MPLS nhãn

Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN

Li cm nEm xin t lng knh trng v bit n su sc ti thy gio PGS.TS Nguyn Kim Giao tn tnh ch bo v gip em hon thnh tt kho lun tt nhip ny. ng thi em cng xin chn thnh cm n cc thy c gio trng i Hc Cng Ngh _i Hc Quc Gia H Ni, nhng ngi b cho em nhng kin thc v to iu kin tt nht cho em trong sut qu trnh hc tp v gip em hon thnh kho lun tt nghip ny. Cui cng ti cng xin gi li cm n cc bn b cng lp nhit tnh gip ti hon thnh kho lun ny. Xin chc cc thy c gio v cc bn sc khe, hnh phc. Em Xin Chn Thnh Cm n!

H ni thng 6 nm 2008 Sinh vinNguyn Ngc Thnh

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TM TT NI DUNG

Trong nhng nm gn y vi s pht trin mnh m ca internet v cng ngh truyn thng gy ra s qu ti trn cc mng hin c, v vy nhu cu cp thit cn phi c mt cng ngh mng th h mi p ng c nhu cu . Cng ngh MPLS l hng gii quyt cho vn v nhng kh nng u vit ca n. Trong ti ny ca em, em xin gii thiu tng quan v cng ngh chuyn mch nhn a giao thc ( MPLS ). Trong em xin gii thiu v nhng khi nim c bn v mng MPLS, nhng thnh phn c bn to nn mng MPLS . V cng ngh MPLS l s kt hp ca cng ngh IP v cng ngh ATM nn n k tha nhng u im ca mng IP v mng ATM l kh nng mm do ca mng IP cng vi kh nng chuyn mch tc cao ca cng ngh ATM. Cng ngh mng MPLS cho php kh nng iu khin lu lng v cung cp cht lng dch v (QoS) theo yu cu ca khch hng. Trong lun vn ny em xin nu ra mt s bc cu hnh c bn d trn thit b Cisco cu hnh cho mng MPLS. c bit trong em nu ra mt v d v kt qu thu cm phng mng li chy MPLS s dng phn mm m phng Dynapic.

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MC LCLI M U................................................................................................................................vi 1.1. Gii thiu................................................................................................................................vii 1.2. Cng ngh chuyn mch nhn a giao thc MPLS..............................................................vii 1.2.1 S ra i ca MPLS....................................................................................................viii 1.2.2 Qu trnh pht trin v chun ho cng ngh MPLS.....................................................x 1.3. Mt s c im ca cng ngh MPLS.................................................................................xii 1.3.1. Tc v tr..........................................................................................................xii 1.3.2. dung pha................................................................................................................xii 1.3.3. M rng cp mng ...............................................................................................xiii 1.3.4. Tnh n gin ............................................................................................................xiii 1.3.5. Tiu tn ngun ti nguyn ........................................................................................xiii 1.4. Cc ng dng ca MPLS......................................................................................................xiv 1.4.1. Tch hp IP+ATM .....................................................................................................xiv 1.4.2. Dch v mng ring o IP (VPN) ..............................................................................xiv 1.4.3. iu khin lu lng v nh tuyn IP r rng.........................................................xiv Kt lun chng.............................................................................................................................xv 2.1. Mt vi khi nin c bn:......................................................................................................xvi 2.1.1. Nhn (label)................................................................................................................xvi 2.1.2. Ngn xp nhn(Label stack):...................................................................................xviii 2.1.3. Hon i nhn (Label Swapping)..............................................................................xix 2.1.4. B nh tuyn chuyn mch nhn (LSR :label switching router):............................xix 2.1.5. Lp chuyn tip tng ng(FEC).........................................................................xix 2.1.6. To nhn ....................................................................................................................xxi 2.1.7. Bng chuyn tip chuyn mch nhn........................................................................xxi 2.1.8. C s thng tin nhn (label information base -LIB).................................................xxi 2.1.9. C s thng tin chuyn tip nhn LFIB...................................................................xxii 2.1.10. NHLFE (Next Hop Label Forwarding Entry).......................................................xxiii 2.1.11. ng chuyn mch nhn (label switching path - LSP).......................................xxiv 2.1.12.Gi tin gn nhn......................................................................................................xxiv 2.1.13. n nh v phn phi nhn.....................................................................................xxv 2.1.14. Khng gian nhn(Label spaces)..............................................................................xxv 2.1.15. C cu bo hiu.......................................................................................................xxv 2.2. Chuyn tip gi trong MPLS.............................................................................................xxvi 2.2.1 Hot ng chuyn tip.............................................................................................xxvi 2.2.2 V d v chuyn tip gi..........................................................................................xxvii 2.3. Cc thnh phn c bn ca mng MPLS..........................................................................xxviii 2.3.1. B nh tuyn bin nhn (Label Edge router LER)..........................................xxviii 2.3.2. B nh tuyn chuyn mch nhn (Label Switching Router - LSR)......................xxix 2.3.3. ATM LSR :...............................................................................................................xxix 2.3.4. ATM LSR bin:........................................................................................................xxix 2.4. Cc giao thc c bn ca MPLS.........................................................................................xxix 2.4.1 Giao thc phn phi nhn LDP..............................................................................xxx

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN 2.4.1.1 Pht hin LSR ln cn :.......................................................................................xxx 2.4.1.2 Cc bn tin LDP:...............................................................................................xxxii 2.4.1.3 Cc ch phn phi nhn...............................................................................xxxv 2.4.2 Giao thc phn phi nhn da trn rng buc CR-LDP.......................................xxxvii 2.4.3. giao thc t trc ngun ti nguyn RSVP (Resource reservation protocol).....xxxix 2.4.4. giao thc MPLS BGP..............................................................................................xli 2.5 Hot ng ca MPLS..............................................................................................................xli 2.5.1 Cc hot ng ca MPLS............................................................................................xli 2.5.2 cc ch hot ng ca MPLS ..............................................................................xliii 2.5.2.1 ch hot ng khung .....................................................................................xliii 2.5.2.2 Ch hot ng t bo MPLS..........................................................................xlvi 2.5.2.3 Hot ng ca MPLS khung trong mng ATM-LSR .......................................xlix Kt lun chng................................................................................................................................l 3.1. K thut lu lng...................................................................................................................li 3.1.1. Khi nin k thut lu lng........................................................................................li 3.1.2. Vn hnh nh hng ngun v nh hng lu lng ..............................................li 3.1.3. Ti thiu ho tc nghn.................................................................................................li 3.1.4. Phn cp lu lng v iu khin dch v da trn nhu cu QoS. ............................lii 3.1.5. Hm i lu lng......................................................................................................liii 3.1.6. Cc vn tn ti vi cc hot ng nh tuyn. ....................................................liii 3.1.7. S tim cn n mng chng ln................................................................................liv 3.2. Qun l lu lng trong mng MPLS...................................................................................liv 3.2.1 Cc vn c bn ca qun l lu lng qua MPLS.................................................liv 3.3. nh tuyn da trn rng buc................................................................................................lv 3.3.1. V d miu t nh tuyn rng buc...........................................................................lvi 3.3.2 nh tuyn hin(Explicit routing : ER)......................................................................lvii 3.3.3 V d thit lp LSP vi CR-LDP...............................................................................lviii 3.3.4 Cc bn tin nh tuyn rng buc v trng TLV : ...............................................lviii 3.4. Cht lng dch v:................................................................................................................lix 3.4.1. M hnh dch v tch hp(IntServ).............................................................................lix 3.4.2. M hnh dch v Diffserv.............................................................................................lx 3.4.3. M hnh cht lng dch v MPLS............................................................................lxi 3.5. Pht hin v nh tuyn vng ...............................................................................................lxii Kt lun chng...........................................................................................................................lxii 4.1 Cu lnh v cc bc cu hnh.............................................................................................lxiii 4.1.1 Cu hnh MPLS mc iu khin. .............................................................................lxiii 4.1.2 Cu hnh lu lng MPLS......................................................................................lxviii 4.1.2.1 Cu hnh mt thit b h tr ng ng (tunnels).............................................lxix 4.1.2.2 Cu hnh mt giao din h tr RSVP-base tunnel signaling v IGP Flooding .........................................................................................................................................lxix 4.1.2.3 Cu hnh k thut lu lng ng ng trn MPLS..........................................lxx 4.1.2.4 Cu hnh IS-IS cho k thut lu lng MPLS....................................................lxx 4.1.3 Cu hnh nhng tuyn k thut lu lng.................................................................lxxi 4.1.4.1 nh ngha VPNs:...............................................................................................lxxi 4.1.4.2 Cu hnh nh tuyn PE to PE:..........................................................................lxxii 4.1.4.3 Cu hnh nh tuyn BGP PE to CE:...............................................................lxxiii 4.1.4.4. Cu hnh nh tuyn RIP PE to CE:................................................................lxxiii 4.1.4.5 Cu hnh nh tuyn tnh PE to CE:.................................................................lxxiii 4.1.4.6 Kim tra hot ng ca VPN:..........................................................................lxxiv

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN 4.1.5 Cu hnh ng trc h tr MPLS CoS..................................................................lxxiv 4.1.6 Cu hnh MPLS CoS:...............................................................................................lxxvi 4.1.6.1 Cu hnh ch PVC trong mt Non-MPLS-Enable core:............................lxxvii 4.1.6.2 Cu hnh ch Multi-VC trong MPLS-Enable core:...................................lxxvii 4.1.6.3 Cu hnh Multi-VCs s dng chc nng CoS-Map :......................................lxxvii 4.1.6.4 Cu hnh DWFQ v changing Queue Weight trn mt giao din ra:............lxxviii 4.1.6.5 Kim tra hot ng CoS:..................................................................................lxxix 4.1.7 Cu hnh b iu khin chuyn mch nhn:............................................................lxxix 4.1.7.1 Cu hnh MPLS trn mt cng LSC-controlled BPX:.....................................lxxxi 4.2. Nhng v d v cu hnh MPLS:.......................................................................................lxxxi 4.2.1 V d cho php thc hin MPLS trong mt mng.................................................lxxxii 4.2.2 V d cho php MPLS cho mt vng mng ch t trc...................................lxxxii 4.2.2 V dnla chn nhng ch trc v nhng tuyn................................................lxxxii 4.2.3 V d hin th MPLS LDP vi cc thng tin........................................................lxxxiii 4.2.4 V d hin th thng tin bng chuyn tip MPLS..................................................lxxxiv 4.2.5 V d hin th thng tin v giao din MPLS...........................................................lxxxv 4.2.6 V d hin th thng tin MPLS LDP hng xm....................................................lxxxvi 4.2.7 V d cho php LSP tunnel signaling...................................................................lxxxvii 4.2.8 V d cu hnh mt ng ng LSP.....................................................................lxxxvii 4.2.9 V d Hin th thng tin ng ng LSP............................................................lxxxviii 4.2.10 V d cu hnh mt k thut lu lng ng ng MPLS...............................lxxxviii 4.2.11 V d cu hnh mng ring o MPLS.........................................................................xc 4.2.12 V d cu hnh MPLS trn mt LSC-Controlled BPX port...................................xciii 4.2.13 V d thc hin MPLS CoS......................................................................................xcv 4.3 M phng v thc nhim........................................................................................................civ 4.3.1. Cc bc cu hnh nh sau:........................................................................................cv 4.3.2. Kt qu thu c sau khi tin hnh m phng :........................................................cvi Kt lun chng..........................................................................................................................cxiv KT LUN..................................................................................................................................cxv THUT NG V VIT TT...................................................................................................cxvi Ti liu tham kho.......................................................................................................................cxx

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LI M U Trong nhng nm gn y, vi s pht trin manh m ca cng ngh truyn thng v thng tin, nghnh cng nghip vin thng v ang tm mt phng thc chuyn mch c th kt hp u im ca IP (nh kh nng nh tuyn mm do) v ca ATM (kh nng chuyn mch tc cao) Cng ngh chuyn mch nhn a giao thc (MPLS Multi Protocol Label Switching) l kt qa pht trin ca nhiu cng ngh chuyn mch IP, s dng c ch hon i nhn ca ATM tng tc truyn gi tin m khng cn thay i cc giao thc nh tuyn ca IP. MPLS tch chc nng ca b nh tuyn IP (IP router )ra lm hai phn ring bit : chc nng chuyn gi v chc nng iu khin . phn chc nng chuyn gi tin, vi nhim v gi gi tin gia cc b nh tuyn IP, s dng c ch hon i nhn nh ca ATM. Trong MPLS nhn l mt thc th c di c nh v khng ph thuc vo lp mng.K thut hon i nhn thc cht l tm nhn ca mt gi tin trong bng cc nhn xc nh tuyn ca gi v nhn mi ca n. vic ny n gin hn nhiu so vi vic s l gi tin theo kiu thng thng v do vy ci thin c kh nng ca thit b. MPLS c th hot ng c vi nhiu giao thc nh tuyn khc nhau nh OSPF, IS-IS, BGP, ngoi ra n cn c th tng thch tt vi cc mng hin ti nh IP, ATM, Frame Relay Ngoi ra MPLS cung cp kh nng m rng mng ln, cung cp vic qun l cht lng dch v theo yu cu, kh nng iu khin lu lng. l mt la chn l tng cho nghnh cng nghip vin thng p ng nhu cu ngy cng cao ca khch hng c v cht lng dch v ln s a dng ho v loi hnh trn mt mng duy nht. Vi ngha nh vy mc ch ca vic nghin cu ti bc u cung cp ci nhn tng quan v cng ngh MPLS v tin ti i su nghin cu c th ng dng v trin khai trong thc t. Vi mc tiu nh vy ti gm cc phn nh sau: Chng 1: Gii thiu tng quan v cng ngh chuyn mch nhn a giao thc (MPLS) Chng 2: Cc thnh phn v hot ng ca MPLS Chng 3: Cc vn k thut c s dng trong mng MPLSChng 4 : Cu hnh MPLS trn thit b Cisco v m phng .

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Chng 11.1. Gii thiu

Gii thiu v cng ngh MPLS

Vi s pht trin nhn chng ca internet, internet tr nn ph bin v tr thnh cng c hiu qu phc v cho gio dc, thng mi gii tr, thng tin lin lc lc gia cc cng ng cc ng dng mi phc v cho thng tin lin lc cng ngy cng pht trin cng vi la nhu cu v truyn thng phc v cho cc ng dng mi ngy cng cao nh yu cu v ng truyn tc cao, yu cu v cht lng dch vdo ti nguyn h tng ca mng internet hin nay khng th p ng c nhu cu . Do yu cu cp thit cn phi c mt cng ngh mng th h mi p ng c yu cu . Mng MPLS ra i cung cp mt nn tng cng ngh cho qu trnh to ra mng a ngi dung, a dch v, hiu nng cao, tc cao, kh nng m rng mng ln, nhiu chc nng ci tin v p ng c nhiu yu cu cht lng dch v. chuyn mch nhn l yu t quan trng nht trong qu trnh m rng mng internet, n cung cp nhng ng dng quan trng trong x l chuyn tip gi bng cch n gin ho qu trnh x l, hn ch to ra cc bn sao mo u ti mi bc trong ng dn, to ra mt mi trng c th h tr cho iu khin cht lng dch v. pht trin ca MPLS cho php tch hp IP v ATM, h tr hi t dch v c sung cp nhng c hi mi cho iu khin lu lng v mng ring o. hiu nng s l gi c th ci tin bng cch thm nhn c kch thc c nh vo cc gi. iu khin cht lng dch v c th c cung cp d dng hn v c th xy dng cc mng cng cng rt ln.MPLS l k thut mi c mong i s pht trin ph bin trn phm vi rng c cc mng IP ring v cng cng m ng cho vic hi t cc dch v mng, video v thoi. Tm li MPLS s ng vai tr quan trng trong nh tuyn, chuyn mch v chuyn tip gi cho mng th h sau cng nh gii quyt cc vn lien quan ti m rng cp mng c th hot n vi cc mng hin c nh ATM, Frame Relay p ng nhu cu cng tng cao ca ngi s dng.

1.2. Cng ngh chuyn mch nhn a giao thc MPLS.Chuyn mch nhn a giao thc MPLS(MultiProtocol Label Switching) l mt bin php linh hot gii quyt nhng vn gp nhiu kh khn trong mng hin nay nh : tc , quy m, cht lng dch v(QoS), qun tr v k thut lu lng. MPLS th hin mt gii php thng minh p ng nhng i hi dch v v qun l gii thng cho mng IP th h sau - da trn ng trc. MPLS gii quyt nhng vn lin quan n tnh quy m v nh tuyn (da trn QoS v dng cht lng dch v) v c th tn ti trn mng ATM (phng thc truyn khng ng b - Asynchronous Transfer Mode ) v mng Frame Relay ang tn ti. MPLS thc hin mt s chc nng sau:

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN -

-

-

-

Xc nh c cu qun l nhiu mc khc nhau ca cc lung lu lng , nh cc lung gia cc c cu, phn cng khc nhau, thm ch cc lung gia nhng ng dng khc nhau. Duy tr s c lp ca cc giao thc lp 2 v lp 3 Cung cp phng php nh x a ch IP vi cc nhn n gin , c di c nh c s dng bi cc cng ngh chuyn tip gi v chuyn mch gi khc nhau. Giao din vi giao thc nh tuyn hin c nh giao thc t trc ti nguyn (RSVP) v giao thc m rng theo m rng theo phng thc u tin tuyn ng ngn nht (OSPF). H tr IP, ATM v giao thc lp 2 Frame Relay.

1.2.1 S ra i ca MPLS. MPLS l s kt hp mt cch hon ho cc u im ca cng ngh IP v ATM. Cng ngh IP IP (Giao thc internet Internet Protocol) l thnh phn chnh ca kin trc mng internet . IP nh ngha c cu nh s, c cu chuyn tin, c cu nh tuyn v cc chc nng iu khin mc thp (giao thc bn tin iu khin internet - ICMP). Gi IP gm a ch bn nhn , a ch l mt s duy nht trong ton mng v mang y thng tin cn cho vic chuyn gi tin ti ch. C cu nh tuyn c nhin v tnh ton ng i ti cc nt trong mng. do vy, c cu nh tuyn phi c cp nht cc thng tin v hnh mng v n phi c kh nng hot ng trong mi trng mng gm nhiu nt. kt qu tnh ton ca c cu nh tuyn c lu trong cc bng chuyn tin cha thng tin v chng tip theo c th gi gi tin ti hng ch . Da trn cc bng chuyn tin, c cu chuyn tin chuyn mch cc gi IP hng ti ch. Phng thc chuyn tin truyn thng l theo tng chng mt. cch ny mi nt mng phi tnh ton bng chuyn tin mt cch c lp. do vy phng thc ny yu cu kt qu tnh ton ca phn nh tuyn ti tt c cc nt phi nht qun vi nhau. s khng thng nht ca kt qu ny ng ngha vi vic mt gi tin . Kiu chuyn tin theo tng chng hn ch kh nng ca mng. v d vi phng thc ny, nu cc gi tin chuyn ti cng mt a ch m i qua cng mt nt th chng s c quyn qua cng mt tuyn ti im ch. iu ny khin mng khng th thc hin m s chc nng khc nh nh tuyn theo ch, theo loi hnh dch v Tuy nhin, bn cnh , phng thc nh tuyn v chuyn tin ny nng cao tin cy cng nh kh nng m rng ca mng. giao thc nh tuyn m rng cho php mng phn ng li vi s c bng vic thay i tuyn khi b inh tuyn bit c s thay i v hnh mng thng qua vic cp nht thng tin v trng thi kt ni . vi

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cc phng thc nh nh tuyn lien min khng phn cp (classless interdomain routing - CIDR), kch thc ca bng chuyn tin c duy tr mc chp nhn c v vic tnh ton nh tuyn u do cc nt thc hin, mng c th c m rng m khng cn thc hin bt k s thay i no. Tm li, IP l mt giao thc chuyn mnh gi c tin cy v kh nng m rng cao. Nhng vic iu khin lu lng rt kh thc hin do phng thc nh tuyn theo tng chng. ngoi gia,IP khong h tr cht lng dch v. - Cng ngh ATM Cng ngh ATM ( Asychronous Transfer Mode phng thc truyn tin khng ng b ) l mt k thut truyn tin tc cao, ATM nhn thng tin nhiu dng khc nhau nh thoi, s liu, video v ct nhau v ct ra thnh nhiu phn nh gi l t bo. Cc t bo ny sau c truyn qua cc kt ni o goi l VC (virtual connection), v ATM h tr thoi, s liu v video vi cht lng lng dch v trn nhiu cng ngh bng rng khc nhau. N c coi l cng ngh chuyn mch hng u v thu ht c nhiu quan tm. ATM khc vi nh tuyn IP mt s im. n l cng ngh chuyn mch hng kt ni . kt ni t im u ti im cui phi c thit lp trc khi thng tin c gi i . ATM yu cu kt ni phi c thit lp bng nhn cng hoc thit lp mt cch t ng thng qua bo hiu. mt im khc na l ATM khng thc hin nh tuyn ti cc nt trung gian. tuyn kt ni xuyn sut c xc nh trc khi chao i d liu v c gi c nh trong thi gian kt ni , trong qu trnh thit lp kt ni cc tng i ATM trung gian cp cho kt ni mt nhn. vic ny thc hin hai iu : dnh cho kt ni mt s nguyn v xy dng bng chuyn t bo ti mi tng i . Bng chuyn t bo ny c tnh cc b v ch cha thng tin v cc kt ni ang hot ng i qua tng i. iu ny khc vi thng tin v ton mng cha trong bng nh tuyn ca b nh tuyn dng IP. Qu trnh chuyn t bo qua tng i ATM cng tng t nh vic chuyn gi tin qua b nh tuyn. tuy nhin ATM c th chuyn mch nhan hn v nhn gn trn cc t bo c kch thc c nh (nh hn ca IP), kch thc ca bng nh tuyn nh hn nhiu so vi b nh tuyn IP, vic ny c thc hin trn cc thit b phn cng chuyn dng. do vy thng lng ca tng i ATM thng ln hn thng lng ca b nh tuyn IP truyn thng. Ni cch khc , cng ngh ATM l mt cng ngh truyn thng tc cao, m bo thi gian thc v cht lng dch v theo yu cu t trc. - Cng ngh MPLS - s kt hp gia cng ngh IP v ATM u im ni bt ca giao thc truyn tin TCP/IP l kh nng nh tuyn v truyn gi mt cch ht sc mm do linh hot v rng khp ton cu, nhng IP khng

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m bo cht lng dch v, tc truyn tin theo yu cu, trong khi cng ngh ATM c th mng u vit v tc truyn tin cao, m bo thi gian thc v cht lng dch v theo yu cu t trc. s kt hp IP v ATM ca th l gii php k vng cho mng vin thng tng lai-mng th h sau NGN. Chuyn mch nhn a giao thc MPLS p ng nhu cu . MPLS kt hp u im ca cng ngh IP v ATM to ra mt gii php linh hot cho vic gii quyt cc vn m cc mng trc phi i mt, l tc , kh nng m rng cp mng, qun l cht lng dch v (QoS) v k thut lu lng. Tht vy cng ngh chuyn mch nhn MPLS l kt qu pht trin ca nhiu cng ngh chuyn mch IP s dng cng ngh hon i nhn nh ca ATM tng tc truyn gi tin m khng cn thay i cc giao thc nh tuyn ca IP. T tng khi a ra MPLs l nh tuyn ti bin chuyn mch ti li. Trong cc mng MPLS cc gi c gn nhn ti bin c mng v chng c nh tuyn xuyn qua mng da trn cc nhn n gin. C th ni MPLS l mt cng ngh chuyn mch IP c nhiu trin vng, vi tnh cht c cu nh tuyn ca mnh, MPLS c kh nng lng cao cht lng dch v cu mng IP truyn thng . bn cnh thng tin lu lng ca mng s c ci thin r rt. 1.2.2 Qu trnh pht trin v chun ho cng ngh MPLS - Tnh hnh trin khai cnng ngh MPLS BIG PIPE nh khai thc dch v IP ca Canada la chn Cisco Systems l nh cung cp thit b cho mng trc IP OC-192 vo thng 10 nm 2001- cc b nh tuyn ca Cisco trong mng trc ny s cho php BIG PIPE cung cp bng thng OC-192. cc b nh tuyn 12410 v 12416 ca cisco s cho php nh cung cp dch v ny trin khai dch v IP th h sau nh MPLS-VPN, IP QoS v voice over IP (VOIP). Juniper Network v Ericsson communication thng bo rng th h internet router trc mi (serie M) c trin khai trong mng trc mi ca TelstraSaturn. TelstraSaturn l cng ty u tin ti Newzealand trin khai mng bng tn ln nht cung cp c IP v thoi. Cc b nh tuyn M160 v M20 c trin khai trong mng trc ti lu lng qua MPLS. y l mng thng mi u tin trin khai y STM16(2.5Gb/s) ti New Zealand Thng 10 Alcatel thng bo k hp ng cung cp thit b bng rng cho Deashe Telecom Group. Cc sn phn ca Acatel bao gm : thit b chuyn mch nh tuyn (RSP) 7670 cho mng chuyn i s liu ATm ca quc ni ti c. thit b ny s cho php Deashe Telecom m rng mng a dch v ca h t 12.8 Gb/s ln 450

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Gb/s tho mn nhu cu trong mng thc. thit b ny c kh nng chuyn mch MPLS trn ATM. NTT America tong bo trin khai dch v Arestar Glbal IP-VPN n tt c cc doanh nghip ti m. dch v Arestar IP-VPN cung cp gii php hon chnh bao gm cng ngh IP-VPN,MPLS. China Telecom la chn Nortel works trong hai hp ng tr gi 12 triu USD lng cp mngTM a dch v ti tnh Jiasngu v Shandong vo thng 10 nm 2001. hai mng ny cho php china telecom cung cp dch v ATM tin tin, duy nht. China telecom c k hot thay th thit b chuyn mch ng trc hin ti bng gii php ca Nortel work . cc thit b bao gm :Passport 15000, Passport 7480 MS. Cc thit b ny cung cp dch v ATM,Frame Relay, chuyn mch v nh tuyn Ip,MPLS River stone Network trin khai mng cho hai nh cung cp chu au l Telenet nh cung cp dch v b v Neosnetwork-nh khai thc ca UK. Nha khai thc ny trin khai mng MPLS u tin ti UK vi router loi RS. Neosnetwork chn RS8600 multiservice v RS3000 metro access router cung cp dch v Ethernet nh mt phn trong mngtruyn s liu ton quc ca U.K. Telenet lu chn Reverstone l nh cung cp cc router mng ung trc IP trong mng truyn s liu v mng cp ca mnh. Telenet s dng reverstone RS 8600 multi-service metro routers. c hai d n ny u c trin khai cui nm 2001. - Qu trnh chun ho MPLS i vi cc cng ngh chuyn mch mi, vic tiu chun ho l mt kha cnh quan trng quyt nh kh nng chim lnh th trng nhanh chng ca cng ngh . Cc tiu chun lien quan n Ip v ATM c xy dng v hon thin trong mt thi gian tng i di. Cc tiu chun v MPLS ch yu c IETF pht trin (Cc tiu chun RFC Request for comment) hin ang c hon thin v thc hin theo mt qu trnh nh sau: - Vo u nm 1997, hin chng MPLS c thng qua. - Vo thng 4 nm 1997, nhm lm vic MPLS tin hnh cuc hp u tin - Vo thng 11 nm 1997, ti liu MPLS c ban hnh - Vo thng 7 nm 1998, ti liu cu trc MPLS c ban hnh - Vo thng 8 v thng 9 nm 1998, 10 ti liu internet b xung c ban hnh, bao gm giao thc phn phi nhn MPLS (MPLS Label Distribution ProtocolMPLS LDP), m ho nh du (Mark Encoding), cc ng dng ATM, . . . MPLS hnh thnh v vn bn. - IETF hon thin cc tiu chun MPLS v a ra cc ti liu RFC trong nm 1999. - Qu trnh chun ho MPLS cn do ITU-T xy dng v pht trin.

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Nh vy, c th thy rng MPLS pht trin nhanh chng v hiu qu. iu ny cng chng minh nhng yu cu cp bch trong cng nghip cho mt cng ngh mi. Hu ht cc tiu chun MPLS hin ti c ban hnh di dng RFC.

1.3. Mt s c im ca cng ngh MPLSMc d thc t rng MPLS ban u pht trin vi mc ch gii quyt vic chuyn gi tin, nhng li im chnh ca MPLS trong mi trng mng hin ti li l kht nng iu khin lu lng ca n. mt s u im khc l: 1.3.1. Tc v tr. Cc chuyn mch da trn phn mn truyn thng th qu chm x l cc ti lu lng lng trong internet .ngay c vi k thut c ci tin th vic tra tm bang nhanh vi mt gi d liu no trn b nh tuyn th thng mt nhiu thi gian hn nhiu so vi tc x l ca b nh tuyn .kt qu l mt ti lu lng ,mt cc kt ni ,tnh nng thc thi s b gim trong mnh da trn IP. Chuyn mch nhn khc xa so vi nh tuyn IP ,n cung cp mt gii php hiu qu cho vn ny .l do chuyn mch nhn nhanh hn nhiu l vic gi tr nhn c t trong tiu ca gi n ,gi tr ny c s dng truy cp vo b chuyn tip trong b nh tuyn , c ngha l gi tr ny c s dng lm a ch tham chiu bng (Index the table) .vic tra tm ny ch yeu cu duy nht mt truy cp , khc vi bng nh tuyn thng ,vic truy cp l hangf ngn ln ( do c s d liu trong bng nh tuyn truyn thng l qu ln ). Kt qu mang li khi s chuyn mch nhn l tc chuyn mch , lng thng tin lu chuyn trn mng nhan hn ,do d lm gim tr v thi gian p ng trng vic trao i gia nhng ngi s dng . 1.3.2. dung pha. i vi my tnh, ngoi cc tham s v tc , s p ng, tr cn c mt thnh phn khc . l s bin thin tr ca lu lng ngi s dng do s chuyn tip cc gi tin ti mt vi nt trong mng ti ch ca n. bin thin tr b tch lu khi gi tin i t ngun ti ch . ti mi nt a ch ch ca gi tin c xem xt v so snh vi mt danh sch di cc a ch c kh nng lm a ch ch trong cc bng nh tuyn ca nt . Khi gi tin c truyn qua cc nt ny, n s tch lu c tr ln bin thin tr, ph thuc vo di ca bng c tra v s cc gi tin c s l trong mt n v thi gian .kt qu cui cng ti cc nt nhn c l dung pha, tri pha v nghim trng hn l trc pha.vn ny nh hng xu ti cc gi d liu ting ni .

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i vi chuyn mch nhn, do vic tra tm thng tin bng nh tuyn l t, nn vic tch lu bin thin gim tr l rt nhiu. kt qu l lu lng ngi s dng s c chuyn tip trong mng mt cch nhanh chng, do s dung pha cng t hn so vi nh tuyn IP truyn thng . 1.3.3. M rng cp mng . Tc l mt kha cnh quang trng trong chuyn mch nhn, vic s l lu lng ngi s dng trong mt mng internet l rt cn thit, tuy nhin cc dch v cn cung cp kh nng m rng cp mng, l kh nng m h thng c th m rng quy m v tng s lng thu bao trong mng internet ln hng ngn thu bao mi c cc nt mng (cc b nh tuyn, cc my ch )h tr ng nhp mi ngy. qun l ht cc thu bao nh vy , c bit l cc thu bao s dng cc dch v a phng tin th cng vic ca b dnh tuyn l ht sc nng n. chuyn mch nhn a ra cch gii quyt cho cc mng ln v tng trng mt cch nhanh chng l bng cch cho php mt s lng ln cc a ch IP gn vo mt hoc mt s t nhn.phng php tip cn ny lm gim i rt nhiu kch thc cc a ch v cho php b nh tuyn h tr nhiu ngi s dng hn . 1.3.4. Tnh n gin . Mt kha cnh hp dn khc ca chuyn mch nhn l giao thc chuyn mch ( n bao gm mt tp cc giao thc )v cc chuyn tip da trn gi. c cu iu khin lung c thc hin to mi lin quan gia nhn v lu lng . cc c cu iu khin ny th phc tp nhng khng nh hng ti vic iu khin lu lng ngi s dng . C mt vi phng php khc nhau c p dng thit lp s kt hp nhn (binging) ca lng ngi s dng. khi s kt hp ny c hon tt th cc hot ng chuyn mch nhn c thc hin trong phn mm, trong ASIC , hoc trong b s l c bit . 1.3.5. Tiu tn ngun ti nguyn . C cu iu khin thit lp nhn phi khng l gnh nng cho mng. iu c ngha l chng khng tiu tn ti nguyn. cc mng chuyn mch nhn khng tiu tn nhiu ngun ti nguyn thc hin c cu iu khin thit lp cc ng mch nhn i vi lu lng ngi s dng .- H tr mm do tt c cc dch v (Hin ti v sp ti ) trn mt mng n. - H tr tt c cc cng c iu khin lu lng mnh m bao gm c nh tuyn lin

tip v chuyn mch bo v.

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN - H tr a kt ni v a giao thc : thit b chuyn tip chuyn mch nhn c th c

dng khi thc hin chuyn mch nhn vi IP cng tt nh vi IPx. Chuyn mch nhn cng c th vn hnh o trn bt k lp giao thc lp lin kt d liu.- H tr cho tt c cc loi lu lng : mt u im khc ca chuyn mch nhn l n

c th h tr tt c cc loi chuyn tip unicast, loi dch v unicast v cc gi multicast.

1.4. Cc ng dng ca MPLS.Mng MPLS c nhiu ng dng trong c 3 ng dng chnh v thng thng 2 trong 3 kh nng c s dng ng thi: 1.4.1. Tch hp IP+ATM Do chuyn mch nhn c th thc hin bi cc chuyn mch ATM. s tch hp ny cn phi t nh tuyn IP v phn mm LDP trc tip trn chuyn mch ATM. Do tch hp hon ton IP trn chuyn mch ATM, MPLS cho php chuyn mch ATM h tr ti u cc dch v IP nh IP a hng (Multicast), lp dch v IP, RSVP (Resource Reservation protocol giao thc h tr ti nguyn) v mng ring o. 1.4.2. Dch v mng ring o IP (VPN) VPN thit lp c s h tng cho mng intranet v extranet, l cc mng IP m cc cng ty kinh doanh s thit lp trn c s ton b cu trc kinh doanh ca h. Dch v VPN l dch v mng intranet v Extranet m cc mng c cung cp bi nh cung cp dch v n nhiu t chc khch hng. MPLS kt hp giao thc cng bin (BGP) cho php mt nh cung cp h tr hng nghn VPN ca khch hng. Nh vy, mng MPLS cng vi BGP to ra cch thc cung cp dch v VPN trn c ATM v cc thit b da trn gi tin rt linh hot, d m rng quy m v d qun l. thm ch trn cc mng ca nh cung cp kh nh, kh nng linh hot v d qun l ca dch v MPLS+BGP VPN l u im ch yu.

1.4.3. iu khin lu lng v nh tuyn IP r rng Vn quan trng trong cc mng IP lin tc l thiu kh nng iu khin linh hot cc lung lu lng IP s dng hiu qu di thng ca mng sn c. do vy thiu ht ny lin quan ti kh nng gi cc lung c chn xung cc ng c chn v d nh chn cc ng trung k c m bo cho lp dch v ring. MPLS s

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dng cc ng chuyn mch nhn (LSPs), chnh l mt dng ca lightweight VC m c th c thit lp trn c ATM v thit b da trn gi tin. kh nng iu khin lu lng IP ca MPLS s dng thit lp c bit cc LSP iu khin mt cch linh hot cc lung IP.

Kt lun chngTrong chng 1 gii thiu tng quan v cng ngh MPLS, MPLS l s kt hp gia cng ngh IP v cng ngh ATM, trong chng ny cng gii thiu s ra i ca MPLS, qu trnh chun ho v tnh hnh trin khai MPLS trn th gii, ti sao MPLS li c k vng nhiu ti vy trong chng ny cng gii thiu mt s c dim ni bt ca MPLS, u im ca MPLS.

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.

Chng 2

Cc thnh phn v hot ng ca MPLS

2.1. Mt vi khi nin c bn:2.1.1. Nhn (label) Nhn l mt thc th c di ngn v c nh khng c cu trc bn trong. Nhn khng trc tip m ho thng tin ca mo u lp mng nh a ch lp mng. nhn c gn vo mt gi tin c th s i din cho mt FEC (forwarding Equivalence Classes: nhm chuyn tip tng ng ) m gi tin c n nh . Thng th mt gi c n nh mt FEC (hon ton hoc mt phn ) da trn a ch ch lp mng ca n. tuy nhin nhn khng phi l m ho a ch .nhn trong mng n gin nht xc nh ng i m g c th truyn qua .nhn c mang hay c ng gi trong tiu lp 2 cng vi gi tin. b nh tuyn kim tra gi thng qua ni dung nhn xc nh cc bc chuyn tip k tip. khi gi tin c gn nhn, cc chng ng cn li ca gi tin thng qua mng ng trc da trn chuyn mch nhn. gi tr ca nhn c ngha cc b ngha l chng ch lin quan ti cc bc chuyn tip gia cc LSR. Dng ca nhn ph thuc vo phung thc truyn tin m gi tin c ng gi. i vi dng Frame Relay s dng gi tr nhn dng kt ni cc lin kt d liu DLCI (data link connection identifier), ATM s dng trng nhn dng ng o trong t bo ng nhn dng knh o trong t bo (virtual path identifier/virtual circuit identifier VPI/VCI).sau gi c chuyn tip da trn gi tr ca chng . nh dng chung ca nhn c gii thch trong hnh 1. nhn c th hin r trong tiu cc lp lin kt (VPI/VCI ca ATM trong hnh 2 v DLCI ca Frame Relay trong hnh 3 ) hoc trong lp d liu shim (gia tiu lp lin kt d liu lp 2 v lp mng lp 3 nh hnh 4 )

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN Tiu lp lin kt Tiu lp mng D liu v tiu lp khc

MPLS SHIM 32 bit

Nhn 20 bit

EXP.Bits 3 bit

BS 1bit

TTL 8 bit

Hnh 1 : nh dng chung ca nhn MPLS i vi cc phng tin gc khng c cu trc nhn, mt on m (shim) c chn thm vo s dng cho nhn. Khun dng on m 4 byte c cu trc nh hnh 3 phn SHIM MPLS bao gm: - LABEL (20bit):cha gi tr nhn - EXP.bits: CoS(3 bit)- cht lng dch v - BS (1 bit) bie-stack: xc nh nhn cui cng trong ngn xp - TTL (8 bit) time to live :trng nh thi

Gi IP

Tiu IP

D liu

Gn nhn vo Gi tin

Tiu SHIM Tiu IP

D liu

Cc t bo ATM

VPI/VCI

D liu

VPI/VCI

D liu

Hnh 2: Lin kt d liu l ATMGi IP Gn nhn vo gi tin Tiu SHIM Tiu IP D liu

Tiu IP

D liu

Cc t bo ATM

DLCI

D liu

DLCI

D liu

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Hnh 3 :Lin kt d liu l Frame Relay i vi cc khung PPP hoc Ethernet, gi tr nhn dng giao thc P- ID(hoc Ether type) c chn vo u khung tng ng thng bo khung l MPLS n hng hay a hngTiu PPP trn gi SONET /SDH Tiu PPP Tiu SHIM Tiu lp 3

Nhn

Tiu MAC LAN Label Creation

Tiu MAC

Tiu SHIM

Tiu lp 3

Hnh 4 : Nhn trong shim - gia lp 2 v lp 3 2.1.2. Ngn xp nhn(Label stack): L mt tp c th t cc nhn gn theo gi chyn ti thng tin v nhiu FEC v v cc LSP tng ng m gi i qua. ngn xp nhn cho php MPLS h tr nh tuyn phn cp (mt nhn cho EGP v mt nhn cho IGP)v t chc a LSP trong mt trung k LSP. iu ny to iu kin thun li cho ch hot ng ng hm trong MPLS . Mt gi c th c dn chng nhiu nhn, cc nhn ny c cha trong stack. Stack th c t chc theo nguyn tc LIFO. ti mi hop trong mng s l nhn s l nhn hin hnh trn nh stack. Chnh nhn ny c LSR s dng chuyn tip gi. Nu gi tin cha c nhn th stack rng ( su ca stack bng 0). nu stack c chiu su l d th mc 1s l y ca stack (bt s trong entry nhn t ln 1)v mc d s l nh stack.mt entry nhn c th c t thm vo (push) hoc ly ra (pop ) khi stack.

Hnh 5: Ngn xp nhn

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2.1.3. Hon i nhn (Label Swapping). Hon i nhn l cch dng cc th tc chuyn tip gi. chuyn tip gi c nhn, LSR kim tra trn nh stack v dung nh x ILM (Incoming Label Map) nh x ti mt entry chuyn tip nhn NHLFE ( Next Hop Label Forwarding Entry). S dng thng tin trong NHLFE, LSR xc nh ra ni chuyn tip gi v thc hin mt tc v trn stack nhn. ri n m ho stack nhn mi vo gi v chuyn gi i. Chuyn tip gi cha c nhn cng tng t nhng sy ra ingress LER. LER phi phn tch header lp mng xc nh FEC ri s dng nh x FTN (FEC-to-NHLFE) nh x FEC vo mt NHLFE. 2.1.4. B nh tuyn chuyn mch nhn (LSR :label switching router): L thit b nh tuyn hay chuyn mch (router hay switch)s dng trong mng MPLS chuyn cc gi tin bng th tc phn phi nhn .c mt s loi LSR nh sau: LSR bin,ATM -LSR li,ATM-LSR bin 2.1.5. Lp chuyn tip tng ng(FEC)

Hnh 6: Lp chuyn tip tng ng FEC Lp chuyn tip tng ng FEC l mt thut ng c s dng trong cc hot ng chuyn tip nhn, n dng m t s kt hp cc gi ri rc vi a ch ch, thng l a ch ca ngi nhn cui cng , chng hn nh my chm .vic thc hin ca FEC cng c th l s kt hp mt gi tr FEC vi a ch ch v lp ti lu lng (class of traffic). lp ti lu lng ny thng kt hp vi s cng ch . tt c cc gi trong mt nhm c i s nh nhau qua mng MPLS ngay c khi c s khc bit gia cc gi tin th hin trong mo ca lp mng . khc vi IP thng thng , trong MPLS ,cc gi tin ring bit c gn vo cc FEC ring ngay sau khi chng vo mng.cc FEC da trn yu cu dch v cho vic thit lp cc gi tin hay n gin cho mt tin a ch

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Ti sao FEC c s dng: u tin n cho php mt nhm cc gi tin vo trong cc lp . t nhm ny , gi tr FEC trong mt gi c th c s dng thit lp u tin s l cc gi. cc FEC c u tin cao s c x l trc cc FEC khc. Cc FEC ny c th c s dng h tr hiu qu cht lng dch v QoS, chng hn cc FEC c th kt hp vi u tin cao, lu lng ting ni thi gian thc, lu lng ting ni vi u tin thp S ph hp ca mt FEC vi mt gi c th t c bng cch s dng mt nhn xc nh mt FEC c bit. i vi cc dch v khc nhau c cc FEC khc nhau v cc nhn km theo . i vi ti internet, cc trng nhn dng sau l cc tham s quan trng cho vic thit lp mt FEC. tuy nhin , trong mt vi h thng ch c a ch IP ch c s dng : - a ch IP ngun v ch - S cng ngun v ch - Trng nhn dng giao thc IP (PIN) - im m cc dch v m rng ca IP phin bn 4 (Ipv4 Differentiated services (DS)codepoint) - Nhn lung Ipv6 Thng tin s dng trong quyt nh chuyn tip

Ti tin TCP ,UDP Ti gi d liu IP Layer 2 trailer User traffic M essage (e.g... email ) Header (layer 7) Segment (TCP ,UDP ) Header (layer 4) Datagram (IP) Header (layer 3) Layer 2 Header

Cha cng s

Cha a ch IP v trng nhn dng giao thc ID (PID )

Cha a ch MAC , hoc ATM ,Fram e RelayVCIDs

Hnh 7Thng tin c s dng trong cc quyt nh chuyn tip Cc trng trong cc gi n c s dng lm nn cc quyt nh chuyn tip cc gi c ch ra hnh 7. l do cc trng ny c cc b nh tuyn, chuyn mch hay cu s dng lm cc quyt nh chuyn mch , nhng thng khng s dng FEC .

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Lp 2 s dng cc a ch LAN (da ch MAC), trng nhn dng tuyn o ATM v Frame Relay(VCID) Lp 3 s dng cc a ch IP ch v ngun Lp 4 s dng s cng ngun v ch , trng nhn dng giao thc IP Ch s cng v giao thc IP c s dng trong FEC ra quyt nh chuyn tip, cc trng ny dng xc nh loi ti tin trong gi d liu IP. V d trng PID c th c m ho bi b pht ca gi d liu gc ch rng loi ti tin (payload) l ti OSPF, mt b nh tuyn c th c lp trnh cho vic s l cc ti tin ny khc vi cc loi ti tin khc (v d ti tin TCP hoc UDP). ch s cng trong tiu TCP v UDP s ch ra loi ti tin trong gi tin m giao thc TCP v UDP mang, v d ch s cng ch c th c m ho ch ra ti tin l m thanh ,th in t, truyn file do , cc trng ny l tng i quan trng i vi cc mng cn h tr cc dch v Qos khc nhau i vi loi lu lng khc nhau . i vi nhn MPLS thng dng c ch ra hnh 7. cn vi VCID ca ATM hoc Frame Relay th mt tiu m c chn vo (shim header) c th c s dng trong gi . 2.1.6. To nhn To nhn da trn cc phng php sau: - Topo: nh giao thc nh tuyn thng thng (OSPF v BGP) - Yu cu : iu khin lu lng da trn yu cu - Lu lng :nhn gi tin phn phi v gn nhn 2.1.7. Bng chuyn tip chuyn mch nhn L bng chuyn tip c cha thng tin v nhn vo, nhn ra giao din vo giao din ra v a ch tip theo . 2.1.8. C s thng tin nhn (label information base -LIB) C s thng tin nhn (label information base - LIB) l bng kt ni LSR c cha gi tr nhn FEC c gn vo cng ra cng nh thng tin ng gi d liu truyn tin xc nh phng thc mt gi tin c chuyn tip . V d v hot ng LIB:

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Hnh 8: V d v LIB M1 LIB InLabel X M2 LIB InLabel 20 Outlabel 20 Outlabel 31 Outinterface 2 Outinterface 2 FEC H2 FEC H2

M3 LIB InLabel 31 M4 LIB Inlabel 43

Outlabel 43 Outlabel X

Outinterface 2 Outinterface 3

FEC H2 FEC H2

1. H1 to ra mt gi v gi n ti M1 ( n l Default Gateway) 2.M1 l mt ingress LSR v quyt nh nhn no c gn vo gi. l 20 .sau khi nhn c gn th gi tin c chuyn tip trn giao din tng ng 2 3.M2 nhn mt gi vi nhn 20, chuyn i n bng nhn 31 v chuyn tip gi i qua giao din 2 4.M3 nhn gi vi nhn 31 , chuyn i bng nhn 43 v gi n i qua giao din 2. 5.M4 nhn gi vi nhn 43 nhng n khng yu cu nhn ra. nhn dng M4 l mt egress LSR choc FEC v v vy n g b nhn v gi gi IP qua giao din 2. 2.1.9. C s thng tin chuyn tip nhn LFIB Trong mng IP, quyt nh chuyn tip gi c xc lp bng cch thc hin tra ku a ch ch trong bng FIB xc nh hop k tip v giao din ra. Trong mng MPLS, mi LSR duy tr mt bng LFIB ring r v tch bit vi FIB. bng LFIB c hai loi entry l ILM (incoming Label Map) v FTN (FEC to - NHLFE).

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NHLFE (Next Hop Label Forwarding Entry) l Subentry cha cc trng a ch Hop k tip, cc tc v stack nhn, giao din ra v thng tin header lp 2. ILM nh x mt nhn n mt hoc nhiu NHLFE. Nhn trong gi n s dng chn ra mt entry ILM c th nhm xc nh NHLFE. Cn FTN nh x mi FEC vo mt hoc nhiu NHLFE. nh cc entry FTN, gi cha c nhn c chuyn thnh gi c nhn.

Hnh 9: FTN,ILM v NHLFE Nh vy , khi mt gi khng nhn thuc mt FEC i vo min MPLS, ingressLER s s dng mt entry LFIB loi FTN chuyn gi khgn nhn thnh c nhn. Sau . ti cc transit-LSR s dng entry LFIB loi ILM hon i nhn vo bng nhn ra. cui cng, ti Egress-LER s dng mt entry LFIB loi ILM g b nhn n v chuyn gi khng nhn n Router k tip. 2.1.10. NHLFE (Next Hop Label Forwarding Entry) NHLFE l subentry ca ILM hoc FTN, n cha cc thng tin sau: - Hop k (chng tip theo) ca gi Tc v s tin hnh trn stack nhn ca gi nh sau: - Swap :Thay nhn nh ca stack nhn bng mt nhn mi c ch nh. - Pop :Bc mt nhn ra khi stack - Push :chng thm mt nhn vo trong stack nhn.

Hnh 10: V d NHLFE Ngoi ra, NHLFE cng c th cha thng tin sau :

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- ng gi lp datalink s dng khi truyn gi - Cch thc m ho stackb khi truyn gi - Bt k cc thong tin khc cn thit x l gi mt cch chnh xc. 2.1.11. ng chuyn mch nhn (label switching path - LSP)

Hnh 11 : ng chuyn mch nhn LSP L tuyn to ra t u vo n u ra ca mng MPLS dng chuyn tip gi ca mt FEC no s dng c ch hon i nhn. cc ng chuyn mch nhn cha mt chui cc nhn ti tt c cc nt dc theo tuyn t ngun ti ch. LSP c thit lp trc khi truyn d liu hoc trong khi xc nh lung d liu no . cc nhn c phn phi bng vic s dng giao thc phn phi nhn (Label distribution protocol - LDP) hoc giao thc dnh trc ti nguyn (resource Reservation Protocol - RSVP) trn cc giao thc nh tuyn ging nh giao thc cng bin (Border Gateway Protocol BGP) v giao thc nh tuyn m ng ngn nht (Open Shortest Path First OSPF). mi gi d liu c ng gi li v mang cc nhn trong sut thi gian di chuyn t ngun ti ch .chuyn mch d liu tc cao hon ton c th thc hin da theo phng php ny, v cc nhn c di c nh c chn vo phn u ca gi tin hoc t bo v c th s dng bi phn cng chuyn mch nhanh cc gi d liu gia cc lin kt. 2.1.12.Gi tin gn nhn. Mt gi tin dn nhn l mt gi tin m nhn c m ho trong .trong mt s trng hp, nhn nm trong mo u ca gi tin dnh ring cho mc ch dn nhn .trong cc trng hp khc, nhn c t chung trong mo u lp mng v lp lin kt d liu min l y c trng tin c th dng cho mc ch dn nhn. cng ngh m ho c s dng phi ph hp vi c thc th m ho nhn v thc th gii m nhn.

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2.1.13. n nh v phn phi nhn Trong mng MPLS ,quyt nh kt hp mt nhn L c th vi mt FEC F c th no do LSR pha trc thc hin .LSR pha trc sau khi kt hp s thng bo vi LSR pha sau v s kt hp .do vy ,cc nhn c LSR pha trc n nh v kt hp nhn c phn phi theo hng t LSR pha trc ti LSR pha sau . hiu r hn v cch n nh nhn, ta a ra khi nin kng gian nhn Label Space dng ch cch m m trong nhn c n nh vi LSR . 2.1.14. Khng gian nhn(Label spaces). Nhn c s dng bi mt LSR cho FEC- gn nhn c chia ra nh sau: Phng php th nht l per interface . phng php ny cc nhn c gn vi giao din c bit trn mt LSR, chng hn giao din DS3 hoc SONET. Thng thng phng php ny c thc hin trong cc mng ATM v Frame Relay, ni m cc nhn ID tuyn o c gn trn mt giao din. phng php ny c s dng khi c hai mng ng cp c gn trn mt giao din v nhn ch c s dng xc nh lu lng c gi trn mt giao din .nu LSR s dng gi tr giao din theo di cc nhn trn mi giao din th gi tr nhn c th s dng li ti mi giao din .trng nhn dng giao din ny s tr thnh mt nhn ni internal label trong LSR ny cho nhn ngoi - External label|c gi gia cc LSR. Phng php th 2 l per platform y cc nhn n c chuyn chung thng qua tt c cc giao din ti mt nt mc ngha l nt ny (chng hn mt my chm hoc LSR)phi t khng gian nhn thng qua tt c cc giao din . Tuy nhin phng php th nht c s dng thng dng hn. 2.1.15. C cu bo hiu. - Yu cu nhn - s dng c cu ny ,mt LSR yu cu mt nhn t dng xung ln cn nn n c th lin kt n FEC xc nh .c cu ny c th c dng d truyn n cc LSR tip theo cho n LSR li ra. - p ng nhn - p ng mt yu cu nhn , LSR lung xung s gi mt nhn n cc b khi ng c cu nh x nhn.

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xLi vo (LER) B nh tuyn A

p ng nhn v d nhn 5

Yu cu nhn cho ch C

xLSR

p ng nhn v d nhn 9

Yu cu nhn cho ch C

xLi ra (LER) B nh tuyn C

B nh tuyn B

Hnh12: C cu bo hiu

2.2. Chuyn tip gi trong MPLS.2.2.1 Hot ng chuyn tip FEC l mt tp con cc gi cn c theo mt s thng tin trong header IP c dung bi FIB. Mt FEC c dung da theo lut longest prefix math trn a ch IP ch. V d :cc a ch IP so trng 16 bit u c dng a.b.*.* (Trong * i din cho gi tr hp l bt k) c biu din l a.b/16 cho entry FEC u tin trong bng FIB. FEC cn c th cn c b sung theo cc trng khc trong header IP nh ToS hay Diffserv. FIB s dng FEC xc nh ra giao tip i n hop k cho cc gi IP, cch thc hin ging nh cc router c in.

Hnh 13: Bn trong mt phng chuyn tip MPLS

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Cho cc v d tng hot ng LFIB hnh trn . Phn ILM (incoming label map) ca LFIB thao tc trn mt gi c nhn v nh x mt nhn vo (incoming label) ti mt tp cc entry NHLFE, ILM uc th hin trong hnh bi cc ct IN-IF v IN-LBL, nhng cng c th l mt bng ring r cho mt giao tip. FTN (FEC to- NHLFE)ca FIB nh x ti nhiu NHLFE, chng hn dung trong cn bng ti. 2.2.2 V d v chuyn tip gi. Trong v d ny th hin ng v hot ng chuyn tip c th hin mi nt cho 2 LSP l LSP-1 v LSP-2. LSP-1 bt u t LER E1, ti c mt gi IP n vi a ch ch l a.b.c.d. LER E1 kin tra bng FIB ca n xc nh rng gi ny thuc v FEC a.b.c/24, n gn nhn A ln gi v xut i trn giao din s 2. tip theo, LSR S1 thy c gi gn nhn A n qua giao din s 1, LFIB ca n ch th rng gi s xut ra trn giao din s 4 v s c thay th bng nhn D. gi c nhn i ra trn giao din s 4 trn LSR S1 ni n giao din s 1 trn LSR 4.

Hnh 14 : V d hot ng chuyn tip gi V LSR S4 l hop p ca LSP-1 nn thao tc c ch th trong LFIB ca n l g nhn (pop) v gi gi i trn giao din s 4. Cui cng, ch l LER E4, entry LFIB thao tc trn FEC a.b.c/24 v chuyn pht gi n hop k tip trn giao din s 3. i vi v d LSP-2, cc entry trong FIB l LFIB cng c th hin tng t nh trnh by i vi LSP-1.

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2.3. Cc thnh phn c bn ca mng MPLSM hnh mng MPLS:

Hnh 15: M hnh mng MPLS Min MPLS l mt tp k tip cc nt hot ng nh tuyn v chuyn tip MPLS.min MPLS c th chia thnh li MPLS (MPLS core) v bin MPLS (MPLS Edge) nh hnh 15. Khi mt gi tin IP i qua min MPLS ,n i theo mt tuyn c xc nh ph thuc vo nhm chuyn tip tng ng FEC m n c n nh cho khi i vo min . tuyn ny gi l ng chuyn mch nhn LSP. LSP ch c tnh mt chiu, tc l cn hai LSP cho mt truyn thng song cng. Cc nt c kh nng chy giao thc MPLS v chuyn tip cc gi tin gc IP c gi l b nh tuyn chuyn mch nhn (LSR Label Switching Router).-

LSR li vo (ingress LSR) x l lu lng i vo min MPLS LSR chuyn tip (Triansit LSR) x l lu lng bn trong min MPLS ; LSR li ra (Egress LSR) x l lu lng ra khi min MPLS LSR bin (Edge LSR) thng c s dng nh l tn chung cho c LSRli vo v li ra.

2.3.1. B nh tuyn bin nhn (Label Edge router LER). L thit b hot ng ti bin ca mng truy nhp v mng MPLS .LER h tr nhiu cng kt ni t nhng mng khc (nh Frame Relay , ATM v Ethernet ).n tip nhn hay gi i cc thng tin n hay i t cc mng khc ti mng MPLS sau khi thit lp ng chuyn mch nhn .LER c vai tr rt quan trng trong vic gn v tch nhn

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khi lu lng i vo hoc i ra trong mng MPLS .cc LER ny c th l b nh tuyn li vo (ingress Router) hoc b nh tuyn li ra (Egress Router). B nh tuyn bin li vo nhn gi IP ,kim tra li lp 3 v t vo ngn xp nhn trc khi gi gi vo mng MPLS. b nh tuyn bin li ra nhn gi tin c nhn ,loi b nhn ,kim tra li lp 3 v chuyn tip gi IP ti nt tip theo. 2.3.2. B nh tuyn chuyn mch nhn (Label Switching Router - LSR) LSR l thnh phn quan trng nht ca mng MPLS ,n l b phn nh tuyn tc cao trong mng li MPLS tham gia vo vic thit lp ng chuyn mch nhn LSP s dng cc giao thc bo hiu nhn thch hp v chuyn cc gi d liu trong phm vi mng MPLS da trn cc ng thit lp bng th tc phn phi nhn . LSR c th kt ni vi LER hay cc LSR khc. 2.3.3. ATM LSR : L cc tng i ATM c th thc hin chc nng nh LSR . Cc ATM LSR thc hin chc nng nh tuyn gi IP ,gn nhn trong mng iu khin v chuyn tip s liu theo c ch chuyn mch t bo ATM trong mng s liu. c th s dng giao thc MPLS trong mng iu khin thit lp knh o ATM , chuyn tip t bo n nt ATM LSR tip theo. Do , cc tng i ATM c th lng cp phn mm thc hin chc nng LSR. 2.3.4. ATM LSR bin: - Nhn gi c nhn hoc khng c nhn phn vo t bo ATM v gi cc t bo n nt ATM LSR tip theo. - Nhn cc t bo ATM t ATM LSR cn k ,ti to cc gi t cc t bo ATM v chuyn tip gi c nhn hoc khng c nhn

2.4. Cc giao thc c bn ca MPLS.Kin trc MPLS khng bt buc mt phng thc bo hiu n no cho phn phi nhn .cc giao thc nh tuyn ang tn ti, nh giao thc cng bin (BGP) c ci tin mang thm thng tin nhn trong ni dung ca giao thc . giao thc dnh sn ti nguyn RSVP cng c m rng h tr chao i nhn . Nhm c trch k thut internet IETF cng xc nh mt giao thc mi c bit n nh giao thc phn phi nhn - LPD lm r hn v bo hiu v qun l khng gian nhn .S m rng ca giao thc LDP c s cng c xc nh h tr nh

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tuyn lin vng (explicit router) da trn cc yu cu v QoS v CoS .nhng m rng ny cng c p dng trong vic xc nh giao thc (CR - LDP) nh tuyn da trn rng buc. -

-

Cc giao thc h tr chao i nhn nh sau: LDP- ch ra cc ch IP vo trong cc bng. RSVP ,CR-LDP - s dng sho k thut lu lng v dnh trc ti nguyn. Protocol-Independent Multicast (PIM) - s dng ch ra nhn trng thi a hng Multicast. BGP cc nhn bin bn ngoi

2.4.1 Giao thc phn phi nhn LDP. Giao thc phn phi nhn c nhn nghin ku MPLS ca IETF xy dng v ban hnh c tn l RFC 3036, phin bn mi nht c cng b nm 2001. Giao thc phn phi nhn c s dng trong qu trnh gn nhn cho cc gi thng tin. Giao thc LDP l giao thc iu khin tch bit c cc LSR s dng chao i v iu phi qu trnh gn nhn FEC. giao thc ny l mt tp hp th tc chao i bn tin cho php cc LSR s dng gi tr nhn thuc FEC nht nh truyn cc gi tin . Mt kt ni TCP c thip lp gia cc LSR ng cp d m bo cc bn tin LDP c truyn theo dng th t. cc bn tin LDP c th xut hin t bt k mt LSR(iu khin ng chuyn mch nhn LSP c lp ) hay t LSR bin li ra (iu khin LSP theo lnh ) v chuyn t LSR pha trc ti LSR pha sau cn k. Vic chao i bn tin LDP c th c khi pht bi s xut hin ca, lung s liu c bit, bn tin lp d ch RSVP hay cp nht thng tin nh tuyn. Khi gp mt LSR chao i bn tin LDP cho mt FEC nht nh th mt ng chuyn mch LSP t u vo ti u ra c thit lp sau khi mi LSR ghp nhn u vo vi u ra tng ng trong LIB ca n . 2.4.1.1 Pht hin LSR ln cn : Th tc pht hin LSR ln cn ca LDP chy trn UDP v thc hin nh sau:

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Hnh16 : Th tc ph hin LSR ln cn 1. mt LSR nh k gi bn tin hello ti cc cng UDP bit trong tt c cc b nh tuyn trong tt c cc mng con ca nhm multicast LSR s bit c tt c cc LSR khc m n c th kt ni trc tip. 3. khi LSR nhn bit c a ch ca LSR khc bng c ch ny th n s thit lp kt ni UDP ti LSR .

2.tt c cc LSR tip nhn bn tin hello ny trn cng UDP. ti mi thi im no ,

4.khi , phin UDP c thit lp gia 2 LSR, phin LDP l phin 2 chiu, tc mi

LSR 2 u kt ni u c th yu cu v gi lin kt nhn. Trong trng hp cc LSR khng kt ni trc tip trong mt mng con th ngi ta s dng c ch b sung sau: LSR nh k gi bn tin hello n cng UDP bit ti a ch IP xc nh c khai bo khi lp cu hnh. u nhn bn tin ny c th tr li bng bn tin hello khc truyn chiu ngc li ti LSR gi v thit lp cc phin LDP c thc hin nh trn . Thng thng trng hp ny thng c p dng khi gi hai LSR c mt ng LSP cho iu khin lu lng v n yu cu phi gi cc gi c nhn qua ng LSP .

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2.4.1.2 Cc bn tin LDP: Cc bn tin LDP c nh ngha theo mt khun dng c lp vi mi trng. Ni dung ca mt vi bn tin c th kt hp vi cc gi d liu n gim thiu qu trnh x l ca CPU. 1 Tiu LDP (header LDP) Mi bn tin LDP cn c gi l dn v d liu giao thc (PDU) bt u vi mt tiu LDP, gm cc trng sau: - Phin bn (version): ch ra s phin bn ca giao thc, hin ti l phin bn s 1. - chiu di PDU : tng chiu di PDU trong cc octet, ngoi tr trng phin bn v chiu di . - LDP ID : y l trng nhn dng khun khng gian nhn ca vic gi LSR ca bn tin ny .4 octet u tin cha a ch IP gn vi LSR,n l trng nhn dng giao thc. 2 octet sau cng xc nh khng gian nhn trong phm vi LSR ny. 0 1-14 version LDP Identifier Hnh 17 Ttiu :LDP 2-M ho gi tr - chiu di - loi (type length value :TLV Encoding). LDP s dng s m ho TLV m ho cc thng tin c mang trong cc bn tin LDP. Trong nh hnh 18 ch ra n bao gm cc trung loi d liu. - Trng loi d liu - Trng chiu di - Trng gi tr 0 1 U F 2-14 type value Hnh 18 M ho gi tr -chiu di - loi 3- Khun dng bn tin LDP: Tt c cc bn tin LDP u c khun dng ging nhau, nh hnh 19 15 16 17-30 lenth 31 15 LDP Identifier 16-30 31 PDU lenth

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0 u

1-14 15 16-30 Message ID Message lenth Message ID Mandatory parameters Optional parameters

31

Hnh 19: Khun dng bn tin LDP - Bt U: bt ny l bt ch ra rng bn tin khng nhn bit c.nu U=1 th bn tin coi nh khong nhn bit c ti b thu v bn tin ny s b loi b. - Loi bn tin: xc nh lai bn tin - Chiu di bn tin : chiu di ca bn tin ID, cc tham s bt buc (mandatory) v cc tham s tu chn. - trng nhn dng bn tin : y l trng nhn dng duy nht n c th c s dng km vi cc bn tin thng bo v bn tin khc. - Cc tham s bt buc - Cc tham s tu chn Cc tham s bt buc v cc tam s tu chn s gii thch sau. v nguyn l mi th xut hin trong bn tin LDP u c th c m ho ging nh TLV. tuy nhin, tu tng trng hp m cc tham s ny c s dng trong gin m ho TLV hay khng ,v nhng ni khng tht s cn thit th s khng s dng v n lng ph khng gian. 4- Khun dng v cc chc nng ca TLV: - FEC :TLV ny mang cc FEC dng trao i gia cc LSR. MPLS v LDP ch s dng a ch cho FEC, khng dng cho cc cng v PID. FEC c th l mt a ch c nh, hoc mt a ch my trm y , n cng c th cha a ch cc mng khc, nh IPX nhng t khi l a ch IP.-

-

-

-

Address list : danh sch a ch TLV xut hin trong bn tin Address v Address withdraw Hin ti ch c a ch Ipv4 c nh ngha cho trng TLV ny Hop count : TLV ny xut hin trong cc bn tin dng thit lp cc LSP, n tnh ton s chng LSR dc theo mt LSP khi LSP c thit lp.n c th s dng d tm vng lp ( trong trng hp c li trong mng lm gi tin khng ti c ch v lu chuyn vng quanh trn mng ). PATH vector : trng TLV ny cng c s dng d tm vng lp vi vic tnh ton chng TLV trong cc bn tin Label request v Label mapping. N s dng cc bn tin Label request ghi li ng i ca cc LSR. Generic Label : trng TLV cha cc nhn cho vic s dng trn cc lin kt i vi cc gi tr nhn l c lp di nn tng cng ngh lin kt (cc dch v ti tin ) nh l cc lin kt PPP v Ethernet. ATM label: nu ATM c s dng mang thng tin th TLV ny s cha gi tr ATM VPI/VCI.

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Frame Relay Label: nu Frame Relay c s dng mang thng tin th TLV ny s cha gi tr DLCI Frame Relay. - Status: trng TLV ny dng cho mc ch chun on ,chng hn s thnh cng hay hng hc ca s kin.- Extended status : y l trng m rng ca status bng vic cung cp thm cc byte

m rng cho mc ch chun on .- Returned PDU : trng ny c th hot ng cng vi trng status TLV,LSR s

dng tham s ns gi phn PDU LDP tr li LSR gi n .gi tr ca TLV ny l tiu PDU v d liu km theo tiu ph hp trong bn tin thng bo.- Return Message : trng ny cng c th di km vi trng status TLV. LSR s dng

tham s ny gi mt phn bn tin LDP ti LSR gi bn tin .- Common Hello Parameters : cc LSRs ln cn c th gi cc bn tin hello mt cch

nh k ti cc LSR khc m bo rng chng ang kt ni v ang trong trng thi hot ng. TLV cha ng cc tham s chung qun l hot ng, v d nh cc bn tin hello c gi v c nhn nh th no, v cc bn tin ny c gi i bao nhiu v nhn li bao nhiu trong mt khong thi gian c chn. - IPv6/IPv4 transport address : nu cc a ch IPv6 c s dng th TLV ny s cho php mt a ch IPv6 c s dng khi m mt TCP cho mt phin LSP. nu n khng c s dng, a ch ngun trong tiu IP c s dng. tng ny cng tng t i vi cc a ch IPv4. - Common session Parameters: TLV ny cng cha tham s tho hip c gi i bi LSR trong mi phin LDP. Cc tham s ny bao gm : + Keep Alive Time :ch ra s giy cc i tri qua nhn thnh cng cc PDU t cc LDP ng cp trong mt phin kt ni TCP.b nh thi ny oc thit lp khi mt PDU n. + Label Advertisement Dicrips line ( lut thng bo bn tin ): lung xung( Downstream) l bt buc theo yu cu. + Loop Detection :ch ra rng s d tm vng lp l cho php (enable) hay khng. PATH vector limit : ch ra di ng cc i cho php. + Maximun PDU length : ch ra di cc i ca mt PDU LDP - ATM session Parameters: TLV ny xc nh kh nng qun l ATM ca mt ATMLSR.tu chn bao gm: +Vic hp nht khng c h tr + Hp nht VP c h tr + Hp nht VC c h tr + C hp nht VP v VC c h tr trng ny cung cp thng tin v kh nng nh hng VC, c ngha vic s dng cc VCI theo mt hng hay c hai hng trong mt lin kt, n cng cha ng trng xc nh mt di cc nhn ATM c h tr bi vic gi LSR.

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-

Frame Relay session Parameters: trng TLV ny cng cha ng cc tham s nh ca ATM session parameters, nhng y TLV l DLCIs. Label Request message ID: gi tr ca tham s ny l trng nhn dng bn tin ca mt bn tin yu cu nhn tng ng. Private : trng TLV v cc bn tin ring ca nh sn xut c s dng thng bo thng tin ring ca nh sn xut gia cc LSR.

-

5 - Cc bn tin trong LDP Bao gm 11 bn tin LDP: - Bn tin Notification - Bn tin hello - Bn tin Initialization - Bn tin KeepAlive - Bn tin Address - Bn tin Addess withdraw - Bn tin Label Mapping - Bn tin Label Request - Bn tin Label Abort Request - Bn tin Label withdraw - Bn tin Label release 2.4.1.3 Cc ch phn phi nhn Chng ta s bit mt s ch hot ng ca phn phi nhn trong mt vi phn mc pha sau nh : khng yu cu pha trc, iu khin LSP theo lnh hay t lp, duy tr tin tin hay lu ch. cc ch ny c tho thun bi LSR trong qu trnh khi to phin LDP. Khi LSR hot ng ch duy tr lu gi, n s ch gi nhng gi tr nhn FEC m n cn ti thi im hin ti.cc chuyn i khc c gii phng . cn trong ch duy tr tin tin, LSR gi tt c cc chuyn i m n c thng bo ngay c nhng chuyn i khng c s dng ti thi im hin ti.hot ng ca ch ny nh sau: + LSR 1 gi lin kt nhn vo mt FEC n mt LSR khc k tip(LSR2) cho FEC . + LSR 2 nhn thy LSR 1 hin ti khng phi l nt tip theo i vi FEC , n khng th s dng FEC ny cho mc ch chuyn tip ti thi im hin ti nhng n vn lu gi lin kt ny li.

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+ Ti thi im no sau ny c s xut hin thay i nh tuyn v LSR 1 tr thnh nt tip theo ca LSR2 i vi FEC th LSR2 s cp nht thng tin trong bng nh tuyn tng ng v c th chuyn tip cc gi c nhn n LSR1 trn tuyn mi.vic ny c thc hin mt cch t ng m khng cn ti bo hiu LDP hay qu trnh phn b nhn mi. u im ln nht ca ch duy tr tin tin l kh nng phn ng nhanh hn khi c s thay i tuyn. Nhc im ln nht l lng ph b nh v nhn. iu ny c bit quan trng v c nh hng rt ln i vi nhng thit b lu tr bng nh tuyn trong phn cng nh ATM LSR.thng thng ch duy tr lu ch oc s dng cho cc ATM - LSR. V d minh ho vic s dng bn tin Label Request v Label Mapping trong ch cng b nhn theo yu cu v iu khin LSP c lp. Trnh t thi gian trao i cc bn tin LDP gia cc i tc (peer) thit lp mt LSP t router li vo R1 qua R2 ri n router li ra R3 cho mt FEC c frefix a.b/16. R1 khi to tin trnh bng cch yu cu mt nhn cho FEC a.b/16 t hop k ca n l R2. v s dng iu khin c lp nn R2 tr ngay mt nh x nhn v cho R1 trc khi R2 nhn c nh x nhn t pha downstream l R3. c R2 v R3 p ng bng bn tin Label Mapping, kt qu l trong FIB ca R1 v LFIB ca R2, R3 c cc entry gn nhn hnh thnh nn ng chuyn mch nhn LSP.

Hnh 20: V d LDP ch iu khin c lp theo yu cu .

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2.4.2 Giao thc phn phi nhn da trn rng buc CR-LDP. Giao thc phn phi nhn nh tuyn da trn rng buc CR-LDP(constraintbased routing-LDP) c s dng iu khin cng bc LDP. giao thc ny l phn m rng ca LDP cho qu trnh nh tuyn cng bc ca LSP. cng ging nh LDP, n s dng cc phin TCP gia cc LSR ng cp gi cc bn ti phn phi nhn . hiu r hn v nh tuyn cng bc da trn rng buc, ta xt vic nh tuyn i vi mt mng IP truyn thng. mt mng c th c xem l mt tp hp cc h thng t tr AS, trong vic nh tuyn mi AS tun theo giao thc nh tuyn trong min (intradomain). vic nh tuyn gia cc AS tun theo giao thc nh tuyn lin min(interdomain).cc giao thc nh tuyn trong min c th l RIP, OSPF, IS IS cn giao thc nh tuyn lin min ang c s dng l BGP .trong phm vi mt h thng t tr, c ch xc nh tuyn trong cc giao thc nh tuyn trong min thng tun theo thut ton ti u. trong giao thc nh tuyn RIP th c s ti u v nt mng trn ng m gi tin c chuyn t ngun ti ch. c nhiu ng i t ngun ti ch nhng mi ng i li c s nt, di ngn , bng thng kh dng khc nhau, do vy vi RIP th thut ton bellman-ford c s dng xc nh sao cho ng i qua t nt nht. cn trong trng hp OSPF v IS IS th thut ton l tm ng ngn nht.nh qun tr mng ng vi giao thc OSPF(hoc IS-IS)s n nh cho mi knh trong mng mt gi tr tng ng vi di ca knh OSPF(hoc IS-IS)s s dng thut ton tm ng ngn nht Dijkstra la chn ng ngn nht trong s cc ng c th ni ti ch, vi nh ngha di ca ng l tng di cc knh trn ng . i vi nh tuyn cng bc, ta c th xem mt mng nh l mt tp hp cc nt mng v mt tp hp kt ni gia cc nt mng . mi knh s c cc c im ring . kt ni gia 2 nt bt k t phi tho mn mt s yu cu(cc rng buc),v coi cc rng buc ny nh l c im cua cc knh.ch c nt u tin trong cp ng gp vai tr khi to ng kt ni mi bit c im ny.nhin v ca nh tuyn cng bc l tnh ton xc nh ng kt ni t nt ny ti nt kia sao cho tho mn mt s iu kin rng buc c th l mt hoc nhiu trong cc tiu ch v d :s nt t nht, ng i ngn nht, bng thng rng nht tuy nhin, vic ti u ho cc tiu ch khc nhau khng th c p ng mt cch ng thi.mt thut ton ti u theo mt tiu ch ch khng th mt lc p ng nhiu tiu ch, v 2 yu cu c th xung t nhau, chng hn ng i ngn nht v s nt t nht cha hn c bng tn ln nht v ng i ngn nht v s nt t nht s l la chn s mt cho nhiu kt ni cc knh nh vy,nn bng tn kh dng cho cc lin kt nh trn c rng s khng th bng bng tn knh c t kt ni i qua.do vy ,thut ton nh tuyn rng buc cng khng th p ng ti u tt c cc tiu ch .n thc hin ti u theo mt tiu ch no ng thi tho mn mt s iu kin rng buc c t ra.khi xc nh c mt ng kt ni th nh tuyn cng bc s thc hin thit lp, duy tr v chuyn trng thi kt ni dc theo cc knh ph hp nht trn ng .

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Ngoi cc iu kin rng buc c t ra i vi knh , cn c cc iu kin c t ra i vi vic qun tr. chng hn nh qun tr mun ngn khng cho mt loi lu lng no i qua mt s knh nht nh trong mng c xc nh bi mt s c im no . Do , thut ton nh tuyn m nh qun tr phi thc hin l tm ra cc knh xc nh m n cho qua lu lng trn, ng thi tho mn mt s iu kin rng buc khc na. nh tuyn cng bc cn c th kt hp c hai u kin rng buc l qun l c im knh mt cch ng thi ch khng phi ch tng iu kin ring r .v d tuyn cng bc phi tm ra mt ng va phi c rng bng tn nht nh ,va loi tr mt s knh c c im nht nh . im khc bit gia nh tuyn IP truyn thng v nh tuyn cng bc l : thut ton nh tuyn IP truyn thng ch tm ra mt ng ti u ng vi duy nht mt tiu ch c t ra , trong khi thut ton nh tuyn cng bc va tm ra mt tuyn ti u theo mt tiu ch no ng thi tho mn mt s iu kin rng buc nht nh . chnh v iu ny m thut ton nh tuyn cng bc trong mng MPLS c th p ng yu cu dch v v cung cp cc kt ni tin cy cho ngi dng theo yu cu trong khi trong khi mng s dng cc thut ton tm ng khc khng th c c, k c giao thc nh tuyn IP. lm c iu ny c rt nhiu gii php .trong gii php chnh l thut ton nh tuyn cng bc yu cu ng i phi c tnh ton v xc nh t pha ngun. cc ngun khc nhau c cc rng buc khc nhau i vi mt ng trn cng mt ch cc iu kin rng buc ng vi b nh tuyn ca mt ngun c th ch c bit n bi b nh tuyn m thi, khng mt b nh tuyn no khc trn mng c bit v iu kin ny, ngc li trong b nh tuyn IP th ng i c tnh ton v xc nh bi tt c cc b nh tuyn phn tn trong mng. Mt l do khc l kh nng nh tuyn hin(Explicit Routing)(hoc ngun ) v cc ngun khc nhau c h tnh ton xc nh cc ng khc nhau ti cng mt ch. V vy ch da vo thng tin v ch l khng xc nh ng truyn cc gi tin. mt l do na l i vi phng php nh tuyn cng bc th vic tnh ton v xc nh ng phi tnh n cc thng tin v c im tng ng ca tng knh trong mng. i vi phng php IP n gin khng h tr kh nng ny. V d cc giao thc nh tuyn truyn thng da vo trng thi knh (nh OSPF, IS-IS) ch truyn duy nht thng tin bn ri ca tng knh v di ca tng knh, cc giao thc nh tuyn vector khong cch (nh RIP)th ch truyn i cc thng tin a ch nt tip theo v khong cch.

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2.4.3. giao thc t trc ngun ti nguyn RSVP (Resource reservation protocol) RSVP l giao thc bo hiu ng vai tr quan trng trong mng MPLS, c s dng t trc ti nguyn cho mt phin truyn trong mng internet. n cho php cc ng dng thng bo v yu cu QoS vi mng v mng s p ng bng thng bo thnh cng hay tht bi. RSVP c dng cung cp kh nng vn hnh bo v bng vic t trc ngun ti nguyn cn thit ti mi my tham gia vic h tr ngun lu lng (v d nh m thanh hoc hnh nh ). i vi giao thc IP, l giao thc khng kt ni n khng h tr vic thit lp cc ng cho lung lu lng, trong khi RSVP c thit k thit lp cc ng truyn cng nh bo v gii thng trn cc ng truyn. RSVP yu cu cc my nhn lu lng v yu cu cht lng dch v QoS cho lung d liu. cc ng dng ti my trm nhn phi quyt nh cc thuc tnh QoS s c truyn ti RSVP. sau khi phn tch cc yu cu ny, RSVP c s dng gi cc bn tin ti tt c cc nt cn truyn d liu . RSVP thao tc vi c th tc n hng v a hng, vic lin mng thi im hin ti l giao thc a hng. RSVP phi mang cc thng tin sau :-

thng tin phn loi, nh n m cc lung lu lng vi yu cu QoS c th c th c nhn bit trong mng. thng tin ny bao gm a ch IP pha ngi gi v ngi nhn, s cng UDP.

ch tiu k thut ca lung lu lng v cc yu cu QoS theo khun dng Tspec v Rspec bao gm cc dch v yu cu . RSVP phi mang thng tin trn t my ch ti tt c cc tng i chuyn mch v cc b nh tuyn dc theo ng truyn t b pht ti b thu . v vy tt c cc thnh phn mng phi tham gia vo vic m bo cc yu cu QoS ca ng dng-

RSVP s dng bn tin chao i ti nguyn t trc qua mng cho lung IP.RSVP l giao thc ring mc IP.n s dng cc gi d liu IP hoc UDP phn bin ca mng thng tin gia cc LSR ng cp .n khng i hi duy tr phin TCP, nhng sau phin ny n phi x l mt mt cc bn tin iu khin. RSVP mang cc loi thng tin trong hai loi bn tin c bn l PATH v RESV xc nh ngun v cc yu cu QoS cho lung. cc yu cu ny ch ra dch v c bo v v d tc cho lung d liu , kch thc cmcc bn tin PATH truyn t b pht ti mt(h tr n hng )hoc nhiu (h tr a hng) b thu cha Tspec v cc thng tin v phn loi cho b pht cung cp.

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Khi b thu nhn c bn tin PATH, n c th gi bn tin RESV tr li cho b pht, bn tin RESV dng xc nhn phin c cha thng tin v s cng dnh ring v Rspec xc nhn mc QoS m b thu yu cu . n cng bao gm mt s thng tin xem xt nhng b pht no c php s dng ti nguyn ang c cp pht. Khi cng dnh ring c thit lp, cc b nh tuyn nm gia b pht v b thu s xc nh cc gi tin thuc cng dnh ring no nh kim tra 5 trng trong phn mo u IP v giao thc truyn ti , l: a ch ngun , s cng ngun , s giao thc (l UDP hay TCP ), a ch ch, s cng ch. tp hp cc gi tin c nhn dng theo cch ny c gi l lung dnh ring . cc thng ti trong lung dnh ring c khng ch m bo khng pht sinh lu lng vt qu so vi thng bo Tspec v c xp vo hm i ph hp theo yu cu v QoS. Mt c im na cn phi nhc n i vi giao thc ny ,RSVP l giao tc trng thi mm. n khc vi cc loi giao thc khc l trng thi s t ng ht hiu lc sau mt thi gian tr trng hp n c ln ti theo nh k , tc l RSVP s lin tc gi cc bn tin PATH v RESV l ti cc cng dnh ring. nu chun khng c gi i trong mt khong thi gian no th cng rnh ring t ng b hu b MPLS h tr RSVP RSVP c s dng trong mng MPLS h tr cht lng dch v QoS v iu khin lu lng .MPLS s dng RSVP cho php cc LSR da vo vic phn loi gi tin theo nhn ch khng phai theo mo u IP nhn bit cc gi tin thuc cc lung ca cng dnh ring .v vy ,cn phi c s kt hp phn phi gia cc lung v cc nhn cho cc lung v cng dnh ring RSVP .ta c th xem mt tp hp cc gi tin to bi cng dnh ring RSVP nh l mot trng hp ring ca FEC. Chng ta nh ngha mt i tng RSVP mi l i tng LABEL c mang trong bn tin RSVP RESV .ki mt LSR mun gi bn tin RESV cho mt lung RSVP mi, LSR cp pht mt nhn t trong tp nhn ri, ti mt li vo trong LFIB ca n vi nhn li vo c t cho nhn cp pht V gi bn tin RESV c cha nhn ny . Khi nhn bn tin RESV cha i tng LABEL, mt LSR thit lp LFIB ca n vi nhn ny l nhn li ra . sau n cp pht mt nhn s dng nh l nhn li vo v chn n vo bn tin RESV trc khi n gi i. Khi cc bn tin RESV truyn n LSR ngc , LSP thit lp dc theo tuyn ng . khi cc nhn c cung cp trong cc bn tin RESV , mi LSR c th r dng kt hp cc ti nguyn QoS ph hp vi LSP. vic thit lp cho mt lung dnh ring RSVP l ch c b nh tuyn u tin trong LSP lin quan ti vic xem xt cc gi tin thuc lung dnh ring no . iu ny cho php RSVP c p dng trong mi trng MPLS theo cch m n khng th thc hin c trong mng IP truyn thng . theo quy c th cc cng dnh ring RSVPch c th to cho nhng lung ng dng ring l ,

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tc ln nhng lung ng dng c xc nh nh 5 trng mo u nh cp trn ,tuy nhin cung c th t cu hnh ca b nh tuyn chn cc gi da trn mt s tiu chun ,v d b nh tuyn c th xem xt cc tin t ng vi cng mt ch v t chng vo LSP. v vy thay v c mt LSP cho mi lung ng dng ring, mt LSP c th cung cp QoS cho nhiu lung lu lng . do vy c tnh ny c th p dng cho kh nng cung cp ng ng vi bng thng m bo yu cu cho mt ng thu bao thay v phi s dng nhiu ng thu bao ring c c cng gii thng nh trn. iu ny l c ch cho cng ty ln mun c nhiu kt ni vi cng ty khc m ch s dng mt ng thu bao nhm gim bt s phc tp trong vic qun l cng nh iu khin lu lng , y l mt lu lng ln cn phi gi dc theo cc LSP vi bng thng ti lu lng. h tr mt s cch s dng tng cng ca RSVP, MPLS nh ngha mt i tng RSVP mi c th mang trong bn tin PATH l i tng Label Request . bn tin ny c cp trong phn loi bn tin trong LDP. 2.4.4. giao thc MPLS BGP MPLS m rng chc nng cho BGP mang cc nhn trong giao thc cng bin BGP, MPLS-BGP cho php b nh tuyn chy BGP phn phi nhn ti cc b nh tuyn bin khc mt cch trc tip thng qua bn tin cp nht BGP. tip cn ny m bo cho qu trnh phn phi nhn v cc thng tin nh tuyn n nh v gim bt tiu bn tin iu khin x l .

2.5 Hot ng ca MPLS2.5.1 Cc hot ng ca MPLS gi tin truyn qua mng MPLS phi thc hin cc bc sau: 1.To v phn phi nhn 2.To bng cho mi b nh tuyn 3. To ng chuyn mch nhn 4.Gn nhn da trn tra cu bng 5. Truyn gi tin. Ngun gi cc d liu ca n ti ch .trong mn MPLS, khng phi tt c cc lu lng ngun cn thit truyn qua cng mt ng. da trn cc c tnh lu lng, cc LSP khc nhau c th to cho cc gi tin vi cc yu cu CoS khc nhau.

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHNPhn phi nhnLER2

LSR 2

LER1

LSR 1 LSR 3

LER4

Ngun Yu cu nhn

LER3

ch Lung d liu

Hnh 21 -To LSP v chuyn tip gi tin thng qua min MPLS Trong hnh 21, LER1 l li vo v LER4 l li ra. bng 2 m t cc bc hot ng ca MPLS khi gi d liu truyn qua min MPLS Bng 2 : cc hot ng MPLS hot ng Miu t MPLS to v - trc khi d liu bt u truyn , cc b nh tuyn quyt nh to phn phi ra lin kt nhn ti cc FEC c th v to bng. nhn - Trong LDP, cc b nh tuyn lung xung bt u phn phi nhn v gn nhn/FEC - thm vo cc c tnh lin quan n lu lng v dung lng MPLS c iu chnh thng qua LDP. - Giao thc bo hiu nn dng giao thc vn chuyn c th t v m bo tin cy. LDP dng TCP To bng - khi chp nhn cc lin kt nhn mi LSR to ra mc trong bng c s d liu (LIB). - ni dung ca bng s xc nh mi lin h gia nhn v FEC, nh x gia cng vo v bng nhn vo n cng ra v bng nhn ra. - Cc mc c cp nht bt k khi vic gn nhn c iu chnh li. to ng Nh hnh 21 , cc LSP c to ra theo chiu ngc vi cc mc chuyn trong cc LIB mch nhn Gn - b nh tuyn u tin (LER 1 trong hnh 21 )s dng bng LIB nhn /bng tm ng tip theo yu cu nhn cho FEC c th. tra cu - Cc b nh tuyn tip theo s dng bng tm ng i tip

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chuyn tip gi tin

theo. - Khi gi tin n LSR li ra (LER4),nhn c loi b v gi c truyn ti ch. Hnh 21 m t ng i ca gi tin khi n c truyn t ngun ti ch hay t LER1,LSR li vo n LER 4 , LSR li ra . - ln u tin ca yu cu nhn, cc gi tin khng c nhn ti LER1 trong mng IP ,n s tm a ch di nht tm cc bc tip theo. LSR1 l bc tip theo ca LER1. - LER1 s khi pht cc yu cu nhn ti LSR1. yu cu ny s c pht trn ton mng nh hnh 21. LDP s xc nh ng dn o m bo QoS, CoS. - mi b nh tuyn trung gian LSR2 v LSR3 s nhn gi tin gn nhn thay i nhn v truyn i. - Gi tin truyn ti LER4 , loi b nhn v gi ra khi min hot ng ca MPLS v phn pht ti ch. ng truyn gi tin c m t hnh 21.

2.5.2 cc ch hot ng ca MPLS C hai ch hot ng i vi MPLS : - Ch khung (Frame mode) - Ch t bo (cell mode) 2.5.2.1 ch hot ng khung . Ch ny xut hin khi s dng MPLS trong mi trng thit b nh tuyn thun iu khin cc gi IP im - im. Cc gi dn nhn c chuyn tip trn c s khung lp 2. C ch hot ng ca mng MPLS trong ch ny c m t trong hnh 22 di y.

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHNBc 2 :kim tra gi lp 3,gn nhn chuyn gi IP n LSR li 1 Bc 3:kim tra nhn,chuyn i nhn, chuyn gi IP n LSR li 3

Bc 1:nhn gi IP ti LSR bin

Bc 4:kim tra nhn chuyn i nhn chuyn gi IP n LSR bin 4

Bc 5:kim tra nhn, xo nhn, chuyn gi IP ti router ngoi tip theo

IP ch 192.1.1.3 LSR bin1 PoP

Gi IP

30

IP 192.1.1.3 LSR bin4 PoP Gi IP Gi IP 28 LSR li 3 37

LSR bin2 PoP

LSR li1

LSR li 2 LSR bin3 PoP LSR bin5 PoP

Hnh 22 - Mng MPLS trong ch hot ng khung Cc hot ng trong mng s liu : Qu trnh chuyn tip gi IP qua mng MPLS c thc hin qua mt s cc bc c bn sau y :- LSR bin li vo nhn gi IP, phn loi gi vo nhm chuyn tip tng ng FEC

v gn nhn cho gi vi ngn xp nhn tng ng vi FEC xc nh. Trong trng hp nh tuyn mt a ch ch, FEC s tng ng vi mng con ch v vic phn li gi s n gin l vic so snh bng nh tuyn lp 3 truyn thng. LSR li nhn gi tin c nhn v s dng bng chuyn tip nhn thay i nhn li vo ca gi n vi nhn li ra tng ng cng vi FEC( trong trng hp ny l mng con IP). Khi LSR bin li ra ca vng FEC nhn c gi c nhn, n loi b nhn v thc hin chuyn tip gi IP theo bng nh tuyn lp 3 truyn thng.

-

Mo u vo MPLS Nhn MPLS c chn trc s liu cn gn nhn ch hot ng khung . tc nhn MPLS c chn vo gia mo u lp 2 v ni dung thng tin lp 3 ca khung lp 2, v tr ca nhn MPLS trong khung lp 2 c th hin nh hnh 23 :

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Nguyn Ngc Thnh Trng i Hc Cng Ngh_HQGHN Gi IP c nhn trong khung lp 2 Khung lp 2 S liu lp 3 Nhn MPLS Mo u lp 2

Hnh 23 - V tr nhn MPLS trong khung lp 2 Do nhn MPLS c chn vo v tr nh vy nn b nh tuyn gi thng tin phi c phng tin g thng bo cho b nh tuyn nhn bit rng gi ang c gi i khng phi l gi IP thun m l gi c nhn (gi IP). n gin chc nng ny , mt s dng giao thc mi c nh ngha trong lp 2 nh sau : - trong mi trng LAN cc gi c nhn truyn ti gi lp 3 n hng hay a hng s dng gi tr 8847H v 8848H cho mng Ethernet.cc gi tr ny s dng trc tip trn phng tin Ethernet(bao gm c Fast Ethernet v Gigabit Ethernet) - trn knh im-im s dng giao thc ppp, s dng giao thc mi c gi l MPLSCP (giao thc iu khin MPLS). Cc gi MPLS c nh du bi gi tr 8281H trong trng giao thc PPP. - Cc gi MPLS truyn qua dch chuyn khung DLCI gia mt cp thit b nh tuyn c nh du bi nhn dng giao thc SNAP ca chun dch khung (NLPIN), tip theo mo u SNAP vi gi tr 8847H cho Ethernet nh trong mng LAN. Chuyn mch nhn trong ch khung Ta xem xt qu trnh chuyn i nhn ( nh hnh 22 ) trong mng MPLS sau khi nhn c mt gi IP - sau khi nhn khung PPP lp2 t b nh tuyn bin s 1,LSR lp tc nhn dng gi nhn c l gi c nhn da trn gi tr trng giao thc PPP v thc hin kim tra nhn trong c s d liu chuyn tip nhn .kt qu nhn vo l 30 c thay bng nhn ra 28 tng ng vi vic gi LSR li 3 - ti LSR li 3 ,nhn c kin tra, nhn s 28 c thay bng nhn s 37 v cng ra c xc nh . gi tin c chuen tip ti LSR bin s 4 - ti LSR bin s 4, nhn 37 b loi b v vic kim tra a ch lp 3 c thc hin, gi c chuyn tip n b nh tuyn tip theo ngoi mng MPLS. Qu trnh chuyn i nhn thc hin trong cc LSR li da trn bng nh tuyn nhn .bng nh tuen ny phi c cp nht y m bo mi LSR trong mng MPLS c y thng tin v tt c cc hng chuyn tip. qu trnh ny sy ra trc khi thng tin c tryn trong mng v c gi l qu trnh lin kt nhn(Label binding). Qu trnh lin kt v lan truyn nhn. Khi xut hin mt LSR mi trong mng MPLS hay bt u khi to mng MPLS, cc thnh vin LSR trong mng MPLS phi c lin lc vi nhau trong qu trnh khai bo thng qua bn tin hello. Sau khi bn tin ny c gi, mt phin giao dch gia hai LSR c thc hin . th tc chao i l LDP.

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Sau khi c s d liu nhn LIB c to ra trong LSR, nhn c gn cho mi FEC m LSR nhn bit c . i vi nh tuyn n hng , FEC tng ng vi tin t bng nh tuyn IP . vy nhn c gn trong mi tin t trong bng nh tuyn IP v bng chuyn i cha trong LIB. bng chuyn i nh tuyn ny c cp nht lin tc khi xut hin nhng tuyn trong min mi. Do LSR gn nhn cho mi tin t IP trong bng nh tuyn ca chng ngay sau khi tin t xut hin trong bng nh tuyn v nhn l phng tin c LSR khc s dng khi gi gi tin c nhn ny c gi l gn nhn iu khin c lp vi qu trnh phn phi ngc khng yu cu. vic qung b cc nhn c qung b ngay n tt c cc b nh tuyn thng qua phin LDP. 2.5.2.2 Ch hot ng t bo MPLS trin khai MPLS qua ATM cn phi gii quyt mt s tr ngi sau : hin ti khng tn ti mt c ch no cho vic chao i trc tip cc gi IP gia nt MPLS ln cn qua giao din ATM.tt c cc s liu chao i qua giao din ATM phi thc hin qua knh o ATM . cc tng i ATM khng th thc hin vic kin tra nhn hay a ch lp 3 . kh nng duy nht ca ATM l chuyn i VC u vo sang VC u ra ca giao din ra. thc hin MPLS qua ATM th cn mt s c ch sau : cc gi IP trong mng iu khin khng th chao i trc tip qua giao din ATM.mt knh o VC phi c thit lp gia 2 nt ln cn chao i gi thng tin iu khin. nhn trn cng trong ngn xp nhn phi c s dng cho cc gi tr VPI/VCI cc th tc gn v phn phi nhn phi c sa i m bo cc tng i ATM khng phi kim tra a ch lp3.

-

-

Cc khi nim : a. Giao din ATM iu khin chuyn mch nhn (LC-ATM)l giao din ATM trong tng i hoc trong b nh tuyn m gi tr VPI/VCI c gn bng th tc iu khin MPLS(LDP). b. ATM-LSR l tng i ATM s dng giao thc MPLS trong mng iu khin v thc hin chuyn tip MPLS gia cc giao din LC- ATM trong mng s liu bng chuyn mch t bo ATM truyn thng. c. LSR theo khung l LSR chuyn tip ton b cc khung gia cc giao din ca n. nh tuyn truyn thng l LSR kiu ny.

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d. Min ATM-LSR l tp hp cc ATM-LSR kt ni vi nhau qua cc giao din LCATM e. ATM-LSR bin l LSR theo khung c t nht mt giao din LC-ATM. Kt ni trong mng iu khin qua giao din LC-ATM : Cu trc MPLS i hi lin kt thun IP gia cc mng iu khin ca cc LSR ln cn chao i lin kt nhn cng nh cc gi iu khin khc. ch hot ng MPLS khung yu cu ny c p ng mt cch n gin bi thit b nh tuyn c th gi, nhn cc gi IP v cc gi c nhn qua bt k giao din ch khung no d l LAN hay WAN . cn tng i ATM khng c kh nng . cung cp kt ni thun IP gia cc ATM-LSR c hai cch sau : - Thng qua kt ni ngoi bng nh kt ni Ethernet gia cc tng i. - Thng qua knh o qun l trong bng tng t cch m giao thc ATM Forum thc hin nh sau : Knh o iu khin MPLS VC thng thng thc hin gi tr VPI/VCI l 0/32 v bt buc phi thc hin phng php ng gi LLC/SNAP cho cc gi IP theo tiu chun RFC 1483 .khi trin khai MPLS trong tng i ATM(ATM-LSR) phn iu khin trung tm ca tng i ATM phi h tr thm bo hiu MPLS v giao thc thit lp knh VC. Chuyn tip cc gi c nhn qua min ATM-LSR Vic chuyn tip cc gi c nhn qua min ATM-LSR c thc hin trc tip qua cc bc sau : - ATM-LSR bin li vo nhn gi c nhn hoc khng c nhn, thc hin vic kim tra c s d liu chuyn tip FIB hay c s d liu chuyn tip nhn LFIB v tm kim tra gi tr VPI/VCI u ra s dng nh nhn li ra.cc gi c nhn c phn chia thnh cc t bo ATM v gi ti ATM-LSR tip theo. gi tr VPI/VCI c gn vo mo u ca tng t bo . Cc nt ATM-LSR chuyn mch t bo theo gi tr VPI/VCI trong mo u ca t bo theo c ch chuyn mch ATM truyn thng. C ch phn b v phn phi nhn phi m bo vic chuyn i gi tr VPI/VCI trong min v ngoi min l chnh xc ATM-LSR ti li ra ti to li cc gi c nhn t cc t bo, thc hin vic kin tra nhn v chuyn tip t bo n LSR tip theo. vic kim tra nhn da vo gi tr VPI/VCI ca t bo n m khng da vo nhn trn nh ca ngn xp trong mo u nhn MPLS do ATM-LSR gia cc bin ca min ATM-LSR ch thay i gi tr VPI/VCI m khng thay i nhn bn trong cc t bo ATM. Trong cn ch rng nhn nh ca ngn xp c lp gi tr bng 0 bi ATM-LSR bin li vo trc khi gi c nhn c phn chia thnh cc t bo.

-

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Phn b v phn phi nhn trong min ATM-LSRBc 1gi yu cu gi tr nhn X ti nt k cnY uc

Bc 3: ATM-LSR li 3 gi yu cu nhn X ti ATMLSR li 4 Buc 2 ATM-LSR li 1 gi yu cu gi tr nhn X ATM -LSR li 3X tr gi u c

LSR bin 1 PoP

u gi t

r X

u Y

Yu cu gi tr X Bc 4: LSR bin 4 gn gi tr VCI/VPI v gi liTM-LSR li 3

ATM-LSR li 1 Bc 6 : gi tr VPI/ VCI ni vng c gn bi ATM-LSR li 1 cho LSR bin 1

X=1/241

ATM-LSR li 3

Bc 5: LSR li 3 gn gi tr VPI/ VCI ni vng chuyn i VPI /VCI vo sang VPI /VCI ra v gi gi tr VPI/VCI mi n ATM-LSR li 1

ATM-LSR li 2

Hnh 24 phn b nhn trong mng ATM-LSR Vic phn b v phn phi nhn trong ch hot ng ny c th s dng c ch ging nh trong ch hot ng khung . tuy nhin nu trin khai nh vy t s dn ti cc hn ch bi mi nhn c gn qua giao din LC-ATM tng ng vi mt ATM VC. V s lng VC qua giao din ATM l hn ch nn cn gii hn s lng VC phn b qua LC-ATM mc thp nht. m bo c iu ny, cc LSR pha sau s nhn trch nhim yu cu phn b v phn phi nhn qua giao din LC-ATM. LSR pha sau cn nhn gi gi n nt tip theo phi yu cu nhn t LSR pha trc n. Thng thng cc nhn c yu cu da trn ni dung bng nh tuyn m khng da vo lung d liu, iu i hi nhn cho mi ch trong phm vi ca nt k tip qua giao din LC-ATM. LSR pha trc c th n gin phn b nhn v tr li yu cu cho LSR pha sau vi bn tin tr li tng ng. Trong mt s trng hp , LSR pha trc c th phi c kh nng kim tra a ch lp 3 (nu khng cn nhn pha trc yu cu cho ch). i vi tng i ATM , yu cu nh vy s khng c tr li bi ch khi no n c nhn c phn phi cho ch pha trc th n mi tr li yu cu. nu ATM-LSR khng c nhn phi trc p ng yu cu ca LSR pha sau th n s yu cu nhn t LSR pha trc n v ch tr li khi n nhn c nhn t LSR pha trc n. Hp nht VC Hp nht VC tc l gn VC cho cc gi n cng ch . y l mt vn quan trng cn gii quyt i vi tng i ATM trong mng MPLS.

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ti u ho qu trnh dn nhn ATM-LSR, c th s dng li nhn cho cc gi cng ch. khi cc gi xut pht t cc ngun khc nhau (cc LSR khc nhau ), nu s dng chung mt gi tr VC cho ch th s khng c kh nng phn bit gi no thuc lung no v LSR pha trc khng c kh nng ti to dng cc gi t t bo. trnh trng hp ny, ATM-LSR phi yu cu LSR pha trc n phn b nhn mi mi khi LSR pha sau n i hi nhn n bt c ch no ngay c trong trng hp n c nhn phn b cho ch . Qu trnh gi k tip cc t bo ra knh VC nh vy c gi l hp nht knh o VC. chc nng hp nht knh o VC ny gim ti a s lng nhn phn b trong min ATM-LSR. 2.5.2.3 Hot ng ca MPLS khung trong mng ATM-LSR Do vic chuyn i cng ngh tc ng n rt nhiu mt trong mng dang khai thc t nhng vn ghp ni mng, cng nh quan nin v cch thc vn hnh khai thc. Qu trnh chuyn i sang mng MPLS c th thc hin theo nhiu cch : hoc l thc hin mt s giai don nht nh , hoc trin khai ng lot t u. MPLS c hai ch hot ng c bn l ch hot ng khung v ch hot ng t bo nh ni trn . i vi h tng c s nh FR hoc ATM-PVC th rt kh trin khai ch hot ng t bo ca MPLS , thng thng th ch khung s c s dng trong cc mi trng nh vy thc hin kt ni MPLS xuyn sut qua mng. Trong mt s iu kin nht nh nh trong giai on chuyn dch sang mng hon ton IP+ATM(MPLS) hoc chuyn mch ATM chuyn tip khng h tr MPLS th cn thit phi phi s dng ch hot ng khung qua mng ATM-PVC.cu hnh ny ph hp, tuy nhin n cng gp kh khn khi s dng IP qua ATM trong ch chuyn dch ( do s lng ln cc VC )

C/M ATM

VPI 0/36 LSR bin 1

Knh ATM-PVC

VPI N0/37 LSR bin 2

C/M ATM

C/M ATM

Hnh 25 - Kt ni MPLS qua mng ATM-PVC kt ni gia hai LSR c thit lp bng knh PVC xuyn sut . cc phin LDP c thc hin thng qua kt ni PVC ny . qu trnh phn phi nhn c thc hin theo

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kiu phn phi nhn chiu i khng yu cu . vic s dng MPLS qua mng ATMPVC yu cu ng gi bng ALL5-SNAP trnh knh PVC . Vic s dng ch khung qua mng ATM-PVC l rt cn thit trong qu trnh chuyn dch sang mng MPLS.

Kt lun chngTrong chng ny gii thiu cc thnh phn v hot ng ca MPLS trong nu ra cc khi nim nh l nhn ( Label ), ngn xp ( Stack ), lp chuyn tip tng ng FEC, ng chuyn mch nhn LSP v cc thnh phn c bn ca mng MPLS nh b nh tuyn bin nhn, trong chng ny gii thiu v cc giao thc phn phi nhn c s dng trong MPLS nh LDP, CR-LDP v cc ch hot ng ca MPLS.

Chng 3

Cc vn k thut c s dng trong mng MPLSl

Kho Lun Tt Nghip


Trong chng trc chng ta cp n nhng vn c bn trong mng MPLS nh : cc khi nin, cc thnh phn ca mng MPLS Trong chng ny chng ta xem xt cc vn k thut lin quan cng nh vic chn lu s dng cc giao thc l. - K thut lu lng - Qun l lu lng - nh tuyn da trn rng buc - M hnh cht lng dch v - Pht hin v ngn nga hin tng nh tuyn vng

3.1. K thut lu lng3.1.1. Khi nin k thut lu lng. K thut lu lng (TE) lm vic lin quan n tnh nng ca mng trong vic h tr khch hng ca mng v nhu cu v cht lng dch v QoS. trng in ca k thut lu lng i vi MPLS l. - o lu lng - iu khin lu lng 3.1.2. Vn hnh nh hng ngun v nh hng lu lng . Vn hnh theo nh hng lu lng h tr cc hot ng cht lng dch v ca ngi s dng. Trong mt lp n , m hnh dch Internet ti s c gng ln nht , mc ch vn hnh theo nh hng lu lng nhm ti thiu ho s mt mt lu lng, ti thiu ho tr, ti a ho thng lng v v tng cng s ph hp mc dch v (SLAs :Service Level Agreements). Vn hnh theo nh hng ngun nhm lm vic vi ngun ti nguyn nh l cc lin kt truyn thng , cc b nh tuyn , cc my ch, cc ngun ti nguyn ny chi phi thc s n cch vn hnh theo nh hng lu lng. vic qun l mt cch hiu qu ngun ti nguyn ny l rt cn thit trong phi k n vic qun l hiu qu bng tn kh dng. 3.1.3. Ti thiu ho tc nghn

Kho Lun Tt Nghip

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Bt k mt mng no cng phi i mt vi cc vn tc nghn . vic qun l lu lng ca tt c ngi dng ngn tnh trng tc nghn sy ra l mt kha cnh quan trng ca QoS. Tc nghn dn ti tnh trng gim thng lng v tng tr. Do lm gim kh nng cung cp QoS mt cch hiu qu. Hu ht cc mng u c c ch truyn dn i vi ngi s dng, bao gm s tho hip mc lu lng c th c gi ti mng trc khi lung lu lng c iu chnh, v gi l iu khin lung. Diu khin lung l cn thit ngn chn tc nghn trong mt mng. Khi lu lng trong mng tng n mt im ti hn no th tc nghn xut hin, v thng lng s gim xung. Nu ch mi mt vi tc nghn xy ra th cha c vn g phc tp, nhng nu tc nghn ko di trong mt thi gian di th lu lng tng ln t ngt vc qu kh nng di thng cho php ca mng. Do vy, cc mng phi cung cp mt vi c cu iu khin cc nt bn trong mng khi c tc nghn xut hin ng thi cung cp mt c

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