chuyen de mpls

7/29/2019 Chuyen de MPLS

1/72

LI NI U

Cng vi s pht trin ca t nc, nhng nm gn y cc ngnh kinh t quc dn upht trin mnh m, v ngnh cng nghip vin thng cng khng l ngoi l. S ngi s dng

cc dch v mng tng ng k, theo d on con s ny ang tng theo hm m. Ngy cng cnhiu cc dch v mi v cht lng dch v cng c yu cu cao hn. ng trc tnh hnhny, cc vn v mng bt u bc l, cc nh cung cp mng v cc nh cung cp dch v cng c nhiu n lc nng cp cng nh xy dng h tng mng mi. Nhiu cng ngh mng vcng ngh chuyn mch c pht trin, trong s chng ta phi k n cng ngh chuynmch nhn a giao thc (MPLS). MPLS ang c nghin cu p dng nhiu nc, tp onBCVT Vit Nam cng p dng cng ngh ny cho mng th h k tip NGN.

ng trc s pht trin nhanh chng ca cng ngh chuyn mch nhn a giao thc MPLS,

vic tm hiu cc vn v cng ngh MPLS l vn quan trng i vi sinh vin. Nhn thc ciu , bn kho lun tt nghip Tm hiu kh nng ng dng cng ngh chuyn mch a giaothc nhn MPLS trn mng ng trc Vit Nam gii thiu v qu trnh pht trin dch v cngnh cng ngh mng dn ti MPLS, tm hiu cc vn k thut ca cng ngh, v ng dng cacng ngh MPLS trong mng th h k tip NGN ca tp on BCVT Vit Nam. B cc ca bnkho lun gm 3 chng.

Chng 1 : Gii thiu tng quan v cng ngh chuyn mch nhn a giaothc MPLS

Chng 2 : Gii thiu cu trc mng ng trc Vit Nam

Chng 3 : ng dng MPLS trn mng ng trc Vit Nam

Cng ngh MPLS l cng ngh tng i mi m, vic tm hiu v cc vn ca cngngh MPLS i hi phi c kin thc su rng, v lu di. Do vy bn kho lun tt nghip khngtrnh khi nhng sai st. Rt mong nhn c s ph bnh, gp ca cc thy c gio v cc bn.

Xin gi li cm n chn thnh ti PGS.TS Nguyn Cnh Tun ngi tn tnh hngdn em trong sut qu trnh hon thnh bn kho lun tt nghip ny.

Xin chn thnh cm n cc thy c gio trong khoa Vin thng gip em trong thi

gian qua.

Xin gi li cm n ti gia nh, bn b v ngi thn - nhng ngi gip ng vinti trong qu trnh hc tp.

CHNG 1

GII THIU TNG QUAN V CNG NGH CHUYN MCH

NHN A GIAO THC (MPLS)

1.1 Qu trnh hnh thnh v pht trin1.1.1 Cc ng lc ra i ca chuyn mch nhn

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Trong nhng nm gn y, mng internet pht trin rt nhanh v tr nn rt ph bin.

Internet tr thnh mt phng tin thng tin rt hiu qu v tin li phc v cho gio dc,

thng mi, gii tr, thng tin gia cc cng ng, cc t chc.. Hin nay ngy cng pht trin

cc ng dng mi c trong thng mi v th trng ngi tiu dng. Cc ng dng mi ny c

vn hnh i hi bng thng rng v cc nhu cu v di thng c m bo trong mng ng

trc. Cng vi cc dch v truyn thng c cung cp qua internet th cc dch v thoi v a

phng tin ang c s dng v pht trin. V s la chn cho vic cung cp l tch hp cc

dch v ang c mong i. Tuy nhin, tc v gii thng ca cc nhu cu v cc dch v v

ng dng ny vt qu h tng internet hin nay.

Vi giao thc nh tuyn internet TCP/IP c kh nng nh tuyn v truyn gi ht sc mm

do linh hot v rng khp ton cu. Nhng IP khng m bo cht lng dch v, tc truyn

tin theo yu cu, trong khi cng ngh ATM c tc truyn tin cao, m bo thi gian thc vcht lng dch v theo yu cu nh trc. Hn na cc dch v thng tin th h sau c chia

thnh hai xu hng pht trin l: Hot ng kt ni nh hng v hot ng khng kt ni. Hai

xu hng pht trin ny dn tim cn v hi t vi nhau tin ti ra i cng ngh IP/ATM. S kt

hp IP vi ATM c th l gi php k vng cho mng vin thng trong tng lai.

S ra i ca chuyn mch nhn a giao thc (MPLS) l tt yu v l gii php p ng

c nhu cu , khi nhu cu v tc pht trin rt nhanh ca mng internet yu cu phi c giao

thc mi m bo cht lng dch v theo yu cu ng thi phi n gin v tc x l phi rt

caoChuyn mch nhn a giao thc l mt gii php linh hot cho vic gii quyt cc vn

m cc mng ngy nay ang phi i mt, l tc , kh nng m rng cp mng, qun l

cht lng dch v (QoS) v k thut lu lng. MPLS xut hin p ng cc yu cu dch v

v qun l bng thng cho giao thc internet th h sau da trn mng ng trc

Tm li, chuyn mch nhn a giao thc s ng vai tr quan trng trong vic nh tuyn

(da trn cc thc o QoS v cht lng dch v) chuyn mch, chuyn tip cc gi tin qua mng

th h sau cng nh gii quyt cc vn lin quan ti kh nng m rng cp v hot ng vi

cc mng Frame Relay v ch truyn ti khng ng b ATM hin nay p ng cc nhu cu

dch v ca ngi s dng mng

1.1.2 Lch s pht trin ca MPLS

Vic hnh thnh v pht trin cng ngh MPLS xut pht t nhu cu thc t, c cc nh

cng nghip vin thng thc y nhanh chng. S thnh cng v nhanh chng chim lnh th

trng m cng ngh ny c c l nh vo vic chun ho cng ngh. Qu trnh hnh thnh v

pht trin cng ngh, nhng gii php ban u ca hng nh Cisco, IBM, Toshiba. Nhng n

lc chun ho ca t chc tiu chun IETF trong vic ban hnh v tiu chun MPLS.s cung cpcho chng ta nhng nhn nh ban u v xu hng pht trin MPLS.

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MPLS c xut u tin do hng Ipsilon mt hng rt nh v cng ngh thng tin trong

trin lm v cng ngh thng tin, vin thng ti Texas. Sau Cisco v hng lot hng khc nh

IBM, Toshibacng b cc sn phm cng ngh chuyn mch ca h di nhng tn khc nhau

nhng u cng chung bn cht cng ngh chuyn mch nhn.

Thit b nh tuyn chuyn mch t bo ca Toshiba nm 1994 l tng i ATM u tin

c iu khin bng giao thc IP thay cho bo hiu ATM. Tng i ca Ipsilon cng l ma trn

chuyn mch ATM c iu khin bi khi x l s dng cng ngh IP. Cng ngh chuyn mch

th ca Cisco cng tng t nhng c b xung thm mt vi k thut nh lp chuy tip tng

ng FEC, giao thc phn phi nhn. n nm 1998 nhm nghin cu IETF tin hnh cc

cng vic a ra tiu chun v khi nim v chuy mch nhn a giao thc.

S ra i ca MPLS c d bo l tt yu khi nhu cu v tc pht trin rt nhanh ca

mng Internet i hi phi c mt giao thc mi m bo cht lng dch v theo yu cu. C rtnhiu cng ngh xy dng trn mng IP

IP trn nn ATM (IPoA)

IP trn nn SDH/SONET (IPOS)

IP qua WDM

IP qua cp quang

Mi loi c nhng u v nhc im ring. Trong cng ngh ATM c s dng rng

ri trong cc mng IP ng trc c tc cao v m bo c dch v, iu khin lung v mt

s c tnh khc m cc mng nh tuyn truyn thng khng c c, trong trng hp i hi

thi gian thc cao th IpoA l gii php ti u. MPLS c hnh thnh da trn k thut .

MPLS thc hin mt s chc nng sau

H tr cc gii php mng ring o VPN

nh tuyn hin (iu khin lu lng)

H tr cc b cho nh tuyn IP trong cc tng i chuyn mch ATM

Khi nim chuyn mch nhn xut pht t hai khi nim: Tng i chuyn mch v b nh

tuyn.Xt trn gc chuyn mch, phng thc iu khin lung, t l gi c v cht lng tng

i chuyn mch s tt hn b nh tuyn. Song b nh tuyn li c kh nng nh tuyn mm do

m tng i chuyn mch khng c c. Do , chuyn mch nhn ra i l s kt hp v k

tha cc u im trn cng nh khc phc nhng nhc im ca c tng i v b nh tuyn

truyn thng.

1.1.3 Qu trnh chun ho MPLS

i vi 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 lin

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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 v hon thin

ITEF hon thin tiu chun MPLS v a ra cc ti liu RFC trong nm 1999.

Sau nm 1999 lin tc ban hnh cc tiu chun MPLS nh v qun l, bo mt, tnh tng

thch vi cc cng ngh khc

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. Sau khi ton b cc RFC c hon thin,

chng s c tp hp li xy dng mt h thng tiu chun MPLS

1.1.4 Nhm lm vic MPLS trong IETF

MPLS l mt nhm lm vic IETF cung cp cc bn phc tho v nh tuyn, gi chuyn

tip v chuyn mch cc lung lu lng qua mng s dng MPLS. Nhm c chc nng sau Xc nh c ch qun l lung lu lng ca cc phn t khc nhau, nh cc lung lu

lng gia cc phn cng, cc my mc khc nhau hoc thm ch l cc lung lu lng

gia cc ng dng khc nhau.

Duy tr c lp ca cc giao thc lp 2 v lp 3

Cung cp cc phng tin sp xp cc a ch ip thnh cc nhn c di c nh v n

gin c cc cng ngh gi chuyn tip gi tin v chuyn mch gi s dng.

Giao din vi cc giao thc nh tuyn c sn nh RSVP v OSPF.

H tr IP, ATM v cc giao thc lp 2 Frame-Relay

Trong MPLS, vic truyn d liu thc hin theo cc ng chuyn mch nhn (LSP). Cc

ng chuyn mch nhn l dy cc nhn ti mi nt v ti tt c cc nt dc theo tuyn t ngun

ti ch. LSP c thit lp hoc l trc khi truyn d liu hoc trong khi tm lung d liu. Cc

nhn c phn phi s dng giao thc LDP hoc RSVP hoc da trn giao thc nh tuyn nh

BGP v OSPF. Mi gi d liu nn v mang cc nhn trong qu trnh i t ngun ti ch. Chuyn

mch tc cao c th chp nhn c v cc nhn vi di c nh c chn vo v tr u ca

gi tin hoc t bo v c th c phn cng s dng d chuyn mch cc gi tin mt cc nhanhchng gia cc ng lin kt.

Nhm lm vic MPLS chu trch nhim chun ho cc cng ngh c s cho s dng chuyn

mch nhn v cho vic thi hnh cc ng chuyn mch nhn v cho vic thi hnh cc ng

mch nhn trn cc loi cng ngh lp lin kt, nh Frame Relay, ATM v cng ngh LAN

(Etherbet, Token Ring,). N bao gm cc th tc v cc giao thc cho vic phn phi nhn gia

cc b nh tuyn, xem xt v ng gi v multicast.

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Cc mc tiu khi u ca nhm lm vic gn nh hon thnh. C th, n xy dng

mt s cc RFC nh ngha giao thc phn phi nhn c s (LDP), kin trc MPLS c s v ng

gi tin, cc nh ngha cho vic chy MPLS qua cc ng lin kt ATM, Frame-Relay.

Cc mc tiu gn y ca nhm lm vic

Hon thnh cc ch mc cn tn ti

Pht trin cc mc tiu chun ngh ca nhm lm vic MPLS thnh cc bn Dratf

Standard bao gm: LDP, CD-LDP v cc tiu chun k thut RSVP-TE cng nh vn

ng gi.

nh r cc m rng ph hp vi LDP v RSVP cho vic xc nhn LSP ngun.

Hon thnh cc cng vic trn MPLS-TE MIB.

Xc nh cc c ch chp nhn li ci tin cho LDP.

Xc nh cc c ch phc hi MPLS cho php mt ng chuyn mch nhn c th cs dng nh l mt bn d tr cho mt tp cc ng chuyn mch nhn khc bao gm cc

trng hp cho php sa cc b

Cung cp ti liu v cc phng thc ng gi MPLS m rng cho php hot ng trn cc

ng chuyn mch nhn trn cc cng ngh lp thp hn, nh phn chia theo thi gian

( Sonet ADM ) di bc sng v chuyn mch khng gian.

1.2 Cc thnh phn ca MPLS:[1], [2], [4].

1.2.1. Khi qut MPLS

Khi mt gi tin tun theo cc phng thc lp mng connectionless t mt b nh tuyn

n b nh tuyn tip theo, mi b nh tuyn phi a ra mt quyt nh gi chuyn tip c lp

gi tin . Do , mi b nh tuyn phn tch mo u gi tin v mi b nh tuyn s chy cc

thut ton nh tuyn lp mng. Mi b nh tuyn la chn Hop tip theo cho gi tin mt cch

hon ton c lp da trn nhng phn tch c n v mo u gi tin v kt qu cu vic chy thut

ton nh tuyn.

Cc mo u gi tin cha ng nhiu thng tin hn l thng tin cn thit la chn Hop

tip theo. La chn Hop tip theo c th xem l s cu thnh ca hai chc nng. Chc nng thnht chia ton b gi tin vo cc tp lp chuyn tip tng ng FEC ( Forwarding Equivalence

Clas ). Chc nng th hai l xp xp mi FEC cho mt Hop tip theo. Khi quyt nh gi chuyn

tip c a ra, vi cc gi tin c xp xp vo cng mt FEC l ging nhau. Tt c cc gi tin

trong cng mt FEC c th v xut pht t mt nt c th s i theo cng mt tuyn ng hoc

theo mt tp cc tuyn ng lin kt vi FEC .

Trong gi chuyn tip IP truyn thng, mt b nh tuyn c th s a hai gi tin vo cng

mt FEC nu nh mt vi tin t a ch X trong bng nh tuyn ca b nh tuyn ph hp vi

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a ch ch ca gi tin. Khi gi tin truyn qua mng, mi Hop ln lt kim tra li gi tin v n

nh n vo mt FEC.

Trong MPLS, vic n nh mt gi tin c th vo mt FEC c thc hin mt ln khi gi

tin i vo mng. FEC m gi tin c n nh m ho thnh mt gi tr c di c nh c gi

l nhn. Khi mt gi tin c chuyn tip ti Hop tip theo ca n, nhn c gi theo gi tin, nh

vy cc gi tin dn nhn trc khi chng c gi chuyn tip.

Ti cc Hop pha sau, khng c nhng phn tch su hn v mo u lp mng. ng hn

l nhn c s dng nh ch s trong bng m n xc nh Hop tip theo v nhn mi. Nhn c

c thay th bng mt nhn mi v gi tin c gi ti Hop tip theo.

Trong m hnh gi chuyn tip MPLS, khi mt gi tin c n nh vo mt FEC th khng

c bt c mt phn tch mo u no c cc b nh tuyn pha sau thc hin. Tt c cng vic

gi chuyn tip c iu khin bng cc nhn. iu ny c mt s cc u im so vi vic gichuyn tip lp mng truyn thng.

Vic gi chuyn tip c th c thc hin bng cc tng i c kh nng tm kim v thay

th nhn, nhng khng c kh nng phn tch mo u lp mng hoc khng c kh nng phn

tch mo u lp mng ti mt tc xc nh.

K t lc gi tin c n nh vo mt FEC khi n i vo mng, b nh tuyn u vo c

th s dng bt c thng tin no m n c v gi tin cho d cc thng tin khng th ly c t

mo u lp mng trong khi quyt nh vic n nh. V d, cc gi tin ti cc cng khc nhau c

th c n nh cho cc FEC khc nhau. Trong khi vic gi chuyn tip truyn thng c thch xem xt n thng tin c mang theo cng vi gi tin trong mo u gi tin.

Mt gi tin i vo mng ti b nh tuyn c th c th c dn nhn khc vi mt gi tin

tng t nhng i vo mng ti mt b nh tuyn khc, kt qu l cc quyt nh gi chuyn tip

ph thuc vo b nh tuyn ni vo. iu ny khng th thc hin c trong vic gi chuyn

tip truyn thng, khi m b nh tuyn li vo ca gi tin khng c mang theo gi tin.

Nhng yu t quyt nh xem liu gi tin c n nh cho mt FEC nh th no c th tr

nn ngy cng phc tp, nu khng c bt c mt tc ng no vo cc b nh tuyn ch n

thun l gi chuyn tip cc gi tin dn nhn.

i khi chng ta mun bt gi tin i theo mt tuyn ng xc nh c chn trc

hoc ti thi im gi tin i vo mng hn l tuyn ng c la chn bng thut ton nh

tuyn ng khi gi tin qua mng. iu ny c th c thc hin nh l vn v chnh sch hoc

h tr iu khin lu lng. Trong gi chuyn tip truyn thng, iu ny i hi gi tin mang

b m v tuyn ng ca n i theo. Trong MPLS, mt nhn c th c s dng i din cho

mt tuyn ng khng cn phi mang theo gi tin.

Mt vi b nh tuyn phn tch mo u lp mng ca gi tin khng phi n thun ch ka chn Hop tip theo m cn quyt nh quyn u tin ca gi tin. Sau chng ta c th p

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dng cc ngng loi b hoc cc lch trnh khc nhau cho cc gi tin khc nhau. MPLS cho php

nhng khng yu cu quyn u tin c th c xc nh hon ton hoc mt phn t nhn

MPLS l chuyn mch nhn a giao thc, a giao thc y c ngha l cc cng ngh ca

n c th p dng trong bt c giao thc lp mng no nh IP, IPX

1.2.2 Cc khi nim c bn ca mng MPLS

1.2.2.1 Nhn (Lable):

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 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 tin 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 ca a ch .Nhn trong dng n gin nht xc nh ng i m gi tin c th truyn qua. Nhn c

mang hay c ng gi trong tiu lp 2 cng vi gi tin. B nh tuyn kim tra cc gi tin

qua ni dung nhn xc nh cc bc chuyn 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 nhn ch

c ngha cc b ngha l chng ch lin quan n cc bc chuyn tip gia cc LSR.

Dng ca nhn ph thuc vo phng thc truyn tin m gi tin c ng gi.

Kiu khung (Frame mode): Kiu khung l thut ng khi chuyn tip mt gi nhn gn

trc tiu lp ba. Mt nhn c m ho vi 20 bt, ngha l c th c 2 m 20 gi tr khcnhau. Mt gi c nhiu nhn gi l chng nhn (Lable stack). mi chng trong mng ch c mt

nhn bn ngoi c xem xt

LABLE EX

P

S TTL STAC

K

LABLE=20 bits

EXP (EXPERIMENTAL)=3 bitsS (BOTTOM OF STACK)=1 bit

TTL (TIME TO LIVE)=8 bits

Trong :

EXP: dnh cho thc nghim. Khi cc gi tin xp hng c th dng cc bt ny tng

t nh cc bit IP u tin (IP Precedence)

S: l bt cui chng . Nhn cui chng bit ny c thit lp ln 1,cc nhn khc cgi tr bt ny l 0.

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TTL: thi gian sng l bn sao ca IP TTL. Gi tr ca n c gim ti mi chng

trnh lp nh IP. Thng dng khi ngi iu hnh mng mun che du cu hnh mng bn

di khi tm ng t mng bn ngoi.

Kiu t bo (Cell mode): Thut ng ny dng khi c mt mng gm cc ATM LSR dng

trong mt phng iu khin trao i thng tin VPI/VCI thay v dng bo hiu ATM. Trong kiu

t bo, nhn l trng VPI/VCI ca t bo. Sau khi trao i nhn trong mt phng iu khin,

mt phng chuyn tip, router cng vo phn tch gi thnh cc t bo ATM, dng gi tr VCI/CPI

tng ng trao i trong mt phng iu khin v truyn t bo i. Cc ATM LSR pha trong

hot ng nh chuyn mch ATM-chng chuyn tip mt t bo da trn VPI/VCI vo v thng

tin cng ra tng ng. Cui cng, router cng ra sp xp cc t bo thnh mt gi.

Kiu khung PPP hoc Ethernet, gi tr nhn dng giao thc P-ID (hoc Ethernet type) c

chn vo mo u khung tng ng thng bo khung l MPLS n hng hay a hng.

Gi tin IP

Tiu Shim

D liu

VPI/VCI

Tiu IP

D liu

Tiu IP

Hnh 1.1: Lp lin kt d liu l ATM

Gi tin IP

Tiu Shim

D liu

DLCI

D liu

Tiu IP

D liu

Tiu IP

Hnh 1.2: Lp lin kt d liu Frame-relay

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Tiu gi PPP trn SDH

Tiu MAC LAN

Tiu PPP Tiu lp 3Tiu Shim

Tiu lp 3Tiu ShimTiu MAC

Nhn

Hnh 1.3: Nhn trong Shim-gia lp 2 v lp 3

1.2.2.2 Ngn xp nhn (Lable stack):

L mt tp hp th t cc nhn gn theo gi chuyn 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

1.2.2.3 Bng chuyn tip chuyn mch nhn:

Cha thng tin v nhn vo, nhn ra, giao din vo, giao din ra.

1.2.2.4 B nh tuyn chuyn mch nhn ( LSR-Lable Switching Router ):L thit b chuyn mch hay thit b nh tuyn s dng trong mng MPLS chuyn cc

gi tin bng th tc phn phi nhn. C mt s lo LSR nh LSR, LSR-ATM.

1.2.2.5 Lp chuyn tip tng ng ( FEC-Forward Equivalence Class ):

FEC l mt nhm cc gi, nhm cc gi ny chia s cng yu cu trong s chuyn tip

chng qua mng. Tt c cc gi trong mt nhm nh vy c cung cp cng cch chn ng ti

ch. Khc vi chuyn tip IP truyn thng, trong MPLS vic gn mt gi c th vo mt FEC cth ch c thc hin mt ln khi cc gi vo trong mng. MPLS khng ra quyt nh chuyn tip

vi mi datagram lp 3 m s dng khi nim FEC. FEC ph thuc vo mt s cc yu t, t nht

l ph thuc vo a ch IP v c th l ph thuc c vo kiu lu lng trong datagram (thoi, d

liu, fax). Sau da trn FEC, nhn c tho thun gia cc LSR ln cn t li vo ti li ra

trong mt vng nh tuyn. Mi LSR xy dng mt bng xc nh xem mt gi phi c

chuyn tip nh th no. Bng ny c gi l c s thng tin nhn (LIB: Label Information

Base), n l t hp cc rng buc FEC vi nhn (FEC-to-label). V nhn li c s dng chuyn tip lu lng qua mng.

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1.2.2.6 C s thng tin nhn ( LIB-Lable Information Base ):

L bng kt ni trong LSR c cha gi tr nhn/ FEC c gn vo cng ra cng nh thng

tin v ng gi d liu truyn tin xc nh phng thc mt gi tin c chuyn tip.

1.2.2.7 Tuyn chuyn mch nhn ( LSP-Lable Switching Path ):

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 tuyn 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 cc giao thc nh LDP,

RSVP. 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 c

s dng bi phn cng chuyn mch nhanh cc gi gia cc lin kt.1.2.2.8 Gi tin dn nhn:

Gi tin dn nhn l gi tin m nhn c m ha 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 th c t chung vo trong mo u lp mng v lp lin kt d liu min l y c

th dng c cho mc ch dn nhn. Cng ngh m ho c s dng phi ph hp vi c thc

th m ho v thc th gii m nhn.

1.2.2.9 n nh v phn phi nhn:

Trong mng MPLS, quyt nh kt hp mt nhn L c th vi mt FEC F c th l doLSR 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 cc kt hp nhn c phn phi theo

hng t LSR pha trc ti LSR pha sau.

1.2.2.10 C cu bo hiu

Yu cu nhn: 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 dng truyn n cc LSR tip theo cho n LER li ra.

p ng nhn: p ng mt yu cu nhn, LSR lung xung s gi mt nhn n cc b

khi ng lung ln s dng c cu nh x nhn.

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p ngnhn

V d nhn 2

p ngnhn

V d nhn 5

Yu cunhn

Cho ch C

Yu cunhn

Cho ch C

LSRLi vo LER

B nhtuyn B

B nhtuyn C

Hnh 1.4: C cu bo hiu

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1.2.3 Cc thnh phn c bn ca mng MPLS

LSR bin

LSR li

Hnh 1.5: M hnh mng MPLS

Mng MPLS bao gm nhiu nt c chc nng nh tuyn v chuyn tip ni vi nhau. Mi

nt tng ng vi mt thit b LSR ( Lable Switching Router)

Mng MPLS c th c chia thnh hai min l min li MPLS ( MPLS core ) v min bin

MPLS ( MPLS Edge ).Tng ng vi mi min ta c thit b tng ng:

- B nh tuyn chuyn mch nhn ( Lable Switching router-LSR ): L thnh phn quan

trng nht trong mng MPLS, n l b 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 tuyn thit lp bng cc th tcphn phi nhn.

- ATM-LSR: L cc tng i ATM c th thc hin cc 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 nng cp phn mm thc hin chc nng ca LSR.

- B nh tuyn bin nhn ( Lable 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-

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Relay, ATM, Ethernet. N tip nhn hay gi i cc gi 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 khi gi tin i vo hay i ra khi mng MPLS. Cc LER ny c th l b nh

tuyn li vo (Ingress Router ) hoc l b nh tuyn li ra (Egress Router ).

- B nh tuyn bin li vo nhn gi tin IP, kim tra li lp 3 v t vo ngn xp nhn

trc khi gi gi tin vo mng LSR.

- B nh tuyn bin li ra nhn gi tin c nhn, loi b nhn kim tra li lp 3 v chuyn

tip gi tin IP n nt tip theo.

ATM-LSR bin:

- Nhn gi c nhn hoc khng c nhn phn vo cc t bo ATM v chuyn tip cc t bo

n nt tip theo.

Nhn cc t bo ATM t ATM-LSR cn k ti to cc gi t cc t bo ATM v chuyntip gi c nhn hoc khng c nhn.

Phn bit chuyn mch nhn v chuyn mch thng thng

C ba im phn bit quan trng gia chuyn mch nhn v nh tuyn gi tin IP thng

thng:

nh tuyn thng thng Chuyn mch nhnPhn tch mo u IP Tn ti mi nt mng Ch tn ti nt binH tr unicast v

multicast

Yu cu nhiu thut ton

chuyn tip

Yu cu mt thut ton

chuyn tipThng s nh tuyn Da vo a ch IP C th da vo thng s

bt k nh cht lng

dch v, mng ring o

1.3 Cc giao thc c bn ca MPLS

Mng MPLS khng bt buc mt phng thc bo hiu n no cho vic phn phi nhn.

Cc giao thc nh tuyn nh BGP ( giao thc cng bin ) c th dng giao thc dnh trc ti

nguyn RSVP m rng h tr trao i nhn. Nhng IETF cng xc nh mt giao thc mic bit n nh giao thc phn phi nhn LDP ( Lable Distribution Protocol ) 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 tuyn lin vng da trn cc yu cu v QoS. Nhng m rng ny cng c p dng

trong vic xc nh giao thc nh tuyn rng buc ( CR-LDP ). Cc giao thc h tr trao i nhn

nh sau:

LDP: ch ra cc ch IP vo trong cc bng.

RSVP, CR-LDP s dng cho k thut lu lng v dnh trc ti nguyn.

1.3.1 Giao thc phn phi nhn ( LDP )

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Giao thc phn phi nhn c nhm nghin cu MPLS ca IETF xy dng v ban hnh c

tn l RFC 3036. Phin bn mi nht c cng b nm 2001 a ra nhng nh ngha v nguyn

tc hot ng ca giao thc LDP.

Giao thc phn phi nhn c s dng trong qu trnh gn nhn cho cc gi tin. Giao thc

LDP l giao thc iu khin tch bit c cc LSR s dng trao i v iu phi qu trnh

gin nhn/ FEC. Giao thc ny l mt tp hp th tc trao i cc nhn bn tin cho php cc LSR

s dng gi tr nhn thuc FEC nht nh truyn gi tin.

Mt kt ni TCP c thit lp gia cc LSR ng cp m bo cc bn tin LDP c

truyn theo ng th t. Cc bn tin LDP c th xut pht t bt k mt LSR (iu khin ng

chuyn mch LSP c lp ) hay t LSR bin li ra (iu khin LSP theo lnh ) v chuyn t LSR

pha trc n LSR pha sau cn k

Vic trao i cc bn tin LDP c th c khi pht bi s xut hin ca lung s liu cbit, bn tin lp d tr RSVP hay cp nht thng tin nh tuyn. Khi mt cp LSR trao i bn

tin LDP cho mt FEC nht nh th mt ng chuyn mch LSP t u vo n u ra c thit

lp sau khi mi LSR ghp nhn u vo ni u ra tng ng trong LIB ca n.

Pht hin LSR ln cn:Th tc LSR ln cn ca LDP chy trn UDP v thc hin nh sau

(minh ho hnh v d i ).

Mt LSR nh k gi bn tin Hello ti tt c giao din ca n. Nhng bn tin ny c gi

trn UDP, vi a ch multicast ca tt c router trn mng con.

Tt c cc LSR tip nhn bn tin Hello ny trn cng UDP. Nh vy, ti mt thi im no

LSR s bit c tt c cc LSR khc m n c kt ni trc tip.

Khi LSR nhn bit c a ch ca LSR khc bng c ch ny th n s thit lp kt ni TCP

n LSR .

Khi phin LDP c thit lp gia 2 LSR. Phin LDP l phin hai chiu c ngha l mi LSR

hai u kt ni u c th yu cu v gi rng buc nhn.

Trong trng hp cc LSR khng kt ni trc tip trong mt mng con, ngi ta s dngmt c ch b sung nh sau:

LSR nh k gi bn tin Hello trn UDP n a i ch IP c khai bo khi lp cu hnh.

Pha nhn bn tin ny c th tr li li bng bn tin HELLO khc truyn ngc li n LSR gi v

vic thit lp cc phin LDP c thc hin nh trn.

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U D P H e llo

U D P H e l lo

T C P O p en

Ini t ial izat ion

L a b e l R e q u e s t

L a b e l M a p p in g

IP

Hnh 1.7: Th tc pht hin LSR ln cn

Thng thng trng hp ny hay c p dng khi gia hai LSR c mt ng LSP cho

iu khin lu lng v n yu cu phi gi cc gi c nhn qua ng LSP .

Cc bn tin LDP Tiu bn tin LDP

Mi mt bn tin LDP c gi l n v d liu giao thc PDU, c bt u bng tiu

bn tin v sau l cc bn tin LDP nh trnh by trn y. Hnh 2.21 ch ra cc trng chc

nng ca tiu LDP v cc trng ny thc hin cc chc nng sau:

Phin bn: S phin bn ca giao thc, hin ti l phin bn 1.

di PDU: Tng di ca PDU tnh theo octet, khng tnh trng phin bn v trng

di.

Nhn dng LDP:Nhn dng khng gian nhn ca LSR gi bn tin ny. Bn octet u tin

cha a ch IP c gn cho LSR: nhn dng b nh tuyn. Hai octet cui nhn dng khng gian

nhn bn trong LSR.Vi LSR c khng gian nhn ln, trng ny c gi tr bng 0.

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.

0 1 5 3 1

P h i n b n d i P D U

N h n d n g L D P

N h n d n g L D P

Hnh 1.8: Tiu LDP

M ho TLV

LDP s dng lc m ho kiu- di-gi tr m ho cc thng tin mang trong bn tin

LDP. Nh ch ra trn hnh 2.22, LDP TVL c m ho thnh mt trng 2 octet trong s dng

14 bt xc nh kiu, v 2 bit xc nh cch hnh ng cho trng hp LSR khng nhn ra c

kiu; 2 octet tip theo xc nh trng di v trng gi tr c di thay i.

Trng kiu qui nh cc m trng gi tr c dch.

Trng di xc nh di ca trng gi tr.

Trng gi tr c th cha cc TLV khc.

0 1 5 3 1

K i u d i

G i t r

U F

Hnh 1.9: M ho TLV

Da trn bn tin nhn c, khi bit U c gi tr 0, LSR s gi thng bo ngc li ni gi

v ton b bn tin s c b qua. Nu U c gi tr 1, LSR s b qua bn tin cha bit kiu m

khng gi thng bo li pha gi v phn cn li ca bn tin vn c x l nh th l bn tin chabit kiu ny khng tn ti.

Bit F ch c s dng khi bit U = 1 v bn tin LDP cha bn tin cha bit kiu ny c

truyn i. Nu bt F bng 0 th bn tin cha bit kiu s khng chuyn i cng bn tin LDP cha n

v nu bit F=1 th bn tin cha bit kiu s chuyn i cng bn tin LDP cha n.

Cc khun dng v chc nng ca cc TLV. Trong phm vi n ny xin php khng

ni n.

Khun dng bn tin LDP

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Tt c cc bn tin LDP c khun dng sau:

Hnh 1.10: Khun dng cc bn tin LDP

Bit U: bit bn tin cha bit. Nu bit ny bng 1 th n khng th c thng dch bi pha

nhn, lc bn tin b b qua m khng c phn hi. Kiu bn tin: Ch ra kiu bn tin l g.

Chiu di bn tin: Ch ra chiu di ca cc phn nhn dng bn tin, cc thng s bt buc,

v cc thng s tu chn.

Nhn dng bn tin: l mt s nhn dng duy nht bn tin. Trng ny c th c s dng

kt hp cc bn tin Thng bo vi mt bn tin khc.

Thng s bt buc, v Thng s tu chn tu thuc vo tng bn tin LDP.

V mt nguyn l, mi th xut hin trong bn tin LDP c th c m ho theo TLV,

nhng cc c t LDP khng phi lun lun s dng lc TLV. N khng c s dng khi n

khng cn thit v s s dng ca n s gy lng ph khng gian. Chng hn khng cn thit phi

s dng khun dng TLV nu chiu di ca gi tr l c nh hay kiu ca gi tr c bit v

khng phi ch nh mt nhn dng kiu

Cc bn tin v chc nng ca 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 Address Withdraw.

Bn tin Lable Mapping.

Bn tin Lable Request.

17

ID bn tin

Thng s bt buc

Thng s tu chn

U Kiu bn tin di bn tin


18/72

Bn tin Lable Abort Request

Bn tin Lable Withdraw.

bn tin Lable Release.

1-Bn tin thng bo ( Notification Message ): Bn tin ny c s dng bi mt LSR

thng bo vi cc LSR ng cp khc v trng thi mng l ang trong iu kin bnh thng

hay b li. Khi LSR nhn c mt bn tin thng bo v mt li, n s ngt phin truyn ngay

lp tc bng vic ng phin kt ni TCP li v xo b cc trng thi lin quan n phin

truyn ny. V d v li: hng s khi ng phin LSP, cc bn tin xu.

2-Bn tin Hello: Bn tin ny dng trao i gia 2 LDP ng cp.

3-Bn tin Initilization: Cc bn tin thuc loi ny c gi khi bt u mt phin LDP gia

2 LSR trao i cc tham s, cc i lng tu chn cho phin. Cc tham s ny bao gm:

Ch phn phi nhnCc gi tr nh thi

Phm vi cc nhn s dng trong knh gia 2 LSR

C hai LSR u c th gi cc bn tin Initilization v LSR nhn s nhn tr li bng Keep

Alive nu cc tham s c chp nhn. Nu c mt tham s no khng c chp nhn th LSR

tr li thng bo v phin kt thc.

4-Bn tin Keep Alive: Bn tin ny dng trao i gia cc thc th ng cp gim st

tnh n nh v lin tc ca vic h tr ca mt kt ni TCP trong mt phin LDP. Cc bn tin ny

c gi nh k khng c bn tin no c gi m bo cho mi thnh phn LDP bit rngthnh phn LDP khc ang hot ng tt. Trong trng hp khng xut hin bn tin Keep Alive

hay mt s bn tin khc ca LDP trong khong thi gian nht nh th LSR s cho rng kt ni b

hng v phin truyn s b dng

5-Bn tin Address: Bn tin ny c gi i bi mt LSR ti cc LDP ng cp thng

bo cc a ch giao din ca n. Mt LSR khc nhn bn tin mang a ch ny duy tr c s d

liu nh x trng nhn dng v cc a ch chng tip theo gia cc LDP ng cp.

6-Bn tin Address Withdraw ( Bn tin hu b a ch ): Bn tin ny dng xo a ch

c thng bo trc . Danh sch a ch LTV cha mt lot cc a ch ang c yu cu

cn xo b bi LSR.

7-Bn tin Lable Mapping ( Bn tin nh x nhn ): Cc bn tin nh x nhn c s dng

qung b lin kt gia FEC ( tin t a ch ) v nhn gia cc thc th ng cp. Bn tin ny

c s dng khi c s thay i trong bng nh tuyn ( thay i tin t a ch ) hay thay i

trong cu hnh LSR tm dng vic chuyn nhn cc gi trong FEC .

Nu mt LSR phn phi mt nh x i vi mt FEC ti nhiu thc th ng cp LDP, vn

cc b c t ra l liu n nh x mt nhn n ti FEC ny v phn phi s nh x ny ti

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tt c cc thc th LDP ng cp ca n hay s dng cc nh x khc nhau cho tng LDP khc

nhau.

8-Bn tin Lable Withdraw: Bn tin ny c nhim v ngc li so vi bn tin nh x a

ch, c s dng xo b cc kin kt gia cc FEC v cc nhn va thc hin. Bn tin ny

c gi ti mt thc th ng cp thng bo rng nt khng cn tip tc s dng cc lin kt

nhn-FEC m LSR gi trc

9-Bn tin Lable Request: Bn tin yu cu nhn c LSR s dng yu cu mt LDP

ng cp cung cp mt s kt hp nhn ( Binding ) cho mt FEC. Mt LSR c th pht bn tin yu

cu nhn di bt k mt trong nhng trng hp sau:

- LSR nhn ra mt FEC mi thng qua bng chuyn tip v Hop tip theo l mt thc th

LDP ng cp nhng LSR khng c nh x t Hop tip theo cho FEC cho.

- C s thay i FEC ca chng tip theo nhng LSR khng c s nh x t chng tip theoi vi FEC cho.

- LSR nhn mt yu cu nhn i vi mt FEC t mt LDP ng cp ln (Upstream LDP

peer ) FEC Hop tip theo l mt LDP ng cp v LSR khng nh x nhn cho chng tip theo

10-Bn tin gii phng nhn ( Lable Release Message): Bn tin ny c LSR s dng khi

nhn c chuyn i nhn m n khng cn thit na. LSR phi pht bn tin gii phng nhn ny

di bt k mt trong nhng trng hp sau.

- LSR gi nh x nhn khng thuc Hop tip theo i vi mt FEC c nh x v LSR

c cu hnh duy tr cho qu trnh hot ng.- LSR nhn mt nh x nhn t mt LSR m chng khng phi l ca Hop tip theo i vi

mt FEC v LSR c cu hnh cho vic duy tr qu trnh hot ng

ch hot ng gn nhn theo yu cu t pha trc, LSR s yu cu gn nhn t LSR

ln cn pha trc s dng bn tin Lable Request. Nu bn tin Lable Request cn phi hu b trc

khi dc chp nhn ( do nt k tip trong FEC yu cu thay i ) th LSR yu cu s loi b yu

cu nh bn tin Lable Request Abort.

11-Bn tin Lable Abort Request ( Bn tin b d nhn ): Bn tin ny c s dng lo

b cc bn tin yu cu nhn bt thng

Cc ch phn phi nhn:

Chng ta bit mt s ch hot ng trong vic phn phi nhn nh: khng yu cu

pha trc, theo yu cu pha trc, iu khin LSP theo lnh hay t lp, duy tr tin tin hay lu

gi. Cc ch ny c tho thun bi LSR trong qu trnh khi to phin LDP.

Khi LSR hot ng ch duy tr lu tr, n s gi nhng gi tr nhn/ FEC m n cn

ti thi im hin ti. Cc chuyn i khc c gii phng. Ngc li trong ch duy tr tin

tin, LSR gi tt c cc chuyn i m n c thng bo ngay c nhng chuyn i khngc s dng ti thi im hin ti, Hot ng ca ch ny nh sau:

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- LSR1 gi lin kt nhn vo mt s FEC n mt trong cc LSR k tip ( LSR2 ) cho FEC

.

- LSR2 nhn thy LSR1 hin ti khng phi l nt tip theo i vi FEC v n khng th

s dng lin kt ny cho mc ch chuyn tip ti thi im hin ti nhng n vn lu gi lin kt

ny li.

- Ti thi im no sau ny c s xut hin thay i nh tuyn v LSR1 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 hi mt

cch t ng m khng cn n 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 nh 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 gi nhn c s dng cho cc ATM-LSR.

1.3.2 Giao thc phn phi nhn da trn rng buc ( CR-LDP ).

Giao thc phn phi nhn nh tuyn da trn rng buc CR-LDP ( Constraint-Based

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 tin phn phi nhn.

hiu r hn v nh tuyn cng bc da trn rng buc, ta xt vic nh tuyn vi mt

mng IP truyn thng. Mt mng c th c xem nh l mt tp hp cc h thng t tr AS,trong vic nh tuyn mi AS tun theo giao thc nh tuyn trong min. Vic nh tuyn

gia cc AS li tun theo nh tuyn lin min. 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. V d: Trong giao thc nh tuyn RIP th l s ti u v s nt mng trn

tuyn ng m gi tin i t ngun ti ch. C nhiu tuyn ng i t ngun n mt ch

nhng mi mt tuyn ng li c s nt, bng thng, tr khc nhau. Do vy vi RIP th thut

ton Bellman-Ford c s dng xc nh sao cho ng i qua t nt nht.

i vi nh tuyn cng bc, ta c th xem mt mng nh l mt tp hp cc nt mng v

mt tp hp cc kt ni ga cc nt mng . Mi knh s c cc c im ring. kt ni gia

hai nt bt k th cn phi tho mn mt s yu cu ( rng buc ) v coi cc rng buc ny nh l

cc c im ca cc knh. Ch c nt u tin trong cp ng vai tr khi to ng kt ni mi

bit c im ny. Nhim v ca nh tuyn cng bc l tnh ton xc nh ng kt ni t nt

ny n nt kia sao cho tho mn mt s iu kin rng buc c t ra vi lin kt , cc

iu kin rng buc c th l mt trong nhiu cc tiu ch. V d nh:

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S nt t nht, ng i ngn nht, bng thng rng nht, dung lng ng truyn, thi

gian thcTuy nhin vic ti u ho theo cc tiu ch khc nhau khng th c p ng mt

cch ng thi. Mt thut ton ch ti u theo mt tiu ch no ch khng th p ng mt thi

im nhiu tiu ch v hai yu cu hai tiu ch c th xung t nhau, chng hn: ng i ngn

nht s nt t nht cha chc bng thng rng nht. Do vy thut ton nh tuyn rng buc cng

khng th p ng ti u theo tiu ch. N ch 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 tuyn ng.

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 lu lng no i qua

mt s knh nht nh trong mng c xc nh bi mt s c im no . Do , thut tonnh tuyn m nh qun tr phi thc hin l tm 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 l s kt hp ca c hai iu kin rng buc l qun l v

c im knh mt cch ng thi ch khng phi ch tng iu kin ring r. V d, nh tuyn

cng bc phi tm ra mt ng va phi c rng bng tn nht nh, va phi loi tr ra mt

s knh c c im nht nh.

im khc bit chnh gia nh tuyn IP truyn thng vi 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 ct ra, trong khi thut ton nh tuyn cng bc va tm ra mt tuyn ng ti u theo mt tiu

ch no ng thi phi 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 c yu cu trong khi cc

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 nguyn nhn. Trong , nguyn nhn chnh l do 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 tuyn 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 cc iu kin ny. Ngc li trong b

nh tuyn IP th ng i c xc nh v tnh ton bi tt c cc b nh tuyn phn tn ton

mng.

Mt nguyn nhn khc l kh nng nh tuyn hin ( hoc ngun ) v cc ngun khc nhau

c th tnh ton xc nh cc ng khc nhau n cng mt ch. V vy, ch da vo thng tin v

ch l khng c th xc nh ng truyn cc gi tin.

Mt nguyn nhn na l i vi phng php nh tuyn cng bc th vic tnh ton xcnh ng phi tnh n cc thng tin v c im tng ng ca tng knh trong mng. i vi

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cc phng php IP n gin khng h tr kh nng ny. V d giao thc nh tuyn truyn thng

da vo trng thi knh ( nh OSPF)ch truyn duy nht cc thng tin bn, ri ca tng knh v

di ca tng knh, cc giao thc nh tuyn vector khonh cch nh RIP th ch truyn o cc

thng tin a ch nt tip theo v khong cch.

1.3.3. Giao thc dnh trc ti nguyn RSVP ( Resource Reservation Protolcol ).

RSVP l giao thc bo hiu ng vai tr quan trng trong mng MPLS, c s dng

dnh trc ti nguyn cho mt phin truyn trong mng Internet. N cho php cc ng dng thng

bo v cc yu cu cht lng dch v ( QoS ) vi mng v mng s p ng bng cc thng bo

thnh cng hay tht bi.

RSVP c dng cung cp kh nng vn hnh c bo v bng vic t trc ti

nguyn cn thit ti mi my tham gia vo h tr lung lu lng v d nh truyn hnh hi ngh,

i vi cc giao thc IP l giao thc khng kt ni n khng h tr vic thit lp cc ngcho 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 nhn phi gii quyt 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 nm trn

tuyn ng ca gi tin.

RVSP thao tc vi tt c t tc n hng v a hng, vic lin mng thi im hin ti

l cc giao thc a hng.RSVP mang cc thng tin sau:

- Thng tin phn loi nh n m cc lung lu lng vi cc yu cu QoS c th c th

c nhn bit trong mng. Thng tin ny bao gm a ch IP pha gi v pha nhn, s cng UDP.

- Ch tiu k thut ca lung lu lng v cc yu cu QoS, theo khun dng TRpec v

Rspec bao gm cc dch v yu cu ( c bo m hoc ti iu khin ).

RSVP phi mang cc thng tin trn t cc my ch ti tt c cc tng i chuyn mch v cc b

nh tuyn dc theo ng truyn t b pht ti b tu. V vy, tt c cc thnh phn mng phi tam

gia vo vic m bo cc yu cu QoS ca ng dng.

RSVP s dng bn tin trao i ti nguyn dnh 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

nhng mt mt ca cc bn tin iu khin.

RSVP mang thng tin trong c hai loi c bn l PATH v RESV xc nh lung v

cc QoS cho lung. Cc yu cu ny ch ra dc v c bo v, v d tc nh cho lung d

liu, kch thc cm. Mt bn tin PATH bao gi cng c gi ti mt a ch gi l a ch phin,

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n c th l a ch n hng hoc a hng. Chng ta thng xem phin i din cho mt ng

dng n, n c xc nhn bng mt a ch ch v s cng ch s dng ring cho ng dng.

Khi b thu nhn 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 nm trng trong mo u IP v giao thc

truyn ti l: a ch ngun, s cng ngun, s giao thc ( UDP,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

tin trong lung dnh ring c khng ch m bo khng pht sinh lu lng vt qu so vi

thng bo trong Tspec v c xp vo hng i ph hp theo yu cu QoS.Mt c im na cn phi nhc n i vi giao thc ny l RSVP l giao thc trng

thi mm. N khc vi cc lo giao thc khc l trng thi s t ng ht hiu lc sau mt thi

gian tr khi n c lm ti theo nh k, tc l RSVP s lin tc gi cc bn tin PATH v

RESV lm ti cc cng dnh ring. Nu chng khng c gi i trong mt khong thi gian

no y th cng dnh ring t ng hu b.

Qu trnh 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 chkhng phi 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 c cc cng dnh ring

RSVP. Ta c th xem mt tp cc gi tin to bi cng dnh ring RSVP nh l mt trng hp

ring ca FEC.

Chng ta nh ngha mt i tng RSVP mi l i tng Lable c mang trong bn tin

RSVP RESV. Khi 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 c bn tin RESV cha i tng Lable, 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 cc LSR ngc, LSP c thit lp dc theo tuyn ng. Khi

cc nhn c cung cp trong cc bn tin RESV, mi LSR c th d dng kt hp cc ti nguyn

QoS ph hp vi LSR. 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 chophp RSVP c p dng trong mi trng MPLS theo cch m n khng th thc hin c

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trong mng IP truyn thng. Theo quy c th cc cng dnh ring RSVP ch c th to nhng

lung ng dng ring l, tc l nhng lung ng dng c xc nh nh vo 5 trng mo u

nh cp trn. Tuy nhin cng c th t cu hnh ca b nh tuyn chn cc gi da

trn mt s tiu chun v d 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 rt hu dng vi cc cng ty

ln mun c nhiu kt ni vi cc cng ty khc m ch s dg mt ng thu bao nhm gim bt

s phc tp trong vic qun tr cng nh iu khin lu lng, y mt lu lng ln cn c

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 tngRSVP mi c th mang trong bn tin PATH l i tng Lable Request. Bn tin ny cp

trong phn cc bn tin LDP.

Kh nng m rng ca RSVP

Mt trong nhng iu chc chn v RSVP l n c th chu tn tht v kh nng m rng mt mc no y. Trong thc t, c tnh ny khng chnh xc hon ton. RSVP khi u cthit k h tr d tr ti nguyn cho cc lung ng dng ring v y l nhim v vi nhngthch thc v kh nng m rng vn c.

Ni chung thut ng ny c s dng ch gii hn s dng ti nguyn tng nhanh nhth no khi mng tng trng. V d, trong mng IP quy m ln nh mng xng sng nh cungcp dch v Internet, chng ta c th quan tm n vic liu mt bng nh tuyn s chim b nhca b nh tuyn ln n mc no, kh nng b x l v bng thng lin kt. V th, bng nhtuyn tng chm hn nhiu so vi s ngi s dng kt ni vo mng.

D tr ti nguyn cho cc lung ng dng ring r rng l nh hng xu n kh nng mrng. Chng ta c th cho rng mi ngi s dng s d tr ti nguyn ti mt vi tc trung

bnh, v th s ti nguyn d tr c to ra qua mng ln c kh nng tng nhanh bng s ngis dng ca mng. iu ny s dn n chi ph ln nu mi b nh tuyn phi lu tr trng thiv tin trnh mt vi bn tin cho mi ti nguyn d tr cho lung ng dng ring.

Ni tm li, s chnh xc hn nu ni rng mc d tr ti nguyn cho cc lung ng dng l

km hn so vi RSVP. S khc nhau ny c bit quan trng khi chng ta xem xt rng RSVP

khng nhng i hi cho vic d tr ti nguyn cho cc lung ng dng ring m cn d tr ti

nguyn cho lu lng tng hp

1.3.4. Giao thc MPLS-BGP

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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 ca BGP. Tip cn ny m bo cho qu trnh phn

phi nhn v cc thng tin nh tuyn n nh v gim bt tiu ca bn tin iu khin x l.

1.4 Hot ng ca MPLS:

gi tin truyn qua mng MPLS, mng s thc hin cc bc sau:

To v phn phi nhn.

To bng cho mi bng nh tuyn.

To ng chuyn mch nhn.

Gn nhn da trn tra cu bng.

Truyn gi tin.

Ngun gi cc d liu ca n ti ch. Trong min MPLS, khng phi tt c cc lu lngt mt ngun cn thit truyn qua cng mt tuyn ng. Da trn cc c tnh lu lng, cc

LSP khc nhau c th c to ra cho cc gi tin vi cc yu cu khc nhau t pha ngun.

To v phn phi nhn: Trc khi d liu truyn, cc b nh tuyn quyt nh to ra lin

kt nhn ti cc FEC c th v to bng

Trong LDP cc b nh tuyn lung xung bt u phn phi nhn

v gn nhn vo FEC.

Cc c tnh lin quan n lu lng v dung lng MPLS c

iu chnh thng qua s dng LDP.

Giao thc bo hiu nn dng giao thc vn chuyn c th t v

m bo tin cy

To bng: Khi chp nhn cc lin kt nhn mi LSR to ra bng c s d liu nhn ( LIB ).

Ni dung ca cc bng ny 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 LIB c cp nht khi c s thay i hoc

iu chnh nhn.

To ng chuyn mch nhn: Cc LSP c to ra theo chiu ngc vi cc mc trongcc LIB.

Gn nhn da trn bng tra cu: B nh tuyn u tin LER1 trong hnh trn s dng bng

LIB tm ng tip theo yu cu nhn cho FEC c th

Cc b nh tuyn tip theo s dng bng tm ng

tip theo.

Khi gi tin n LSR li ra LER4 hnh trn nhn c loi

b v gi tin c truyn ti ch.

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Chuyn tip gi tin: Hnh trn m t ng i ca gi tin khi n c truyn t ngun

ti ch.

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. LDP s xc nh ng dn o m bo QoS.

Mi b nh tuyn trung gian LS2 v LS3 s nhn gi tin gn nhn

thay i nhn v truyn i.

Gi tin n LER4, loi b nhn v gi ra khi min hot ng ca

MPLS v phn pht ti ch. ng truyn gi tin c ch ra trong hnh trn.

C hai ch hot ng i vi MPLS: ch hot ng khung ( Frame-mode) v ch t bo ( Cell-mode ).

1.4.1 Ch hot ng khung.

Ch hot ng ny xut hin khi s dng MPLS trong mi trng cc thit b nh tuyn

thun iu khin cc gi tin IP im-im. Cc gi tin dn nhn c chuyn tip trn c s khung

lp 2.C ch hot ng ca MPLS trong ch ny c m t hnh di y.

LSR bin 1

LSR bin 2

LSR bin 3

LSR li 2

LSR li 1 LSR li 3

LSR bin 4

Bc1: nhn gitin IP ti LSR bin

Bc2: Kim tra lp3 gn nhn, nhuyngi IP n LSR li 1

Bc3:Kim tra nhn chuyni nhn chuyn gi IP n

LSR li 3

Bc4: Kim tra nhnchuyn i nhn

chuyn gi IP nLSR bin 4

Bc5:Kim tra nhn xo bnhn i chuyn gi IP n ch

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Hnh 1.11: Mng MPLS trong hot ng ch khung

Cc hot ng trong mng s liu:

Qu trnh chuyn tip mt gi IP qua mng MPLS c thc hin qua mt 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 vi cng FEC ( trong trng hp mng con l mng

IP ).

Khi LSR bin li ra ca vng FEC ny nhn c gi tin c nhn, n loi b nhn vthc hin chuyn tip gi tin IP theo bn nh tuyn lp 3 truyn thng.

Mo u nhn MPLS.

Nhn MPLS c chn trc s liu cn gn nhn ch hot ng khung. Tc l 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 trong hnh v.

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 inh tuyn nhn bit rng gi ang c gi i khng phi l

gi IP thun m l gi c nhn. 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 hng hay a hng s

dng gi tr 8847H v 8848H cho dng Ethernet. Cc gi tr ny c s dng trc tip trn

phng tin Ethernet ( bao gm c Ethernet v Gigabit Ethernet ).

Trn knh im-im s dng giao thc PPP, s dng giao thc mi c gi ny

MPLS ( giao thc iu khin ). Cc gi MPLS c nh du bi gi tr 8281H trong trng giaothc PPP

Cc gi MPLS truyn qua chuyn dch khung DLCI gia mt cp thit b nh tuyn

c nh du bi nhn dng giao thc SNAP ca chuyn dng khung, tip theo mo u SNAP

vi gi tr 8847H cho Ethernet nh trong mng LAN.

Chuyn mch nhn trong ch khung:

Ta s xt qu trnh chuyn i nhn nh hnh trn trong mng MPLS sau khi nhn c mt

gi tin IP.

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Sau khi nhn khung PPP lp 2 t b nh tuyn bin s 1, LSR li lp tc nhn dng gi

nhn c l gi c nhn da trn gi tr trng giao thc PPP v thc hin vic kim tra nhn

trong c s d liu chuyn tip nhn. Kt qu nhn 30 c thay bng nhn ra 28 tng ng vi

vic gi tin s chuyn tip n LSR3 li 3.

Ti li 3, nhn c kim tra, nhn s 28 c thay bng hn s 37 v cng ra c xc

nh. Gi tin c chuyn tip n LSR bin s 4

Ti LSR bin s 4, nhn 37 b loi b v vic kim tra a ch IP a ch lp 3 c thc

hin, gi tin c chuyn tip n b nh tuyn ngoi mng MPLS.

Qu trnh chuyn i nhn c thc hin trong cc LSR li da trn bng nh tuyn nhn.

Bng nh tuyn ny phi c cp nht y m bo mi LSR trong mng MPLS c y

thng tin v tt c cc hng chuyn tip. Qui trnh ny xy ra trc khi thng tin c truyn

trong mng v c gi l qu trnh lin kt nhn ( Lable 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 qua bn tin Hello. Sau

khi bn tin ny c gi, mt phin giao dch gia hai LSR c thc hin th tc trao i l LDP.

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 trong bng nh

tuyn IP v bn chuyn i cha trong LIB. Vy nhn c gn trong mi tin t trong bng 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 dn tt c cc b nh tuyn thng qua phin

LDP.

1.4.2 Ch hot ng t bo MPLS.

trin khai MPLS qua mng ATM cn phi gii quyt mt s vn sau. Hin ti khng tn ti c ch no cho vic trao i trc tip cc gi IP gia cc nt MPLS

ln cn qua giao din ATM. Tt c cc s liu trao i qua giao din ATM phi c thc

hin qua knh o ATM.

Cc tng i ATM khng th thc hin vic kim tra nhn ha 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 thi MPLS qua ATM th cn mt s c ch sau.

Cc gi tin IP trong mng iu khin khng th trao i trc tip qua giao din ATM. Mt

knh o VC phi c thit lp gia 2 nt ln cn trao i gi thng tin iu khin.

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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 c sa i m bo cc tng i ATM khng phi

kim tra a ch lp 3.

Trong phn ny mt s thut ng sau c s dng.

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).

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 truyn thng.

LSR theo khung l LSR chuyn tip ton b cc khung gia cc giao din ca n. B nh

tuyn truyn thng l LSR kiu ny. Min ATM-LSR l tp hp cc ATM-LSR kt ni vi nhau qua cc giao din LC-ATM

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

trao 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 cc 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

LAN hay Wan. Cn tng i ATM khng c kh nng . cung cp kt ni IP thun gia cc

ATM-LSR c hai cch thc 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 Fourum thc hin

nh sau: Knh o iu khin MPLS VC thng thng s dng gi tr VPI/VCI l 0/32 v

bt buc phi s dng phng php ng gi LLC/SNAP cho cc gi IP theo tiu chun

RFC1483. 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 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 kim tra c s d

liu chuyn tip LIB hay c s cuyn tip d liu chuyn tip nhn c phn chia thnh t

bo ATM v gi n ATM-LSR tip theo. Gi tr VPI/VCI c gn vo mo u tng t

bo.

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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 bo m

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 kim 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 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

li gi tr bang 0 bi ATM-LSR bin li vo trc khi gi c nhn c phn chia thnh t

bo.

Phn b v phn phi nhn trong min ATM-LSR.

LSR bin 1

LSR bin 2

LSR bin 3

ATM-LSR li 2

ATM-LSR li 1 ATM-LSR li 3

LSR bin 4

Bc1: Gi yucu nhn X n

nt k

Bc2: ATM-LSR1gi yu cu nhn X

n ATM-LSR3

Bc3: ATM-LSR3 gi yucu nhn X n LSR 4

Bc4: LSR bin4gn gi tr VPI/VCI vgi tr li ATM-LSR3

Bc5: ATM-LSR3 gn gi trVPI/VCI ni vng chuyn iVo sang VPI/VCI ra v gi

VPI/VCI mi n ATM-LSR1

Bc6: Gi tr VPI/VCI nivng c gn bi ATM -LSR1

co LSR bin1 tr li cho yucu

Hnh 1.12: Phn b nhn trong mng ATM-MPLS

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 th s dn ti cc hn ch bimi nhn c gn qua giao din LC-ATM tng ng vi mt ATM VC. V s lng VC qua

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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 m nhn trch nhim yu cu phn b v phn

phi nhn qua giao din LC-ATM. LSR pha sau cn nhn gi tin 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 n 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 b cho ch pha

trc th n mi tr li yu cu. Nu ATM-LSR khng c nhn pha 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 nhn c nhn tLSR pha trc n.

Hp nht VC.

Hp nht VC tc l gn cng VC cho cc gi n ch. y l mt vn quan trng cn

gii quyt i vi tng i ATM trong mng MPLS. ti u ho qu trnh gn nhn ATM-LSR

c th s dng li nhn cho cc gi cg 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 li ng gi t cc t

bo. trnh trng hp ny, ATM-LSR phi yu cu LSR pha trc n phn b nhn mi mikhi 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.

1.4.3 Hot ng ca MPLS khung trong mng ATM-LSR.

Do vic chuyn i cng ngh mng tc ng n rt nhiu mt trong mng khai thc t

nhng vn ghp ni mng cng nh quan nim v cch thc vn hnh khai thc.

Qu trnh chuyn i sang mng MPLS c th c thc hin theo nhiu cch: hoc l thc

hin qua mt s giai on 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. i vi h tng c s nh Frame-Relay hoc ATM-PVC th rt kh trin khai c hot

ng t bo ca MPLS, thng thng th ch khung s c s dng trong mi trng nh vy

thc hin kt ni MPLS xuyn sut mng.

Trong mt s iu kin nht nh nh trong giai on chuyn dch sang mng

IP+ATM=( MPLS ) hoc chuyn mch ATM chuyn tip khng h tr MPLS th cn thit phi s

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dng ch hot ng khung qua mng ATM-PVC. Cu hnh ny phi 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 ).

VPI 08

Chuyn mchATM

Knh ATM PVC

LSR bin1 LSR bin2

VPI 01

Hnh 1.13: 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 kiu phn phi

nhn chiu i khng yu cu. Vic s dng MPLS qua mng ATM-PVC yu cu ng gi bng

ALL5-SNAP trn knh PVC .

Vic s dng ch khung qua mng ATM-PVC l rt cn thit trong qu trnh chuyndch sang mng MPLS.

1.5 Cc u im ca MPLS

- H tr mm do v linh hot cho tt c cc dch v trn mt mng n.

- n gin ho cu hnh mng so vi gii php IP trn nn ATM.

- H tr tt c cc cng c iu khin lu lng mng m bao gm c nh tuyn lin tip

v chuyn mch bo v.

- H tr a kt ni v a giao thc.

- Kh nng m rng chc nng iu khin v chuyn tip. Mi phn c th pht trin khngcn n cc phn khc, to s pht trin khng cn n cc phn khc, to s pht trin mng d

dng hn, gi thp hn v t li hn.

- H tr cho tt c cc loi lu lng

- nh tuyn gin tip: mt thuc tnh ca MPLS l n h tr cho nh tuyn gin tip. Cc

ng chuyn mch nhn nh tuyn gin tip c hiu qu hn nh tuyn ngun trong IP. Cung

cp cc chc nng cho k thut iu khin lu lng. Cc ng nh tuyn gin tip cng nh

cc ng hm o c th mang loi lu lng bt k nh SNA, IPX..

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- nh tuyn lin vng: chuyn mch nhn cung cp kh nng tch hon thin hn gia nh

tuyn lin vng v trong vng. Nhng kh nng ci tin ny ca qu trnh x l nh tuyn v thc

t to li cc tuyn bit c yu cu bn trong mt vng. Li ch ny ca ISP v nhng ti tin c

th c mt lng ln lu lng truyn thng.

1.6 ng dng ca MPLS

Mng MPLS c nhiu ng dng trong c 3 ng dng ch yu

- Tch hp IP v ATM: do chuyn mch nhn c th thc hin c bi cc chuyn mch

ATM, MPLS l mt phng php tch hp cc dch v IP trc tip trn chuyn mch ATM. S

tch hp cn phi t nh tuyn IP v phn mm LDP trc tip trn chuyn mch ATM. Do tch

hp hon ton IP trn 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 dnh

trc ti nguyn h tr QoS) v mng ring o.- Dch v mng ring o IP (VPN): VPN thit lp c s h tng cho mng Intranet v

Extranet l 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 Intranet v Etranet m cc mng c cung cp bi nh

cung cp dch v n nhiu t chc khch hng. MPLS kt hp vi giao thc cng bin ( BGP )

cho php mt nh cung cp mng 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 nh,

kh nng linh hot v d qun l ca cc dch v MPLS+BGP VPN l u im ch yu.- iu khin lu lng v inh tuyn IP hin: Vn quan trng trong cc mng IP lin tc

l thiu kh nng linh hot cc lung lu lng IP s dng hiu qu di thng mng c sn. Do

vy, thiu ht ny lin quan kh nng gi cc lung c chn sn v d nh chn cc ng

trung k c m bo cho cc lp dch v ring. MPLS s dng cc ng chuyn mch nhn

(LSPs). 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 lu lng IP

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CHNG 2

GII THIU CU TRC MNG NG TRC CA VIT NAM

2.1 Cu trc vt l mng vin thng.

2.1.1 Khi nim v mng vin thng.

Mng vin thng l phng tin truyn a thng tin t u pht ti u thu. Mng c

nhim v cung cp cc dch v cho khch hng.

Mng vin thng bao gm cc thnh phn chnh: Thit b chuyn mch, thit b truyn dn,

mi trng truyn v thit b u cui.

Hnh 2.1: Cc thnh phn chnh ca mng vin thng

- Thit b chuyn mch gm c tng i ni ht v tng i qu giang. Cc thu bao c

ni vo cc tng i ni ht v tng i ni ht c ni vo tng i qu giang. Nh cc thit b

chuyn mch m ng truyn dn c dng chung v mng c th s dng kinh t.

- Thit b truyn dn dng ni thit b u cui vi tng i, hay gia cc tng i

thc hin vic truyn cc tn hiu. Thit b truyn dn chia lm hai loi: thit b truyn dn phathu bao v thit b truyn dn cp quang. Thit b truyn dn pha thu bao dng mi trng

thng l cp kim loi, tuy nhin c mt s trng hp mi trng truyn l cp quang hoc v

tuyn.

- Mi trng truyn dn bao gm truyn hu tuyn v v tuyn. Truyn hu tuyn bao gm

cp kim loi, cp quang. Truyn v tuyn bao gm vi ba ,v tinh.

Mng vin thng cng c th c nh ngha nh sau: Mng vin thng l mt h thng

gm cc nt chuyn mch c ni vi nhau bng cc ng truyn dn to thnh cc cp mng

khc nhau.

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Mng vin thng hin nay c chia thnh nhiu loi. l mng mc li, mng sao,

mng tng hp, mng vng kn. Cc loi mng ny c u im v nhc im khc nhau ph

hp vi cc vng a l khc nhau.

Mng vin thng PSTN hin nay c phn cp nh sau

Tng i quc t

Tng i chuyn tipmin

Tng i ni ht

Truy nhp thu bao

Hinh 2.2: Cu trc mng PSTN phn cp

Trong mng hin nay gm 3 nt:

- Nt cp 1: Trung tm chuyn mch quc t

- Nt cp 2: Trung tm chuyn mch ng di.

- Nt cp 3: Trung tm chuyn mch ni ht.

2.1.2. Cc c im ca mng vin thng hin nay.

Cc mng vin thng hin ti c c im chung l tn ti mt cch ring l, ng vi mi

loi dch v thng tin li c t nht mt loi mng vin thng ring bit phc v dch v .- Mng Telex: Dng gi cc bc in dng k t c m ho c tc truyn rt thp.

- Mng in thoi cng cng ( POTS: Plain Old Telephone Service ): y thng tin ting

ni c s ho v chuyn mch h thng chuyn mch in thoi cng cng PSTN.

- Mng truyn s liu: Bao gm cc mng chuyn mch gi trao i d liu gia cc

my tnh da trn giao thc ca X.25.

- Cc tn hiu truyn hnh bng sng v tuyn, cp

- Trong phm vi c quan, s liu gia cc my tnh c trao i thng qua mng cc b

LAN ( Local Area Network ) l cc mng Ethernet, Token Bus ,Token Ring

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Qu kh l bn p cho tng lai. Do vy trc khi tm hiu cng ngh vin thng mi ta

cn rt kinh nghim t lch s pht trin ca mng:

- Xt v gc dch v th gm cc mng sau : Mng in thoi c nh, mng in thoi di

ng v mng truyn s liu.

- Xt v gc k thut bao gm cc mng chuyn mch, mng truyn dn, mng truy

nhp, mng bo hiu v mng ng b.

2.1.3 Mng vin thng cng cng (PSTN)

Xt v mt chc nng cung cp dch v, cu trc mng vin thng VNPT c phn thnh

hai lp: chuyn ti dch v v truy nhp dch v.

- Lp chuyn ti dch v s bao gm cc tng i quc t, tng i chuyn tip, tng i ni

ht.

- Lp truy nhp dch v gm phn thu bao ca Host, cc v tinh, thit b truy nhp thubao quang, cp ng, v tuyn.

2.1.3.1 H thng chuyn mch

Vi cu trc mng hin nay th mng chuyn mch ca VNPT chia lm 3 cp da trn cc

tng i chuyn tip quc t, chuyn tip quc gia, ni tnh v ni ht. Cc tng i chuyn tip

quc t c t ti ba trung tm l H Ni, Tp HCM v Nng, cc tnh thnh khc nhau c cc

cu trc mng khc nhau vi nhiu tng i Host. Cc tng i hin c ph bin trn mng vin

thng Vit Nam l: cc tng i VKX lin doanh gia Vit Nam v Hn Quc, A1000E10 ca

Alcatel, NEAX61 ca NEC, AXE10 ca Ericsson, EWSD ca Siemens. Cc cng ngh chuynmch ang s dng l chuyn mch knh cho mng PSTN, X.25 cho mng Frame relay v ATM

cho truyn s liu.

V mt cu trc mng, mng vin thng Vit Nam hin ti c th chia thnh 3 cp

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GatewayQuc t

GatewayQuc t

Tollquc gia

Tollquc gia

Host HostTng i ni tnh

Tng i quc t

Tng i quc gia(lin tnh)

Hnh 2.3: Cu trc mng Vin thng PSTN Vit Nam hin ti

- Cp quc t: bao gm cc tng i Gateway, cc ng truyn dn quc t nh: cc trm

v tinh mt t, cc h thng cp quang bin TVH, SE-ME-WE3, tuyn p quang CSC.- Cp quc gia: bao gm cc tng i chuyn tip Transit quc gia, cc tuyn truyn dn

ng trc.

- Cp ni tnh: Gm cc tng i Host, cc v tinh, truy nhp, tng i c lp, thit b truy

nhp thu bao, cc tuyn truyn dn ni tnh. S sau l s kt ni mng chuyn mch.

Da theo s liu thu bao theo vng a l, mng VNPT c t chc thnh 5 vng lu lng

phn nh nh sau:

- Vng 1: Khu vc min Bc kt ni cc tng i thuc 27 tnh thuc khu vc tnh min Bc

(t H Giang n H Tnh, tr H Ni).

- Vng 2: Thuc khu vc H Ni.

- Vng 3: Khu vc min Trung, cc tnh t Qung Bnh tr vo n Khnh Ho, akLak.

- Vng 4: Khu vc T.P H Ch Minh.

- Vng 5: 18 Tnh ng bng Nam b v ng bng Sng Cu Long ( cc tnh cn li).

Mi vng lu lng c chia thnh cc khu vc chuyn tip (Transit Area), vic chuyn

tip lu lng vo, ra v trong cc khu vc do cc nt chuyn mch quc gia (National Transit

Switch) m trch. S lng c th cc nt chuyn mch quc gia trong mt vng lu lng tuthuc vo s lng thu bao ca tng vng lu lng.

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Lu lng i v ca cc vng no c nh tuyn qua cc tng i Transit quc gia ca

vng qua cng Gateway i quc t. S dng phng thc nh tuyn

Nhn chung mng chuyn mch hin nay cn nhiu cp v vic iu khin b phn tn trong

mng (iu khin nm ti cc tng i).

Mng chuyn mch quc gia

Mng chuyn mch quc gia bao gm 09 tng i Transit quc gia TOLL/VTN nh sau:

- Tng i AXE 10 local 6 ( BYB 202): 03 h thng vi nng lc x l ti a l 600.000

BHCA v dung lng ti a 24.000 trung k c lp t ti H Ni, T.P H Ch Minh, Nng.

- Tng i AXE 10 local 7.2 ( BYB 501): 04 h thng vi nng lc x l ti a l 1.500.000

BHCA v dung lng ti a 60.000 trung k c lp t ti H Ni, Nng, Tp H Ch Minh

v Cn Th.

- Tng i loi TDX 10 lp t ti H Ni (160 E1) v Tp H Ch Minh (272 E1). Tuynhin hin nay do cht lng dch v khng tt, khng m bo c yu cu ca khch hng nn

ang trong k hoch s chuyn sang ch d phng cho mng chuyn mch lin tnh.

- 07 tng i AXE u c tnh nng STP lm im chuyn tip bo hiu cho h thng bo

hiu C7 ca ton mng v tnh nng SCCP phc v cho dch v Roaming cho mng di ng. Mi

vng c trang b t nht 2 tng i Transit, cc tng i Transit trong vng c u cho

khc phc s mt cn bng lu lng. Lu lng qua tuyn trc tip ny ch chim 5% tng lu

lng Transit ca tng i.

2.1.3.2 H thng truyn dnMng truyn dn ca Vit Nam hin nay s dng c v tuyn v hu tuyn. V v tuyn c

cc h thng viba s dng cng ngh PDH bn cnh cn c cc ng truyn qua v tinh i

quc t. Trong truyn dn hu tuyn th ph bin l cp quang tuy vy vn c nhng on dng cc

loi cp khc. V truyn dn quang th Vit Nam ang khai thc cc thit b ca nhiu hng khc

nhau cho tng h thng. Cc h thng truyn dn quang ch yu s dng cng ngh SDH vi cc

cp ghp khc nhau nh STM-4, STM-16 hay STM-64 cho cc tuyn lin tnh cn trong tnh c

th l STM-1 hay STM-4 ty vo nhu cu dung lng thc t v tng lai.

Tuyn trc Bc-Nam s dng mng Ring cp quang 2,5 Gbit/s (trn cp quang quc l 1A

v cp quang 500 KV) v tuyn viba PDH 140 Mbit/s

Mng truyn dn cp quang lin tnh pht trin c ti hu ht cc trung tm tnh, vi:

- Tng chiu di tuyn cp quang quc l 1A l 1.935 km.

- Tng chiu di cc tuyn cp quang lin tnh l 5.090 Km. Nng dung lng mch trc

Backbone ln 20 Gbit/s s dng cng ngh DWDM a vo s dng vo thng 10/2003.

Hon chnh 13 mng Ring lin tnh theo cu trc c duyt, nng cp cc mng Ring

ln c dung lng p ng nhu cu x hi ( 2.5 Gbit/s- 5 Gbit/s).Nng cp Ring trung k lin i ti H Ni, T.P H Ch Minh v Nng ln 5- 10 Gbit/s.

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Va qua VNPT a vo khai thc h thng truyn dn Backbone Bc Nam 20Gbit/s da

trn cng ngh ghp knh phn chia theo bc sng DWDM s dng thit b ca Nortel

2.1.3.3 H thng truy nhp

Hin ti trn mng c nhiu loi truy nhp khc nhau tu thuc vo tng loi mng vi tng

loi dch v. Trong di ng, truyn hnh ta c truy nhp v tuyn vi nhiu cng ngh khc nhau

nh MMDS, LMDS, GPRS, CDMA, FDAMGn y cn c thm truy nhp WLAN cng c

trin khai ti mt s a im. V truy nhp hu tuyn ta c truy nhp bng thoi truyn thng,

ADSL, truy nhp qua ng cp truyn hnh, qua ng in lc v cng ngh mong i s l truy

nhp quang ti tng h gia nh

2.1.3.4 H thng bo hiu

Hin ti mng vin thng Vit Nam s dng c hai loi bo hiu l R2 v SS7. Mng bo

hiu SS7 v ang thay th dn bo hiu R2 trong tng cng on bo hiu, tuy vy vi mngthoi th bo hiu R2MFC vn c s dng ph bin. H thng SS7 c trin khai vi mt

cp STP (im chuyn giao bo hiu) ti ba trung tm H Ni,Tp HCM v Nng.

Hnh 2.4: H thng bo hiu Vit nam

2.1.3.5 H thng qun l

Vic khai thc v bo dng mng vin thng tp chung ( TMN) c nhiu u im cho ccnh khai thc mng. Bi nhiu chc nng c th c qun l mt cch hiu qu t mt hoc vi

im trn mng iu ny c ngha l ch cn t nhn vin cho iu hnh mng li . Xu hng ti

y s l t ng ho cho cc chc nng qun l mng.

Vit Nam ang trong qu trnh xy dng mng qun l vin thng tp trung TMN. Cn hin

ti th mi h thng mng ring c qun l bi cc phng thc qun l khc nhau.

2.1.3.6 H thng ng b

Mng ng b Vit Nam hot ng theo nguyn tc ch t c d phng, bao gm 4 cp v

hai loi giao din chuyn giao tn hiu ng b ch yu l 2MHz v 2Mb/s. Mng c phn chialm 3 vng c lp, mi vng c hai ng h mu, mt ng h chnh (Cesium) v mt ng h d

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phng (GSP). Cc ng h c t ti trung tm ca 3 vng v c iu khin theo nguyn tc

ch t. Cc tng i quc t v tng i Toll trong mi vng c iu khin bi ng h ch theo

phng thc ch t. Cc tng i Tandem v Host ti cc tnh hot ng bm theo cc tng i

Toll v cc tng i v tinh ng b theo tng i Host m n u ti, tt c u theo phng thc

ch t.

2.2 Cu trc mng vin thng NGN

2.2.1. nh ngha mng NGN

Cho ti nay cc t chc v cc nh cung cp thit b vin thng trn th gii rt quan tm

n NGN nhng vn cha c mt nh ngha r rng. Do vy ta ch c th tm nh ngha NGN

nh sau:

NGN l mng c h tng thng tin duy nht da trn cng ngh chuyn mch gi, trin

khai cc dch v mt cch a dng v nhanh chng, l s hi t gia thoi v d liu, gia c nhv di ng.

2.2.2. Cc yu t thc y tin ti NGN

2.2.2.1. Ci thin chi ph u t

Cng ngh chuyn mch knh truyn thng chm thay i so vi s thay i nhanh chng

ca cng ngh my tnh. Cc chuyn mch knh chim phn ln trn mng PSTN nhng khng

thc s ti u cho truyn s liu. Trong khi nhu cu trao i thng tin gia mng PSTN v

mng Internet ngy cng tng, do xut hin nhu cu xy dng h thng chuyn mch tng lai

da trn cng ngh hon ton gi cho c thoi v d liu.Cc giao din m ti mi lp cho php la chn linh hot nh cung cp thit b. Truyn ti

da trn gi cho php phn b bng tn hiu qu v linh hot. Nh gip nh khai thc qun l

d dng, nng cp mt cch hiu qu phn mm ti cc nt iu khin, d dng trin khai dch v

mi m khng cn thay i mng qua gip gim chi ph vn hnh khai thc mng.

2.2.2.2. Xu th i mi vin thng

Trong vng hi nhp kinh t th gii xu th hi nhp cng din ra mnh m trong vin

thng. Cnh tranh ngy cng khc lit khi th gii buc cc chnh ph phi m ca th trng vin

thng. thch ng vi xu th , p ng c kh nng cung cp loi hnh dch v cho nhiu

dng khch hng th yu cu h thng mng phi c m cao c th kt ni nhiu nh cung

cp dch v vi nhau. Vi yu cu ny cc mng c khng th thc hin c trong khi NGN

thch ng rt tt vi i hi ny nh mt cu trc m hp l.

2.2.2.3. Cc doanh thu mi

D bo hin nay cho thy doanh thu t thoi gn nh t mc bo ho v khng th tng

thm c na. Trong khi doanh thu t cc dch v gi tr gia tng ngy cng tng, xu hng s

vt doanh thu t thoi trong tng lai gn. Trc vin cnh nhiu nh cung cp, khai thc vinthng khng th b qua c hi tng doanh thu ny. Do vy vic pht trin mt mng mi p

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ng tt c cc dch v gia tng hin c cng nh nhng nhu cu dch v mi trong tng lai l

khng th khng lm. Tt c cc iu trn cho thy s pht trin mng vin thng ln NGN l mt

iu thit yu v cn thit cho cuc sng cng nh s tn ti ca cc nh khai thc cung cp dch

v vin thng.

Yu cu pht trin NGN

Trc ht cc nh khai thc dch v vin thng phi xem xt mng TDM m h tn rt

nhiu chi ph u t quyt nh xy dng mt NGN xp chng hay thm ch thay th cc tng

i truyn thng bng nhng chuyn mch cng ngh mi sau ny. Cc nh khai thc cn tm ra

phng php cung cp cc dch v mi cho khch hng ca h trong thi k qu trc khi cc

mng ca h chuyn sang NGN mt cch y .

Vn ln nht cn nhc ti l phi h tr dch v thoi qua IP v hng lot cc dch v gi

tr gia tng khc trong khi c ch best effort phn phi cc gi tin khng cn p ng na.Mt thch thc cn bn na l m rng mng IP theo nhiu hng, nhiu kh nng cung cp dch

v trong khi vn gi c u th ca mng IP.

Mt kha cnh khc l quy m mng phi ln cung cp cho khch hng nhm chng

li hin tng tc nghn c chai trong lu lng ca mng li. Vic tng s lng cc giao din m

cng lm tng nguy c mt an ninh mng. Do m bo an ton thng tin mng chng li s xm

nhp tri php t bn ngoi tr thnh vn sng cn ca cc nh khai thc mng.

Vn cng khng km phn quan trng l cc gii php qun l thch hp cho NGN trong

mi trng a nh khai thc, a dch v. Mc d cn mt nhiu thi gian v cng sc trc khi hthng qun l mng c trin khai nhng mc tiu ny vn c gi tr v s mang li nhiu li ch

nh gim chi ph khai thc, dch v a dng.

Mt vn quan trng na khi trin khai NGN l cc cng ngh p dng trn mng li

phi sn sng:

* V cng ngh truyn dn: phi pht trin cc cng ngh truyn dn quang SDH, WDM

hay DWDM vi kh nng hot ng mm do linh hot, thun tin cho khai thc v iu hnh

qun l.

* V cng ngh truy nhp: phi a dng ho cc dng truy nhp c v tuyn v hu tuyn.

Tch cc pht trin v hon thin em vo ng dng rng ri cc cng ngh truy nhp tin tin

nh truy nhp quang, truy nhp WLAN, truy nhp bng rng, c bit l trin khai rng truy nhp

ADSL v h thng di ng 3G.

* V cng ngh chuyn mch: Mc d c nhiu tranh lun v vic la chn cng ngh no

cho NGN trong cc cng ngh IP, ATM, IP/MPLS, song c th ni chuyn mch gi s l s la

chn trong NGN. Gn y vi s hon thin v nghin cu cng ngh MPLS s ha hn l cng

ngh chuyn mch ch o trong NGN. Bn cnh mt cng ngh khc l chuyn mch quangcng ang c nghin cu, hy vng s sm c ng dng trong thc t.

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2.2.4. Cu trc chc nng

NGN c cu trc chc nng nh sau:

- Lp kt ni (truy nhp v truyn dn/ phn li)

- Lp trung gian hay lp truyn thng (Media)

- Lp iu khin

- Lp qun l

Trong cc lp trn, lp iu khin hin nay rt phc tp vi nhiu loi giao thc, kh nng

tng thch gia cc thit b ca cc hng l vn ang c cc nh khai thc quan tm.

Lp ng dng

Lp iu khin

Lp truy nhp

Lp chuyn ti

Lpqunl

Hnh 2.5: Cu trc mng NGN cp dch v

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Hnh 2.6 : Cu trc chc nng ca NGN

* Lp truyn dn v truy nhp

Phn truyn dn- Ti lp vt l truyn dn quang vi cng ngh ghp knh theo bc sng DWDM s c

s dng.

- Cng ngh IP/MPLS c th c s dng truyn dn trn mng li m bo QoS.

- Cc router c s dng bin mng li khi lu lng ln v ngc li khi lu lng nh

Switch router c th m nhn lun chc nng nhng router ny.

- Lp truyn dn c kh nng h tr cc mc QoS khc nhau cho cng mt dch v v cho

cc dch v khc nhau. Lp ng dng s a ra cc yu cu v nng lc truyn ti v n s thc

hin yu cu .Phn truy nhp

- Vi truy nhp hu tuyn: c cp ng v xDSL ang c s dng. Tuy vy trong tng

lai truyn dn quang DWDM, PON s dn chim u th, th trng ca xDSL v modem s dn

thu nh li.

- Vi truy nhp v tuyn ta c h thng thng tin di ng GSM hoc CDMA, truy nhp v

tuyn c nh, v tinh. Trong tng li cc h thng truy nhp khng dy s pht trin rt nhanh

nh truy nhp hng ngoi, bluetooth hay WLAN.

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- Lp truy nhp cung cp cc kt ni gia thu bao u cui v mng ng trc qua cng

giao tip thch hp. NGN cng cung cp hu ht cc truy nhp chun cng nh khng chun ca

cc thit b u cui nh: truy nhp a dch v, in thoi IP, my tnh PC, tng i ni b PBX

* Lp truyn thng

* Gm cc thit b l cc cng phng tin nh:

- Cng truy nhp: AG kt ni gia mng li v mng truy nhp, RG kt ni mng li v

mng thu bao nh.

- Cng giao tip: TG kt ni mng li vi mng PSTN/ISDN, WG kt ni mng li vi

mng di ng.

Lp ny chu trch nhim chuyn i cc loi mi trng (FR, PSTN, LAN, v tuyn)

sang mi trng truyn dn gi c p dng trn mng li v ngc li.

* Lp iu khinLp iu khin bao gm cc h thng iu khin m thnh phn chnh l Softswitch cn gi

l MGC hay Call agent, c kt ni vi cc thnh phn khc nhau nh: SGW MS FS AS kt

ni cuc gi hay qun l a ch IP.

Lp iu khin c nhim v kt ni cung cp cc dch v truyn thng sut t u cui

n u cui vi bt k loi giao thc v bo hiu no. Cc chc nng qun l v chm sc khch

hng cng c tch hp trong lp iu khin. Nh c giao din m nn c s tch bit gia dch

v v truyn dn, iu ny cho php cc dch v mi c a vo nhanh chng v d dng.

* Lp ng dngLp ny gm cc nt thc thi dch v ( thc cht l cc server dch v) cung cp cc ng

dng cho khch hng thng qua lp truyn ti.

Lp ng dng cung cp cc dch v c bng thng khc nhau v nhiu mc . Mt s

dch v s thc hin lm ch vic iu khin logic ca chng v truy nhp trc tip ti lp ng

dng, cn mt s dch v khc s thc hin iu khin t lp iu khin. Lp ng dng kt ni vi

lp iu khin thng qua giao din m API. Nh m cc nh cung cp dch v c th pht trin

cc ng dng v trin khai nhanh chng trn dch v mng.

* Lp qun l

Lp qun l l mt lp c bit xuyn sut cc lp t kt ni cho n lp ng dng. Ti lp

qun l ngi ta c th khai thc hoc xy dng mng gim st vin thng TMN nh mt mng

ring theo di v iu phi cc thnh phn mng vin thng ang hot ng.

2.2.5. Cc thnh phn ca NGN

NGN l mng th h k tip khng phi l mng hon ton mi do vy khi xy dng NGN ta cn

ch vn kt ni NGN vi mng hin hnh v tn dng cc thit b vin thng hin c trn mng nhm

t c hiu qu khai thc ti a.

Cu trc vt l ca NGN

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Hnh 2.7: Cu trc vt l ca NGN

2.2.5.1. Cc thnh phn ca NGN

Trong NGN c rt nhiu thnh phn song y ch trnh by nhng thnh phn th hin r

nt s tin tin ca NGN so vi mng vin thng truyn thng c th l:

- Media Gateway (MG)

- Media Gateway Controller (MGC)

- Signalling Gateway (SG)

- Media Server (MS)

- Application Server (Feature Server)

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Hnh 2.8: Cc thnh phn ca NGN

* Media Gateway MG

Media Gateway cung cp phng tin truyn ti thng tin thoi, d liu, fax v video

gia mng gi IP v mng PSTN. Trong mng PSTN, d liu thoi c mang trn knh DSo.

truyn d liu ny vo mng gi mu thoi cn c nn li v ng gi. c bit y ngi ta

s dng mt b x l tn hiu s DSP.

* Media Gateway Controller MGC

MGC l n v chnh ca Softswitch. N a ra cc quy lut x l cuc gi, cn MG v SG s

thc hin cc quy lut . N iu khin SG thit lp v kt thc cuc gi. Ngoi ra n cn giao

tip vi h thng OS v BSS

MGC chnh l cu ni gia cc mng c c tnh khc nhau, nh PSTN, SS7, mng IP. Nchu trch nhim qun l lu lng thoi v d liu qua cc mng khc nhau. N cng c gi l

Call Server do chc nng iu khin cc bn tin.

Mt MGC kt hp vi MG, SG to thnh mt cu hnh ti thiu cho Softswitch.

* Signalling Gateway SG

Signalling Gateway to ra chic cu ni gia mng bo hiu SS7 vi mng IP di s iu

khin ca Media Gateway Controller (MGC).

SG lm cho Softswitch ging nh mt nt SS7 trong mng bo hiu SS7. Nhim v ca SG

l x l thng tin bo hiu.

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* Media Server

Media Server l thnh phn la chn ca Softswitch, c s dng x l cc thng tin

c bit. Mt Media Server phi h tr phn cng DSP vi hiu sut cao nht.

* Application Server /Feature Server

Server c tnh l mt server mc ng dng cha mt lot dch v ca doanh nghip. Chnh

v vy n cn c gi l Server ng dng thng mi. V hu ht cc server ny t qun l cc

dch v v truyn thng qua mng IP nn chng khng rng buc nhiu vi Softswitch v vic

phn chia hay nhm cc thnh phn ng dng.

Cc dch v cng thm c th trc thuc Call Agent hoc cng c th thc hin mt cch c lp.

Nhng ng dng ny giao tip vi Call Agent thng qua cc giao thc nh SIP, H323 Chng

thng c lp vi phn cng nhng li yu cu truy nhp c s d liu c trng.

Feature Server xc nh tnh hp l v h tr cc thng s dch v thng thng cho h thng achuyn mch.

2.2.5.2 Nguyn tc t chc cu trc mng th h sau - NGN

Phn vng lu lng: Cu trc mng th h sau c xy dng da trn phn b thu bao

theo vng a l, khng t chc theo a bn hnh chnh m c phn theo vng lu lng. Trong

mt vng c nhiu khu vc v trong mt khu vc c th gm mt hoc nhiu tnh, thnh. S lng

cc tnh thnh trong mt khu vc tu thuc vo s lng thu bao ca cc tnh thnh . Cn c

vo phn b thu bao, mng NGN ca VNPT c phn thnh 5 vng lu lng nh sau:

- Vng 1: Cc tnh pha bc tr H ni, H Ty, Bc Ninh, Bc Giang v Hng Yn.- Vng 2: H Ni, H Ty, Bc Ninh, Bc Giang v Hng Yn.

- Vng 3: Cc tnh Min Trung v Ty Nguyn.

- Vng 4: TP H Ch Minh.

- Vng 5: Cc tnh pha Nam tr TP H Ch Minh.

T chc lp ng dng v dch v

- Lp ng dng v dch v c t chc thnh mt cp cho ton mng.

- S lng nt ng dng v dch v ph thuc vo lu lng dch v cng nh s lng v

loi hnh dch v. Giai on u ton mng s c 2 node t ti H Ni v Tp H Ch Minh.

T chc lp iu khin

Lp iu khin c t chc thnh mt cp chung cho ton mng thy v c 4 cp nh hin

nay gm: quc t, lin tnh, tn m v ni ht) v c phn theo khu vc qun l c 3 node iu

khin t ti H Ni, TP H Ch Minh v Nng.

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Service Nodes Service Nodes

(Lp iu khin)

Min Nam

TP.HCM HN

Min Bc

Min Trung(N)

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Hnh 2.9: M hnh kt ni lp iu khin v ng dng mng NGN

Lp iu khin c chc nng iu khin lp chuyn ti v lp truy nhp cung cp cc dch

v ca mng NGN, gm nhiu module nh module iu khin kt ni IP/MPLS, iu khin nh

tuyn kt ni IP, iu khin kt ni cuc gi thoi bo hiu s 7...

T chc lp chuyn ti.

Lp chuyn ti: c t chc thnh 2 cp: cp ng trc quc gia v cp vng)

- Cp ng trc quc gia: gm ton b cc note chuyn mch ng trc (li IP/MPLS) v

cc tuyn truyn dn kt ni cc nt trc. Cp ng trc c t chc gm 2 plane A v B, kt

ni cho gia cc node ng trc tc l 2,5 Gbit/s nhm m bo an ton mng, c nhim v

chuyn mch cuc gi gia cc khu vc.

- Cp vng: Gm ton b cc note chuyn mch (IP/MPLS) cng nh cc b tp

trung ni vng m bo vic chuyn mch cuc gi trong ni vng v sang vng khch.Kt ni t node vng ln node trc 155 Mbit/s.

- Cc node chuyn mch IP/MPLS trong vng phi c tnh nng tch hp lu lng

mng XDSL (kt ni vi cc BRAS hoc tch hp tnh nng BRAS trong mng (xDSL) hoc

cung cp dch v cho cc thu bao bng rng xDSL. B tp trung IP/MPLS c th dng thu

gom lu lng knh kt ni ln cc node vng.

T chc lp truy nhp

- Lp truy nhp: gm cc node truy nhp hu tuyn v v tuyn, cc node ny c t chc

khng theo a gii hnh chnh

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- Cc node truy nhp ca cc vng lu lng ch c kt ni n node chuyn mch ng

trc ca vng .

- Cc thit b truy nhp th h mi phi c kh nng cung cp cng dch v truyn thng

PSTN cng nh cc dch v mi bao gm POTS, VOIP, IP/MPLS, FR, X25, IP2 VPN, xDSL..

2.2.6 Kt ni mng NGN vi mng truyn thng

2.2.6.1 Kt ni vi mng PSTN

Kt ni mng NGN vi mng PSTN hin ti c thc hin thng qua thit b ghp lung

trung k (trunking Gateway TGW) mc n x E1 v bo hiu s 7, khng s dng bo hiu R2

cho kt ni ny.

Cc thit b Trunking Gateway c tnh nng chuyn tip cc cuc gi thoi tiu chun 64

Kbit/s hoc cc cuc gi thoi VoIP qua mng NGN.

im kt ni c thc hin ti tng i Host hoc tandem ni ht v tng i Gatewayquc t nhm gim cp chuyn mch, gim chi ph u t cho truyn dn v chuyn mch ca

mng PSTN v tn dng nng lc chuyn mch ca mng NGN. i vi mng PSTN, mng NGN

s ng vai tr nh h tng i Transit quc gia ca mng PSTN cho cc dch v thoi tiu chun

64 Kbit/s.

Cc cuc thoi lin tnh tiu chun 64 kbit/s lin tnh hoc quc t t cc tng i Host

PSTN s c chuyn tip qua mng ti cc Host khc hoc ti tng i Gateway quc t.

Cu hnh kt ni nh m t hnh v sau

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Tng iquc t

Tng ichuyn

tipmin

Tng ini ht

Truy nhpthu bao

Lp ng dng

Lp iu khin

IP/MPLS

IP/MPLS

Acess

TGW

TGW

Lp truy nhpthu bao

Lp truyn ti

Lp iukhin

Lp ng dng

Cptrc

Cpvng

PSTN NGN

Hnh 2.10: Cu hnh kt ni NGN PSTN

2.2.6.2 Kt ni vi mng Internet

Kt ni mng NGN vi trung tm mng Internet ISP v IAP c thc hin ti node

IP/MPLS quc gia thng qua giao tip mc LAN. Tc cng LAN khng thp hp tc theo

chun Gigabit Ethernet (GE). Nu trung tm mng khng cng v tr t node IP/MPLS quc gia

th s dng kt ni LAN qua cng GBE

im kt ni mng NGN vi cc node truy nhp mng internet POP c lp cho thu bao truy

nhp gin tip c thc hin ti node IP/MPLS ni vng th s dng kt ni LAN qua cngquang.

i vi cc v tinh ca tng i Host PSTN c tch hp tnh nng truy nhp Internet POP

th im kt ni mng NGN vi cc node truy nhp Internet POP tch hp c thc hin ti b tp

trung IP/MPLS hoc ti cc node IP/MPLS ni vng thng qua giao tip IP/MPLS tu thuc vo

v tr ca POP tch hp.

Tc cng IP/MPLS ph thuc vo quy m ca POP nhng t nht l n x E1. Cu hnh kt

ni c m t nh (hnh 2.20)

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2.2.6.3 Kt ni vi mng FR, X25 hin ti

Cc mng FR, X25 hin nay s thuc lp truy nhp ca mng NGN, do vy s c kt ni

vi mng NGN qua b tp trung IP/MPLS.

Tng iquc t

Tng i

chuyen de mpls

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