Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

Network Layer 4-43




carried trafficAD

C

B1 1+e

e0

e1 1

0 0

initially

AD

C

B



2+e 0

001+e 1

AD

C

B



0 2+e

1+e10 0

AD

C

B



2+e 0

001+e 1

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

The End is Near

Slide 1

Lecture 9 outline

TCP flow control





TCP 3-way handshake


















TCP Slow Start




TCP throughput




Graph abstraction






Slide 40




The End is Near

lecture 9

Documents

server server

tcp receiver

buffering transport

connectionsend tcp segment

tcp header of receiver

tcp socket buffers

connectionoriented transport

ysend tcp synackmsg