chuyển mạch ATM và ứng dụng

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Transcript of chuyển mạch ATM và ứng dụng

Thut ng vit tt .3 Danh mc hnh v .4 LI NI U ..5 1.Gii thiu chung v ATM .6 2. KIN TRC CHUNG CA H THNG CHUYN MCH BNG RNG ATM......................................................................................................7 2.1.M un iu khin u vo (IM).............................................................8 2.2. M un iu khin u ra (OM).............................................................9 2.3. Khi iu khin chp nhn kt ni (CAC) ............................................9 2.4. Khi qun l h thng (SM) ..................................................................9 2.5. Khi chuyn mch t bo (CSF) ...........................................................9 3. NGUYN TC CHUYN MCH V NH TUYN ...........................10 3.1. Qu trnh chuyn mch v x l gi qua cc h thng chuyn mch ATM............................................................................................................10 3.2. Nguyn tc nh tuyn trong chuyn mch ATM ...............................12 4. HOT NG CHUYN MCH ATM ....................................................14 5. CC YU CU I VI H THNG CHUYN MCH BNG RNG ATM ...............................................................................................................15 6.Giao Tip ATM............................................................................................16 7. Lin Kt Dng Mng ATM: .......................................................................17 8. Kt Ni Cc Mng LAN C Vo ATM......................................................18 9. Cch Thay i Trn ATM..........................................................................20 10. Kt Lun....................................................................................................21 CHNG II : ng Dng ATM..............................................21 1.Tng vt l................................................................................................22

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2.Tng ATM................................................................................................22 3.Tng Thich nghi ATM..............................................................................24

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Thut ng vit tt : ATM (Asynchronous Transfer Mode) : Ch truyn khng ng b CAC :iu khin chp nhn kt ni SM: qun l chuyn mch OC : module iu khin u ra IM : M un iu khin u vo CSF : Khi chuyn mch t bo SVCs: kt ni o chuyn mch Routing Information Table RIT :bng nh tuyn VPI :nhn dng lung o VCI: nhn dng knh o VCC :kt ni knh o VPC :kt ning o PVC :knh o c nh (Permanent virtual circuit) SVC : knh o chuyn mch UNI (User Network Interface ): Giao din Mang Ngi dung LAN (local area network) :mng cc b WAN (wide area network) :mng din rng ARP (Address Resolution Protocol )- Giao thc Phn giai ia chi

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Danh Mc Hnh VHnh 2.1 Kin trc chung ca chuyn mch ATM Hnh 2.2 S khi chc nng ca mt h thng chuyn mch ATM Hnh 2.3 S khi module u vo (a) v m un u ra (b) Hnh 3.1 Qu trnh x l t bo Hnh 3.2 Nguyn tc t nh tuyn Hnh 3.3 Nguyn tc bng iukhin Hnh 4.1 PVC Mng ATM Hnh 4.2. SVC mng ATM

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LI NI U Ngy nay , cng vi s pht trin v kinh t- x hi, nhu cu trao i thng tin ca con ngi ngy cng cao. Bi vy cng ngh in t vin thng c vai tr c bit quan trng nht l trong giai on bng n thng tin nh hin nay. Cc h thng in t vin thng l phng tin rt hu ch phc v cho nhu cu trao i thng tin mt cch cp thit. U ban t vn vin thng quc t CCITT a ra m hnh mng vin thng s ho a dch v bng rng B-ISDN ( Broadband Integrated Service Digital Network). B-ISDN c xy dng trn c s ca mng cp quang ng b , mng thng minh ( IN)v cng ngh chuyn ti khng ng b (ATM) cho php truyn ting ni, hnh nh, d liu trn cng mt mng duy nht. ATM l mt cng ngh mi da trn cu trc t bo ATM, n kt hp c cc c im k thut gia chuyn mch c in ca mng in thoi vi chuyn mch gi p ng c nhu cu thng tin ca con ngi mt cch ton din. C th ni h thng chuyn mch ATM l phn quan trng nht ca cng ngh ATM v th vic i su nghin cu s nh hng ca cu trc phn cng chuyn mch ATM n cht lng dch v l mt vn rt quan trng v rt cn thit. Vi nhng nhn nh trn chng em tp trung tm hiu v ch chuyn mch ATM v ng dng. Mc d cc thnh vin trong nhm tch cc tm hiu nhng bi bo co cng khng trnh khi nhng thiu st,rt mong thy v cc bn gp bi bo co ca chng em t kt qu cao.Chng e xin chn thnh cm n thy L Nht Thng hng dn chng em lm ti ny !

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CHNG I: CHUYN MCH ATM 1. Gii Thiu Chung V ATM - Da trn kiu truyn khng ng b ATM (Asynchronous Transfer Mode) cung cp nhiu loi dch v trn mt mng truyn thng duy nht. ATM c xem l k thut chuyn mch chn gi tc cao c xy dng trn c s t hp cc u im ca chuyn mch gi v chuyn mch knh. ATM c kh nng cung cp nhiu loi dch v vi cc yu cu khc nhau v QoS nhng vn m bo hiu qu s dng ti nguyn mng. T bo * Cell ) l n v thng tin c bn trong ATM, c di c nh 53 byte, bao gm 48 byte thng tin v 5 byte tiu cha cc thng tin lin quan thit lp v iu khin kt ni .Cc dch v trong mng ATM gm: CBR (Constant Bit Rate), rt-VBR (real time - Variable Bit Rate ), nrt-VBR (non real time - Variable Bit Rate), ABR (Avalible Bit Rate ), UBR (Unspecific Bit Rate). Cc dch v ny c th phn thnh hai loi l dch v thi gian thc (CBR v rt-VBR) v dch v khng theo thi gian thc (nrt-VBR, ABR v UBR).ATM co cac tinh nng QoS (quality of service - cht lng dich vu), cho phep khach hang chon kiu lu thng cn u tin, nh cho ting noi va video phai n ung luc, am bao rng thng tin it quan trong khng chim linh dong lu thng thi gianthc. No la mt cng ngh co th m rng, vn hanh t 25 Mbits/sec n 2.46 Gbits/sec, no co th d dang tich hp vi cac mang cua cac hang truyn tai, va no h tr vic tich hp vi cac cng ngh co sn (vi nhng s iu chinh phu hp).Kha nng m rng cua ATM co y nghia quan trong i vi nhng cng ty ang phat trin.

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2. KIN TRC CHUNG CA H THNG CHUYN MCH BNG RNG ATMATM l mng kt ni nh hng, tt c cc t bo ATM trong mt kt ni thc t c truyn theo mt tuyn ng nh sn. Nhng t bo thuc v mt u ni c xc nh bi trng nhn dng ng o v knh o VPC/VCI. Cc chuyn mch gi thng thng hot ng trong di 1 4000 gi tin/giy, trong khi , chuyn mch ATM cn phi x l s lng gi tin rt ln t 100 000 n hng triu gi tin trong mt giy. V c bn, mt nt chuyn mch ATM phi thc hin ba hot ng: nh tuyn, xp hng v bin dch tiu ca cc t bo. Qu trnh nh tuyn l xc nh r t bo c chn ng no t mt u vo n mt u ra yu cu. Vic xp hng c s dng gii quyt vn xung t khi ti mt thi im c hn mt u vo c cng mt u ra yu cu. Trn thc t c nhiu thit k khc nhau cho cu trc chuyn mch ATM. Tuy nhin, m hnh chc nng chung ca mt h thng chuyn mch ATM thng bao gm ba phn chnh l: * Giao din chuyn mch: Gm mt module iu khin u vo (IC) v mt module iu khin u ra(OC). * Trng chuyn mch t bo * B x l iu khin: Bao gm hai phn chnh l iu khin chp nhn kt ni (CAC) v qun l chuyn mch (SM).

Hnh 2.1 Kin trc chung ca chuyn mch ATM H thng chuyn mch ATM c chc nng: Chuyn tip cc t bo d liu ngi dng t cc cng u vo n cc cng u ra thch hp. H tr cc chc nng tng ng trong mt phng iu khin v mt phng qun l ca m hnh tham chiu giao thc B-ISDN. Cc h thng chuyn mch ATM c th gi vai tr nh cc cng giao tip vi nhng mng khc nh N-ISDN, LAN Ngoi ra, n cn cha cc giao din khc trao i thng tin iu khin v qun l vi cc mng c mc ch c bit nh mng thng minh (IN) v mng qun l vin thng (TMN).

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Hnh 2.2 S khi chc nng ca mt h thng chuyn mch ATM H thng chuyn mch ATM gm 5 khi chc nng c bn: M un u vo (IM), m un u ra (OM), iu khin chp nhn kt ni (CAC), qun l h thng (SM) v khi chuyn mch t bo (CSF). Hot ng ca IM v OM c th c m t tng quan nh hnh v

Hnh 2.3 S khi modul u vo (a) v m un u ra (b) 2.1.M un iu khin u vo (IM) Thc hin chc nng tch lung ATM khi khung truyn dn v x l cc chc nng sau i vi mi t bo ATM: Kim tra li tiu t bo s dng trng HEC Bin dch cc gi tr VPI/VCI. Xc nh cng u ra Chuyn t bo bo hiu n CAC Thc hin iu khin tham s ngi dng/mng (UPC/NPC) cho mi 8

kt ni knh o/ng o (VCC/VPC) - Thm vo t bo d liu ngi dng cc bt a ch b sung (c gi l th nh tuyn) trn c s trng VPI/VCI trong tiu t bo. Th ny sau c CSF s dng thc hin chc nng nh tuyn v b loi khi ra khi CSF. 2.2. M un iu khin u ra (OM) Thc hin vic phn phi t bo n ch hoc ti mt cng u vo ca mt nt chuyn mch khc sau khi bin dch t bo. N thc hin cc chc nng sau: - Loi b th nh tuyn c gn IM. - C th bin dch cc gi tr VPI/VCI. - To trng HEC mi. - Chn cc t bo qun l v iu khin (nhn c t CAC v SM) vo lung t bo u ra. - Thch ng lung t bo vo khung truyn dn. 2.3. Khi iu khin chp nhn kt ni (CAC) CAC c chc nng thit lp, gim st v gii phng cc kt ni o. CAC nhn t bo bo hiu t IM, tch ly thng tin bo hiu, bin dch v cp nht. Cui cng CAC to ra t bo bo hiu mi v gi chng n OM. 2.4. Khi qun l h thng (SM) Cc chc nng qun l gm qun l li, qun l hiu nng, qun l cu hnh, qun l tnh cc, qun l bo mt v qun l lu lng. thc hin cc chc nng ny cn rt nhiu s truyn thng bn trong chuyn mch gia SM v cc khi chc nng khc. - X l OA&M lp vt l - OA&M lp ATM - Qun l cu hnh cc thnh phn chuyn mch - Kim sot bo mt cho cc c s d liu chuyn mch - o lng mc s dng cc ti nguyn chuyn mch - Qun l lu lng - T chc thng tin qun l, - Qun l khch hng - mng, - Giao din vi h thng vn hnh - H tr qun l mng. 2.5. Khi chuyn mch t bo (CSF) L phn trung tm ca h thng chuyn mch ATM, thc hin chc nng chnh l nh tuyn cc t bo d liu (c th bao gm c cc t bo bo hiu v nh tuyn) t IM n OM thch hp. V mt s chc nng khc bao gm: 9

- m t bo - Multicast/Broadcast - Dung sai, lp lch t bo trn c s cc u tin v tr. - Gim st tc nghn v kch hot ch th tc nghn chuyn tip ngay lp tc (ECFI).

3. NGUYN TC CHUYN MCH V NH TUYN3.1. Qu trnh chuyn mch v x l gi qua cc h thng chuyn mch ATM Giao thc ATM tng ng vi lp 2 nh nh ngha trong m hnh tham chiu (OSI) cc h thng m. ATM l kt ni c hng, mt kt ni cui- cui (hay knh o) cn c thit lp trc khi nh tuyn cc t bo ATM. Cc t bo c nh tuyn da trn hai gi tr quan trng cha trong 5 byte mo u t bo: nhn dng lung o (VPI) v nhn dng knh o (VCI), trong mt lung o bao gm mt s cc knh o. S cc bit dnh cho VPI ph thuc vo kiu giao din. Nu l giao din ngi s dng (UNI), gia ngi s dng v chuyn mch ATM u tin, 8 bit c dnh cho VPI. iu ny c ngha l c ti 28 = 256 lung o sn c trong im truy nhp ngi s dng. Mt khc nu n l giao din node mng (NNI), gia cc chuyn mch trung gian ATM, 12 bit s dn