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Sinh vin:PHM VN T

Lp 4-TVT

Giao thc kim sot li - RQ lin tc

1. iu khin dng d liu-Bo m bn pht khng gi d liu qu nhanh

Ngn nga vic trn bm-Mt s khi nim+Thi gian truyn (tframe): thi gian cn thit gi tt

c cc bit d liu ln ng truyn+ Thi gian lan truyn (tprop): thi gian cn thit 1 bit

i t ngun n chM hnh truyn khung

a) Nghi thc Idle RQ (StopandWait)-c im

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+c dng ch yu trong cc ng dng character-oriented.(byte-oriented)

+S dng knh truyn hot ng trong ch half-duplex

- C ch hot ng

+Ngun pht d liu (di dng cc frame)+ch nhn d liu v tr li bng ACK+Ngun i ACK trc khi pht tip d liu+ch c th ngng truyn d liu bng cch khng gi

ACK

Idle RQ Hiu sut

Nhc im Idle RQ- D liu ln c chia thnh cc frame c kchthc nh+Kch thc bm c gii hn+Li c pht hin sm

+Khi c li, ch cn truyn li frame nh+Ngn nga tnh trng 1 trm lm vic chim ng

truyn luStop-and-wait protocol khng thch hp

2. iu khin li-Cung cp c ch cho vic truyn d liu trong trng hp d liub mt hay sai st trn ng truyn+ Bo m d liu nhn c ng v chnh xc

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-Loi li+Mt frame: frame khng n ch hoc n nhng thng tin iukhin trn frame b h, khng thxc nh c+ Frame h: thng tin iu khin trn frame xc nh c, nhng dliu trong frame b h

- K thut dng iu khin li+ Pht hin li (CRC, Parity, )+ Positive ACK xc nhn cc frame nhn c+ Negative ACK (NAK) yu cu truyn li cho cc frame b h+ Truyn li sau mt thi gian time-out

C ch- Da trn iu khin dng- ARQ (Automatic Repeat Request)

+ C ch cho php cc nghi thc lin kt d liu qun l li vyu cu truyn li+ Phn loi

Idle RQ (stop-and-wait)

Dng vi c chiu khin dng stop-waitc dng ch yu trong truyn d liu l k t hay byte thng tin

(character-oriented or byte-oriented)

Continuous RQ

Dng vi c chiu khin dng sliding-windowc dng ch yu trong truyn d liu l bit thng tin (bit-oriented)Selective repeat

Go-back-N

a)StopandWait

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b) GobackN

Go-back-N - Sa li

GobackN V d

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GobackN Cc trng hp li

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c) Selective Repeat

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d) Continuous ARQ So snh

iu khin li Hiu sut