Chapter 3 Transport Layer - cc.ntut.edu.thtwu/courses/Fall2009CN/Edited Chapter3 5th … · 2...

1

Transport Layer 3-1

Chapter 3Transport Layer

Computer Networking A Top Down Approach 5th edition Jim Kurose Keith RossAddison-Wesley April 2009

All material copyright 1996-2009JF Kurose and KW Ross All Rights Reserved

Transport Layer 3-2

Chapter 3 Transport LayerOur goals

understand principles behind transport layer services

multiplexingdemultiplexingreliable data transferflow controlcongestion control

learn about transport layer protocols in the Internet

UDP connectionless transportTCP connection-oriented transportTCP congestion control

2

Transport Layer 3-3

Chapter 3 outline

31 Transport-layer services32 Multiplexing and demultiplexing33 Connectionless transport UDP34 Principles of reliable data transfer

35 Connection-oriented transport TCP

segment structurereliable data transferflow controlconnection management

36 Principles of congestion control37 TCP congestion control

Transport Layer 3-4

Transport services and protocolsprovide logical communicationbetween app processes running on different hoststransport protocols run in end systems

send side breaks app messages into segments passes to network layerrcv side reassembles segments into messages passes to app layer

more than one transport protocol available to apps

Internet TCP and UDP

applicationtransportnetworkdata linkphysical


logical end-end transport

3

Transport Layer 3-5

Transport vs network layer

network layer logical communication between hoststransport layer logical communication between processes

relies on enhances network layer services

Household analogy12 kids sending letters

to 12 kidsprocesses = kidsapp messages = letters in envelopeshosts = housestransport protocol = Ann and Billnetwork-layer protocol = postal service

Transport Layer 3-6

Internet transport-layer protocols

reliable in-order delivery (TCP)

congestion control flow controlconnection setup

unreliable unordered delivery UDP

no-frills extension of ldquobest-effortrdquo IP

services not available delay guaranteesbandwidth guarantees


networkdata linkphysical








4

Transport Layer 3-7

Chapter 3 outline





Transport Layer 3-8

Multiplexingdemultiplexing

application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1

host 1 host 2 host 3

= process= socket

delivering received segmentsto correct socket

Demultiplexing at rcv hostgathering data from multiplesockets enveloping data with header (later used for demultiplexing)

Multiplexing at send host

5

Transport Layer 3-9

How demultiplexing workshost receives IP datagrams

each datagram has source IP address destination IP addresseach datagram carries 1 transport-layer segmenteach segment has source destination port number

host uses IP addresses amp port numbers to direct segment to appropriate socket

source port dest port

32 bits

applicationdata

(message)

other header fields

TCPUDP segment format

Transport Layer 3-10

Connectionless demultiplexing

Create sockets with port numbers

DatagramSocket mySocket1 = new DatagramSocket(12534)


UDP socket identified by two-tuple

(dest IP address dest port number)

When host receives UDP segment

checks destination port number in segmentdirects UDP segment to socket with that port number

IP datagrams with different source IP addresses andor source port numbers directed to same socket

6


Connectionless demux (cont)DatagramSocket serverSocket = new DatagramSocket(6428)

ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

SP provides ldquoreturn addressrdquo


Connection-oriented demux

TCP socket identified by 4-tuple

source IP addresssource port numberdest IP addressdest port number

recv host uses all four values to direct segment to appropriate socket

Server host may support many simultaneous TCP sockets

each socket identified by its own 4-tuple

Web servers have different sockets for each connecting client

non-persistent HTTP will have different socket for each request

7


Connection-oriented demux(cont)

ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Connection-oriented demux Threaded Web Server

ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline






UDP User Datagram Protocol [RFC 768]

ldquono frillsrdquo ldquobare bonesrdquoInternet transport protocolldquobest effortrdquo service UDP segments may be

lostdelivered out of order to app

connectionlessno handshaking between UDP sender receivereach UDP segment handled independently of others

Why is there a UDPno connection establishment (which can add delay)simple no connection state at sender receiversmall segment headerno congestion control UDP can blast away as fast as desired

9


UDP moreoften used for streaming multimedia apps

loss tolerantrate sensitive

other UDP usesDNSSNMP

reliable transfer over UDP add reliability at application layer

application-specific error recovery


32 bits

Applicationdata

(message)

UDP segment format

length checksumLength in

bytes of UDPsegmentincluding

header


UDP checksum

Sendertreat segment contents as sequence of 16-bit integerschecksum addition (1rsquos complement sum) of segment contentssender puts checksum value into UDP checksum field

Receivercompute checksum of received segmentcheck if computed checksum equals checksum field value

NO - error detectedYES - no error detected But maybe errors nonetheless More later hellip

Goal detect ldquoerrorsrdquo (eg flipped bits) in transmitted segment

10


Internet Checksum ExampleNote

When adding numbers a carryout from the most significant bit needs to be added to the result

Example add two 16-bit integers

1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11


Principles of Reliable data transferimportant in app transport link layerstop-10 list of important networking topics

characteristics of unreliable channel will determine complexity of reliable data transfer protocol (rdt)




12





Reliable data transfer getting started

sendside

receiveside

rdt_send() called from above (eg by app) Passed data to

deliver to receiver upper layer

udt_send() called by rdtto transfer packet over

unreliable channel to receiver

rdt_rcv() called when packet arrives on rcv-side of channel

deliver_data() called by rdt to deliver data to upper

13


Reliable data transfer getting startedWersquoll

incrementally develop sender receiver sides of reliable data transfer protocol (rdt)consider only unidirectional data transfer

but control info will flow on both directionsuse finite state machines (FSM) to specify sender receiver

state1

state2

event causing state transitionactions taken on state transition

state when in this ldquostaterdquo next state

uniquely determined by next event

eventactions


Rdt10 reliable transfer over a reliable channel

underlying channel perfectly reliableno bit errorsno loss of packets

separate FSMs for sender receiversender sends data into underlying channelreceiver read data from underlying channel

Wait for call from above packet = make_pkt(data)

udt_send(packet)

rdt_send(data)extract (packetdata)deliver_data(data)

Wait for call from

below

rdt_rcv(packet)

sender receiver

14


Rdt20 channel with bit errors

underlying channel may flip bits in packetchecksum to detect bit errors

the question how to recover from errorsacknowledgements (ACKs) receiver explicitly tells sender that pkt received OKnegative acknowledgements (NAKs) receiver explicitly tells sender that pkt had errorssender retransmits pkt on receipt of NAK

new mechanisms in rdt20 (beyond rdt10)error detectionreceiver feedback control msgs (ACKNAK) rcvr-gtsender


rdt20 FSM specification

Wait for call from above

snkpkt = make_pkt(data checksum)udt_send(sndpkt)

extract(rcvpktdata)deliver_data(data)udt_send(ACK)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt)

rdt_rcv(rcvpkt) ampamp isACK(rcvpkt)

udt_send(sndpkt)

rdt_rcv(rcvpkt) ampampisNAK(rcvpkt)

udt_send(NAK)

rdt_rcv(rcvpkt) ampamp corrupt(rcvpkt)

Wait for ACK or

NAK

Wait for call from

belowsender

receiverrdt_send(data)

Λ

15


rdt20 operation with no errors






udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ


rdt20 error scenario






udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16


rdt20 has a fatal flaw

What happens if ACKNAK corruptedsender doesnrsquot know what happened at receivercanrsquot just retransmit possible duplicate

Handling duplicates sender retransmits current pkt if ACKNAK garbledsender adds sequence number to each pktreceiver discards (doesnrsquot deliver up) duplicate pkt

Sender sends one packet then waits for receiver response

stop and wait


rdt21 sender handles garbled ACKNAKs

Wait for call 0 from

above

sndpkt = make_pkt(0 data checksum)udt_send(sndpkt)

rdt_send(data)

Wait for ACK or NAK 0 udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||isNAK(rcvpkt) )


rdt_send(data)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp isACK(rcvpkt)

udt_send(sndpkt)



Wait forcall 1 from

above

Wait for ACK or NAK 1

ΛΛ

17


rdt21 receiver handles garbled ACKNAKs

Wait for 0 from below

sndpkt = make_pkt(NAK chksum)udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp not corrupt(rcvpkt) ampamphas_seq0(rcvpkt)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp has_seq1(rcvpkt)

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)




rdt_rcv(rcvpkt) ampamp (corrupt(rcvpkt)

sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)






rdt21 discussion

Senderseq added to pkttwo seq rsquos (01) will suffice Whymust check if received ACKNAK corrupted twice as many states

state must ldquorememberrdquowhether ldquocurrentrdquo pkt has 0 or 1 seq

Receivermust check if received packet is duplicate

state indicates whether 0 or 1 is expected pkt seq

note receiver can notknow if its last ACKNAK received OK at sender

18


rdt22 a NAK-free protocol

same functionality as rdt21 using ACKs onlyinstead of NAK receiver sends ACK for last pkt received OK

receiver must explicitly include seq of pkt being ACKed duplicate ACK at sender results in same action as NAK retransmit current pkt


rdt30 channels with errors and loss

New assumptionunderlying channel can also lose packets (data or ACKs)

checksum seq ACKs retransmissions will be of help but not enough

Approach sender waits ldquoreasonablerdquo amount of time for ACK retransmits if no ACK received in this timeif pkt (or ACK) just delayed (not lost)

retransmission will be duplicate but use of seq rsquos already handles thisreceiver must specify seq of pkt being ACKed

requires countdown timer

19


rdt30 in action


rdt30 in action

20


Performance of rdt30

rdt30 works but performance stinksex 1 Gbps link 15 ms prop delay 8000 bit packet

U sender utilization ndash fraction of time sender busy sending

U sender =

00830008

= 000027 L R RTT + L R

=

1KB pkt every 30 msec -gt 33kBsec thruput over 1 Gbps linknetwork protocol limits use of physical resources

dsmicrosecon8bps10bits8000

9 ===RLdtrans


rdt30 stop-and-wait operation

first packet bit transmitted t = 0

sender receiver

RTT

last packet bit transmitted t = L R

first packet bit arriveslast packet bit arrives send ACK

ACK arrives send next packet t = RTT + L R

U sender =

00830008

= 000027 L R RTT + L R

=

21


Pipelined protocolsPipelining sender allows multiple ldquoin-flightrdquo yet-to-

be-acknowledged pktsrange of sequence numbers must be increasedbuffering at sender andor receiver

Two generic forms of pipelined protocols go-Back-N selective repeat


Pipelining increased utilization


sender receiver

RTT

last bit transmitted t = L R



last bit of 2nd packet arrives send ACKlast bit of 3rd packet arrives send ACK

U sender =

02430008

= 00008 3 L R RTT + L R

=

Increase utilizationby a factor of 3

22


Pipelining Protocols

Go-back-N big pictureSender can have up to N unacked packets in pipelineRcvr only sends cumulative acks

Doesnrsquot ack packet if therersquos a gap

Sender has timer for oldest unacked packet

If timer expires retransmit all unackedpackets

Selective Repeat big picSender can have up to N unacked packets in pipelineRcvr acks individual packetsSender maintains timer for each unacked packet

When timer expires retransmit only unackpacket


Go-Back-NSender

k-bit seq in pkt headerldquowindowrdquo of up to N consecutive unackrsquoed pkts allowed

ACK(n) ACKs all pkts up to including seq n - ldquocumulative ACKrdquomay receive duplicate ACKs (see receiver)

timer for each in-flight pkttimeout(n) retransmit pkt n and all higher seq pkts in window

23


GBN receiver

ACK-only always send ACK for correctly-received pktwith highest in-order seq

may generate duplicate ACKsneed only remember expectedseqnum

out-of-order pkt discard (donrsquot buffer) -gt no receiver bufferingRe-ACK pkt with highest in-order seq


GBN inaction

24


Selective Repeat

receiver individually acknowledges all correctly received pkts

buffers pkts as needed for eventual in-order delivery to upper layer

sender only resends pkts for which ACK not received

sender timer for each unACKed pktsender window

N consecutive seq rsquosagain limits seq s of sent unACKed pkts


Selective repeat sender receiver windows

25


Selective repeat

data from above if next available seq in window send pkt

timeout(n)resend pkt n restart timer

ACK(n) in [sendbasesendbase+N]

mark pkt n as receivedif n smallest unACKed pkt advance window base to next unACKed seq

senderpkt n in [rcvbase rcvbase+N-1]

send ACK(n)out-of-order bufferin-order deliver (also deliver buffered in-order pkts) advance window to next not-yet-received pkt

pkt n in [rcvbase-Nrcvbase-1]

ACK(n)otherwise

ignore

receiver


Selective repeat in action

26


Selective repeatdilemma

Example seq rsquos 0 1 2 3window size=3

receiver sees no difference in two scenariosincorrectly passes duplicate data as new in (a)

Q what relationship between seq size and window size


Chapter 3 outline





27


TCP Overview RFCs 793 1122 1323 2018 2581

full duplex databi-directional data flow in same connectionMSS maximum segment size

connection-orientedhandshaking (exchange of control msgs) initrsquossender receiver state before data exchange

flow controlledsender will not overwhelm receiver

point-to-pointone sender one receiver

reliable in-order byte steam

no ldquomessage boundariesrdquopipelined

TCP congestion and flow control set window size

send amp receive buffers

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

applicationwrites data

applicationreads data


TCP segment structure


32 bits

applicationdata

(variable length)

sequence numberacknowledgement number

Receive windowUrg data pnterchecksum

FSRPAUheadlen

notused

Options (variable length)

URG urgent data (generally not used)

ACK ACK valid

PSH push data now(generally not used)

RST SYN FINconnection estab(setup teardown

commands)

bytes rcvr willingto accept

countingby bytes of data(not segments)

Internetchecksum

(as in UDP)

28


TCP seq rsquos and ACKsSeq rsquos

byte stream ldquonumberrdquo of first byte in segmentrsquos data

ACKsseq of next byte expected from other sidecumulative ACK

Q how receiver handles out-of-order segments

A TCP spec doesnrsquot say - up to implementor

Host A Host B

Seq=42 ACK=79 data = lsquoCrsquo


Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt

of echoedlsquoCrsquo

host ACKsreceipt oflsquoCrsquo echoes

back lsquoCrsquo

timesimple telnet scenario


TCP Round Trip Time and Timeout

Q how to set TCP timeout valuelonger than RTT

but RTT variestoo short premature timeout

unnecessary retransmissions

too long slow reaction to segment loss

Q how to estimate RTTSampleRTT measured time from segment transmission until ACK receipt

ignore retransmissionsSampleRTT will vary want estimated RTT ldquosmootherrdquo

average several recent measurements not just current SampleRTT

29



EstimatedRTT = (1- α)EstimatedRTT + αSampleRTT

Exponential weighted moving averageinfluence of past sample decreases exponentially fasttypical value α = 0125


Example RTT estimationRTT gaiacsumassedu to fantasiaeurecomfr

100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)

SampleRTT Estimated RTT

30



Setting the timeoutEstimtedRTT plus ldquosafety marginrdquo

large variation in EstimatedRTT -gt larger safety marginfirst estimate of how much SampleRTT deviates from EstimatedRTT

TimeoutInterval = EstimatedRTT + 4DevRTT

DevRTT = (1-β)DevRTT +β|SampleRTT-EstimatedRTT|

(typically β = 025)

Then set timeout interval


Chapter 3 outline





31


TCP reliable data transfer

TCP creates rdtservice on top of IPrsquos unreliable servicePipelined segmentsCumulative acksTCP uses single retransmission timer

Retransmissions are triggered by

timeout eventsduplicate acks

Initially consider simplified TCP sender

ignore duplicate acksignore flow control congestion control


TCP sender eventsdata rcvd from app

Create segment with seq seq is byte-stream number of first data byte in segmentstart timer if not already running (think of timer as for oldest unacked segment)expiration interval TimeOutInterval

timeoutretransmit segment that caused timeoutrestart timer

Ack rcvdIf acknowledges previously unackedsegments

update what is known to be ackedstart timer if there are outstanding segments

32


TCP retransmission scenariosHost A

Seq=100 20 bytes data

ACK=100

timepremature timeout

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100


TCP retransmission scenarios (more)Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

Cumulative ACK scenario

Host B

X


ACK=120

time

SendBase= 120

33


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-backIf segment is lost there will likely be many duplicate ACKs

If sender receives 3 ACKs for the same data it supposes that segment after ACKeddata was lost

fast retransmit resend segment before timer expires


Host A

tim

eout

Host B

time

X

resend 2nd segment

Figure 337 Resending a segment after triple duplicate ACK

34


Chapter 3 outline






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 overflowreceiverrsquos buffer by

transmitting too muchtoo fast

flow control

35


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 segmentsSender limits unACKeddata to RcvWindow

guarantees receive buffer doesnrsquot overflow


Chapter 3 outline





36


TCP Connection ManagementRecall TCP sender receiver

establish ldquoconnectionrdquobefore exchanging data segmentsinitialize TCP variables

seq sbuffers flow control info (eg RcvWindow)

client connection initiatorSocket clientSocket = new Socket(hostnameport

number)

server contacted by clientSocket connectionSocket = welcomeSocketaccept()

Three way handshakeStep 1 client host sends TCP

SYN segment to serverspecifies initial seq no data

Step 2 server host receives SYN replies with SYNACK segment

server allocates buffersspecifies 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 socketclientSocketclose()

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

37



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

38


Chapter 3 outline






Principles of Congestion Control

Congestioninformally ldquotoo many sources sending too much data too fast for network to handlerdquodifferent from flow controlmanifestations

lost packets (buffer overflow at routers)long delays (queueing in router buffers)

a top-10 problem

39


Causescosts of congestion scenario 1

two senders two receiversone router infinite buffers no retransmission

large delays when congestedmaximum achievable throughput

unlimited shared output link buffers

Host Aλin original data

Host B

λout



one router finite buffers sender retransmission of lost packet

finite shared output link buffers

Host A λin original data

Host B

λout

λin original data plus retransmitted data

40


Causescosts of congestion scenario 2always (goodput)Offered load contains original plus retransmission data

retransmission of delayed (not lost) packet makes larger(than perfect case) for same

λin

λout=λ

inλoutgt

λin

λout

ldquocostsrdquo of congestionmore work (retrans) for given ldquogoodputrdquounneeded retransmissions link carries multiple copies of pkt

R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3


Causescosts of congestion scenario 3four sendersmultihop pathstimeoutretransmit

λin

Q what happens as and increase λ

in



Host B

λout


41



Another ldquocostrdquo of congestionwhen packet dropped any ldquoupstream transmission capacity used for that packet was wasted

Host A

Host B

λou

t


Approaches towards congestion control

End-end congestion controlno explicit feedback from networkcongestion inferred from end-system observed loss delayapproach taken by TCP

Network-assisted congestion controlrouters 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

42


Chapter 3 outline






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 detectedmultiplicative decrease cut CongWin in half after loss

timecong

estio

n w

indo

w s

ize

Saw toothbehavior probing

for bandwidth

43


TCP Congestion Control details

sender limits transmissionLastByteSent-LastByteAcked

le CongWin

Roughly

CongWin is dynamic function of perceived network congestion

How does sender perceive congestionloss event = timeout or3 duplicate acksTCP sender reduces rate (CongWin) after loss event

three mechanismsAIMDslow startconservative after timeout events

rate = CongWinRTT Bytessec


TCP Slow Start

When connection begins CongWin = 1 MSS

Example MSS = 500 bytes amp RTT = 200 msecinitial 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

44


TCP Slow Start (more)

When connection begins increase rate exponentially until first loss event

double CongWin every RTTdone 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 inferring lossAfter 3 dup ACKs

CongWin is cut in halfwindow then grows linearly

But after timeout eventCongWin instead set to 1 MSS window then grows exponentiallyto a threshold then grows linearly

3 dup ACKs indicates network capable of delivering some segments

timeout indicates a ldquomore alarmingrdquocongestion scenario

Philosophy

45


RefinementQ When should the

exponential increase switch to linear

A When CongWingets to 12 of its value before timeout

ImplementationVariable Threshold At loss event Threshold is set to 12 of CongWin just before loss event


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 Thresholdset to CongWin2 and CongWin set to Threshold

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

46


TCP sender congestion control

SS or CA

SS or CA

SS or CA

CongestionAvoidance (CA)

Slow Start (SS)

State

CongWin and Threshold not changed

Increment duplicate ACK count for segment being acked

Duplicate ACK

Enter slow startThreshold = CongWin2 CongWin = 1 MSSSet state to ldquoSlow Startrdquo

Timeout

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

Threshold = CongWin2 CongWin = ThresholdSet state to ldquoCongestion Avoidancerdquo

Loss event detected by triple duplicate ACK

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

CongWin = CongWin+MSS (MSSCongWin)

ACK receipt for previously unackeddata

Resulting in a doubling of CongWin every RTT

CongWin = CongWin + MSS If (CongWin gt Threshold)

set state to ldquoCongestion Avoidancerdquo


CommentaryTCP Sender Action Event


TCP throughput

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

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

47


TCP Futures TCP over ldquolong fat pipesrdquo

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

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

LRTTMSSsdot221


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

48


Why is TCP fairTwo competing sessions

Additive increase gives slope of 1 as throughout increasesmultiplicative decrease decreases throughput proportionally

R

R

equal bandwidth share

Connection 1 throughput

Conn

ecti

on 2

thr

ough

put

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 UDPpump audiovideo at constant rate tolerate packet loss

Research area TCP friendly

Fairness and parallel TCP connectionsnothing prevents app from opening parallel connections between 2 hostsWeb browsers do this Example link of rate R supporting 9 connections

new app asks for 1 TCP gets rate R10new app asks for 11 TCPs gets R2

49


Chapter 3 Summaryprinciples behind transport layer services

multiplexing demultiplexingreliable data transferflow controlcongestion control

instantiation and implementation in the Internet

UDPTCP

Nextleaving the network ldquoedgerdquo (application transport layers)into the network ldquocorerdquo

2

Transport Layer 3-3

Chapter 3 outline





Transport Layer 3-4

Transport services and protocolsprovide logical communicationbetween app processes running on different hoststransport protocols run in end systems

send side breaks app messages into segments passes to network layerrcv side reassembles segments into messages passes to app layer

more than one transport protocol available to apps

Internet TCP and UDP




3

Transport Layer 3-5






Transport Layer 3-6
















4

Transport Layer 3-7

Chapter 3 outline





Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




5

Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields












6



ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428











7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


3

Transport Layer 3-5






Transport Layer 3-6
















4

Transport Layer 3-7

Chapter 3 outline





Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




5

Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields












6



ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428











7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


4

Transport Layer 3-7

Chapter 3 outline





Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




5

Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields












6



ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428











7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


5

Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields












6



ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428











7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


6



ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428











7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


7



ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



ClientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


8


Chapter 3 outline











9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


9








32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum





10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


10





1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum


Chapter 3 outline





11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


11







12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


12






sendside

receiveside







13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


13





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver

14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


14













udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ

15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


15








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ

16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


16






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ

17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


17


















rdt21 discussion






18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


18












19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


19


rdt30 in action


rdt30 in action

20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


20





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

00830008

= 000027 L R RTT + L R

=

21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


21








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


22










Go-Back-NSender




23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


23


GBN receiver





GBN inaction

24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


24


Selective Repeat








25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


25


Selective repeat








ACK(n)otherwise

ignore

receiver



26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


26







Chapter 3 outline





27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


27











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)

28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


28







Host A Host B



Seq=43 ACK=80

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo











29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


29







100

150

200

250

300

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

RTT

(mill

iseco

nds)


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


30










Chapter 3 outline





31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


31














32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


32




ACK=100


Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

Seq=

92 t

imeo

ut

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

loss

tim

eout

lost ACK scenario

Host B

X

Seq=92 8 bytes data

ACK=100

time

Seq=

92 t

imeo

ut

SendBase= 100

SendBase= 120

SendBase= 120

Sendbase= 100



Seq=92 8 bytes data

ACK=100

loss

tim

eout


Host B

X


ACK=120

time

SendBase= 120

33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


33


Fast Retransmit








Host A

tim

eout

Host B

time

X

resend 2nd segment


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


34


Chapter 3 outline






TCP Flow Control






flow control

35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


35





LastByteRead]




Chapter 3 outline





36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


36






number)













client

FIN

server

ACK

ACK

FIN

close

close

closed

tim

ed w

ait

37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


37







client

FIN

server

ACK

ACK

FIN

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle

38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


38


Chapter 3 outline









a top-10 problem

39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


39







Host B

λout






Host B

λout


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


40




λin

λout=λ

inλoutgt

λin

λout


R2

R2λin

λ out

b

R2

R2λin

λ out

a

R2

R2λin

λ out

c

R4

R3



λin


in



Host B

λout


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


41




Host A

Host B

λou

t







42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


42


Chapter 3 outline







8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



timecong

estio

n w

indo

w s

ize


for bandwidth

43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


43




le CongWin

Roughly






TCP Slow Start






44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


44






Host A

one segment

RTT

Host B

time

two segments

four segments







Philosophy

45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


45












46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


46



SS or CA

SS or CA

SS or CA


Slow Start (SS)

State



Duplicate ACK


Timeout













TCP throughput



47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


47





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness

48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


48




R

R



Conn

ecti

on 2

thr

ough

put











49





UDPTCP


49





UDPTCP


Chapter 3 Transport Layer - cc.ntut.edu.thtwu/courses/Fall2009CN/Edited Chapter3 5th … · 2...

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Transcript of Chapter 3 Transport Layer - cc.ntut.edu.thtwu/courses/Fall2009CN/Edited Chapter3 5th … · 2...