Bi 2: Cc cng ngh chuyn mchChuyn mch knh.Chuyn mch bn tin.Chuyn mch gi.Cc cng ngh chuyn mch tin tin

1. Cc khi nim v cng ngh chuyn mch v cc dch v vin thngCng ngh chuyn mch th hin cng ngh mng Cng ngh chuyn mch: phng php kt ni, nh tuyn thng tin qua cc node mng, phc v vic trao i thng tin gia cc im trong cc mng a im, kt ni linh hotThit b chuyn mch l tn gi chung cho cc thit b c kh nng nh hng thng tin qua mng (Router, Switch, Hub). Thit b chuyn mch c t ti cc node mngThng thng mi loi hnh dch v vin thng s dng mt cng ngh chuyn mch tng ng. V d, dch v thoi s dng mng chuyn mch knh, dch v d liu, tin nhn s dng mng chuyn mch giXu hng tin ti mt cng ngh mng duy nht c kh nng cung cp a dch v, a phng tin, a giao thc

2. Chuyn mch knh (circuit switching)a. Khi nim v chuyn mch knhKnh: ng dn tn hiu gia hai thit b: Knh khng gian, knh thi gian, knh tn s Knh khng gian: cc on mch ni tip nhau to thnh knh cho tng cuc gi. Knh ca cuc gi ny c lp vi knh ca cc cuc gi khc ang cng tn ti. Cc cuc gi ng thi khng c cc on mch chungKnh thi gian: Mi cuc gi c phn mt khe thi gian trn on mch dng chung cho nhiu cuc gi ng thiChuyn mch knh: Phn phi ti nguyn mng (kt ni cc on mch, cc khe thi gian) cho tng cuc gi to thnh knh dn tn hiu gia cc thit b u cui tham gia mi cuc gi.

TS1TS2TS4TS5TS1TS2TS4TS5S-SwitchS-SwitchT-SwitchT-SwitchHnh 1.9 : M hnh chuyn mch knh

b. Nguyn l hot ng: Cuc gi tri qua 3 giai onThit lp knh: Phn b ti nguyn, kt ni to thnh knh theo yu cu t pha ch giTruyn tin qua knh (song cng)Gii phng knh (cc ti nguyn c hon li ti phc v cc yu cu mi)c. Cc c im:Cc cuc gi ng thi c phc v trn cc knh c lp nhauThng tin c truyn trong sut (knh hon ton dnh cho thng tin ngi s dng, khng kim sot v sa li, truyn tc thi, khng tr) Knh b chim lin tc t khi bt u n khi kt thc cuc gi.X l trn c s cuc gi.Ph hp vi cc dch v thi gian thc, tc bt c nhKhng thch hp vi cc lu lng dng burstHiu sut s dng knh thp d. ng dng:

3. mng chuyn mch bn tin (Message switching) a. Khi nim v mng chuyn mch bn tin L mng chuyn mch phc v vic trao i cc bn tin (in tn, th in t, file d liu my tnh) gia cc i tng vi nhauHnh 1.10 : M hnh mng chuyn mch bn tinb.Nguyn l chuyn mch bn tin :Thng tin cn truyn c DTE gn thm mt tip u H (Header cha a ch nh tuyn bn tin qua mng) v gi n Node truy cpBn tin c nh tuyn qua mng theo tng chng trn nguyn l Store- and- ForwardThit b u cui d liu

c. Cc c imGing hnh thc phc v trong Bu chnh, ni dung mang theo a chC th p dng cc bin php kim sot pht hin v sa li hoc yu cu truyn li nng cao tin cyHiu qu s dng ti nguyn cao, khng yu cu thit lp knhThi gian truyn bn tin trong mng khng th kim sot c (tr hng i)d. ng dng: Truyn d liu my tnh, vn bn v cc dch v phi thi gian thc khc

Bn tin Bn tin Hnh 1.11 : M hnh mng chuyn mch gi4. Chuyn mch gi: (packet switching)a. Khi qut v chuyn mch gi:Bn tin cn truyn c chia thnh nhiu gi. Mi gi c gn mt Header nh tuyn gi n ich

b. Cc nguyn l chuyn mch gi:- D liu biu (Datagram): cc gi ca cng bn tin c th c truyn qua mng theo cc ng khc nhau. Header ca gi cha a ch nh tuyn (a ch ch v c th c a ch ngun, s th t gi) - Chuyn mch knh o (Virtual Channel Packet Switch): thit lp knh o v truyn gi theo knh o, gii phng knh o. Header cha s kt ni logic o VLCN (Virtual Logical Connection Number), s th t gic. c im:- Ghp knh thng k, DTE ch pht gi khi c d liu gi i- Nguyn l chung Store-and-Forward- X l trn c s gi- m bo tin cy cao nh p dng mt s bin php pht hin v sa li- Pht huy c cc u im ca chuyn mch knh v chuyn mch bn tin

5. cc cng ngh chuyn mch tin tinMc tiu: Tch hp cc dch v vo mt mng bng rng duy nht Chuyn tip khung FR (Frame Relay)Cng ngh chuyn giao khng ng b ATM (Asynchronous Transfer Mode) Chuyn mch a giao thc MPLS (MultiProtocol Label Switch)

Hnh 1.14 M hnh iu khin c lp-trc tip trong tng i nhy ncKKCp chn s bCp chn nhm 1Cp chn nhm 2Cp chn ng dy6. Minh ha cc cng ngh chuyn mch

Hnh 1.15 Phng thc iu khin gin tip trong tng i to B dy phchB iu khin cp chn ng dy khu ABThanh ghi a chB iu khin cp chn thanh ghi a chB iu khin cp chn nhmGiao tip trung kB iu khin cp chn ng dy khu CDABCDAB6. Minh ha mt vi cng ngh chuyn mch

FramingChannel 1Channel 2Channel na. Ch truyn ng b STM

Hnh1.12 Minh ho cc ch ghp knh ng b v khng ng b

b. Ch truyn khng ng b ATM

Nguyn l chuyn mch a ch (Address Switching Mode)Port1

Port2

bacPort1

Port2

oPort1

Port2

edcPort1

Port2

nopoabebccdbnm

Hnh 1.16 S khi tng qut ca tng i SPC

Hnh 1.17 : S tng quan tng i SPC chuyn mch s.

Ni dung n tpKhi nim chuyn mch knh. Cc c im v ng dng Khi nim v chuyn mch gi, hai phng php chuyn mch gi v c im ca chng

khng