the future r homework questions> r the next test is coming the 19 th (just before turkey day!) r...

Transport Layer

The Future

Homework questionsgt The next test is coming the 19th (just

before turkey day) Wednesday = review + anything not

done today Friday will cover threaded Java

programming

3-1

Transport Layer 3-2

Chapter 3Transport Layer

Computer Networking A Top Down Approach 4th edition Jim Kurose Keith RossAddison-Wesley July 2007

A note on the use of these ppt slidesWersquore making these slides freely available to all (faculty students readers) Theyrsquore in PowerPoint form so you can add modify and delete slides (including this one) and slide content to suit your needs They obviously represent a lot of work on our part In return for use we only ask the following If you use these slides (eg in a class) in substantially unaltered form

that you mention their source (after all wersquod like people to use our book) If you post any slides in substantially unaltered form on a www site that

you note that they are adapted from (or perhaps identical to) our slides and note our copyright of this material

Thanks and enjoy JFKKWR

All material copyright 1996-2007JF Kurose and KW Ross All Rights Reserved

Transport Layer 3-3

TCP ACK generation [RFC 1122 RFC 2581]

Event at Receiver

Arrival of in-order segment withexpected seq All data up toexpected seq already ACKed

Arrival of in-order segment withexpected seq One other segment has ACK pending

Arrival of out-of-order segmenthigher-than-expect seq Gap detected

Arrival of segment that partially or completely fills gap

TCP Receiver action

Delayed ACK Wait up to 500msfor next segment If no next segmentsend ACK

Immediately send single cumulative ACK ACKing both in-order segments

Immediately send duplicate ACK indicating seq of next expected byte

Immediate send ACK provided thatsegment startsat lower end of gap

Transport Layer 3-4

Fast Retransmit

Time-out period often relatively long long delay before resending lost packet

Detect lost segments via duplicate ACKs Sender often sends many segments back-to-back If segment is lost there will likely be many duplicate

ACKs

If sender receives 3 ACKs for the same data it supposes that segment after ACKed data was lost fast retransmit resend

segment before timer expires

Transport Layer 3-5

event ACK received with ACK field value of y if (y gt SendBase) SendBase = y if (there are currently not-yet-acknowledged segments) start timer else increment count of dup ACKs received for y if (count of dup ACKs received for y = 3) resend segment with sequence number y

Fast retransmit algorithm

a duplicate ACK for already ACKed segment

fast retransmit

Transport Layer 3-6

Chapter 3 outline

31 Transport-layer services 32 Multiplexing and demultiplexing 33 Connectionless transport UDP 34 Principles of reliable data transfer

35 Connection-oriented transport TCP segment structure reliable data transfer flow control connection

management 36 Principles of

congestion control 37 TCP congestion

control

Transport Layer 3-7

TCP Flow Control

receive side of TCP connection has a receive buffer

speed-matching service matching the send rate to the receiving apprsquos drain rate app process may be

slow at reading from buffer

sender wonrsquot overflow

receiverrsquos buffer bytransmitting too

much too fast

flow control

Transport Layer 3-8

TCP Flow control how it works

(Suppose TCP receiver discards out-of-order segments)

spare room in buffer= RcvWindow= RcvBuffer-[LastByteRcvd -

LastByteRead]

Rcvr advertises spare room by including value of RcvWindow in segments

Sender limits unACKed data to RcvWindow guarantees receive

buffer doesnrsquot overflow

Transport Layer 3-9

Chapter 3 outline





control

Transport Layer 3-10

TCP Connection Management

Recall TCP sender receiver establish ldquoconnectionrdquo before exchanging data segments

initialize TCP variables seq s buffers flow control

info (eg RcvWindow) client connection

initiator Socket clientSocket = new

Socket(hostnameport

number) server contacted by

client Socket connectionSocket =

welcomeSocketaccept()

Three way handshake

Step 1 client host sends TCP SYN segment to server specifies initial seq no data

Step 2 server host receives SYN replies with SYNACK segment server allocates buffers specifies server initial

seq Step 3 client receives

SYNACK replies with ACK segment which may contain data


TCP Connection Management (cont)

Closing a connection

client closes socket clientSocketclose()

Step 1 client end system sends TCP FIN control segment to server

Step 2 server receives FIN replies with ACK Closes connection sends FIN

client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait



Step 3 client receives FIN replies with ACK

Enters ldquotimed waitrdquo - will respond with ACK to received FINs

Step 4 server receives ACK Connection closed

Note with small modification can handle simultaneous FINs

client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control


Principles of Congestion 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


Causescosts of congestion scenario 1

two senders two receivers

one router infinite buffers

no retransmission

large delays when congested

maximum achievable throughput

unlimited shared output link buffers

Host Alin original data

Host B

lout



one router finite buffers sender retransmission of lost packet

finite shared output link buffers

Host A lin original data

Host B

lout

lin original data plus retransmitted data


Causescosts of congestion scenario 2 always (goodput)

ldquoperfectrdquo retransmission only when loss

retransmission of delayed (not lost) packet makes

larger (than perfect case) for same

lin

lout

=

lin

lout

gtl

inl

out

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

pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3


Causescosts of congestion scenario 3 four senders multihop paths timeoutretransmit

lin

Q what happens as and increase

lin



Host B

lout




Another ldquocostrdquo of congestion when packet dropped any ldquoupstream

transmission capacity used for that packet was wasted

Host A

Host B

lo

u

t


Approaches towards congestion control

End-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 systems single bit indicating

congestion (SNA DECbit TCPIP ECN ATM)

explicit rate sender should send at

Two broad approaches towards congestion control


Case study ATM ABR congestion control

ABR available bit rate

ldquoelastic servicerdquo if senderrsquos path

ldquounderloadedrdquo sender should use

available bandwidth if senderrsquos path

congested sender throttled to

minimum guaranteed rate

RM (resource management) cells

sent by sender interspersed with data cells

bits in RM cell set by switches (ldquonetwork-assistedrdquo) NI bit no increase in rate

(mild congestion) CI bit congestion

indication RM cells returned to sender

by receiver with bits intact



two-byte ER (explicit rate) field in RM cell congested switch may lower ER value in cell senderrsquo send rate thus maximum supportable rate on

path EFCI bit in data cells set to 1 in congested

switch if data cell preceding RM cell has EFCI set sender sets

CI bit in returned RM cell


Chapter 3 outline





control


TCP congestion control additive increase multiplicative decrease

8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow

Approach increase transmission rate (window size) probing for usable bandwidth until loss occurs additive increase increase CongWin by 1

MSS every RTT until loss detected multiplicative decrease cut CongWin in half

after loss

timecong

estio

n w

indo

w s

ize

Saw toothbehavior probing

for bandwidth


TCP Congestion Control details

sender limits transmission LastByteSent-LastByteAcked CongWin Roughly

CongWin is dynamic function of perceived network congestion

How does sender perceive congestion

loss event = timeout or 3 duplicate acks

TCP sender reduces rate (CongWin) after loss event

three mechanisms AIMD slow start conservative after

timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start

When connection begins CongWin = 1 MSS Example MSS = 500

bytes amp RTT = 200 msec

initial rate = 20 kbps available bandwidth

may be gtgt MSSRTT desirable to quickly

ramp up to respectable rate

When connection begins increase rate exponentially fast until first loss event


TCP Slow Start (more)

When connection begins increase rate exponentially until first loss event double CongWin every RTT done by incrementing CongWin 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


Refinement

Q When should the exponential increase switch to linear

A When CongWin gets to 12 of its value before timeout

Implementation Variable Threshold At loss event Threshold

is set to 12 of CongWin just before loss event


Refinement inferring loss

After 3 dup ACKs CongWin is cut in half window then grows

linearly But after timeout event

CongWin instead set to 1 MSS

window then grows exponentially

to a threshold then grows linearly

3 dup ACKs indicates

network capable of delivering some segments

timeout indicates a ldquomore alarmingrdquo congestion scenario

Philosophy


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


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)


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


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 occurs

When window is W throughput is WRTT Just after loss window drops to W2

throughput to W2RTT Average throughout 75 WRTT


TCP Futures TCP over ldquolong fat pipesrdquo

Example 1500 byte segments 100ms RTT want 10 Gbps throughput

Requires window size W = 83333 in-flight segments

Throughput in terms of loss rate

L = 210-10 Wow New versions of TCP for high-speed

LRTT

MSS221


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


Why is TCP fair

Two competing sessions Additive increase gives slope of 1 as throughout increases multiplicative decrease decreases throughput proportionally

R

R

equal bandwidth share

Connection 1 throughputConnect

ion 2

th

roughput

congestion avoidance additive increaseloss decrease window by factor of 2



Fairness (more)

Fairness and UDP Multimedia apps

often do not use TCP do not want rate

throttled by congestion control

Instead use UDP pump audiovideo at

constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connections

nothing prevents app from opening parallel connections between 2 hosts

Web browsers do this Example link of rate R

supporting 9 connections new app asks for 1 TCP

gets rate R10 new app asks for 11 TCPs

gets R2


Chapter 3 Summary principles behind

transport layer services multiplexing

demultiplexing reliable data transfer flow control congestion control

instantiation and implementation in the Internet UDP TCP

Next leaving the

network ldquoedgerdquo (application transport layers)

into the network ldquocorerdquo

The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control


Chapter 3 outline (2)



TCP Connection Management (cont) (2)






Causescosts of congestion scenario 2 (2)





Case study ATM ABR congestion control (2)


TCP congestion control additive increase multiplicative decre


TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-2

Chapter 3Transport Layer

Computer Networking A Top Down Approach 4th edition Jim Kurose Keith RossAddison-Wesley July 2007

A note on the use of these ppt slidesWersquore making these slides freely available to all (faculty students readers) Theyrsquore in PowerPoint form so you can add modify and delete slides (including this one) and slide content to suit your needs They obviously represent a lot of work on our part In return for use we only ask the following If you use these slides (eg in a class) in substantially unaltered form

that you mention their source (after all wersquod like people to use our book) If you post any slides in substantially unaltered form on a www site that

you note that they are adapted from (or perhaps identical to) our slides and note our copyright of this material

Thanks and enjoy JFKKWR

All material copyright 1996-2007JF Kurose and KW Ross All Rights Reserved

Transport Layer 3-3


Event at Receiver





TCP Receiver action





Transport Layer 3-4

Fast Retransmit



ACKs



Transport Layer 3-5




fast retransmit

Transport Layer 3-6

Chapter 3 outline





control

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-3


Event at Receiver





TCP Receiver action





Transport Layer 3-4

Fast Retransmit



ACKs



Transport Layer 3-5




fast retransmit

Transport Layer 3-6

Chapter 3 outline





control

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-4

Fast Retransmit



ACKs



Transport Layer 3-5




fast retransmit

Transport Layer 3-6

Chapter 3 outline





control

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-5




fast retransmit

Transport Layer 3-6

Chapter 3 outline





control

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-6

Chapter 3 outline





control

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-7

TCP Flow Control






much too fast

flow control

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-8




LastByteRead]




Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-9

Chapter 3 outline





control







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







Socket(hostnameport




Three way handshake











client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline





control






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






a top-10 problem





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





no retransmission





Host B

lout






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






Host B

lout







lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






lin

lout

=

lin

lout

gtl

inl

out


pkt

R2

R2lin

l ou

t

b

R2

R2lin

l ou

t

a

R2

R2lin

l ou

t

c

R4

R3



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



lin


lin



Host B

lout






Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





Host A

Host B

lo

u

t

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

































Chapter 3 outline





control



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



after loss

timecong

estio

n w

indo

w s

ize


for bandwidth









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary









timeout events

rate = CongWin

RTT Bytessec


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


TCP Slow Start











exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





exponentially fast

Host A

one segment

RTT

Host B

time

two segments

four segments


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Refinement















Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary











Philosophy










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary










Slow Start (SS)












Enter slow start





TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


TCP throughput











LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







LRTT

MSS221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Why is TCP fair


R

R



ion 2

th

roughput




Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Fairness (more)












gets R2






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






Next leaving the



The Future

Slide 2


Fast Retransmit


Chapter 3 outline

TCP Flow Control




















TCP Slow Start


Refinement




TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

the future r homework questions> r the next test is coming the 19 th (just before turkey day!) r...

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