TP ON BU CHNH VIN THNG VIT NAM HC VIN CNG NGH BU CHNH VIN THNG

VIN KHOA HC K THUT BU IN

BO CO CHUYN

Thuc nhim v: 003-2006-T-VT

Tn chuyn :

GII THIU TNG QUAN V CNG NGH MNG MAN ETHERNET MPLS

+ Tin trnh pht trin cng ngh + M hnh phn lp + ng dng dch v Ethernet L2VPN trong mng MAN

Ethernet MPLS

Nhng ngi thc hin chnh: Hong Vn Bnh

H ni 2007

MC LC 1. Tin trnh pht trin cng ngh ............................................................................3 1.1. Qu trnh pht trin Ethernet. ...............................................................................3 1.1.1. Ethernet th h u tin: 10 Mbps truyn dn qua cp ng trc. .......................3 1.1.2. 10BASE-T Ethernet: 10 Megabit qua cp in thoi...........................................4 1.1.3. 100BASE-X Fast Ethernet:100 Megabit qua cp ng v cp quang. ................5 1.1.4. Chuyn mch Ethernet: mt gii php khc cho Fast Ethernet............................7 1.1.5. Gigabit Ethernet: 1000 Mbps qua cp ng hay si quang. ................................8 1.1.6. 10 Gigabit Ethernet: 10 Gbps qua cp si quang. ................................................8 1.2. Hin trng v xu hng pht trin cng ngh Ethernet. ......................................9 2. M hnh phn lp (mng v th tc) [1],[2].......................................................12 3. ng dng dch v Ethernet L2 VPN trong mng MAN Ethernet MPLS ..........17 4. Ti liu tham kho..............................................................................................19

1. Tin trnh pht trin cng ngh [1],[2] Ethernet v m hnh kin trc c bn c hnh thnh vo nhng nm 1970 v tr thnh mt cng ngh ch o xy dng mng LAN vo nhng nm 1980. Tri qua hn hai thp k pht trin, vi mc tiu xuyn sut l xy dng mt giao thc mm do, c linh hot v tin cy ln, gim gi thnh lp t mng, thun tin cho vic vn hnh v bo dng, p ng c nhng i hi ngy cng cao ca mng chuyn mch gi, Ethernet ngy nay tr nn ph bin trong cc im tp trung lu lng ca mng Internet, v ti cc kt ni ca cc my tnh trong mng vn phng. Cng vi s pht trin ca cng ngh thng tin, tc Ethernet c ci thin t Mbps ln Gbps. Song song vi n, cu hnh mng my tnh s dng cng ngh Ethernet cng pht trin t cu trc bus dng chung ln cu trc mng chuyn mch hnh sao. y l nhng nhn t quan trng xy dng cc mng my tnh c dung lng cao, cht lng cao, v hiu sut cao, p ng c nhng i hi ngy cng kht khe ca yu cu v cht lng dch v (QoS). Thng 3 nm 1999, ngnh cng nghip Ethernet tng tc ca Ethernet t mt gigabit ln mi gigabit trong mt giy. y l mt bc tin quan trng, c ngha ln v n khng ch gip tng tc Ethernet ln 10 gigabit trong cc kt ni ca mng LAN, m cn gip cho Ethernet vt qua phm vi ca mng LAN s dng trong cc mng th (MAN), hay mng din rng (WAN).

hiu r hn v Ethernet, trong phn tip theo s tm hiu su hn v qu trnh pht trin ca cng ngh ny.

1.1. Qu trnh pht trin Ethernet. 1.1.1. Ethernet th h u tin: 10 Mbps truyn dn qua cp ng trc. Tiu chun v Ethernet th h u tin (sau ny c t tn l 10BASE5) c xy dng nm 1985 v c ban hnh di dng tiu chun IEEE 802.3-1985. Vic xy dng Ethernet LAN theo tiu chun ny tng i tn km v gp mt s kh khn. Bus Ethernet s dng cp ng trc kch thc ln, vi ng knh khong mt phn ba inch, cng, bn knh un cong ti thiu l 10 inch. Giao din gia bus ng trc v DTE cng ln, cn ti by cp cp xon i cng thm vi lp bo v bn ngoi. Cc DTE c th ni vi cp ng trc ti cc im c xc nh trn cp nh hnh v sau.

DTE DTEDTE

Cp ng trc di ti a - 500m

Tr truyn dn t u cui ti u cui ti a l 2165 ns

Cp ni vi thit b (AUI) - di ti a l 50 m, tr ti a t u cui ti u cui l 257 ns

Thit b kt ni vi cp ng trc (MAU) - Ti a l 100thit b trn si cp, cch nhau mt khong l 2.5 m

u cui cp Hnh 1. Cu hnh c bn trn cp ng trc.

Do mng c xy dng trn mt on mng n nh hnh v trn, nn cu hnh ny ch p ng c vi nhng mng c qui m nh, cn i vi mng my tnh c s dng trong cc to nh ln, cn phi c mt cu hnh bao gm nhiu on mng nh vy. Yu cu ny dn ti vic phi lin kt gia cc tuyn cu thnh nn mng, v a ra cc hn ch v cu hnh ca cc tuyn lin kt m bo rng di cc bus di nht s khng gy ra xung t trong mng. Thit b c bn dng kt ni gia cc on mng l b lp (repeater), c s dng

ni hai on mng t gn nhau trong phm vi cho php ca cc bus kt ni vi thit b AUI nh hnh v di y.

DTE DTEDTE

DTE DTEDTE

Repeater

Hnh 2. Cu hnh kt ni s dng mt b lp

Trong trng hp hai on mng xa nhau, th vic kt ni phi cn n hai b lp, c ni vi nhau bng mt on cp lin kt im-im, nh trn hnh 3.

DTE DTEDTE

Repeater

DTE DTEDTE

Repeater

on c p link im-im

Khi thu ph t ca tuynkt ni im-im

Tuyn c p gn Tuyn c p xa

Hnh 3. Cu hnh kt ni s dng hai b lp.

Cc b lp c ni vi cp qua cc b MAU, v c th t ti bt c v tr no trn on cp, cc MAU ca b lp cng phi ph thuc vo s lng cc MAU trn on cp, tc l tng s MAU trn mt on cp khng c vt qu 100.

1.1.2. 10BASE-T Ethernet: 10 Megabit qua cp in thoi. Ethernet tip tc pht trin theo nhiu hng khc nhau sau khi h thng thuc th h u tin da trn cp ng trc c chun ho; tuy nhin, mc quan trng nht trong thi k u ca qu trnh pht trin v chun ho mng LAN l vic xy dng tiu chun 10BASE-T nm 1990. 10BASE-T l mt phin bn mang tnh thng mi ch thc u tin ca Ethernet. Thnh cng ca n ch yu da trn vic s dng cc b lp nhiu cng v cu trc mng cp in thoi. u tin l mng LAN hnh sao (StarLAN), s dng bus truyn dn dng chung. Tuy nhin, mng LAN thng dng nht ca 10BASE-T v IEEE 802.5 l mng vng Ring th bi (Token Ring LAN) c xy dng ch yu da trn s pht trin ca cc tiu chun v cu trc cp mt s quc gia v th gii, v tr thnh yu t c bn chun ho mng LAN. S thay i v nguyn l trong tiu chun 10BASE-T l lp vt l. Cc giao thc v cc phng php x l tn hiu th khng thay i, nhng n yu cu thay i v cc khi thit lp mng, tiu chun v cp, v cc th tc thit lp. 10BASE-T c ba thay i ln so kin trc Ethernet c bn l:

Cc on cp ng trc ni vi b lp v cc b lp ca chng c thay th bng mt b lp mi c nhiu cng (c bit n nh l Hub). on cp ng trc s tr thnh mt kt ni bn trong b lp v v tr ca cc MAU trn on

cp ng trc s tr thnh cc cng kt ni ti giao din ca b lp. Cu hnh MAU nh vy s cho php b lp c th kt ni vi bus v cc on mng khc.

Cc AUI v cc MAU ca cc trm s c gn vo bn trong cc DTE, v tr thnh mt phn giao din ca DTE.

Dy dn ni gia Hub v cc DTE l mt loi cp in thoi mi, vi cu to c trnh by nh trong hnh v di y.

MAUMAU

MDI MDI

i y xon

u ra cpin thoi Panel ni xuyn

on dy xon ca tuyn kt ni

Tuyn kt ni bng i dy xon

MDI-giao din ph thuc phng tin, vi mt u ni ti MAU v mt u nign vo on dy xon

Hnh 4. Tuyn kt ni bng i dy xon 10BASE-T.

Kt qu ca nhng thay i trn s to ra mng hnh sao nh trong hnh v di y.

Repeater

M AU M AU ... M AU

B chuyn tip

D TE

M AU

AU I

D TE

M AU

A UI

D TE

M AU

AUI

on kt ni10BASE-T, 100m

Ch : M A U v A UI nm trong b chuyn tip v cc DTE Hnh 5. Cu hnh mng 10BASE-T vi mt b lp.

1.1.3. 100BASE-X Fast Ethernet:100 Megabit qua cp ng v cp quang. Fast Ethernet xut hin vo cui nm 1993 v 100BASE-X tr thnh tiu chun vo nm 1995. C s xy dng tiu chun ny ging nh tiu chun 100BASE-T v: khun dng khung Ethernet, b lp a cng, cu ni, cu trc ca dy dn, nhng tc truyn dn tng ln gp 10 ln. V vy, n cn phi c thay i mt s yu t t c tc nh trn. Cp in thoi c dng trong tiu chun 10BASE-T khng th truyn dn c tc cao nh Fast Ethernet yu cu. Th nht, ti tc 100 Mbps, suy hao tn hiu trong cp in thoi s qu ln. Th hai, trong qu trnh truyn dn, s bc x ca sng in t s vt qu mc cho php (theo tiu chun ca hai u ban truyn thng M v Chu u). Do vic

truyn dn trong Fast Ethernet cn phi c mt loi cp mi. Cc loi cp hin ti ang c s dng l:

100BASE-T4 s dng bn i dy cn bng cp UTP Cat-3 hoc Cat-5. 100BASE-TX s dng hai i dy dn UTP Cat-5 hoc i dy xon c lp bo

v (cp STP). Tuy nhin, yu t thay i quan trng nht trong Fast Ethernet l kch thc ca mng. Cn nhc li rng bt k hai DTE no trn mng cng c kh nng xung t khi truy cp mng vo cng mt thi im, nn mi trm phi c kh nng nhn c tn hiu xung t phn hi trong khong thi gian c quy nh bi ca s xung t, bt k v tr xy ra xung t nm u. Ca s xung t bng tng thi gian i v v ca tn hiu khi truyn dn trn bus di nht, v ca s xung t phi nh hn thi gian truyn lung bt theo cc khung c di nh nht. Do vn tc truyn dn trn cp l khng i, v thi gian truyn dn khung c di nh nht by gi ch bng mt phn mi thi gian truyn dn khung nhng vi tc 10 Mbps. Do , di ca ng truyn dn di nht s phi gim i. Ba khi thnh phn c bn c nh ngha cho mng 100 Mbps gm:

Kt ni DTE-DTE cho php kt ni gia hai u cui c lu lng trao i cao. Do cu hnh ny ch h tr vic kt ni gia hai v ch hai my tnh nn y l mt m hnh khp kn.

Mng s dng mt b lp nh trong hnh 7 s dng b lp lp 1 v cc tuyn kt ni l si 100BASE-FX hoc i dy xon. Cc b lp lp 1 c s dng kt ni cc h thng c phng thc truyn dn tn hiu vt l khc nhau. (Truyn dn s dng 100BASE-T4 s dng phng thc truyn dn khc so vi 100BASE-TX hay 100BASE-FX). Do tr trong mng c b lp lp mt s ln hn.

Cu hnh s dng hai b lp nh trong hnh 8 s dng cc b lp lp hai c tr t hn v s dng phng php pht ra tn hiu trn mt trong hai 100BASE-T4 hoc 100BASE-TX/FX.

DTE DTE

Bus

Min va chm 100 Mbps

Hnh 6. Kt ni 100BASE gia DTE-DTE.

DTE DTE

B chuyn tiplp 1 100BASE

A B

ng knh min va chm

di A + di B

Min va chm 100 Mbps

Hnh 7. M hnh mng s dng mt b lp

DTE DTE

Min va chm 100 Mbps

B chuyn tiplp 2 100BASE

B chuyn tiplp 2 100BASE

A

B C

ng knh min va chm

di A + di B + di C

Hnh 8. M hnh mng s dng hai b lp

1.1.4. Chuyn mch Ethernet: mt gii php khc cho Fast Ethernet. Ti thi im chuyn mch Ethernet u tin xut hin vo nm 1994, min va chm ca mng Fast Ethernet nh hn nhiu so vi min va chm ca mng 10BASE-T. S ra i ca chuyn mch Ethernet lm min va chm ca Fast Ethernet tng ln ng k. V mt khi nim, chuyn mch c th coi l thit b th h sau ca cu ni nhiu cng, c ra i trc . Mi cng ca chuyn mch s kt ni vi DTE ging nh l cc DTE khc, v c trang b cc b m a khung. Khi chuyn mch nhn c mt khung ti mt cng, n s gii m ra a ch ch v kim tra xc nh cng ca DTE ch c bn hay khng. Nu cng khng bn v bn trong chuyn mch c bus ri, th cuc ni s c thit lp v khung c truyn i. Nu cng ang bn hay khng c bus ri bn trong chuyn mch th khung s c gi li ti b m ca cng nhn cho n khi cuc ni c thc hin. M hnh chuyn mch c bn 10BASE-T c trnh by nh trong hnh v 9.

Chuyn mch 10 Mbps

DTE DTE DTE

...

i dy xon10BASE-T, 100m

Hnh 9. Cu hnh c bn ca chuyn mch 10BASE-T.

Chuyn mch c th c s dng thay th cho c b lp cng nh cu ni trong mng hnh sao. Cc mng chuyn mch c mt s u im hn so vi mng s dng b lp. Mt vi u im trong s l:

Phn tch c cc min va chm gia cc cng v cc DTE kt ni vi chng, hn ch c kh nng xy ra xung t trong qu trnh truyn khung d liu.

Nhiu ng dn i qua chuyn mch s cho php nhiu khung c truyn i ti cng mt thi im.

Nhiu cuc kt ni chuyn mch - chuyn mch cho php nhiu khung c th truyn gia cc chuyn mch ti cng mt thi im.

Cc link b hng c cch ly d dng khi mng. 1.1.5. Gigabit Ethernet: 1000 Mbps qua cp ng hay si quang. S ra i ca Gigabit Ethernet m ra mt k nguyn mi l Ethernet tc cao. Gigabit Ethernet c thit lp da trn cc nguyn l c bn ca 10BASE-T, ca Fast Ethernet v ca chuyn mch Ethernet, v khun dng khung Ethernet qua cc phng tin truyn dn dng chung hoc chuyn mch trong mng s dng cp c cu trc c chun ho. Nhm xy dng Gigabit Ethernet ly cng ngh truyn dn trn cp si quang, ci tin, v tch hp n vi tng vt l ca Gigabit Ethernet. Kt qu l tc d liu tng ln gp 10 ln, gi thnh gim, v qua gim c thi gian yu cu tm ra cng ngh mi. Gigabit Ethernet c chun ho vo nm 1998. Phng tin truyn dn c bn cho php tng di kt ni trong mng Gigabit Ethernet l si quang n mode (SMF) vi ng knh li l 10 m, hay si quang a mode vi ng knh li l 50 m hoc 62.5 m. Tn hiu c truyn dn ch yu trn hai bc sng l 850nm (bc sng ngn) v 1310 nm (bc sng di). Nu s dng cp ng th l loi cp bn i Cat-5 UTP, vi khong cch c th ln ti 100m.

1.1.6. 10 Gigabit Ethernet: 10 Gbps qua cp si quang. Phin bn mi nht ca Ethernet l 10 Gigabit Ethernet (GbE) c trnh by trong d tho tiu chun IEEE 802.3ae. Trong phin bn ny, tc Ethernet tng t 1 Gbps ln 10 Gbps, cho php Ethernet c th tch hp vi nhng cng ngh tc cao trn mng ng trc WAN, OC-192, vi tc xp x 9,5 Gbps. Ngoi ra, 10 GbE cn a ra cc giao din vi tc pht i t c th tng thch vi cc h thng SONET/SDH. Cc giao din lp vt l WAN cho php truyn ti cc gi tin c xy dng trn c s IP/Ethernet truyn ti qua cc thit b truy cp ca mng SONET/SDH. 10 GbE c th h tr tt c cc dch v ti cc lp bc 2 v bc 3, v thm ch ti cc lp cao hn trong m hnh by lp OSI. Ngoi ra do hu ht lu lng trn cc mng ngy nay c bt ngun t Ethernet v IP, nn thit lp mt mng Ethernet tc cao l mt phng thc d nht gn kt cc nh kinh doanh cng nh cc nh cung cp mng vi nhau. Nguyn tc c bn khi xy dng cc mng chuyn mch l dng cng ngh tc cao kt hp nhiu on mng tc thp li vi nhau. Khi mt v s lng cc on c tc 100 Mbps trong mng tng ln th 1000BASE-X v 1000BASE-T tr thnh cng ngh truyn dn mc cao hn c s dng trn cc li mng. Cui nhng nm 2000, khi s lng cc cng Gigabit tng n 250 nghn trong mt thng th cng ngh 10 Gbps l rt cn tng hp cc on tc mt Gbps. Bng sau tm tt qu trnh pht trin v chun ho cng ngh Ethernet ca IEEE.

Bng 1. Qu trnh pht trin v chun ho cng ngh Ethernet

Nm Tiu chun ra i

1973 Cng ty Xerox pht trin Ethernet

1980 Phin bn u tin c tiu chun (10Mbps)

1983 IEEE pht hnh tiu chun 802.3

1985 Tiu chun 802.3a, Ethernet qua cp ng

1987 Tiu chun 802.3d, khong cch ln nht gia cc b lp 10 Mbps l 1000 m

1990 Tiu chun 802.3i, Ethernet 10 Mbps hot ng qua cp UTP Cat 3

1993 Tiu chun 802.3j, khong cch gia cc b lp tng ln 2000 m

1995 Tiu chun 802.3u, Ethernet tng tc ln 100Mbps

1997 Tiu chun 802.3x, Ethenet song cng cho php pht v thu ng thi

1998 Tiu chun 802.3z, Ethernet tc 1 Gbps

1999 Tiu chun 802.3ab, 1 Gbps Ethernet hot ng qua 4 i cp UTP Cat 5

2000 IEEE thnh lp nhm 802.3ea pht trin 10Gbps

2001 Phi hp cng RPR pht trin Ethernet vo mng MAN

2004 Tiu chun IEEE 802.3ah 2004

2005 Tiu chun IEEE 802.3ah 2005

1.2. Hin trng v xu hng pht trin cng ngh Ethernet. Ethernet ang bc sang thp k th ba trong qu trnh pht trin, so vi phin bn ban u th hin ti c rt nhiu thay i v cc yu t la chn cho vic cu hnh mng Ethenet cng tng ln r rt.

Tc truyn dn: Thay i ni bt nht ca mng Ethernet trong thp k qua l tc truyn dn tng gp nhiu ln. Tuy nhin s gia tng ny cng bao hm cc nh hng rt bt li v bn knh ca vng va chm.

Chuyn mch: S pht trin ca cc chuyn mch a tc l mt yu t c ngha tng t trong vic chp nhn cc mng Ethernet c tc cao hn. Chuyn mch a ra mt s ci thin cho mng Ethernet nh:

o Cu hnh mt cch linh hot, cho php bn knh hot ng ca mng c hi phc hoc m rng.

o Cung cp tng bng tn mng ln hn so vi cc cu hnh c k thut tng t nhng trong mi trng dng chung.

Cu hnh sao v cc tc ng n qu trnh lp t mng: Vic th trng chp nhn cu hnh sao 10BASE-T khng nhng bin Ethernet thnh giao thc chnh cho mng LAN m cn dn n s ra i ca cc tiu chun xy dng cp hin nay ang c dng. iu ny cng vi s ra i ca cc loi cp mi v cc k thut truyn s liu mi dn n lp t cc tuyn cp vt l d dng v bo dng cng t tn km hn.

Mt s kh nng mi: Hot ng song cng, iu khin lung v nhn VLAN l ba kh nng mi ng ch nht.

o Hot ng song cng: Hot ng song cng cho php truyn ng thi hai hng trong cu hnh DTE-DTE, chng hn nh chuyn mch n chuyn mch v chuyn mch n my ch. Nh loi b c tnh trng xung t v hiu qu bng tn cc lin kt tng gp di.

o iu khin lung: Kh nng iu khin MAC to ra phng tin iu khin cc lung d liu v gim xc sut mt khung do cc b m trong cc cu ni v chuyn mch b trn.

o nh nhn VLAN: nh nhn VLAN l mt kh nng tu chn c thit k cho php to ra cc mng o ring bit cho cc nhm ngi dng da trn vic xc nh a ch logic. Do , lm gim c s a ch cn duy tr trn cc bng chuyn mch v thi gian cn thm, di chuyn v thay i trong cu hnh mng. Nhng tng ng vi tm quan trng ca cc LAN Ethernet ni ht, nh nhn VLAN cng phi cho php thc hin quyn u tin i vi ngi s dng, ngha l c dng ch ra cc quyn u tin truyn cho cc khung gii hn v thi gian.

Vin cnh i vi cc mc tiu Ethernet ban u: Hai trong s cc mc tiu ban u ca Ethernet vn cn nguyn gi tr.

Tc cao: Mc tiu u tin l xy dng mng hot ng vi tc 10 Mbps. Mc tiu ny c thay i trong tiu chun n bn u tin. V ln lt cc n bn sau tc tng ln 100 Mbps, 1000 Mbps v 10 Gbps v khng cn phi thay i cc giao thc Ethernet.

Tnh tng thch: Mc tiu ban u l tt c cc thc hin ca Ethernet phi c kh nng trao i d liu mc lin kt s liu. V mt s l do, vic xc nh ny trnh mt s tu chn, loi tr tmh trng khng tng thch ca Ethernet. Vic nh nhn VLAN yu cu thm vo 4 octet cho khun dng khung.

i vi mng MAN, cng ngh Ethernet c quan tm cao v cc l do sau:

- Tit kim: chi nh hn rt nhiu so vi FR, ATM - Nhu cu lp t nhanh theo nhu cu: Cc dch v Ethernet cung cp di tc t 1

Mbps n 1 Gbps. Cc tc ny c th c cung cp nhanh v theo nhu cu, thm ch c th c cung cp bi t cc khch hng thng qua mt cng c trn WEB.

- Lu lng gi ngy cng chim u th: Lu lng gi hin nay c cung cp qua mng hin ti khng linh hot v chi ph cao.

- Cng ngh da trn k thut gi: C th cung cp bng thng nhanh theo nhu cu. - D dng kt ni: Vic loi b cc vn v kt ni gia cc c s v mi trng khc

nhau lm cho vic cung cp v kch hot dch v n gin hn. Ethernet loi b

mt lp phc tp (v d SONET, ATM) khi truy nhp WAN, do lm gim c cc yu cu xy dng cu hnh.

- S chp nhn khp ni: l cng ngh ch o trong cc LAN doanh nghip v trng hc trong nhiu nm qua. Cc giao din tiu chun c th s dng l 10/100/1000 Mbps Ethernet, tiu chunt 10 Gbps cng s sm c a ra. Cng ngh Ethernet cng d hc v d hiu hn cc cng ngh khc.

Nhng gii hn hin nay ca vic s dng Ethernet trong metro: - m bo QoS end-to-end: qun tr kt ni cho cc yu cu dch v mi, sp xp v

quy nh duy tr truy nhp n nh, thit lp ng dn ti u qua mng, u tin gi. - Cc c ch bo v - Gim st cht lng v OA&M trong dch v - Kh nng m rng v s dng ti nguyn mng

loi b cc gii hn ca vic s dng Ethernet trong mng MAN, mt trong nhng gii php c cho l hiu qu nht l s dng cng ngh chuyn mch nhn MPLS. MPLS l cha kho cung cp cc dch v Ethernet. C th s dng MPLS chng ln cc kt ni im-im hoc im-a im qua mt mng Ethernet. S kt hp ny cho php cc nh cung cp dch v xy dng mt cu hnh bt k cho cc dch v ca khch hng: im-im, sao hoc li.

- Mt trong nhng chc nng quan trng nht ca MPLS l nng cao Ethernet trong Metro. MPLS cung cp kch c, phm vi mng cn thit v kh nng linh hot m khng nh hng ti tc , tnh n gin.

- C mt s cch s dng MPLS vi GE hoc RPR khai thc cc dch v gi tr gia tng. V d MPLS c th c trin khai trn nn mt Metro Ethernet hoc RPR cung cp cc dch v IP VPN.

- i vi cc nh cung cp mng: c th xy dng cc mng Ethernet/MPLS cung cp cc dch v Ethernet ng thi s dng c s h tng ang cung cp cc mng truy nhp Frame Relay.

- Cn i vi cc nh cung cp dch v: to ra cng c phc v 2 mc ch ng thi: cung cp cc dch v Ethernet tc cao v m rng khai thc FR ang c.

Da trn MPLS c th cung cp cc dch v:

- Dch v knh thu - Dch v LAN ring o - Dch v VPN IP - M rng cc ng dng FR ang c - Mm do hn trong cc phn mng khng c RPR - Cc ng dng Ethernet khc: truyn ti Ethernet, d phng lu tr.

MPLS l giao thc c trin khai trong tt c cc thit b ca nh cung cp dch v trong mng Metro, n ng vai tr lm c s kin to dch v. Trong phn ny chng ta s xem xt vai tr ca MPLS trong mng Metro.

MPLS nm di lp IP, n cung cp cc tnh nng mi cho mng chuyn mch IP. ng thi MPLS l lp trn, n h tr cc cng ngh nm lp 2 nh Ethernet hoc RPR.

Ni cch khc MPLS h tr Ethernet trong mng Metro. Hn ch ln nht ca cng ngh mng LAN Ethernet l kh nng m rng. Ethernet khng c thit k hot ng trong mi trng mng c kch thc cng nh phc tp nh mi trng mng Metro.

MPLS khng thay th Ethernet, n ng vai tr b sung khc phc cc hn ch ca cng ngh ny. Cho n nay, Ethernet vn l cng ngh c gi thnh r n gin v c trin khai rng ri nht. MPLS b sung kh nng m rng, linh hot cho Ethernet m khng lm nh hng n cc u im ca Ethernet. Trin khai kt hp MPLS/Ethernet thay i cc c tnh ca mng lp 2 m khng nh hng n tc , tnh n gin v rt ph hp vi lu lng IP ca Ethernet.

2. M hnh phn lp (mng v th tc) [1],[2] 2.1. M hnh phn lp

Hnh 10: M hnh tham chiu Layer 2 VPN

Mc d c nhiu m hnh trin khai v gii php mng Layer 2 VPN, chng u c cng tnh cht chung v pseudowire v cc thnh phn mng khc trong cu trc pseudowire emulation c trnh by trong hnh 10

PE (Provider Edge) l thit b nm pha nh cung cp. N c nhim v cung cp dch v pseudowire emulation ti CE (Customer Ejdge) thuc min qun l ca khch hng.

CE v PE kt ni vi nhau thng qua mt hay nhiu attachment circuit. Mt attachment circuit c th l mt cng Ethernet, Ethernet VLAN, PPP session, High-Level Data Link Control (HDLC) link, Frame Relay data-link connection identifier (DLCI), ATM virtual path identifier (VPI)/virtual connection identifier (VCI), hoc mt giao din kt ni khc.

Pseudowire l mt virtual circuit gia hao PE c nhim v kt ni hai attachment circuit. Pseudowire c th thit lp bng nhn cng hoc t ng bo hiu. Sau khi thit lp pseudowire gia hai PE, Cc khung nguyn bn nhn t attachment circuit c ng gi vo cc pseudowire PDU v gi qua pseudowire ti PE cng cp. Sau khi nhn c cc pseudowire PDU, PE bn nhn s chuyn i ngc li thnh cc khung nguyn bn v truyn tip ti attachment circuit thch hp.

Thit b P (Provider) nh dng mng li ca mng chuyn mch gi v trong sut i vi thit b CE. Chng khng nhn bit cc pseudowire v lu lng pseudowire do cc PE qun l. Tnh trong sut ny lm nh bt s phc tp trong vic thit k mng li. Do cho php ti u ha mng li cho php nawng cao hiu qu nh tuyn mng li v truyn gi d liu m khng cn quan tm n s phc tp ca cc dch v bin.

2.1.1. Cc cu trc Layer 2 VPN

K t sau hi ngh IETF ln th 49 t chc nm 2000, c hai m hnh t chc mng cng ng thi c xem xt v c trnh by trong hai bn draft l "draft-martini" v "draft-kompella.". C hai bn draft ny u a ra c cch thit lp pseudowire emulation trn mng packet-based network nhng gii php ca mi xut rt khc nhau v u c nhng li th v nhc im ring. Ni dung chnh ca cc xut ny c trnh by s lc sau y

draft-martini

c im quan trng nht trong m hnh xut draft-martini l tnh n gin v d thc hin. Bn draft ny m t cch thc thit lp mt pseudowire gia hai attachment circuit c nh v ti hai thit b PE ngang hng nhau. Bn xut ny cng quy nh phng php encapsulation cho mi dch v Layer 2, c ch phn b nhn (Label Distribution Protocol LDP) cho cc dch v MPLS khc nhau bao gm c pseudowire emulation, cc cu trc c lin quan n vic khi to v qun l cc pseudowires point-to-point ring bit, khng c s lin quan n nhau.

Trc khi bt u mt pseudowire ti mt remote PE, cn cung cp cho local PE mt virtual circuit (VC) ID hoc mt pseudowire ID chia s bi c hai local v remote attachment circuit v mt a chit IP ca remote PE. Bi v gii hn ca LDP khng sn sng c giao thc c bn cho vic bo hiu pseudowire signaling, bn draft xc nh mt phn m rng pseudowire cho LDP. Mt pseudowire c xem nh c thit lp khi cc thit b PE ngang hng trao i thng tin nhn cho pseudowire thng qua s dng LDP. iu ny c ngha l khi mi PE gi v nhn c mt bn tin label mapping cho pseudowire xc nh.

Ngi iu hnh mng c th cung cp pseudowire thng qua cu trc c trnh by trong draft-martini bng tay hoc thng qua h thng qun l mng. iu ny tng t nh cung cp cc dch v truyn thng nh Frame Relay hay ATM PVC trn Layer 2 VPN. Bn xut ny nhn c nhiu kin nh gi khc nhau: u im ca n l thn thin vi tnh thng mi v c th gip gim bt cc th tc v cng c trong cc mng Layer 2 VPN truyn thng, tuy nhin cng c nhng kin cho rng cu trc ny li lp li cc vn cn tn ti trong mng Layer 2 VPN truyn thng nh tnh scalability.

Cu trc Layer 2 VPN ny h tr cc dch v point-to-point Layer 2, bao gm Frame Relay, ATM AAL5, ATM Cell, Ethernet, Ethernet VLAN, PPP, v HDLC trong phn thm vo ca dch v Layer 1, nh TDM.

draft-kompella

Kin trc c xut trong draft-kompella khng ging vi draft-martini hay cc Layer 2 VPN truyn thng. Trong mt chng mc no , kin trc ny chia s mt s chc nng nh tuyn ng ca Layer 3. Khng nh draft-martini, kin trc ny bao gm cc thut ton, th tc bo hiu, provisioning scheme phc tp nhm lm cho cc dch v trn Layer 2 hot ng tt hn.

Muc ch chnh ca draft-kompella l gii quyt vn mang tnh c hu ca Layer 2 VPN truyn thng l scalability. thit lp VPN, cn to mt pseudowire kt ni hai thit b CE ghp vi hai PE khc nhau, to kt ni y gia cc thit b CE khi s lng cc CE tng ln th s lng cc pseudowire cn c thit lp v qun l tng theo cp s nhn.

Hn na, mi khi thm no mt thit b CE mi hoc loi b mt CE ghp vo mt PE khc, phi cu hnh li tt c cc thit b PE thnh phn trong VPN duy tr cu hnh kt ni full-mesh. iu ny l mt kh khn ln i vi nh khai thc mng. M hnh bn draft ny xut cch gii quyt vn ny bng cch cung cp tha s lng cc attachment circuit cho mi thit b CE cho cc CE v PE khng phi cu hnh li khi thm CE vo VPN. C s cho vic thm tha s lng cc attachment circuit l gi thnh cc thit b ny tng i r.

cung cp mt Layer 2 VPN s dng cu trc c xut trong draft-kompella, mi CE thuc VPN c gn cho mt CE ID v mi CE c cu hnh kt ni vi s lng ti a c th c vi cc CE cn li, s lng ny c gi l CE range. Mi attachment circuit gia CE v PE c gn cho mt gi tr index value tng ng vi mt remote CE ID trong VPN. Bng cch sp xp , mi CE c th nhn din attachment circuit kt ni vi remote CE. Mi PE c cu hnh trong cc VPN theo cch mi VPN c mt nhn VPN ID, PE c cung cp mt danh sch cc CE trong VPN v cc thng s CE ID, CE range, v the index values ca cc attachment circuit ca mi CE .

Khi mt PE c cu hnh vi tt cc cc thng tin cn thit ca mt CE, n xc nh mt di gi tr MPLS label lin tc tng ng vi CE range. Gi tr nh nht ca MPLS label c gi l label base. i vi mi CE, PE s qung b cc thng s router ID, VPN ID, CE range, v label base thng qua bn tin BGP update c pht broadcast ti tt c cc PE cn li. Thm ch mt s PE khng phi l thnh vin ca VPN cng vn c th nhn c bn tin ny v lu thng tin li dng trong trng hp mt CE c kt ni vi VPN trong tng lai. Do BGP c bn khng c cc giao thc c bn cho bo hiu pseudowire, bn draft ny a ra mt phn m rng cho BGP dnh cho pseudowire

Cu trc ny gii quyt c vn v scaling mng bng vic chuyn nhim v cp pht CE mi v cc im a phng. iu ny c ngha l khi nhn thm mt CE mi, ch CE v PE ti v tr c thm vo phi cu hnh li, cc thit b remote CE v PE khng cn cu hnh li v chng c th tnh ton la chn attachment circuit cn d truyn thng vi CE mi. Thit b remote PE c th nhn bit CE mi thng qua cc bn tin BGP update. Cc bn tin BGP broadcast ny lm cho cc PE c kh nng t ng khm ph v nhn bit cc thnh phn trong Layer 2 VPN v lm gim cc thao tc v cu hnh cc thit b PE

Nhc im ca cu hnh ny li chnh do cn c xy dng ln n cha c m bo chc chn. cc attachment circuit c th c gi thnh h khi CE v PE kt ni trc tip thng qua virtual circuit nh Frame Relay v ATM PVC. Nhng khi chng kt ni thng qua chuyn mch Frame Relay hoc mng ATM, hoc cc attachment circuit c cc kt ni vt l v cng tch bit nh PPP hay HDLC th gi thnh ca cc attachment circuit tr ln t hn hn v vic cung cp tha cc AC ny tr nn khng hin thc. Hn na, cc mng VPN ngy nay t khi c xy dng trn cu hnh mesh y nn cng t gp vn v scaling cho nh tuyn Layer 3 khi thit k phn cp. Nu Layer 2 VPN ch bao gm cc kt ni point-to-point th vic gi thng tin qung b n tt c cc PE v gi cc thng tin ny trn cc PE s lm lng ph ti nguyn mng v cc thng tin ny ch hu ch cho mt remote PE.

Bng sau so snh cc c im chnh ca hai cu trc Layer 2 VPN c trnh by trong draft-martini v draft-kompella

Bng 2. So Snh cu trc Pseudowire Emulation draft-martini draft-kompella

Cu trc mng

Cc ng dy o point-to-point ring bit

Mesh y ca cc ng dy o point-to-point

Phc tp Thp Cao

Tnh n hi Thp i vi cu trc mesh y ; kh tt vi cu trc bt k Cao i vi cu trc mesh y ; km i vi cu trc bt k

Kh nng ng dng

Cao; Lm vic tt trn cc dch v c lp 1 v lp 2

Kh tt; lm vic tt hn khi kt ni trc tip vi cc PVC Frame Relay v ATM

Giao thc bo hiu

LDP BGP

Giao thc khai ph

Khng h tr t ng khai ph BGP

H tr ca nh sn xut

Nhiu nh sn xut h tr S nh sn xut h tr hn ch

Tin trnh chun ha

ang c tin hnh bi nhm PWE3

Khng cn c xem xt

Mc d draft-martini ginh c nhiu kt qu trong vic chun ha v pht trin, nhng cc nhc im cn bn ca cu trc ny l thiu chc nng h tr cho Layer 2 VPN autodiscovery c ghi nhn. Nhiu gii php gii quyt vn ny cn ang c nghin cu v pht trin.

2.1.2. Cc cu trc Layer 2 VPN khc

Cu trc Layer 2 VPN trn pseudowire emulation l cu trc tng qut vch r cc th tc thit lp cc pseudowire ring l v phng php encapsulation cho cc dch v Layer 2 khc nhau. Cu trc ny l nn tng v m hnh nguyn l cho cc loi cu trc Layer 2 VPN khc.

VPWS c xy dng trc tip trn pseudowire emulation. Mt VPWS v bn cht l mt mng bao gm cc point-to-point pseudowire kt ni cc thit b CE trong mt Layer 2 VPN. Hn cnh cc dch v pseudowire emulation c bn, VPWS a ra cc c tnh cho dch v point-to-point Layer 2 VPN rng hn nh cht lng dch v (QoS), bo mt, redundancy, VPN membership discovery v mt s tnh cht khc. VPWS trong mt s trng hp c xy dng thay th cho cc Frame Relay hoc ATM-based Layer 2 VPN truyn thng.

VPLS cng s dng cc dch v pseudowire emulation c bn, nhng c cu trc khc vi VPWS. Mc tiu ca VPLS l gi lp Transparent LAN Service (TLS) trong mt mng packet-based, thng thng nhn t mng Layer 2 chuyn mch Ethernet. Thay cho vic ng voi tr l mt point-to-point cross-connect gia attachment circuit v pseudowire, mt VPLS PE c chc nng nh l mt bridge Ethernet. Khi nhn c mt Ethernet frame t mt CE, PE s kim tra trng destination MAC address ca khung trong bridging table ca n, Nu

n tm thy, n s chuyn tip frame ti giao din c xc nh trong bng bridging table. Trng hp ngc li, n s lu source MAC address vo bridging table v truyn broadcast frame ti tt c cc giao din trong cng broadcast domain. Trong khi VPWS yu cu mt attachment circuit ring bit cho mi thit b remote CE, VPLS cho php mt attachment circuit truyn cc khung t mt CE ti nhiu remote CE. V mt ny, VPLS c cc tnh nng gn vi Layer 3 VPN hn so vi VPWS.

IP-only LAN Service (IPLS) c cu trc tng t nh VPLS, nhng n c thit k n gin ha truyn duy nht lu lng IP. Trong IPLS, mt thit b CE c th l mt host hoc router nhng khng c l switch trong khi VPLS khng c s hn ch ny.

2.2. ng gi Pseudowire

a cc giao thc Layer 2 trn pseudowires, cn phi ng gi cc phn ti tin Layer 2 theo c trng ca Layer 2 gn n mc c th.

Bn cnh MPLS label stack, pseudowire encapsulation cn bao gm thng tin payload-specific c tnh thay i theo per-transport v per-packet basis. C 5 loi ti bao gm:

ATM Frame Relay HDLC PPP Ethernet

i vi Ethernet pseudowire encapsulation, phn preamble v FCS c loi b khi cc khung Ethernet ti router ingress PE trc khi gi chng qua pseudowire v chng c phc hi li ti router egress PE. Phn control word thig ty chn c gi hay khng.

Ethernet pseudowire c hai ch hot ng:

Raw mode: trong ch raw mode, mt khung ethernet c th c hoc c th khng bao gm IEEE 802.1q VLAN tag. Nu khung khng c tag, th tag khng c ngha i vi ingress v egress PE router

Tagged mode: trong ch tagged mode, mi khung bt buc phi c IEEE 802.1q VLAN tag, ga tr ca tag c ngha i vi c ingress v egress PE router

Trong mng Metro Ethernet, CE router v PE router kt ni vi nhau thng qua mng Ethernet switched access, cc gi nhn c PE router c th c hai IEEE 802.1q VLAN tag. Loi gi ny c gi l QinQ packet. Khi outer VLAN tag l service-delimiting VLAN tag, cc gi QinQ c x l ging nh cc gi c mt VLAN tag trong c hai ch raw mode v tagged mode. Khi t hp ca outer v inner VLAN tag c s dng quyt nh service-delimiting, cc gi c x l nh l mt VLAn tag vi mt gii gi tr m rng

Trong trng hp quan tm n QoS, ingress PE router c th ghp cc user priority bit trong VLAN header vo cc MPLS EXP bit trong MPLS label stack. Trong trng hp ny, cc transit LSR trong mng MPLS c th p dng chnh sch QoS i vi cc khung Ethernet c mang trn cc pseudowire.

3. ng dng dch v Ethernet L2 VPN trong mng MAN Ethernet MPLS [4]

Dch v Metro Ethernet l dch v mng cung cp n khch hng cng kt ni Ethernet tiu chun (standard Ethernet User-to-Network Interface (UNI)). nh ngha ny bao hm rt nhiu cng ngh c th c s dng cung cp dch v Metro Ethernet bao gm optical cross-connects (OXC), mng Layer 2 thun ty, hoc mng chuyn mch gi.

Do c nh ngha rng nh vy, rt kh c th phn loi cc dch v Metro Ethernet. Cch phn loi ph bin nht hin nay c:

Phn loi da trn kiu kt ni: Point-to-point tng t nh virtual circuit (PVC). Multipoint.

Phn loi da trn kiu dch v: Wire services: Cung cp mt cng kt ni khng c multiplexing tng t nh leased line. Relay services: Cung cp dch v c multiplexing da trn VLAN tng t nh Frame Relay port.

Kt hp cc kiu phn loi trn, ta c bn dch v Metro Ethernet c bn:

1. Ethernet Wire Service (EWS) dch v khng multiplexed point-to-point. 2. Ethernet Relay Service (ERS) dch v VLAN-multiplexed point-to-poin. 3. Ethernet Multipoint Service (EMS) dch v khng multiplexed point-to-cloud. in hnh

l Virtual Private LAN Service (VPLS) 4. Ethernet Relay Multipoint Service (ERMS) dch v VLAN-multiplexed point-to-cloud.

Pha nh cung cp c VLAN mapping. VPLS c th cung cp dch v ny

Cc dch v Metro Ethernet khc bao gm:

Ethernet Private Line (EPL) tng t EWS, nhng c cung cp Layer 1 bi cc OXC.

Layer 2 VPN access: Layer 2 access to Multiprotocol Label Switching (MPLS) VPNs. ATM to Ethernet over MPLS hoc Ethernet over L2TPv3 Interworking Frame Relay to Ethernet over MPLS hoc Ethernet over L2TPv3Interworking

Bng 3 v 4 trnh by cc c im ca cc dch v Metro Ethernet.

Bng 3. Cc dch v Metro Ethernet Dch v Metro Ethernet Cu trc c im Kt ni

EPL Layer 1 Trong sut (nonmultiplexed)

Point-to-point

EWS VPWS[1] Trong sut (nonmultiplexed)

Point-to-point

ERS VPWS Multiplexed Point-to-point

EMS VPLS Trong sut (nonmultiplexed)

Multipoint-to-multipoint

ERMS VPLS Multiplexed Multipoint-to-multipoint

ATM/Frame Relay Ethernet Interworking

VPWS Multiplexed Point-to-multipoint

[1] VPWS = Virtual Private Wire Service

Bng 4. Cc dch v Metro Ethernet

Dch v Metro Ethernet U-PE CustomerN-PE Service Provider

EPL QinQ[1] WDM[2] wavelength SONET/SDH[3] circuits

EWS QinQ EoMPLS[4]

ERS 802.1q Trunk EoMPLS

EMS QinQ Ethernet or EoMPLS

ERMS 802.1q Trunk EoMPLS

ATM/Frame Relay Ethernet Interworking

Frame Relay or ATM

EoMPLS

[1] QinQ = Stands for 802.1q in 802.1q and is also referred to as 802.1q tunneling

[2] WDM = wavelength division multiplexing

[3] SDH = Synchronous Digital Hierarchy

[4] EoMPLS = Ethernet over MPLS

4. Ti liu tham kho [1] Metro Ethernet , Sam Halabi, Cisco Press, October 01, 2003, ISBN: 1-58705-096-X [2] Layer 2 VPN Architectures , Wei Luo, ..., Cisco Press, March 10, 2005, ISBN: 1-58705-168-0 [3] MPLS-Enabled Applications : Emerging Developments and New Technologies, Ina Minei, Julian Lucek, John Wiley & Sons