! "# $ $ %&&' 3-1. Thanks and enjoy! JFK/KWR. All material copyright J.F Kurose and K.W. Ross, All Rights Reserved

Transcription

1 A note on the use of these ppt slides: We e making these slides feely available to all (faculty, students, eades). They e in PowePoint fom so you can add, modify, and delete slides (including this one) and slide content to suit you needs. They obviously epesent a lot of wok on ou pat. In etun fo use, we only ask the following: If you use these slides (e.g., in a class) in substantially unalteed fom, that you mention thei souce (afte all, we d like people to use ou book!) If you post any slides in substantially unalteed fom on a www site, that you note that they ae adapted fom (o pehaps identical to) ou slides, and note ou copyight of this mateial.! "# %&&' Thanks and enjoy! JFK/KWR All mateial copyight J.F Kuose and K.W. Ross, All Rights Reseved 3-1

2 ( ) * m +, + m ) - m - m ). m /0 m 0 " m 0 3-2

3 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m ' 0 3-3

4 * * ) -- m ) " m * ) *) m. 0 /0 3-4

5 * ) ) m * 5 1% 1% 6 6 * " 6 * 3-5

6 . " ) " * 809 m m - m ) * /0 m "- + - :)"--;.0 * *) m m ) " 3-6

7 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m ' 0 3-7

8 2 +, + + * * * * % 0 1 % 3-8

9 5 + *.0 m.0.0 m 1 " m ).0 < ) % ) = = ,/0-3-9

10 + ) DatagamSocket mysocket1 = new DatagamSocket(12534); DatagamSocket mysocket2 = new DatagamSocket(12535); /0 - ) " 8.0 )9 # * /0 m ) m /0 ) , ) 3-10

11 + 89 DatagamSocket sevesocket = new DatagamSocket(6428); 0% >0 4%? >0 4%? 0 3''3 >0 3'' %? *.0 0 4%?.07 >0 * : ; 3-11

12 " ) " m.0 >* 0 m ) m.0 m - ) " m ) * - * # ) * * -- - m " 5 0 * -- - A 3-12

13 " % 010 >0 3''3 0?& >".0 7 ".0 0?& >".0 ".0 *.0 0?& >".0 7 "

14 " + # ) >* % 010 >0 3''3 0?& >".0 7 ".0 0?& >".0 ".0 *.0 0?& >".0 7 "

15 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

16 /0 / 0 B!C ' 4?D : - ; :) );. :) --; * /0 ) m m * - m ) /0 * m /0 - # /0E ) 8 9 * /0 )

17 /0 - - m m * /0 m > m >2 0 ) - * /0 ) m "- *F ) - /0 % ) = = 8 9 /0-3-17

18 /0 K :; 8 - )9 > A - 14") 81G 9 - * /0 -!* - * - A - * m ( " m HI> " 7 ) E 2 J 3-18

19 . I+ m # ) - - ) ) I+ 14") 3-19

20 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

21 0 -!) - "1& - F - ) + - )

22 0 -!) - "1& - F - ) + - )

23 0 -!) - "1& - F - ) + - )

24 !) - dt_send(): - )* 8 ) 9 0 * * delive_data(): ) dt * * udt_send(): ) - * ) * dt_cv(): * *"

25 !) - # G * * - ) m ) - - ) F - 8C>2 9 - * :; + A ) + * 1 * * % 3-25

26 !1& ) - * ) - ) m ) m - C>2 - * m m * - Wait fo call fom above dt_send(data) packet = make_pkt(data) udt_send(packet) Wait fo call fom below dt_cv(packet) extact (packet,data) delive_data(data) * 3-26

27 !%& ) - ) m ) A * - m 89 * + * ( m * 89 * + m - dt2.0 8) dt1.09 m m * -) 8 9 *"L 3-27

28 %& C>2 - dt_send(data) snkpkt = make_pkt(data, checksum) udt_send(sndpkt) Wait fo call fom above dt_cv(cvpkt) && isack(cvpkt) Λ Wait fo ACK o NAK dt_cv(cvpkt) && isnak(cvpkt) udt_send(sndpkt) * dt_cv(cvpkt) && coupt(cvpkt) udt_send(nak) Wait fo call fom below dt_cv(cvpkt) && notcoupt(cvpkt) extact(cvpkt,data) delive_data(data) udt_send(ack) 3-28

29 %& dt_send(data) snkpkt = make_pkt(data, checksum) udt_send(sndpkt) Wait fo call fom above dt_cv(cvpkt) && isack(cvpkt) Λ Wait fo ACK o NAK dt_cv(cvpkt) && isnak(cvpkt) udt_send(sndpkt) dt_cv(cvpkt) && coupt(cvpkt) udt_send(nak) Wait fo call fom below dt_cv(cvpkt) && notcoupt(cvpkt) extact(cvpkt,data) delive_data(data) udt_send(ack) 3-29

30 %& dt_send(data) snkpkt = make_pkt(data, checksum) udt_send(sndpkt) Wait fo call fom above dt_cv(cvpkt) && isack(cvpkt) Λ Wait fo ACK o NAK dt_cv(cvpkt) && isnak(cvpkt) udt_send(sndpkt) dt_cv(cvpkt) && coupt(cvpkt) udt_send(nak) Wait fo call fom below dt_cv(cvpkt) && notcoupt(cvpkt) extact(cvpkt,data) delive_data(data) udt_send(ack) 3-30

31 %& - -F # -, E G *F G M ) 5 -, ) A ) * 8G * 9 > - * 3-31

32 %1 ), dt_cv(cvpkt) && notcoupt(cvpkt) && isack(cvpkt) Λ dt_cv(cvpkt) && ( coupt(cvpkt) isnak(cvpkt) ) udt_send(sndpkt) dt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt) Wait fo call 0 fom above Wait fo ACK o NAK 1 dt_send(data) Wait fo ACK o NAK 0 Wait fo call 1 fom above dt_cv(cvpkt) && ( coupt(cvpkt) isnak(cvpkt) ) udt_send(sndpkt) dt_cv(cvpkt) && notcoupt(cvpkt) && isack(cvpkt) sndpkt = make_pkt(1, data, checksum) udt_send(sndpkt) Λ 3-32

33 %1 * ), dt_cv(cvpkt) && (coupt(cvpkt) sndpkt = make_pkt(nak, chksum) udt_send(sndpkt) dt_cv(cvpkt) && not coupt(cvpkt) && has_seq1(cvpkt) sndpkt = make_pkt(ack, chksum) udt_send(sndpkt) dt_cv(cvpkt) && notcoupt(cvpkt) && has_seq0(cvpkt) extact(cvpkt,data) delive_data(data) sndpkt = make_pkt(ack, chksum) udt_send(sndpkt) Wait fo 0 fom below Wait fo 1 fom below dt_cv(cvpkt) && notcoupt(cvpkt) && has_seq1(cvpkt) dt_cv(cvpkt) && (coupt(cvpkt) sndpkt = make_pkt(nak, chksum) udt_send(sndpkt) dt_cv(cvpkt) && not coupt(cvpkt) && has_seq0(cvpkt) sndpkt = make_pkt(ack, chksum) udt_send(sndpkt) extact(cvpkt,data) delive_data(data) sndpkt = make_pkt(ack, chksum) udt_send(sndpkt) 3-33

34 %1 > A = A =G 8& # E - *, m : ); :; & 1 A =!* - * m & 1 + A = * -, * ( 3-34

35 %% "- - %1 - * - * ( m * + A = - ) 3-35

36 %% * - dt_cv(cvpkt) && (coupt(cvpkt) has_seq1(cvpkt)) udt_send(sndpkt) dt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt) Wait fo call 0 fom above Wait fo 0 fom below C>2 - * C>2 - Wait fo ACK 0 dt_cv(cvpkt) && ( coupt(cvpkt) isack(cvpkt,1) ) udt_send(sndpkt) dt_cv(cvpkt) && notcoupt(cvpkt) && isack(cvpkt,0) Λ dt_cv(cvpkt) && notcoupt(cvpkt) && has_seq1(cvpkt) extact(cvpkt,data) delive_data(data) sndpkt = make_pkt(ack1, chksum) udt_send(sndpkt) 3-36

37 & 8 9 m A = ) - ) :); * M 8 9 m ) ) - A =G m * - A = - ) A 3-37

38 & dt_cv(cvpkt) Λ Wait fo call 0fom above dt_cv(cvpkt) && notcoupt(cvpkt) && isack(cvpkt,1) stop_time timeout udt_send(sndpkt) stat_time dt_cv(cvpkt) && ( coupt(cvpkt) isack(cvpkt,0) ) Λ Wait fo ACK1 dt_send(data) sndpkt = make_pkt(0, data, checksum) udt_send(sndpkt) stat_time dt_send(data) Wait fo ACK0 Wait fo call 1 fom above sndpkt = make_pkt(1, data, checksum) udt_send(sndpkt) stat_time dt_cv(cvpkt) && ( coupt(cvpkt) isack(cvpkt,1) ) Λ timeout udt_send(sndpkt) stat_time dt_cv(cvpkt) && notcoupt(cvpkt) && isack(cvpkt,0) stop_time dt_cv(cvpkt) Λ 3-38

39 & 3-39

40 & 3-40

41 0- - & & ) K) 13 " )9! 8 )9 6?), 1&NN@ ), 6? m / O P - - ) / =,!! Q,! =.&&? &&&? = &&&&%' m 17 * & "L 7, * 1 K) m - F 3-41

42 & "" fist packet bit tansmitted, t = 0 last packet bit tansmitted, t = L / R sende eceive RTT fist packet bit aives last packet bit aives, send ACK ACK aives, send next packet, t = RTT + L / R / =,!! Q,! =.&&? &&&? = &&&&%' 3-42

43 0 0 :"-; "" )" m - A ) ) m )--, * - - "7" * 3-43

44 0 O fist packet bit tansmitted, t = 0 last bit tansmitted, t = L / R sende eceive RTT ACK aives, send next packet, t = RTT + L / R fist packet bit aives last packet bit aives, send ACK last bit of 2 nd packet aives, send ACK last bit of 3 d packet aives, send ACK. O ) - - F / = N,!! Q,! =.&% &&&? = &&&&? 3-44

45 K"7" > ") A = :; - * G 89 A = " : * ; m * 8 *9 - "- 89 A = 3-45

46 K7 + C>2 dt_send(data) Λ base=1 nextseqnum=1 dt_cv(cvpkt) && coupt(cvpkt) if (nextseqnum < base+n) { sndpkt[nextseqnum] = make_pkt(nextseqnum,data,chksum) udt_send(sndpkt[nextseqnum]) if (base == nextseqnum) stat_time nextseqnum++ } else efuse_data(data) Wait timeout stat_time udt_send(sndpkt[base]) udt_send(sndpkt[base+1]) udt_send(sndpkt[nextseqnum-1]) dt_cv(cvpkt) && notcoupt(cvpkt) base = getacknum(cvpkt)+1 If (base == nextseqnum) stop_time else stat_time 3-46

47 K7 * + C>2 default udt_send(sndpkt) Λ expectedseqnum=1 Wait sndpkt = make_pkt(expectedseqnum,ack,chksum) dt_cv(cvpkt) && notcuupt(cvpkt) && hasseqnum(cvpkt,expectedseqnum) extact(cvpkt,data) delive_data(data) sndpkt = make_pkt(expectedseqnum,ack,chksum) udt_send(sndpkt) expectedseqnum++ " - "* " A = m m ) expectedseqnum "-" m 8G )--9 "L * )--F m!" " A = 3-47

48 K7 3-48

49 >*! * * * m )-- - * " * - * m - m * A =G m A =

50 >* * 3-50

51 >* - )* - + *) A = B) )Q" 1D * - * ) + A = * B*) *)Q"1D 89 "-" )-- " * 8 * )-- " 9 * + ""* B*)" *)"1D

52 >* 3-52

53 >* I+ A =G & 1 % O6 * -- F 89 R ) A = O OE 3-53

54 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

55 0 ( **!C '@ 11%% 1% %&1? %3?1 "" - + m * ) " ) m : ); m 0 - O < * )-- m )" - m 2 >> + O " m G * )- + - socket doo application wites data TCP send buffe application eads data TCP eceive buffe socket doo m * * segment 3-55

56 0 /!K 8 9 = * 0>5 8 9!> >H C. ) /09 % ) = = A ) ) /0!>C!* / ( 8*) 9 8*) 9 ) ) - 8 F9 = ) * 3-56

57 0 A =G >A =G m ) : ); - - ) G m A = - + ) + - m * R * "-" m 0 G " / SG - SG Seq=42, ACK=79, data = C Seq=79, ACK=43, data = C Seq=43, ACK=80 - SG ) SG 3-57

58 0! R 0 *E! m )! * m R!E SampleRTT - m SampleRTT *! : ; m * * M SampleRTT 3-58

59 0! EstimatedRTT = (1- α)*estimatedrtt + α*samplertt I + * * * α = &1%3 3-59

60 I+! SampleRTT Estimated RTT 3-60

61 0! > EstimtedRTT :- ; m * EstimatedRTT -> >! * - I! DevRTT = (1-β)*DevRTT + β* SampleRTT-EstimatedRTT (typically, β = 0.25) * TimeoutInteval = EstimatedRTT + 4*DevRTT 3-61

62 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

63 0 ) - 0 * -.0G ) *! ) m * 0 * 0 m. - 0 m m

64 0 * * - A = A = )" ) - - ) * TimeOutInteval *.- * m ) m

65 NextSeqNum = InitialSeqNum SendBase = InitialSeqNum loop (foeve) { switch(event) event: data eceived fom application above ceate TCP segment with sequence numbe NextSeqNum if (time cuently not unning) stat time pass segment to IP NextSeqNum = NextSeqNum + length(data) event: time timeout etansmit not-yet-acknowledged segment with smallest sequence numbe stat time event: ACK eceived, with ACK field value of y if (y > SendBase) { SendBase = y if (thee ae cuently not-yet-acknowledged segments) stat time } } /* end of loop foeve */ T >7"1 * G ) I+ T >7"1 6 '1U 6 ' * 'Q U L >7 3-65

66 Seq=92, 8 bytes data Seq=92, 8 bytes data Seq=100, 20 bytes data ACK=120 ACK=100 >A6@% ACK=100 X Seq=92, 8 bytes data Seq=92, 8 bytes data ACK=120 >A6@% ACK=100 >7 6 1&& >) 6 1&& >7 6 1%& >7 6 1%& 3-66

67 Seq=92, 8 bytes data ACK=100 X Seq=100, 20 bytes data ACK=120 >7 6 1%& * 3-67

68 0 B!C 11%%!C %3?1D Event at Receive Aival of in-ode segment with expected seq #. All data up to expected seq # aleady ACKed Aival of in-ode segment with expected seq #. One othe segment has ACK pending Aival of out-of-ode segment highe-than-expect seq. #. Gap detected Aival of segment that patially o completely fills gap TCP Receive action Delayed ACK. Wait up to 500ms fo next segment. If no next segment, send ACK Immediately send single cumulative ACK, ACKing both in-ode segments Immediately send duplicate ACK, indicating seq. # of next expected byte Immediate send ACK, povided that segment stats at lowe end of gap 3-68

69 C! " - * m )- * m > - )"" ).- * - - m - )- + m.- ) 3-69

70 C event: ACK eceived, with ACK field value of y if (y > SendBase) { SendBase = y if (thee ae cuently not-yet-acknowledged segments) stat time } else { incement count of dup ACKs eceived fo y if (count of dup ACKs eceived fo y = 3) { esend segment with sequence numbe y }

71 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

72 0 C * - 0 * )-- - G *- *G )-- ) - ) - )-- " * * G 3-72

73 0 C 8> 0 * "-" 9 )-- = RcvWindow = RcvBuffe-[LastByteRcvd - LastByteRead]!* * ) * - RcvWindow > RcvWindow m * )-- G *- 3-73

74 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

75 0 2! 0 * ) :; )- + O 0 *) m A = m ) RcvWindow9 Socket clientsocket = new Socket("hostname","pot numbe"); * ) Socket connectionsocket = welcomesocket.accept(); > 1 0 >H * m - A = m > % * * >H >H m * )-- m - * A = > * >H 3-75

76 clientsocket.close(); FIN * > 1 0 C. * ACK FIN > % * * C. C. ACK 3-76

77 > * C. m I : ; " * C. > * * FIN ACK FIN * - C. ACK 3-77

78 *

79 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

80 0 - - : - - ; F - m 8)-- *- 9 m 8A )--9 "1& ) F 3-80

81 , - 1 * Host A λ in : oiginal data λ out - )-- Host B unlimited shaed output link buffes + *) 3-81

82 , - % - )-- - Host A λ in : oiginal data λ' in : oiginal data, plus etansmitted data λ out Host B finite shaed output link buffes 3-82

83 , - % λ = λ 89 in out :-; λ > λ in out λ in λ out R/2 R/2 R/2 R/3 λ out λ out λ out R/4 λ in R/2 λ in R/2 λ in R/2 :; - a. b. c * :;

84 , - -, R E λ in λ in Host A λ in : oiginal data λ' in : oiginal data, plus etansmitted data finite shaed output link buffes λ out Host B 3-84

85 , - H o s t A λ o u t H o s t B :; - : - F 3-85

86 ) I" + -) " )* ) 0 " * -) m ) 8> I) 0,.0 I 2 9 m

87 2 7! 7! *) ) : *; - G :; m *) ) - G m!2 8 9 ) )!2 ) 8:";9 m. ) 8 9 m. )!2 ) * ) 3-87

88 2 7! ") I! !2 m I! * m G + ) IC. ) 1 m -!2 IC.. )!2 3-88

89 1 " * % /0 0 - ) - 3 " 0 m m ) - m - m '

90 0 * * 8 O9 ) - ) ) m * ) 1 2 >> *! m * - - > )* ) - ) congestion window size 24 Kbytes 16 Kbytes 8 Kbytes congestion window time time 3-90

91 0 LastByteSent-LastByteAcked! 6 #! CongWin 7, CongWin - - * 5 * E * 6 0 8CongWin9 - * m.2 m m ** - * 3-91

92 0 > > # ) CongWin >> m I+ 2 >> 6 3&& ) <! 6 %&& # ) * m 6 %& ) *) ) ) LL 2 >>,! m ) A ) 3-92

93 0 > > 8 9 # ) + - *! one segment m ) CongWin *! two segments m ) CongWin - * * fou segments > )

94 !- R # + E # CongWin 1,% - * )-. V) * 1,% - # M )- * 3-94

95 !- - - m CongWin m 7 - * m CongWin 1 2 >>U m + 0 ) - * : ; 3-95

96 > 0 # CongWin ) Theshold " + # CongWin )* Theshold "* # Theshold CongWin/2 CongWin Theshold # Theshold CongWin/2 CongWin 1 2 >> 3-96

97 0 State Event TCP Sende Action Commentay Slow Stat (SS) ACK eceipt fo peviously unacked data CongWin = CongWin + MSS, If (CongWin > Theshold) set state to Congestion Avoidance Resulting in a doubling of CongWin evey RTT Congestion Avoidance (CA) ACK eceipt fo peviously unacked data CongWin = CongWin+MSS * (MSS/CongWin) Additive incease, esulting in incease of CongWin by 1 MSS evey RTT SS o CA Loss event detected by tiple duplicate ACK Theshold = CongWin/2, CongWin = Theshold, Set state to Congestion Avoidance Fast ecovey, implementing multiplicative decease. CongWin will not dop below 1 MSS. SS o CA Timeout Theshold = CongWin/2, CongWin = 1 MSS, Set state to Slow Stat Ente slow stat SS o CA Duplicate ACK Incement duplicate ACK count fo segment being acked CongWin and Theshold not changed 3-97

98 0 # G * O!E m. # ) O # # #,! - #,% #,%! * ' 3 #,! 3-98

99 0 C 0 * : - ; I+ 13&& ) 1&&! 1& K)!A O # 6? " MSS RTT L 6 %W1& "1& # * " 3-99

100 0 C C - 0 ) - )! * * -!, % )! 3-100

101 # 0 -E * * - 1 *! A ) % 1 ) - - % * * ) - - % * *! 3-101

102 C 8 9 C /0 2-0 m ). /0 m,*! 0 - C 0 * - ) % # ) ) I+ U m - 1 0!,1& m !,% F 3-102

103 > ) * m + + m ) - m - m. m /0 m 0 + * :; 8 9 :; 3-103