03b - transport layer - new

Tng Vn chuyn

CHC NNG - 1

03/2011

Cung cp knh truyn d liu mc logic gia 2 tin trnh trn 2 myapplication transport network data link physical network data link physical

TTMTRANG - BM MMT&VT - KHOA CNTT - H KHTN TP.HCM

Application Presentation Session

network data link physical

network data link physical network data link physical network data link physical

TransportNetwork Data link

Physicalapplication application transport transport network network data link data link physical physical

2

NI DUNGGii thiu Nguyn tc truyn d liu ng tin cy Giao thc TCP Giao thc UDP

03/2011 TTMTRANG - BM MMT&VT - KHOA CNTT - H KHTN TP.HCM

3

NHC LIsourcemessageM M M M

03/2011

segmentpacket frame

Ht Hn Ht

Hl Hn Ht

application transport network link physical link physical switch


destinationM Ht Hn Ht M M

Hn Ht Hl Hn Ht

M M

application transport network link physical

network link physical

Hn Ht

M

4 router

TNG VN CHUYN

-1


P2M M

P3Process nhn?Ht D Ht D M

P1Gi n Process?Ht D M D Ht D H n segment M

application transport network

P4

H n segment



5

TNG VN CHUYN

-2

03/2011

Thc thi end-system Bn gi: thc hin Dn knhNhn d liu t tng ng dng (t cc socket) Phn on thng ip tng ng dng thnh cc segment Dn nhn d liu: ng gi theo giao thc ti tng Transport Chuyn cc segment xung tng mng (network layer)


Bn nhn: thc hin Phn knhNhn cc segment t tng mng Phn r cc segment thnh thng ip tng ng dng Chuyn thng ip ln tng ng dng (n socket tng ng)6

TNG VN CHUYN

-3

03/2011

H tr

Truyn d liu ng tin cyiu khin lung iu khin tt nghn Thit lp v duy tr kt ni


Truyn d liu khng ng tin cy

N lc gi d liu hiu qu nht

Khng h trm bo thi gian tr m bo bng thng

7

DN KNH PHN KNH - 1 Dn

03/2011

knh (Multiplexing):

Thc hin ti bn gi Thu thp d liu t cc socket dn nhn d liu vi 1 header Phn


knh (Demultiplexing):

Thc hin ti bn nhn phn phi cc segment nhn c cho socket tng ng

Khi

ng gi d liu tng transport, header s thm vo:Source port Destination port

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DN KNH PHN KNH - 232 bits


source port #

dest port #

other header fields

application data (message)

Cu trc ca mt segment

9

DN KNH PHN KNH - 3


P26428

P1 P15775

SP: 6428 DP: 5775

server IP: B

SP: 5775 DP: 6428

ClientIP:A

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NI DUNGGii thiu Giao thc UDP Nguyn tc truyn d liu ng tin cy Giao thc TCP


11

UDP - 1

03/2011

UDP: User Datagram Protocol [rfc768]Dch v n lc truyn nhanh Gi tin UDP c th:


Mt Khng ng th t

Khng kt ni:Khng c handshaking gia bn gi v nhn Mi gi tin UDP c x l c lp Khng c trng thi kt ni

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UDP - 232 bits Chiu di gi tin (tnh c header) source port # length dest port # checksum


Application data (message)

UDP segment format13

UDP - 3Application Transport .. U Cc segment n khng ng th t??? U1 M U2 U3


Application Transport ..14

Mt segment?

UDP - 4

03/2011

Ti sao li s dng UDP?Khng thit lp kt ni n gin:


khng qun l trng thi ni kt Khng kim sot lung

Header nh Nhanh

Truyn thng tin cy qua UDP

Tng application pht hin v phc hi li

15

UDP - 5

03/2011

Thng s dng cho cc ng dng multimedia

Chu li Yu cu tc


Mt s ng dng s dng UDPDNS SNMP TFTP

16



17

03/2011


BI TON

Lm sao truyn ng tin cy???

18

NGUYN L TRUYN D LIU NG TIN CYapplication Bn gi Bn nhn


transport

ng truyn tin cy

Nghi thc truyn tin cy

Nghi thc truyn tin cy

ng truyn khng tin cy a. Cung cp dv b. Trin khai dv

c tnh ca ng truyn khng tin cy quyt nh phc tp ca nghi thc truyn tin cy19

NI DUNG

03/2011

Nghi thc truyn d liu ng tin cyRDT 1.0 RDT 2.0, RDT 2.1, RDT 2.2 RDT 3.0


PipelineGo-back-N Gi li c chn

20

GII QUYT LI BIT

03/2011

Bn giGi km theo thng tin kim tra li S dng cc phng php kim tra li


Checksum, parity checkbit, CRC,..

Bn nhnKim tra c xy ra li bit? Hnh ng khi xy ra li bit?

Bo v bn gi

21

GII QUYT MT GI

03/2011

Bn nhn

Gi tn hiu bo


Gi gi tin bo hiu ACK, NAK

Bn ginh ngha trng hp mt gi Ch nhn tn hiu bo Hnh ng khi pht hin mt gi

22

GIAO THC RDT

03/2011

RDT = Reliable Data Transfer Nguyn tc: dng v ch


Bn gi

Gi gi tin km theo thng tin kim tra li Dng v ch n khi no gi tin va gi n c bn nhn an ton: nhn c gi tin ACK Gi li khi c li xy ra: li bit, mt gi Kim tra li, trng lp d liu Gi gi tin phn hi

Bn nhn:

Phin bn:

RDT 1.0 RDT 2.0 RDT 2.1 RDT 2.2 RDT 3.023

NGUYN L PIPE LINE

03/2011

Cho php gi nhiu gi tin khi cha nhn ACK


S dng buffer lu cc gi tinBn gi: lu gi tin gi nhng cha ack Bn nhn: lu gi tin nhn ng nhng cha ng th t

Gii quyt mt giGo back N Selective Repeat (gi li c chn)24

RDT1.0 : NG TRUYN L TNG

03/2011

Gi thit: knh truyn bn di tuyt i

Khng li bit Khng mt gi tin Bn gi chuyn d liu xung knh bn di Bn nhn c d liu t knh truyn bn di


FSM (finite state machine) cho bn gi v nhn

Wait for call from above

rdt_send(data) packet = make_pkt(data) udt_send(packet)

Wait for call from below

rdt_rcv(packet) extract (packet,data) deliver_data(data)

sender

receiver25

RDT2.0 KNH TRUYN C LI BIT - 1 Gi

03/2011

thit: knh truyn c th xy ra li bitchecksum

S dng cc c ch kim tra li


Lm

sao khc phc khi nhn ra li?

Acknowledgement(ACKs): bn nhn bo cho bn gi nhn c d liu Nagetive acknowledgement(NAKs): bn nhn bo gi tin b li Bn gi s gi li gi tin khi nhn NAK

So

vi rdt1.0, rdt2.0:

Nhn dng li C ch phn hi: ACK, NAK26

RDT2.0 FSM - 2rdt_send(data) snkpkt = make_pkt(data, checksum) udt_send(sndpkt) rdt_rcv(rcvpkt) && isNAK(rcvpkt) Wait for Wait for call from above ACK or NAK udt_send(sndpkt)

03/2011

receiverrdt_rcv(rcvpkt) && corrupt(rcvpkt) udt_send(NAK)Wait for call from below rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) extract(rcvpkt,data) deliver_data(data) udt_send(ACK)27


rdt_rcv(rcvpkt) && isACK(rcvpkt) L

sender

ACK/NAK sai???

RDT2.0 - 3

03/2011

Gii quyt:Bn gi gi li gi tin khi nhn ACK/NAK sai Bn gi nh s th t cho mi gi tin Bn nhn s loi b gi tin trng.


Dng v i

Bn gi gi mt gi tin v ch phn hi t bn nhn

28

RDT2.1 BN GI X L LI ACK/NAKrdt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt) rdt_rcv(rcvpkt) &&Wait for call 0 from above Wait for ACK or NAK 0


( corrupt(rcvpkt) || isNAK(rcvpkt) ) udt_send(sndpkt) rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt) L

rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt) L rdt_rcv(rcvpkt) && ( corrupt(rcvpkt) || isNAK(rcvpkt) ) udt_send(sndpkt)Wait for ACK or NAK 1

Wait for call 1 from above

rdt_send(data) sndpkt = make_pkt(1, data, checksum) udt_send(sndpkt)29

RDT2.1 BN NHN X L LI ACK/NAKrdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && has_seq0(rcvpkt)extract(rcvpkt,data) deliver_data(data) sndpkt = make_pkt(ACK, chksum) udt_send(sndpkt) rdt_rcv(rcvpkt) && (corrupt(rcvpkt) sndpkt = make_pkt(NAK, chksum) udt_send(sndpkt) Wait for 0 from below Wait for 1 from below


rdt_rcv(rcvpkt) && (corrupt(rcvpkt) sndpkt = make_pkt(NAK, chksum) udt_send(sndpkt) rdt_rcv(rcvpkt) && not corrupt(rcvpkt) && has_seq1(rcvpkt) sndpkt = make_pkt(ACK, chksum) udt_send(sndpkt)

rdt_rcv(rcvpkt) && not corrupt(rcvpkt) && has_seq0(rcvpkt)sndpkt = make_pkt(ACK, chksum) udt_send(sndpkt)

rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && has_seq1(rcvpkt) extract(rcvpkt,data) deliver_data(data) sndpkt = make_pkt(ACK, chksum) udt_send(sndpkt)

30

RDT2.1 THO LUNBn gi Thm s th t vo gi tin

03/2011

0 v 1???

Phi kim tra: ACK/NAK sai khng Phi nh gi tin hin thi c th t 0 hay 1

Bn nhn Phi kim tra nu nhn trng So snh trng thi ang ch (0 hay 1) vi trng thi gi tin nhn c


Bn nhn khng bit ACK/NAK cui cng c chuyn ti bn gi an ton khng?31

C CH TRUYN NG TIN CY - RDT

03/2011

C ch:Checksum: kim tra c li xy ra khng? ACK: bn nhn nhn ng gi tin NAK: bn nhn nhn sai gi tin Sequence Number (1 bit = 0 hoc 1)


32

RDT2.2 KHNG S DNG NAKHot ng ging rdt2.1, nhng khng dng NAK Bn nhn gi ACK cho gi tin khng li nhn c cui cng.


Bn nhn phi thm s th t vo gi tin ACK

Bn gi nhn trng gi tin ACK xem nh gi tin NAK gi li gi va gi v gi ny cha nhn c ACK

33

RDT2.2: BN GI V BN NHNrdt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt)Wait for call 0 from above Wait for ACK 0


rdt_rcv(rcvpkt) && ( corrupt(rcvpkt) || isACK(rcvpkt,1) )udt_send(sndpkt)

sender FSM fragmentrdt_rcv(rcvpkt) && (corrupt(rcvpkt) || has_seq0(rcvpkt) ) sndpkt = make_pkt(ACK0, chksum) udt_send(sndpkt)

rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt,0)

Wait for 1 from below

L

receiver FSM fragment

rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && has_seq1(rcvpkt) extract(rcvpkt,data) deliver_data(data) sndpkt = make_pkt(ACK1, chksum) udt_send(sndpkt)

34

RDT3.0 KNH TRUYN C LI V MT - 1

03/2011

Gi thit:Li bit mt gi Checksum, s th t, ACKs, truyn li vn cha

X l?

Gii php: bn gi i mt khong thi gian hp l cho ACK Gi li nu khng nhn c ACK trong khong thi gian ny Nu gi tin (hay ACK) b tr (khng mt) Gi li c th trng, phi nh s th t Bn nhn phi xc nh th t ca gi tin ACK


Yu cu m thi gian35

RDT3.0 BN GI - 2rdt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt) start_timer Wait for call 0from above rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt,1) stop_timer Wait for ACK1 rdt_send(data) sndpkt = make_pkt(1, data, checksum) udt_send(sndpkt) start_timer 36 Wait for call 1 from above Wait for ACK0 rdt_rcv(rcvpkt) && ( corrupt(rcvpkt) || isACK(rcvpkt,1) )


Ltimeout udt_send(sndpkt) start_timer rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt,0) stop_timer

timeout udt_send(sndpkt) start_timer rdt_rcv(rcvpkt) && ( corrupt(rcvpkt) || isACK(rcvpkt,0) ) L

rdt_rcv(rcvpkt)

L

03/2011


RDT3.0 - 3

37

03/2011


RDT3.0 - 4

38

03/2011


RDT3.0 DNG V I - 5

39

RDT3.0 HIU QU - 6Rdt3.0 lm vic, nhng khng hiu qu Vd:bng thng 1Gbps, 15ms end2end delay, gi tin 8Kb


Usender : t l thi gian bn gi gi gi tin Nghi thc hn ch vic s dng ti nguyn mng40

NGHI THC PIPELINE - 1

03/2011

Pipelining: bn gi cho php gi nhiu gi tin khi cha c bo nhn (ACK)


Gi tin: sp theo th t tng dn Dng b m bn gi hoc/v bn nhn: Sliding window

C hai gii php chnh ca nghi thc pipeline: go-Back-N gi li c chn.41

03/2011


NGHI THC PIPELINE - 2

Tng hiu qu s dng ln 3 ln

42

GO-BACK-N 1 S

03/2011

th t: k-bit window = N s gi tin c gi lin tc khng ACK


ACK(seq#): nhn ng n seq#

43

GO-BACK-N: BN NHN - 2

03/2011

Bn gi:

S dng buffer (window) lu cc gi tin gi nhng cha nhn c ACK Gi nu gi tin c th a vo window Thit lp ng h cho gi tin c nht (gi tin u window) Timeout: gi li tt c cc gi tin cha ACK trong window Ch gi ACK cho gi tin nhn ng vi s th t cao nht


Bn nhn:

C th pht sinh trng ACK

Ch cn nh s th t ang i Gi tin khng theo th t:

Loi b: khng c b m Gi li ACK vi s th t ln nht

44

03/2011


GO-BACK-N V D - 3

45

GI LI C CHN - 1

03/2011

Bn nhn:

Bo nhn ring l tng gi tin nhn ng


ACK(seq#): nhn ng gi tin seq#

dng b m lu cc gi tin khng ng th t Nhn 1 gi tin khng ng th t

a vo b m nu cn ch Hy gi tin

Bn gi:

C ng h cho mi gi tin cha nhn c ACK Time out: ch gi nhng gi tin khng nhn c ACK

46

GI LI C CHN - 2Bt u bn gi Th t k tip ACK Gi, cha ACK Cha dng khng dng c


Th t bn gi

Sai th t nhng ACK ang i, cha nhn c

C th nhn c khng dng c

Bt u bn nhn Th t bn nhn 47

03/2011


GI LI C CHN - 4

48

GI LI C CHN - 503/2011

Vd:

S th t:0,1,2,3 Window size: 3


Mi quan h gia s th t v window size???

49



50

TCPGii thiu Nguyn tc hot ng Qun l kt ni iu khin lung iu khin tt nghn


51

TCP GII THIU - 1 TCP

03/2011

= Transport Control Protocol


rfc: 793,1122,1323,2018,2581 Point to point

1 ngi gi v 1 ngi nhn

Full-duplex

D liu truyn 2 chiu trn cng kt ni MSS: maximum segment size

Hng kt ni

Handshaking trc khi gi d liu52

TCP - GII THIU - 2 TCP

03/2011

= Transport Control Protocol


TCP cung cp kt ni theo kiu dng (stream-of-bytes)

Khng c ranh gii gia cc gi tin S dng buffer gi v nhnsocket door application writes data TCP send buffersegment

application reads data TCP receive buffer

socket door

Tin cy, theo th t

PipelineKim sot lung Kim sot tt nghn53

TCP CU TRC GI TIN32 bits URG: urgent data (generally not used) ACK: ACK # valid PSH: push data now (generally not used) RST, SYN, FIN: connection estab (setup, teardown commands)

03/2011

source port #

dest port #


sequence numberacknowledgement numberhead not U AP R S F len used

rcvr window size

checksum

ptr urgent data

Options (variable length)

# bytes rcvr willing to accept

application data (variable length)

54

TCP NH NGHA CC TRNG - 1 Source

03/2011

& destination port

Port ca ni gi v ni nhn


Sequence

number

S th t ca byte u tin trong phn data ca gi tin

Acknowledgment

number

S th t ca byte ang mong ch nhn tip theo

Window

size

Thng bo c th nhn bao nhiu byte sau byte cui cng c xc nhn nhn

55

TCP NH NGHA CC TRNG - 2

03/2011

Checksum

Checksum TCP header


Urgent pointer

Ch n d liu khn trong trng d liuURG = trng urgent pointer valid ACK = trng Acknowledge number valid PSH = d liu cn phn phi ngay RST = ch nh ni kt cn thit lp li (reset) SYN = s dng thit lp kt ni FIN = s dng ng kt ni

C:

56

TCP V DHost A Seq: s th t ca byteUser types C

03/2011

Host B


u tin trong vngdata

host ACKs receipt of C, echoes back C

ACK: s th t ca byte ch nhn tip theo

host ACKs receipt of echoed C

simple telnet scenario57

TCP TRUYN D LIU NG TIN CY

03/2011

Nguyn tc: dng pipelineBn gi nh km thng tin kim tra li trong mi gi tin S dng ACK bo nhn Thit lp thi gian timeout khi cho gi tin u buffer Gi li ton b d liu trong buffer khi ht time out


58

TCP BN GI

03/2011

Nhn d liu t tng ng dngTo cc segment Bt ng h (nu cha bt) Thit lp thi gian ch, timeout


Nhn gi tin ACKNu trc cha nhn: trt ca s Thit lp li thi gian ca ng h

Ht time outGi li d liu cn trong buffer Reset ng h

59

TCP BN NHN

03/2011

Nhn gi tin ng th tChp nhn Gi ACK v cho bn gi


Nhn gi tin khng ng th tPht hin khong trng d liu (GAP) Gi ACK trng

60

TCP V DHost A Host B Host A Host B


loss

X

time

SendBase = 120 time lost ACK scenario

Seq=92 timeout

Sendbase = 100 SendBase = 120

Seq=92 timeout

timeout

premature timeout61

TCP THIT LP KT NI Thc

03/2011

hin thao tc bt tay 3 ln (Three way handshake)My A My B


SYN_RCVD state

ESTABLISHED state

62

TCP NG KT NI

03/2011

Thc hin thao tc bt tay 2 lnclient server


close

close

closed63

timed wait

TCP QUN L KT NI


TCP server lifecycle

TCP client lifecycle

64

TCP - IU KHIN LUNG - 1

03/2011

Nguyn nhn:


Bn gi lm trn b m ca bn nhn khi gi qu nhiu d liu hoc gi qu nhanh Window size: lng DL c th a vo buffer

S dng trng window size

65

TCP - IU KHIN LUNG - 2ng dng gi 2K Gi Nhn B m bn nhn 0 4K


Empty

2K ng dng gi 2K Full Bn gi b kha

Bn gi c th gi n 2K

2K

1K

2K

66

KIM SOT TT NGHN - 1

03/2011

Vn : 1 node c th nhn d liu t nhiu ngunBuffer: gii hn gi tin: n t


x l khng kp tt nghn Hin tng:Mt gi Delay cao

S dng ng truyn khng hiu quHost A

lin : original data

lout

Host B

unlimited shared output link buffers

67

KIM SOT TT NGHN - 2

03/2011

Gii quyt trong TCP:RTT

Host A

Host BTTMTRANG - BM MMT&VT - KHOA CNTT - H KHTN TP.HCM

Bn gi:

Thit lp tc gi da trn phn hi t bn nhn

Nhn ACK Mt gi tr gi tin time

Tc gi: c 2 pha

Slow-Start Congestion Avoidance68

TI LIU THAM KHO

03/2011

Bi ging ca J.F Kurose and K.W. Ross v Computer Networking: A Top Down Approach


69

03b - transport layer - new

Documents

iu khin lung

nghi thc pipeline

tng vn chuyn

bm mmtamp

application

cho bn gi

host acks

gi tin