Bo co Lab 3Wireshark Lab TCP

Sinh vin thc hin:-Nguyn c Anh Minh -ng Nht Nam -L Qu Ngc Quang Lp : 10DT2

1. Hi S hiu cng TCP v a ch IP c s dng bi my tnh client (ngun) l g, tc th ang truyn file ti gaia.cs.umass.edu? Tr li: S hiu cng TCP: 49849 a ch IP: 192. 168. 1. 6

2. Hi a ch IP ca gaia.cs.umass.edu l g? S hiu ca cng n ang gi v nhn cc phn TCP cho kt ni ny l g?Tr li: a ch IP: 128. 119. 245. 12 S hiu cng: 803. S hiu cng TCP v a ch IP c s dng bi my tnh client ca bn (ngun) trao i fiel ti gaia.cs.umass.edu l g?Tr li: S hiu cng TCP: 49849 a ch IP: 192. 168. 1. 64. S hiu cc chui ca phn TCP SYN c s dng khi to kt ni TCP gia my tnh client v gaia.cs.umass.edu l g? N l g trong cc phn , th nh danh cc phn nh 1 phn SYN?Tr li: S hiu chui: 0 Bit c trng SYN: 1

5. S hiu chui ca phn SYNACK gi bi gaia.cs.umass.edu ti my tnh client phn hi SYN l g? Gi tr ca trng ACKnowledgement trong phn SYNACK l g? gaia.cs.umass.edu xc nh gi tr nh th no? N l g trong phn m dng nh danh phn nh 1 phn SYSACK?Tr li:S hiu chui ca phn SYNACK gi bi gaia.cs.umass.edu ti my tnh client phn hi SYN : 0Gi tr ca trng ACKnowledgement trong phn SYNACK: 1Bit c ca trng ACK = 1 v bit c trng SYN: 1, chng c nh danh phn nh 1 phn SYNACK.

6. S hiu chui ca phn TCP cha lnh HTTP POST l g? Tr li:S hiu chui ca phn TCP cha lnh HTTP POST : 1

7. Xem xt phn TCP cha HTTP POST nh l phn u tin trong kt ni TCP. Cc S hiu chui ca 6 phn u tin trong kt ni TCP ( bao gm c phn cha HTTP POST) l g? Thi gian mi phn gi l bao lu? Khi no ACK cho mi phn c nhn? a s khc bit gi mi phn TCP c gi, v khi acknowledgement ca n c nhn, gi tr RTT cho mi mt trong 6 phn l bao nhiu? Gi tr EstimatedRTT (xem trang 249 trong ti liu) sau khi nhn mi ACK l bao nhiu? Cho rng gi tr ca EstimatedRTT l bng vi gi tr RTT o c trong segment u tin, v sau c tnh ton s dng ng thc EstimatedRTT trong trang 249 cho cc segment n sau. Ch : Wireshark c 1 tnh cht tt l cho php bn v th RTT cho mi cc phn TCP c gi. Chn TCP segment trong ca s listing of captured packets, tc th c gi t client ti server gaia.cs.umass.edu . Sau chn Statistics->TCP Stream Graph->Round Trip Time Graph.Tr li:Cc s hiu ca 6 phn u tin trong kt ni TCP:1: s hiu chui phn 1 2: s hiu chui phn 13613: s hiu chui phn 27214: s hiu chui phn 4081 5: s hiu chui phn 54416: s hiu chui phn 6801

HTTP POST segment c cc s th t: 40, 41, 45, 46, 48, 49

ACK segment c cc s th t: 44, 47, 50, 53, 56, 59

Thi gian giACKRTT

Segment 10,3233250,6619060,338581

Segment 20,3233370,6781020,354775

Segment 30,6619871,0005210,338534

Segment 40,6619991,0173800,355381

Segment 50,6781821,0345690,356387

Segment 60,6781961,0528680,374672

Tnh ton gi tr EstimatedRTT : EstimatedRTT = 0.875 * EstimatedRTT + 0.125 * SampleRTTEstimatedRTT of Segment 1 = 0,338581 EstimatedRTT of Segment2 = 0.875 *0,338581+ 0.125 *0,354775= 0.340605EstimatedRTT of Segment3 = 0.875 *0.340605+ 0.125 *0,338534= 0.340346EstimatedRTT of Segment4 = 0.875 *0.340346+ 0.125 *0,355381= 0.342225 EstimatedRTT of Segment5 = 0.875 *0.342225+ 0.125 *0,356387= 0.343995 EstimatedRTT of Segment6 = 0.875 *0.343995 + 0.125 *0,374672= 0.347829 Round Trip Time Grap

8. rng ca mi mt trong s 6 TCP segment u tin l bao nhiu? Tr li: rng ca segment th nht l: 1360 bytes rng ca segment th hai l: 1360 bytes rng ca segment th ba l: 1360 bytes rng ca segment th t l: 1360 bytes rng ca segment th nm l1360 bytes rng ca segment th su l: 1360 bytes9. Gi tr nh nht ca khng gian m c th phn nhn cho ton b trace? C th xy ra s thiu khng gian m vng nhn khi tc nghn ng gi khng? Tr li:Gi tr nh nht ca khng gian m c th phn nhn cho ton b trace l 66560 bytes (kch thc ca window trong khi to kt ni u tin).Khng xy ra hin tng thiu khng gian m vng m nhn khi tc nghn ng gi .10. Cc segment c c ti truyn i trong file trace? Bn kim tra ci g (trong trace) tr li cu hi ny?Tr li:Cc segment c th c ti truyn i trong file trace. C th kim tra l 1 s s hiu chui c gi i hai ln hoc nhiu hn .11. Bao nhiu d liu receiver bo nhn trong ACK? Bn c th nhn ra cc trng hp ni m receiver ang bo nhn mi khi segment khc c nhn khng?Acknowledged sequence numberAcknowledged data

Ack 111360

Ack 213611360

Ack 327211360

Ack 440811360

Ack 554411360

Ack 668011360

Ack 781611360

12. Lu lng (s byte trao i mi n v thi gian) cho kt ni TCP ny l bao nhiu? Gii thch bn tnh ton gi tr ny nh th no ? Tr li:Lu lng trung bnh ca 1 kt ni = (0,75*W)/RTT W: windown size (bytes) RTT : round trip time hin ti (seconds)V d: S dng cc s liu bi 7, ta c lu lng trung bnh ca kt ni TCP u tin: W = 66560 bytes RTT = 0,338962 seconds Lu lng trung bnh ca kt ni TCP = (0,75*66560)/0,338962 = 147273,477 (bytes/sec)

13. S dng cng c v th Time-Sequence-Graph (Stevens) xem s chui trn thi gian v ca cc segment ang gi t client t server gaia.cs.umass.edu server. Bn c th nhn ra on TCP bt u chm t lc no ti lc no, v ni no s trnh tc nghn t c? Dn gii con ng m d liu c o khc vi hnh vi c l tng ha ca TCP, tc th m chng ta c hc trong ti liu.Tr li: Qua th Time-Sequence-Graph (Stevens) ta c th nhn ra n TCP bt u chm v ni c th trnh tc nghn. V th ch ra s trn mng, nhng im tc nghn c th xy ra.Khi TCP kt ni c gia Sender v Reciever, n c 1 gi tr duy nht(chnh l windows size), n cho bit kch thc thng tin c th c gi gia Sender v Receiver.