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I HC QUC GIA H NITRNG I HC CNG NGH

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Tin Dng

CHUYN MCH NHN A GIAO THC MPLS

KHO LUN TT NGHIP I HC H CHNH QUY

Ngnh : in t- Vin Thng

H NI - 2005


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Kho lun tt nghip

MU

p ng nhu cu pht trin khng ngng ca ngi s dng, nh cung cp

dch v cn phi c cc thit bnh tuyn v chuyn mch tc cao. Mc d vy,

mng li ca nh iu hnh v nh cung cp dch v thng chy trn mng ngtrc ATM, nhng phn ln cc kt ni ti nh cung cp vn duy tr tc chuyn

mch chm v cc kiu kt ni im-im, dn ti tr v tc nghn ti cc im truy

cp bin. Cc bnh tuyn li cng gp phn vo trng i, v mi bnh tuyn

phi thc hin cc gii php c l p trn ng tt nht chuyn ti p gi. Thng

thng IP phi c nh tuyn trn ATM bng vic s dng IP qua ATM qua cc

knh o hoc cc giao thc trn ATM. Cc phng thc chuyn ti p ny c

chng minh l khng thun tin v phc tp.

Hn na vi s pht trin rng khp ca mng Internet lm ra i mt lot

cc ng dng mi trong thng mi. Nhng ng dng ny i hi phi tng v m

bo bng thng trong mng ng trc. Ngoi ra bn cnh cc dch v d liu truyn

thng, thoi v cc dch va phng tin ang c pht trin v trin khai. N

lm ny sinh vn cn phi c mt mng hi t cung cp y cc dch v.

Nhu cu v mt mng hi t vi phng thc chuyn tip n gin, thng

minh m c cc c tnh qun l lu lng v cht lng dch v l mt nhu cu cp

thit. Tt c cc yu cu c thc p ng bi chuyn mch nhn a giao thc

MPLS, n khng b hn ch bi cc giao thc lp 2 v lp 3. Cng vi kthut iu

khin lu lng, MPLS l mt gii php quan trng trong vic nh tuyn, chuyn

mch v cung cp cht lng dch vp ng c s pht trin ca cc ng dng

cng nh cc nhu cu dch v ca khch hng.

Lun vn ca em s trnh by nhng kin thc cbn v cng ngh chuyn

mch nhn a giao thc, v cht lng dch v v vic trin khai, h trcht lng

dch v trong mng MPLS.

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Chuyn mch nhn a giao thc MPLS

MC LC

T VN .......

MC LC ...

THUT NGVIT TT.......

CHNG 1 : CHUYN MCH NHN A GIAO THC MPLS

1.1. Tng quan chuyn mch nhn a giao thc..

1.1.1. Gii thiu...

1.1.2. nh tuyn v chuyn mch gi truyn thng...

1.1.3. MPLS l g ?..............................................................................................

1.1.4. Li ch ca MPLS..

1.2. MPLS v cc thnh phn.

1.2.1. LERs v LSRs

1.2.2. Lp chuyn tip tng ng FEC

1.2.3. Nhn...

1.2.4. Tuyn chuyn mch nhn (LSP)1.2.5. Giao thc phn phi nhn..

1.2.6. Kthut iu khin lu lng

1.2.7. nh tuyn rng buc.........

1.3. Hot ng ca mng MPLS.

1.4. ng hm trong MPLS..

1.5. Kin trc h thng giao thc MPLS1.6. Cc ng dng ca MPLS.

1.7. Tm tt chng.........

CHNG 2 : CHT LNG DCH V.

2.1. Mu...

2.1.1. ng lc QoS.

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2.2. Cc nh ngha cbn..

2.2.1. QoS l g ?..................................................................................................

2.2.2. Mt s khi nim cbn ca QoS.........

2.2.3. iu kin cn thit cho QoS. ....

2.3. Kin trc cbn ca QoS.

2.3.1. Phn bit v nh du.

2.3.2. QoS trong cc phn t mng ring l.

2.3.3. Qun l cht lng dch v

2.4. Mc cht lng dch vu cui-u cui....

2.5. Tm tt chng.........

CHNG 3 : CHT LNG DCH V TRONG MNG MPLS

3.1. Mu...

3.2. M hnh QoS v TE ban u

3.2.1. IntServ vi RSVP...

3.2.2. DiffServ..

3.2.3. MPLS.........

3.3. MPLS vi DiffServ

3.3.1. MPLS h trDiffServ

3.3.2. Kthut iu khin lu lng DiffServ-Aware MPLS..

3.4. Thc hin qun l hng i trong MPLS-DiffServ

3.5. Cc thnh phn QoS trong MPLS UNI..3.6. Tm tt chng..

KT LUN...

TI LIU THAM KHO

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THUT NGVIT TT

ATM Asynchnorous Tranfer Mode Truyn dn khng ng b

BA Behavior Aggregate Hnh vi ton th

BGP Border Gateway Protocol Giao thc cng bin

CAPEX Capital Expenditure Vn chi

CE Custom Edge Bin pha khch hng

CoS Class of Service Cp dch v

CQ Custom Queue Hng i tu

CR Constraint-based routing nh tuyn rng buc

CR-LDP Constraint-based routing-Label

Distribution Protocol

Giao thc phn phi nhn-

nh tuyn rng buc

CT Class Type Kiu cp

DiffServ Differentiated Services Dch v khc bit

DSCP DiffServ Code Point M im dch v khc bit

DS-TE DiffServ-aware MPLS Traffic

Engineering

Cng nghiu khin lung

MPLS quan tm ti DiffServ

E-LSR Egress LER LER bin ra

E-LSP EXP-Infered-PSC-LSP LSP c PSC c suy ra tEXP

FEC Forwarding Equivalency Class Lp chuyn tip tng ng

FTP File Tranfer Protocol Giao thc truyn file

IETF Internet Engineering Task

Force

U ban t vn kthut

Internet

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IGP Interior Gateway Protocol Giao thc nh tuyn trong

phm vi min

I-LSR Ingress LSR LSR bin vo

IntServ Integrated Services Dch v tch hp

IP Internet Protocol Giao thc Internet

IS-IS Intermediate System to

Intermediate System Protocol

Giao thc h thng trung

gian-ti-h thng trung gian

LAN Local Area Network Mng a phng

LDP Label Distribution Protocol Giao thc phn phi nhn

LER Label Edge Router Bnh tuyn nhn bin ra

L-LSP Label-only-Infered-PSC-LSP LSP c PSC chc suy ra

t nhn

LIB Label Information Base Bng csd liu nhn

LSP Label Switch Path Tuyn chuyn mch nhn

LSR Label Switch Router Bnh tuyn chuyn mch

nhn

MAC Media Access Control iu khin truy cp mi

trng

MAM Maximun Allocation Model M hnh cp pht ti a

MPLS Multiprotool Label Switching Chuyn mch nhn a giao

thc

OA Orded Aggregate Th t ton th

OPEX Operating Expenditure Chi ph hot ng

OSPF Open Shortest Path First Giao thc OSPF

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PE Provider Edge Bin nh cung cp

PHB Per-Hop Behaviour Hnh vi c x mi chng

PNNI Private network-to-networkInterface

Giao din kn mng-ti-mng

PPP Point-to-Point Protocol Giao thc im-im

PQ Priority Queue Hng i u tin

PSC PHB Scheduling Class Cp sp xp PHB

PVC Permanent Virtual Circuit Mch o cnh

QoS Quanlity of Service Cht lng dch v

Rd down-stream Router Bnh tuyn lung xung

RDM Russian Doll Model M hnh bp b Lin X

RFC Request for comment Cc ti liu chun do IETF

a ra

RSVP Resource Reservation Protocol Giao thc dnh sn ti

nguyn

Ru up-stream Router Bnh tuyn lung ln

SLA Service Level Agreements Tho thun cp dch v

SONET Synchronous Optical Network Mng quang ng b

SP Service Provider Nh cung cp

SVC Switch Virtual Connection Chuyn mch kt ni o

TA Traffic Aggregate Lu lng ton th

TCP Tranmission Control Protocol Giao thc iu khin truyn

dn

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TE Traffic Engineering Kthut iu khin lu lng

TLV Type Length Value Kiu gi tr di

TT Traffic Trunk Tuyn lu lng

TTL Time To Live Thi gian sng

UDP User Datagram Protocol Giao thc UDP

UNI User-to-Network Interface Giao din ngi dng ti

mng

VC Virtual Channel Knh o

VCI Virtual Channel Identifier nh danh knh o

VoATM Voice over ATM Thoi qua ATM

VoIP Voice over IP Thoi qua IP

VP Virtual Path Tuyn o

VPI Virtual Packet Indentifier nh danh gi o

VPN Virtual Pravite network Mng ring o

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CHNG 1: CHUYN MCH NHN A GIAO THC MPLS

1.1. Tng quan v chuyn mch nhn a giao thc MPLS

1.1.1. Gii thiu

Trong mt vi nm gn y, Internet pht trin thnh mt mng li rng

kh p v to ra mt lot cc ng dng mi trong thng mi. Nhng ng dng ny

mang n i hi phi tng v bo m c yu cu bng thng trong mng ng

trc. Thm vo , ngoi cc dch v d liu truyn thng c cung cp qua Internet,

thoi v cc dch va phng tin ang c pht trin v trin khai. Internet lm

ny sinh vn hnh thnh mt mng hi t cung cp y cc dch v. Tuy nhin

vn t ra i vi mng bi cc dch v v ng dng mi l yu cu v bng thng

v tc li t gnh nng cho ngun ti nguyn trn csh tng Internet c sn.Bn cnh vn qu ti ngun ti nguyn mng. Mt thch thc khc lin

quan ti vic truyn cc byte v bit qua mng ng trc cung cp cc cp dch

v khc nhau i vi ngi dng. S pht trin nhanh chng ca s ngi dng v lu

lng lm tng thm s phc tp ca vn . Vn cp dch v ( CoS ) v cht

lng dch v ( GoS ) phi c quan tm c thp ng c nhng yu cu khc

nhau ca lng ln ngi dng mng.

Nhu cu v mt phng thc chuyn tip n gin m cc c tnh qun l lulng v cht lng vi phng thc nh tuyn, chuyn tip thng minh l mt yu

cu cp thit. Tt c cc yu cu c thc p ng bi chuyn mch nhn a

giao thc, l mt phng thc khng b hn ch bi cc giao thc lp 2 v lp 3. Vi

cc c tnh MPLS ng mt vai tr quan trng trong vic nh tuyn, chuyn

mch v chuyn tip gi thng qua cc mng th h sau p ng cc yu cu ca

ngi dng mng.

1.1.2.nh tuyn v chuyn mch gi truyn thng

Bc pht trin khi u ca mng Internet ch quan tm ti nhng yu cu

truyn d liu qua mng. Internet ch cung cp cc ng dng n gin nh truyn file

hay remote login. thc hin nhng yu cu ny , mt nh tuyn nn da trn phn

mn n gin, vi giao din mng h trmng ng trc da trn T1/E1- hay

T3/E3 c l . Vi nhng yu cu i hi tc cao v bng thng ln, cc thit

b c kh nng chuyn mch lp 2 ( Lp lin kt d liu ) v lp 3 ( Lp mng )

ngay mc phn cng phi c pht trin. Thit b chuyn mch lp 2 quan tm n

vn nghn trong mng con ca mi trng mng cc b. Thit b chuyn mch lp

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3 gip gim bt nghn trong nh tuyn lp 3 bng cch chuyn vic tm kim tuyn

cho mt chuyn mch phn cng tc cao.

Cc gii php trc y ch quan tm ti tc truyn ca cc gi khi chng

truyn qua mng ch khng quan tm ti thng tin yu cu dch v c trong gi. Huht cc giao thc nh tuyn s dng ngy nay u da trn thut ton c thit k

tm ra con ng ngn nht trong mng vi cc gi truyn ti m khng quan tm ti

cc yu t khc ( nh tr, rung pha, nghn), m c th lm gim bt ng k chc nng

mng.

1.1.3. MPLS l g?

MPLS l mt framework do IETF a ra , cung cp thit k hiu qu cho vic

nh tuyn, chuyn tip, chuyn mch cho lung lu lng qua mch.MPLS thc hin nhng chc nng sau:

o nh qu trnh qun l lu lng lung ca cc mng khc nhau, nh lung

gia cc my, phn cng khc nhau hoc thm ch lung gia cc ng dng

khc nhau.

o Duy tr sc lp ca giao thc lp 2 v lp 3.

o Cung cp cch thc nh x cc a ch IP thnh cc nhn n gin c

di khng i c s dng bi cc cng ngh chuyn tip gi v chuynmch gi khc nhau.

o Giao din chung i vi cc giao thc nh tuyn nh RSVP v OSFP.

o H trIP, ATM, Frame Relay.

Trong MPLS, d liu c chuyn theo LSP. LSP l mt chui cc nhn

mi node t ngun ti ch. LSP c thit lp theo chu k truyn d liu (control-

driven) hoc da trn s pht hin c mt lung d liu no (data-driven). Cc

nhn, theo giao thc c nh sn sc phn phi s dng LDP hoc RSVP

hoc c cng trn mt giao thc nh tuyn nh BGP v OSFP. Mi gi d liu

c ng gi v mang nhn trong sut hnh trnh t ngun ti ch. Tc chuyn

mch cao v nhn c chiu di cnh c chn vo u gi hay t bo v c th

c s dng bi phn cng chuyn tip gi nhanh chng gia cc tuyn.

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1.1.4. Li ch ca MPLS

MPLS mang li nhiu li ch nh :

o K thut lu lng : Cung cp cc kh nng thit lp ng truyn m lu

lng s truyn qua mng v kh nng thit lp cht lng cho cc cp dch v (CoS) v cht lng dch v (QoS) khc nhau. MPLS l s pht

trin ch yu trong cc cng ngh Internet m h trvic b sung cc kh

nng cn thit cho mng IP ngy nay.

o Cung cp IP da trn cc mng ring o : Bng vic s dng MPLS, cc

nh cung cp dch v c th cung cp ng hm IP i qua mng ca h m

khng cn thit m ho hay cc ng dng u cui-ngi s dng.

o Loi b cu hnh a lp : Thng thng, phn ln cc nh iu hnh mngcung cp m hnh chng ln m ATM c s dng ti lp 2 v IP c s

dng ti lp 3. Bng vic s dng MPLS, cc nh iu hnh mng c th

mang chc nng ca mt iu khin ATM vo lp 3, do s lm n gin

ha mng v vic qun l mng.

o Tuyn hin : Mt c im chnh ca MPLS l s h trca n i vi cc

tuyn hin. Cc ng chuyn mch nhn c nh tuyn sn hiu qu

hn so vi tu chn tuyn ngun trong IP. Chng cng c th cung cp mtvi chc nng cn thit cho kthut lu lng.

o H tra lin kt v a giao thc : Thnh phn chuyn tip chuyn mch

nhn l khng xc nh vi mt lp mng c th. V d cng mt thnh

phn chuyn tip cng c th c s dng khi ang thc hin chuyn

mnh nhn vi IP cng nh IPX. Chuyn mch nhn cng c th hot ng

o trn mi giao thc lin kt d liu thng qua ATM.

1.2.MPLS v cc thnh phn

1.2.1. LSRs v LERs

Thit b trong giao thc MPLS c thc phn loi thnh LERs v LSRs

Mt LSR l mt thit bnh tuyn tc cao trong li ca mng MPLS tham

gia vo qu trnh thit lp LSP s dng giao thc thch hp v chuyn mch tc cao

lung d liu da trn con ng c thit lp.

Mt LER l mt thit b hot ng bin ca mng truy cp v mng MPLS.

LER h trnhiu cng (port) ni ti cc mng khng tng ng ( nh ATM, Frame

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Relay, Ethenet) v chuyn nhng lung lu lng ny ti mng MPLS sau khi thit

lp cc LSP, s dng giao thc bo hiu nhn u vo v phn phi lu lng trli

mng truy cp u ra. LERng vai tr rt quan trng trong vic gn v b nhn khi

cc lung lu lng vo v tn ti trong mng MPLS.

Hnh 1 : V tr ca LSR v LER trong mng MPLS

1.2.2. Lp chuyn tip tng ng FEC

FEC l biu din mt nhm cc gi chia s nhng yu cu nh nhau v victruyn ti. Tt c cc gi trong mt nhm c i x nh nhau trn tuyn cho ti

ch. Ngc li so vi chuyn tip ca gi IP, trong MPLS vic gn mt nhn nht

nh cho mt FEC nht nh chc thc hin mt ln, khi gi vo mng. Cc FEC

da trn yu cu dch vi vi mt tp cc gi cho sn. Mi LSR xy dng mt bng

xc nh mt gi c chuyn tip nh th no. Bng ny gi l bng csd liu

nhn (LIB), gm cc rng buc FEC-ti-nhn.

1.2.3. Nhn

Mt nhn, dng n gin nht, phn bit con ng mt gi si. Nhn c

mang hoc ng gi tiu lp 2 ca gi. Bnh tuyn nhn c s kim tra ni

dung nhn ca gi xc nh chng k tip. Khi mt gi c gn nhn , cuc hnh

trnh ca gi qua mng ng trc s da trn chuyn mch nhn. Gi tr ca nhn ch

c gi tra phng, ngha l ch gn lin vi chng gia cc LSR.

Mt khi mt gi c xp vo mt FEC c hay mi, th nhn sc gn

cho gi. Gi tr nhn c ly t lp lin kt d liu. Vi lp lin kt d liu ( nh

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Frame Relay hay ATM), nh danh lp 2, nh DLCI trong trng hp mng Frame

Relay hay VPIs/VCIs trong trng hp mng ATM c thc s dng trc tip nh

nhn. Cc gi c chuyn da trn gi tr nhn.

Nhn c rng buc ti mt FEC theo mt vi s kin hoc mt vi cchthc ch ra s cn thit i vi s rng buc.Nhng s kin c th l rng buc data-

driven hay rng buc control-driven.

Gn nhn c thc quyt nh da trn cstiu chun chuyn tip nh:

o nh tuyn n hng

o Cng nghiu khin lu lng (TE)

o Multicast

o Cht lng dch v (QoS)

nh dng thng thng ca nhn c cho nh hnh 2. Nhn c thc

nhng trong tiu ca l p lin kt d liu ( ATM VCI/VPI nh hnh 3 v Frame

Relay DLCI nh hnh 4) hoc c chn vo ( gia tiu lp 2 v tiu lp 3 nh

trong hnh 5)

Hnh 2 : nh dng chung ca nhn MPLS

Tiu lp mng

20 bit

Tiu lplin kt

8 bit1 bit3 bit

BS TTLBit ExpNhn

32 bit

D liu v cc tiu cc lp khcMPLSSHIM

Tiu IP DataGi IP

nh nhn gi Shim header Tiu IP Data

VPI/VCI data VPI/VCI data..T bo ATM

Hnh 3 : ATM vi lp lin kt d liu

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IP header data

Shim header IP header data

DLCI data DLCI data

Gi IP

nh nhn gi

Khung FR

Hnh 4 : Frame Relay vi lp lin kt d liu

Tiu PPP(gi quaSONET/SDH)

PPP header Shim header Tiu lp 3

Tiu MAC Shim header Tiu lp 3Tiu MACTo nhn

Hnh 5 : Nhn c chn vo gia lp 2 v lp 3

To nhnC mt vi phng php to nhn:

o Phng php da trn giao thc ( topology-base method) s dng qu trnh

ca cc giao thc nh tuyn ( nh OSPF v BGP).

o Phng php da trn yu cu (Request-base method) s dng qu trnh

yu cu da trn iu khin lu lng.

o Phng php da trn lu lng (Traffic-base method) s dng mt gi

kch hot s gn v phn phi nhn.

Phng php da trn giao thc v da trn yu cu l v d ca rng buc

nhn control-driven, trong khi phng php da trn lu lng l v d ca rng buc

data-driven

Phn phi nhn

Kin trc MPLS khng giao ch mt phng php bo hiu cho vic phn phi

nhn. Cc giao thc nh tuyn ang tn ti, nh BGP c nng cao c th

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cng thng tin nhn trong ni dung ca giao thc. RSVP cng c mrng

h trchuyn giao nhn. IETF nh ngha mt giao thc mi gi l giao thc phn

phi nhn (LDP) thc hin bo hiu v qun l khng gian nhn. Mrng da trn

csgiao thc LDP c th h tr thc hin nh tuyn da trn cc yu cu QoS v

CoS. S m rng ny to ra giao thc CR-LDP.

Khng gian nhn

Nhn c s dng bi mt LSR cho rng buc nhn-FEC c thc phn

chia nh sau:

o per platform : Gi tr nhn l c nht qua ton b LSR. Nhn c cp

pht t mt qu chung. Khng c hai nhn trn hai giao din khc nhau c

cung gi tr.o per interface : Phm vi ca nhn kt hp vi giao din. Nhng qu nhn

c nh ngha cho mi giao din, v cc nhn c cung cp nhng

giao din c cp pht t nhng qu tch bit. Gi tr nhn cc giao

din khc nhau c th ging nhau.

Kt hp nhn

Lung u vo ca lu lng t cc giao din khc nhau c thc kt hp

li vi nhau v thc hin chuyn mch da trn mt nhn chung nu n c truynqua mng ti cng ch cui cng.

Nu mng truyn ti lp di l mng ATM, cc LSR c th thc hin vic

kt hp VP v VC.

Cm ginhn

MPLS nh ngha cch i x vi rng buc nhn nhn c t cc LSR m

khng c chng tip vi mt FEC cho. C hai mode c nh ngha:

o Conservative : Trong mode ny, rng buc gia nhn v FEC nhn c t

cc LSR m khng c chng tip vi mt FEC cho s b b. Mode ny

yu cu cc LSR duy tr t nhn hn. y l mode c khuyn co cho

ATM-LSRs

o Liberal : Trong mode ny, rng buc gia nhn v FEC nhn c t cc

LSR m khng c chng tip vi mt FEC cho c gi li. Mode ny

i hi thch ng nhanh hn vi s thay i topo mng v cho php chuyn

lu lng ti cc LSP khc trong trng hp thay i.

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iu khin nhn.

MPLS nh ngha cc mode cho vic phn phi nhn ti cc LSR bn cnh

o c lp (Independent) : Trong mode ny, mt LSR nhn mt FEC no

v quyt nh rng buc mt nhn ti mt FEC c lp vi vi s phnphi rng buc. FEC mi c nhn ra khi no tuyn mi trnn xc nh

i vi router.

o Th t (Ordered) : Trong mode ny, mt LSR rng buc mt nhn ti mt

FEC no khi v ch khi n l router pha bin vo hay n nhn mt rng

buc nhn vi FEC t LSR chng ti p theo. Mode ny c khuyn co

dng cho ATM-LSR.

Qu trnh bo hiuo Yu cu nhn : S dng qu trnh ny, LSR yu cu nhn t lung xung

cnh n v th n c th rng buc ti mt FEC nht nh. Qu trnh ny c

thc giao xung cho mt chui cc LSR cho ti khi ti LER bin ra.

o nh x nhn : p ng li yu cu nhn, lung xung LSR s gi mt

nhn ti khi u lung ln s dng qu trnh nh x nhn.

Hnh 6 : Qu trnh bo hiu

Ngn xp nhn.

Qu trnh ngn xp nhn cho php hot ng mt cch phn cp trong min

MPLS. N cho php MPLS c s dng ng thi cho vic nh tuyn mc nhn

(v d gia cc router ring bit trong mt ISP v mc domain-by-domain cao hn).

Mi mc trong ngn x p nhn gn lin vi mc phn c p no . N to iu kin

thun li cho chng hm trong MPLS.

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1.2.4. Tuyn chuyn mch nhn (LSPs)

Tp h p cc thit b MPLS biu din mt min MPLS. Trong min MPLS,

mt tuyn c to cho mt gi c sn da trn mt FEC. LSP c thit lp theo chu

k truyn d liu. MPLS cung cp 2 ty chn cho vic thit lp mt LSPo nh tuyn chng tip chng (hop-by-hop): Mi LSR chn chng tip theo

mt cch c lp vi mt FEC cho. Phng php ny tng t nh

phng php ang c s dng trong mng IP. LSR s dng bt k giao

thc nh tuyn no nh OSPF, PNNI

o nh tuyn hin (explicit routing) : nh tuyn hin tng t nh nh

tuyn ngun. LSRu vo s quyt nh cc danh sch cc node m ER-

LSR qua.Con ng c chn c th khng ti u. Dc theo tuyn, cc tinguyn c thc phc vm bo QoS vi lu lng d liu. Cch

ny d dng iu khin lu lng qua mng, v cc dch v khc c th

c cung cp s dng cc lung da trn cc iu kin hay phng php

qun l mng.

LSP c thit lp vi FEC ch theo mt chiu. Lu lng trli phi do LSP

khc.

1.2.5. Giao thc phn phi nhn (LDP)LDP l mt giao thc mi cho vic phn phi thng tin rng buc nhn ti cc

LSR trong mng MPLS. N c s dng nh x cc FEC ti nhn, to cc LSP.

Cc phin LDP c thit lp gia cc LDP ngang hng trong mng MPLS (khng

nht thit k nhau). Cc LDP ngang hng trao i cc loi thng bo LDP sau :

o Discovery message : Thng bo v duy tr s c mt ca mt LSR trong

mng

o Session message : Thit l p, duy tr, kt thc phin gia cc LDP nganghng

o Advertisement message : To, thay i, v xo nh x nhn cho cc FEC.

o Notification message : Cung cp thng tin tham kho v thng tin bo hiu

li.

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1.2.6. Kthut iu khin lu lng

Kthut iu khin lu lng l mt qu trnh nng cao, tn dng ton b kh

nng ca mng bng cch c gng to mt sng u hoc phn b thng lng lu

lng khc nhau qua mng. Mt kt qu quan trng ca qu trnh ny l trnh c tcnghn bt k tuyn no. Mt ch quan trng l iu khin lu lng khng nht

thit phi chn con ng ngn nht gia hai thit b. C th vi hai lung ti cc gi

d liu, cc gi c th theo nhng con ng khc nhau thm ch qua im gc ca

chng v im ch cui cng l nh nhau. Theo cch ny cc phn on mng t s

dng hay t bit ti c thc s dng v c th cung cp cc dch v khc nhau.

1.2.7. nh tuyn rng buc

nh tuyn rng buc mang thm mt vi tham s, nhc tnh tuyn (bngthng, tr..), hoch nh chng, v QoS. Cc LSP c thit lp c th l CR-LSP, ni

m rng buc c th l cc chng hin hay cc yu cu QoS. Tuyn hin chnh cc

tuyn, hng i, hay cc qu trnh sp xp phi c chim dng cho lung.

Khi s dng CR, r rng rng tuyn di hn ( trong phm tr gi c) nhng

chn c tuyn t ti hn. Tuy nhin, trong khi CR tng c s tn dng mng th

n thm s phc tp trong tnh ton nh tuyn, khi m tuyn c chn phi tho mn

cc yu cu v QoS ca LSP. CR c thc s dng im tip gip vi MPLS

thit l p cc LSP. IETF nh ngha mt thnh phn CR-LDP ph hp vi nh

tuyn rng buc.

1.3. Hot ng ca mng MPLS

Hnh 7 : To LSP v chuyn tip gi tin qua min MPLS

Phi tin hnh nhng bc sau y c th truyn gi tin quan min MPLS

o To nhn v phn phi

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o To bng mi router

o To LSP

o Chn nhn/ tm kim bng

o Chuyn tip gi

Ngun gi d liu ca n ti ch. Trong min MPLS, khng phi tt c cc

ngun lu lng phi nht thit truyn qua cng mt ng. Ph thuc vo c tnh

lu lng, cc LSP khc nhau c thc to ra cho cc gi vi cc yu cu cp

dch v khc nhau

Bng 1 biu din tng bc hot ng ca mng MPLS xy ra khi c gi d

liu trong min MPLS

Bng1: Cc bc hot ng

MPLS actions M t

To nhn v phn

phi nhn

Trc khi bt u truyn bt c lu lng no, router to

quyt nh rng buc nhn vi mt FEC nht nh v xy

dng bng ca n

Trong LDP, lung xung router khi pht s phn b nhn

v rng buc FEC/nhn

Ngoi ra, cc c tnh lin quan ti lu lng v kh nng

MPLS c dn xp s dng LDP

Mt giao thc truyn ti tin cy v trt tc s dng

lm giao thc bo hiu. LDP s dng TCP

To bng Khi nhn c rng buc nhn, mi LSRs to cc u vo

trong bng csd liu nhn (LIB)

Ni dung ca bng s xc nh nh x gia nhn v FEC

nh x gia port li vo v bng nhn u vo ti port li

ra v bng nhn u ra

Cc li vo c cp nht bt c khi no nhn ra c rng

buc nhn xy ra

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Kho lun tt nghip

To tuyn chuyn

mch nhn

Nhng t on trong hnh 7, cc LSP c to theo

hng ngc li vi s to thnh cc li vo trong LIB

Chn nhn/tm

kim bng

Routeru tin (LER1 trong hnh 7) s dng bng LIB

tm chng tip theo v yu cu nhn vi mt FEC nht nh

Chui router con s dng nhn tm chng tip theo

Khi mt gi ti LSR bin li ra (LSR4), nhn s b b v

gi c cp ti ch

Chuyn ti p gi T hnh 7 chng ta hy xem con ng ca mt gi khi n

i ti ch t LSR1, LSR bin li vo, ti LSR4, LSR bin

li raLER1 c th khng c bt k nhn no cho gi ny khi xy

ra yu cu ny ln u tin. 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 sc pht trn ton mng nh hnh 7. LDP

s xc nh ng dn o m bo QoS, CoS.

Mi bnh tuyn trung gian LSR2 v LSR3 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 7

Bng 2 : V d bng LIB

Cng vo Nhn cng vo Cng ra Nhn cng ra

1 3 3 6

2 9 1 7

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Xem xt v d v 2 lung gi tin vo mt min MPLS:

o Mt lung gi tin l s trao i d liu theo quy tc gia cc server (v d

FTP-file transfer protocol ).

o Mt lung gi tin khc l lung video cht lng cao yu cu cc k thutlu lng QoS.

o Cc lung gi tin ny c phn ra thnh 2 FEC ring bit ti LSR li vo.

o Cc nhn tng ng c kt hp vi lung gi tin ln lt l 3 v 9 mt

cch tng ng

o Cc cng vo ti LSR l 1 v 2.

o Giao din li ra cng p ng ln lt l 3 v 1.

o nh x nhn c thc hin, cc nhn trc ln lt c trao i cho 6

v 7.

1.4. ng hm trong MPLS

c tnh duy nht ca MPLS l c thiu khin ton bng truyn gi tin

m khng cn xc nh c th cc bnh tuyn trung gian. iu c to ra bi

cc ng hm thng qua cc bnh tuyn trung gian c th cch nhiu on. Khi

nim ny c s dng trong VPN da trn MPLS.Kho st hnh 8. Cc LER (LER1, LER2, LER3 v LER4) tt c s dng BGP

v to LSP gia chng (LSP1). LER1 thng bo bc tip theo l LER2 khi n ang

truyn d liu ngun phi i qua hai phn ca mng. Cng vy, LER2 thng bo bc

tip theo l LER3 v v.v Cc LER ny s s dng giao thc BGP nhn v lu tr

nhn t LER egress (LER4 trong don ch) theo ton bng i ti LER li vo

(LER1).

Tuy nhin, LER1 gi d liu n LER2 n phi i qua mt vi LSR (trongtrng hp ny l ba). Do vy, mt LSP ring c to ra gia hai LER (LER1 v

LER2) qua LSR1, LSR2 v LSR3. iu ny th hin ng hm gia hai LER. Nhn

trong ng ny khc nhn cc LER to cho ng truyn LSP1. iu ng cho c

LER3 v LER4 cng nh cc LSR gia chng. Trong phn ny c ng truyn

LSP3.

c cu trc ny, khi gi tin truyn qua hai phn mng , cc khi nim ngn

x p nhn c s dng. Khi truyn qua LSP1, LSP2 v LSP3, gi tin s mang hai

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Kho lun tt nghip

nhn hon chnh cng lc. Hai nhn c s dng cho mi phn l (1) phn u tin

nhn cho LSP1 v LSP2 v (2) phn th hai nhn cho LSP1 v LSP3.

Khi cc LER3 nhn cc gi tin tn ti trong mng u tin, cc gi tin s loi

b nhn ca LSP2 v thay bng nhn LSP3 trong khi qu trnh trao i nhn LSP1 bntrong gi tin vi nhn ca ng i tip theo. LER4 s loi b c hai nhn trc khi

gi gi tin n ch.

Hnh 8: ng hm trong MPLS

1.5. Kin trc h thng giao thc MPLS

Thnh phn MPLS li c th chia thnh cc phn sau:

o Giao thc nh tuyn lp mng (IP)

o Bin chuyn tip lp mng

o Chuyn mch da trn nhn mng li

o chi tit v lc nhn

o Giao thc bo hiu cho phn phi nhn

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o iu khin lu lng

o Kh nng tng thch vi cc loi chuyn tip lp 2 khc nhau (ATM,

Frame Relay, PPP)

Hnh 9 miu t cc giao thc c th s dng trong hot ng MPLS. Phng

thc nh tuyn c th l bt k mt trong cc giao thc ph bin. Ph thuc vo mi

trng hot ng, cc giao thc nh tuyn c th l OSPF, BGP, hay PNNI ca ATM,

v.v Module LDP tn dng giao thc iu khin truyn tin (TCP) m bo qu

trnh truyn d liu iu khin t mt LSRn LSR khc trong sut mt phin. LDP

cng duy tr LIB. LDP s dng giao thc UDP trong sut giai on vn hnh tm kim

ca n. Trong trng hp ny, LSR c gng xc nh cc phn t ln cn v ng thi bo hiu s c mt ca chng trong mng. iu ny c thc hin thng qua mt

trao i cc gi tin hello.

IP Fwd l phng thc chuyn tuyn lp IP tm ng tip theo bng cch

khp a ch di nht trong bng ca chng. Vi MPLS, iu ny c thc hin bi

cc LER. MPLS Fwd l phng thc chuyn tip kt ni mt nhn vi mt cng li

ra cho cc gi tin. Cc lp vi miu t trong hnh hp vi ng nt t c th thc

hin bng phn cng to nn hot ng nhanh v hiu qu.

Hnh 9 : H thng giao thc MPLS

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1.6. Cc ng dng ca MPLS

MPLS quan tm mt cch c hiu qun cc i hi ca mng ng trc ngy

nay bng cch cung cp gii php chun csthc hin nhng mc ch sau:

o Ci thin chc nng chuyn tip gi trong mng

MPLS tng cng v n gin ho chuyn tip gi qua router s dng

m hnh chuyn mch lp 2

MPLS n gin, cho php trin khai mt cch d dng

MPLS tng chc nng mng bi v n cho php vic nh tuyn bi

chuyn mch tc ng dy

o H trQoS v CoS vi cc dch v khc nhau

MPLS s dng thit lp tuyn c iu khin lu lng v gip t c

cc mc dch vm bo

MPLS kt hp thit lp tuyn rng buc v lp tuyn hin

o H trs linh hot ca mng

MPLS c thc s dng trnh vn chng ph N2 kt hp vi

mng li IP-ATM

o Tch hp IP v ATM vo mng

MPLS cung cp cu ni gia mng truy cp IP v li ATM

MPLS c th s dng li cc chuyn mch cng/ router c sn ca ATM,

kt hp mt cch c hiu qu hai mng ring bit

o Xy dng kh nng vn hnh lin mng

MPLS l mt gii php chun m c tht c s hp lc gia mng

IP v ATM

MPLS lm cho IP d dng kt hp qua SONET tch hp chuyn mch

quang

MPLS gip xy dng cc mng VPN mm do vi kh nng iu khin

lu lng

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1.7. Tm tt chng

Trong chng 1, trnh by nhng vn cbn ca chuyn mch nhn a

giao thc MPLS vi cc vn c cp ti nh : cc thut ng, cc thnh phn,

cc giao thc s dng trong mng MPLS cng nh nguyn tc hot ng ca mng.

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Kho lun tt nghip

CHNG 2 : CHT LNG DCH V

2.1. Mu

Cht lng dch v (QoS) lin quan ti kh nng cung cp cc dch v tt hn

ca mt mng i vi mt lu lng mng chn vi nhng cng ngh khc nhau bao gm Frame Relay, ATM, Ethernet v cc mng 802.1, SONET, IP. Mc ch

chnh ca QoS l cung cp th tu tin bao gm cp bng thng, iu khin rung

pha v tr (cn thit i vi cc ng dng thi gian thc v lu lng tng tc), ci

thin s mt mt. Mt iu quan trng na l cung cp su tin cho mt hay nhiu

lung m khng lm cho cc lung khc b li. Cng ngh QoS cung cp nhng khi

csxy dng sn c th dng trong cc ng dng thng mi trong tng lai trong

cc mng WAN v i vi cc nh cung cp dch v mng.

2.1.1. ng lc QoS

Lc khi u, mng IP khng c bt c qu trnh no thc hin QoS. Internet

da trn TCP/IP khng c hoch nh cho vic cung cp thoi hay cc dch v khc

m i hi rt cht ch v bng thng, tr v rung pha. TCP c nh ngha vi FTP,

SMTP, TELNET v cc kiu truyn d liu khc. N c trng bi ca s trt vi

kch c thay i, khi pht chm, trnh tc nghn bng cch gim na mi mt mt,

iu chnh khong thi gian timeout cho vic nhn c xc nhn. Qu trnh cbn

lin quan ti gii quyt tc nghn, v d khi ti lu lng ln hn bng thng cho

php, l loi b gi. Trong mi trng cht lng dch v, nh cung cp dch v

thm bng thng gim mc tc nghn khi lng lu lng trn Internet tng ln.

Kt qu ko theo l vn ca nh cung cp dch v s b chi cho dung lng lu lng,

m iu ny khng cn thit lin quan ti thu nhp t dch v, dn ti kh khn trong

kinh doanh.

Hn na, cc nh cung cp dch v sau ny tp trung chuyn sang trin khai

qun l lu lng v cc qu trnh QoS. C mt vi l do cho vic . Th nht, vis gia tng dung lng lu lng trong mng ca h, cc nh cung cp nhn ra rng

rt kh gim bt tc nghn ch vi bng thng. Thay i trong phn b lu lng v

li ca node/ tuyn c th dn ti kiu tc nghn khng on trc, v s vt tri d

trng k qua ton b mng tr nn t gh gm. Th hai, nt c chai vn thnh

thong xy ra khi truy cp, trong khi vt qu d tr l khng kinh t. Th ba, s suy

sp trong nn kinh t hin nay trong ngnh cng nghip mng dn ti cc cng ty

phi ct gim vn mi cn thit cho yu cu thm bng thng, v thay vo l vic

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tp trung vo vic nng cao chc nng mng trn csvt cht c sn hin ti. Th

t, rt quan trng l vic a ra m hnh kinh doanh trn cstip cn cc dch c

b sung v nng cao. Mng hi t c th cung cp thoi, d liu, v cc dch v video

c hi vng l d dng vn hnh v qun l hn cc mng song song ang tn ti, m

nh hng ng k ti chi ph vn hnh. Nhng c th thc hin hi ngh t xa da

trn chuyn mch gi v cc dch v multimedia vi i tng doanh nghip, mng

hi t phi cung cp cht lng hon ho v h trtho thun cp dch v cht ch.

2.2. Cc nh ngha cbn

2.2.1. QoS l g ?

Trc khi tho lun cc qu trnh QoS v lin h ca n ti MPLS, chng ta

nn xem li mt vi nh ngha chnh v cc khi nim lin quan. Trong khi khng cmt nh ngha chnh thc ca QoS th nhng nh ngha sau c xem l c hiu lc

trong phm vi ti ny.

Mt cch cbn nht, QoS cho php bn ci thin cht lng dch v tt hn

i vi cc lung nht nh. iu ny c thc hin bng cch tng mc u tin i

vi mt lung v gim mc u tin ca lung khc. Khi s dng cc cng c qun l

nghn mch, bn c tng mc u tin ca mt lung bng hng i v m bo hng

i theo cc cch khc nhau.Cng c qun l hng i c s dng trnh tc

nghn tng mc u tin bng cch b cc lung u tin thp trc cc lung u tin

cao. Kim sot (policing) v hoch nh (shaping) cung cp mc u tin i vi mt

lung bng cch hn ch thng lng (throughput) ca lung khc.

Yoram Bernet phn bit gia nh ngha QoS thng v chng. nh

ngha thng miu t cht lng dch v nh l lu lng chuyn ti qua mng.

Trong khi nh ngha chng lin quan ti qu trnh iu khin cht lng dch v

thu c bi lu lng chuyn qua mng. nh ngha chng ca Bernet v cht

lng dch v mng l Kh nng iu khin cc qu trnh x l lu lng trongmng mng c th gp c i hi dch v ca ng dng no v cc chnh sch

m ngi dng a ra i vi mng.

Jerry Ash cung cp mt tp hp m rng cc nh ngha lin quan ti TE v

QoS t quan im ca nh cung cp dch v. Trong khi kh nng qun l v hoch

nh mng m bo cho chc nng ca mng trong tng lai, qun l lu lng li

lin quan ti vic ti u ngun ti nguyn c sn ca mng di cc iu kin khc

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nhau. Qun l lu lng bao gm cc chc nng iu khin nh tuyn, qun l bng

nh tuyn, nh tuyn ng.

Trong [TE-QoS], QoS c nh ngha l mt tp hp cc yu cu gp phi

bi mng khi truyn dn mt kt ni hay mt lung, hay tp hp cc nh hng cachc nng dch v m xc nh mc tho mn ca ngi dng dch v. nh ngha

ny l thng theo phn bit ca Bernet, nhng nh ngha sau ca Qun l ti

nguyn QoS l chng : chc nng mng m bao gm phn bit cp dch v,

rt ra bng nh tuyn, qun l kt ni, cp pht bng thng, bo v bng thng, dnh

sn bng thng, nh tuyn u tin, hng i u tin.

Tm li, ta s ni v QoS nh l s yu cu dch v ca rt nhiu cc ng

dng, v v cc qu trnh QoS / cc chc nng qun l ti nguyn QoSnh qu trnh

iu khin mng m cho php mt mng tho mn QoS.

Yu cu dch v ca cc ng dng khc nhau c th biu din bng mt tp

cc tham s bao gm bng thng, tr, rung pha, mt mt gi, quyn u tin v mt vi

th khc. V d thoi v cc ng dng multimedia rt nhy cm vi tr v rung pha,

trong khi cc ng dng truyn d liu c thi hi mt mt gi rt thp. Chng ta s

xem cc tham s l cc bin QoS.

2.2.2. Mt s khi nim cbn ca QoS

Tr

Tr l khong thi gian mt bn tin chim khi truyn tim ny sang im

khc trn mng. Tr bao gm mt s thnh phn nh thi gian tiu tn trong hng i

ca bnh tuyn-tr xp hng, thi gian cn thit thc hin quyt nh trong b

nh tuyn-tr chuyn tip, thi gian cn thit tuyn vt l truyn d liu-tr lan

truyn v thi gian s dng t gi tin ln mng-tr ni tip ho. Thnh phn c th

c qun l vi QoS l tr xp hng. Gi c u tin cao hn sc a ra truyn

trc cc gi c u tin thp hn v cc k thut qun l hng i nh RED c th

c s dng.

Rung pha

Rung pha c nh ngha nh s bin i trong cc tr chuyn tip u cui-

u cui. Trong mt sng dng, nh cc ng dng thi gian thc khng th chp

nhn rung pha. Giao thc TCP cng thc hin rt km di tc dng ca rung pha, v

n c gng iu chnh tc truyn dn ca n tng ng.

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Bng thng

Bng thng biu th tc tryn d liu cc i c tht c gia hai im

kt cui

Tn hao

Tn hao gi tin l trng hp khi gi tin khng ti c ch ca n trc thi

gian timeout ca b thu. Trong mng TCP/IP th tn hao gi tin ch yu l do nghn,

y l nguyn nhn to ra s trn b nhhoc loi b gi tin bi cc phng tin qun

l lu lng.

Cp dch v (CoS)

Khi nim cp dch v CoS c ngha hp hn QoS v ch ra mt cch n

gin rng cc dch v c th phn loi c trong cc cp khc nhau, c thccung cp cho ngi s dng v c qun l c lp.

Tho thun mc dch v (SLA)

SLA l hp ng gia khch hng v nh cung cp dch v SP, SLA nh mc

dch v no SP nh cung c p. tng rt n gin : khch hng no bo co bao

nhiu lu lng h s gi v tr tin cho mc ti thiu c m bo trong lu

lng .

2.2.3. iu kin cn thit cho QoS.

Vi QoS nhc nh ngha trn, chng ta hy xem xt cc yu cu cbn

m cn phi c c th thu c n. c th cung cp QoS cho nhiu loi yu cu

ca ng dng (v d : thoi, multimedia..), mng phi tho mn hai iu kin cn thit

o iu kin th nht l bng thng phi c m bo cho mt ng dng

di cc iu kin khc nhau, bao gm c nghn v li.

o iu kin th hai l khi mt ng dng truyn qua mng, n phi nhn csi x da trn cp thch hp, bao gm c s sp xp v vic loi b

gi. Chng ta c th nghl hai iu kin l trc giao. Mt lung c th

c bng thng hiu qu nhng phi chu tr (iu kin th nht t c

cn iu kin th hai th khng). Hoc mt lung c thc phc v mt

cch thch hp trong mi node mng nhng b chm dt hoc b mo bi s

dao ng mt cht ca bng thng (iu kin th hai t c nhng iu

kin th nht th khng). V th cn phi tho mn c hai iu kin ny

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thu c m bo QoS chc chn m c yu cu bi nh cung cp

dch v v khch hng ca h.

2.3 Kin trc cbn ca QoS

Kin trc cbn i vi vic thc thi QoS bao gm ba phn cs

o Kthut phn bit (identification) v nh du (marking) QoS cho vic nh

QoS tu cui ti u cui gia cc phn t mng

o QoS trong cc phn t mng ring l ( V d : hng i, sp x p v cc

cng c hoch nh lu lng)

o Chc nng kim sot, qun l, hoch nh (accouting) i vi vic iu

khin v qun tr lu lng u cui-u cui qua mng

Hnh 10 : Kin trc cbn ca QoS

2.3.1. Phn bit v nh du QoS

Phn bit v nh du c thc hin thng qua phn loi (classification) v

iu phi (reservation)

- Phn loi

cung cp dch v hon ho cho mt loi lu lng th u tin n phi

c phn bit. Bc th hai gi c thc nh du. Hai bc to thnh qu

trnh phn loi. Khi mt gi c phn bit nhng khng c nh du, phn loi

c xem l trn csmi chng (per hop), khi m vic phn loi ch lin quan ti

thit b m n vo, khng lin quan ti router tip theo. iu ny xy ra vi hng i

u tin (PQ) v hng i ty (CQ). Khi gi c nh du cho vic s dng rng ri

trn mng, bit IP u tin c thc t.

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Cc phng php phn bit lung thng dng gm iu khin danh sch truy

cp (ACL-Access control list), nh tuyn kim sot (policy-base routing), tc truy

c p cam kt (CAR-commited access rate), tha nhn ng dng mng (NAR-

network-base application recognition)

2.3.2. QoS trong cc phn tmng ring l

Qun l tc nghn, qun l hng i, hiu sut tuyn v cc cng c hoch

nh/kim sot cung cp QoS vi cc phn tn l ca mng

- Qun l tc nghn

Bi bn cht bng n t nhin ca voice/video/d liu, thnh thong s lng

lu lng vt qu tc ca tuyn. Trong trng hp , router s lm g? Liu n

s lu tr cc lu lng trong mt hng i v gi u tin l gi u s ra? Hay nst cc gi trong cc hng i khc nhau v phc v hng i no thng xuyn

hn? Cng c qun l tc nghn s quan tm ti cu hi ny. Cng c bao gm hng

i u tin (PQ), hng i ty (CQ), hng i trng s (WFQ-weighted fair

queuing), hng i c trng s da trn cp (CBWFQ-class-base weighted fair

queuing).

- Qun l hng i

Bi v hng i khng phi kch thc v hn, nn n sy v trn. Khi hngi y. Bt c mt gi thm na bt k s khng th vo trong hng i v n s b

b. y l hin tng bui (tail drop). Vn vi bui l router s khng th

bo v nhng gi ny khi b b( k c nhng gi u tin cao). V vy cn thit c mt

qu trnh thc hin hai vic:

o C gng m bo rng hng i khng b lm y, v th cn c mt khng

gian cho cc gi u tin cao

o Cn c mt vi loi tiu chun i vi vic b mt gi c mc u tin thptrc khi b gi c mc u tin cao

Pht hin trng s sm ngu nhin(Weighted early random detect-WERD)

cung cp phng thc thc hin nhng qu trnh ny

- Hiu sut tuyn

Nhiu ln cc tuyn tc thp ny sinh vn vi cc gi ln. V d tr ni

tip ca gi 1500 byte trong mt tuyn 56kbps

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Kho lun tt nghip

-Kch thc ca gi: 1500byte . 8bit/byte = 12000bit

-Tc tuyn : 56000 bps

Kt qu : Tr s l 12000/56000 = 0.214s hay 214ms

Nu mt gi thoi ti sau mt gi kch thc ln. Tr ca thoi s qu ln

thm ch ngay c trc khi gi ri router! Chia nh tuyn v ghp xen cho php chia

cc gi ln thnh cc gi nh hn v ghp xen vo cc gi thoi. Ghp xen cng quan

trng nh chia nh. Khng c l do g chia nh gi m nhng gi thoi theo sau

nhng gi c chia nh.

Mt yu tnh hng khc na l vic loi tr qu nhiu cc bit mo u

(overhead bit). V d tiu gi RTP c 40byte, vi mt ti cnh cng phi khong

20 byte, v trong mt s trng hp th mo u c th b gp i.- Kim sot v hoch nh lu lng

Hoch nh c s dng to mt lung lu lng m gii hn kh nng

bng thng ti a ca lung. N c s dng rt nhiu trnh vn trn nh

cp phn gii thiu. V d, nhiu topo mng s dng Frame Relay trong thit k hub-

and-spoke. Trong trng h p ny, im trung tm thng c tuyn bng thng cao

(T1), trong khi cc im xa c bng thng thp hn (384kbps). Trong trng hp

ny c th lu lng tim trung tm s b trn ti tuyn bng thng thp. Hochnh l mt cch hon ho lu lng gn vi 384Kbps trnh trn im xa.

Lu lng c lu tr tm thi truyn dn sau duy tr tc nh.

Kim sot tng t nh hoch nh, nhng khc mt kha cnh rt quan trng:

Lu lng mt tc xc nh khng c lu tr tm thi (v thng b b).

2.3.3. Qun l cht lng dch v

Qun l cht lng dch v cho php t v nh gi mc ch v kim sot

cht lng dch v. Cc phng php thng thng theo nhng bc sau:

o Bc 1 : Vch ranh gii mng vi cc thit b. N gip cho vic xc nh

c tnh lu lng ca mng. Cng nh th cc ng dng vi mc tiu v

cht lng dch v c thc phn chia ( thng da vo thi gian p

ng).

o Bc 2 : Trin khai cc kthut QoS khi thu c cc c tnh lu lng

v cc ng dng v mc tiu tng cht lng dch v.

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o Bc 3 : nh gi kt qu bng vic kim thp ng ca cc ng dng

xem khi no mc tiu cht lng dch v t c.

d dng pht trin, c th s dng Qun l kim sot cht lng dch v

ca Cisco(QPM-QoS policy manager), Qun l thit b cht lng dch v (QDM-QoSdevices manager). kim nh mc dch v, c th s dng Gim st chc nng

mng ca Cisco (IPM-Internetwork Performance Monitor)

2.4. Mc cht lng dch vu cui-u cui

Mc dch v lin quan ti kh nng cht lng dch vu cui-u cui

thc t, c ngha l kh nng cung cp cc dch v cn thit bng cch xc nh r lu

lng u cui-u cui hay bin-bin(edge-to-edge). Cc dch v khc nhau mc

cht lng dch v, miu t cht ch cch thc xc nh gii hn dch v bng cchxc nh bng thng, tr, rung pha, v c tnh mt mt.

C ba mc cbn ca cht lng dch vu cui-u cui c thc cung

cp bi mng khng ng nht:

Hnh 11 : Ba mc ca Cht lng dch vu cui-u cui

o Best-efford service : C rt t cht lng dch v, best-efford service cbn

da trn kt ni khng c sm bo. c c trng bi hng i FIFO,

khng c s khc bit gia cc lung.

o Differentiated service ( cn gi l cht lng dch v mm) : Mt vi lung

c i x tt hn cc lung khc ( tin hnh nhanh hn, bng thng trung

bnh cao hn, tc mt mt trung bnh thp hn). y l su tin mang

tnh thng k, khng phi l m bo cng v nhanh. N c thc hin

bng cch phn loi lu lng v s dng cc cng c cht lng dch v

nh PQ, CQ, WFQ, v WRED.

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Kho lun tt nghip

o Gruaranteed service ( cn gi l cht lng dch v cng) : Thc s l cch

dnh ring ti nguyn mng cho lu lng xc nh thng qua cc cng c

cht lng dch v nh RSVP, CBWFQ.

Quyt nh loi dch v thch hp vi mng trin khai ph thuc vo vi nhnt:

o ng dng hay kh khn m khch hng ang c gng gii quyt. Mi loi

dch v thch hp cho ng dng nht nh.

o Tc m khch hng thc t c th nng cao h thng ca h. C mt

phng thc nng cao t nhin t cng ngh cn thit cung cp cc dch

v khc nhau cho ti s cn thit cung cp cc dch v bo m.

o Ci gi cho vic thc thi v trin khai cc dch vm bo (GruaranteedService) cao hn so vi dch v phn bit (Differentiated service).

2.5. Tm tt chng

Trong chng 2, chng ta l quen vi cc khi nim cbn v cht lng

dch v (QoS) cng nh kin trc cbn ca QoS.

Cht lng dch v (QoS) cung cp dch v khc bit ( Differentiated service),

cung cp mc u tin cao hn cho cc lung hay dch vm bo (Guranteed service)

cung cp sm bo mc dch v. C hai tng phn vi Best-effort service, cungcp nhng g m c xem nh l c rt t QoS.

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CHNG 3 : CHT LNG DCH V TRONG MNG MPLS

3.1. Mu

Chuyn mch nhn a giao thc thng xuyn c cp ti ch yu xung

quanh vn cng ngh cht lng dch v cho mng chuyn mch gi. Trong khithc t rng MPLS ng vai tr rt quan trng trong vic cho php QoS, QoS li

khng phi l mt thnh phn cbn ca MPLS. C th hn, MPLS cung c p mi

trng hng kt ni cho php kthut iu khin lung ca mng chuyn mch gi.

Kthut iu khin lung c thm bo bng thng cho rt nhiu lung khc nhau,

l iu kin cn cho QoS. iu khin tr v rung pha trong cc ng dng nhy

cm v thi gian (l mt i hi ch yu khc ca cht lng dch v). MPLS-TE phi

kt hp cng ngh cung cp lung lu lng vi cch i xi vi nhng cp

nht nh ca chng, v d nh Giao thc dnh sn ti nguyn (RSP) vi mrng bo

hiu ng hm (RSVP-TE), v chuyn tip da trn dch v phn bit (DiffServ).

Chng ny tho lun cc kin trc khc nhau v vic trin khai cc mt ca mng

ng trc chuyn mch gi cho php MPLS, cng nh cc thnh phn QoS ca giao

din MPLS UNI c nh ngha bi MPLS/ Frame Relay Alliance.

3.2. M hnh QoS v TE ban u

Khi cng ng lin mng nhn ra s cn thit ca QoS trong mng chuyn

mch gi, mt vi hng h m. Dch v tch hp (IntServ) cng vi giao thc bo

hiu RSVP, cung c p kin trc QoS xc thc u tin. Tuy nhin sau khi xem xt

nhng vn v s linh hot v vn hnh ca IntServ vi RSVP, IETF nh ngha

kin trc dch v phn bit (DiffServ), vi dng cbn khng i hi giao thc bo

hiu. Sau MPLS c a ra nh mt cch tip cn hng kt ni thch hp vi

khng kt ni da trn mng IP, v n cho php cng nghiu khin lu lng.

3.2.1 IntServ vi RSVP

IntServ nh ngha nhng i hi cho cc qu trnh QoS tho mn hai

mc ch:

1. phc v cc ng dng thi gian thc

2. iu khin vic chia s bng thng gia cc cp lu lng khc nhau

Hai kiu dch v c nh ngha tun theo kin trc IntServ :

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Kho lun tt nghip

Dch v m bo ( Guaranteed Service ) v Dch v ti c iu khin

(Controlled Load Service), c hai u tp trung vo nhng i hi ca ng dng ring

l.

Dch vm bo c nh ngha cung cp mc chc chn ca bngthng, mt bin tru cui-u khng i, khng mt mt hng i; v n c d

kin cho cc ng dng thi gian thc nh thoi v video. nh ngha dch v ti c

iu khin khng bao gm bt k mt sm bo cht lng chc chn nhng n ng

hn l s xut hin ca mt mng ti nh. N dnh dnh cho cc ng dng m c

th dung sai trong mt khong gii hn lng mt mt v tr, bao gm cc ng dng

thi gian thc thch nghi.

c tht c cc mc tiu ra v cung cp cc dch v d kin, m

hnh IntServ gm rt nhiu cc tham s lu lng nh tc v gii hn chng (slack

term) cho dch vm bo; v tc trung bnh v kch cbng n (burst size) cho

dch v ti c iu khin. thit lp gi tr nhng tham s ny trong mt mng v

cung cp dch vm bo cho lu lng thi gian thc, RSVP c pht trin nh

giao thc bo hiu cho vic dnh sn v iu khin hin.

Kin trc IntServ tho mn c hai iu kin cho mng QoS. N cung cp

bng thng thch h p v ti nguyn hng i cho mi lung ng dng ( mt vi

lung). Tuy nhin trin khai IntServ vi RSVP i hi trng thi mi vi lung v bohiu mi chng. N thm s phc tp ng ki vi vic vn hnh mng v khng

linh hot. V th m hnh IntServ chc trin khai mt s hu hn mng, v IETF

chuyn sang pht trin hng DiffServ thay th vi s phc tp ti thiu.

3.2.2 DiffServ

Kin trc DiffServ tha nhn mt kha cnh tri ngc vi IntServ. N nh

ngha Cp dch v (CoS), gi l ton th (Aggregates), v chc nng qun l ti

nguyn QoS vi mi node, hay mi chng (Per-Hop). Cc nh ngha CoS bao gmhnh vi ton th (BA) xc nh nhng yu cu cho vic sp xp (scheduling) v loi b

gi, v th t ton th (OA) thc hin da trn phn loi ch da trn yu cu sp xp,

v c th gm vi gi tr loi bu tin. V th OA l cch phn loi th hn BA v c

th gm vi BA. Hnh vi ca node nh ngha tng ng vi cc nh ngha CoS.

Hnh vi cho mi chng (PHB) lin quan ti BA, trong khi sp xp cp hnh vi mi

chng (PSC-PHB Scheduling Class) phc v OA. Cc qu trnh PHB gm sp xp v

loi b gi, trong khi PSC ch cp ti vic sp xp.

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M hnh DiffServ da vo vic nh ngha li ngha ca 8 bit trng ToS

trong tiu IP. nh ngha ToS gc khng c trin khai rng ri, v by gin b

chia thnh 6 bit gi tr DSCP v 2 bit phn ECN

u tin D T R C O

DiffServ Code Point(DSCP) ECN ECN

Xc nh trng DiffServ

8 Bit ToS ca IP

Hnh 12 : Mi lin h gia ToS v DiffServ/ECN

Trong hnh 12, Cc ch ci biu th nh sau : D = Delay, T = Throughput, R =

Reliability, C = Cost, ECN = Explicit Congestion Notification

Gi tr ca trng DSCP c dng nh BA ( v d : mt lp), c s

dng tu theo node DiffServ chn PHB ph h p. Mi bn PHB c nh

ngha, gm mt cho chuyn tip gii quyt (EF), mi hai cho chuyn ti p chc

chn (AF), v mt cho mc nh hoc Best-Effort PHB. Mi hai AF PHB c chia

thnh 4 PSC, v mi AF-PSCs cha ba hnh vi ph lin quan ti cch thc loi b gi

khc nhau.

Tm li, m hnh DiffServ cho php mng phn loi (kt hp) cc vi lung

thnh lung ton th (BAs) v sau cho php c x khc nhau ton thmi node

c kh nng DiffServ. Cch c x ny c phn nh trong qu trnh phc v hng i

bao gm sp xp v loi b gi. PHB c phn nh trong c sp xp v loi b gi

trong khi PSC ch p dng cho sp xp.

3.2.3 MPLS

a) MPLS-TE

Phng php chuyn mch nhn u tin c hnh thnh ci thin chc

nng nh tuyn, nhng s thc y ny c gim bt vi cc thnh tu trong thit

k router v tc chuyn mch ng ca gi IP t nhin. Nhng sau u im

quan trng nht ca kin trc MPLS qua chuyn tip IP t nhin trnn r rng. Bn

cht hng kt ni ca MPLS cho php cc nh cung cp dch v c th trin khai TE

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Kho lun tt nghip

trong mng ca h v t c rt nhiu mc ch, gm m bo bng thng, nh

tuyn thay i, cn bng ti, d tha tuyn, v cc dch v khc dn ti QoS

[TE-REQ] nu vn v i hi trin khai TE trong mng MPLS. N cung

cp nh ngha chung ca TE nh tp hp cc qu trnh cho vic ti u ha chc nngvn hnh mng thu c cc mc tiu t ra v miu t cch thc MPLS h tr

TE bng vic iu khin v cc qu trnh o kim.

[TE-REQ] s dng khi nim tuyn lu lng (TT) MPLS l ton th cc

lung lu lng cng cp t trong mt LSP. Phn bit mt cch nguyn tc gia

TT v LSP l TT l lung lu lng ton th, trong khi LSP l mt tuyn m mt TE

i qua mng. V d, trong sut qua trnh, TT c th s dng nhiu LSP khc nhau,

[TE-REQ] miu t mt framework cho vic nh x cc TT thnh cc LSP bng vic

xem xt tp hp ba kh nng:

o Cc thuc tnh TT

o Phn b ti nguyn m c sp xp rng buc cho TT

o phng php nh tuyn rng buc m cho php chn cc LSP cho cc TT

Thuc tnh TT ca i tng c quan tm l cc tham s lu lng, mc u

tin, quyn u tin. Thuc tnh tham s lu lng c th bao gm cc gi tr tc

nh, tc trung bnh, kch thc bng n v cc yu cu ti nguyn khc ca mttuyn lu lng m c thc s dng cp pht ti nguyn v trnh tc nghn.

Thuc tnh mc u tin cho php qu trnh nh tuyn rng buc thit lp mt th t

trong vic la chn tuyn m cc TT u tin cao hn s c chi i hi ti nguyn

mng trc so vi cc TTs u tin thp hn. Tham s quyn u tin xc nh khi no

mt TT c th hay khng thu tin v c th hay khng thc u tin bi TT

khc.

Thuc tnh ti nguyn l cc tham s trng thi giao thc nh cp pht hp

knh ti a (MAM) cho php ngi vn hnh mng cp pht hn hoc km ti nguyn

hn kh nng ca tuyn thu c mc ch ng k rt sm hay d tr trc mt

cch thch hp; v thuc tnh cp ti nguyn cho php ngi vn hnh mng phn

loi ti nguyn mng v p dng vo vic kim sot da trn cp ti nguyn.

nh tuyn rng buc, i khi cn xem nh nh tuyn QoS cho php mt

nhu cu c thc y (demand-driven), mi trng nh tuyn nhn thc dnh sn ti

nguyn ni mt I-LER tng xc nh tuyn hin cho mi TT m n x l.

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CR yu cu vi kh nng mng bao gm:

o Mrng iu khin lu lng cho IGPs OSPF v IS-IS, v d OSPF-TE v

ISIS-TE c nh ngha trong [OSPF-TE] v [ISIS-TE] mt cch tng

ng, mang thm thng tin v bng thng cc i ca tuyn, bng thngdnh sn cc i, bng thng dnh sn hin ti mi mc u tin, v cc

gi tr khc cho php h thng qun l mng pht hin tuyn m gp cc

TT rng buc, s sn sng ti nguyn, cn bng ti v tm li i tng.

o Thut ton m chn tuyn kh thi da trn thng tin thu c t IGPs-TE

(v d bng vic ct b cc tuyn khng c kh nng v chy thut ton SPF

trn tuyn ang duy tr dn n tuyn ngn nht bt buc (CSPF)) v sinh

tuyn hin.

o Phn phi nhn bi giao thc cho php TE nh RSVP-TE; RSVP-TE mang

thng tin v tuyn hin c xc nh bi thut ton CR v vi i tng

bao gm bo hiu thit lp v thuc tnh nm gi mc u tin, thuc tnh

quyn u tin, v vi ci khc na.

o Qun l bng thng hay chc nng qun trmi node m thc hin nh

gi ti nguyn s dng v vn cn ti mi node, v cung c p nhng

thng tin ny ti IGP-TE v RSVP-TE.

Vi nhng qu trnh ny, MPLS-TE cho php nh cung cp to tuyn linh

hot vi bng thng dnh sn v iu khin lu lng ca chng qua rt nhiu i

tng mng. m bo bng thng gia cc tuyn, nhng s dnh sn MPLS-TE

phi c b xung cc qu trnh bo v lung t giao din vi cc lung khc trong

sut qu trnh bng n ngoi nhng gi tr c d tr. Nhng qu trnh ny bao

gm kim sot lung, d tr trc hoc nhng quy tc hng i m thc y phn chia

cn bng ca tuyn trong s c mt ca s cnh tranh lu lng cc lung. Vi hai

iu kin ca QoS : m bo bng thng v cc dch v khc nhau-MPLS-TE quantm ti iu kin u tin v RSVP-TE cung cp cch thc cho vic iu khin tr v

s bin thin tr trong cc ng dng nhy cm vi s bin thin thi gian.

b) RSVP-TE

RSVP c s dng rng ri cho vic phn phi nhn trong mng m i hi

QoS v TE. RSVP-TE c nh ngha trong [RSVP-TE] nh l mt tp cc mrng

ng hm i vi giao thc RSVP gc nh miu t trn. RSVP-TE c pht

trin cho rt nhiu cc ng dng mng khc nhau, vi ch mt th l k thut iu

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Kho lun tt nghip

khin lu lng (TE). V vy phn TE ca RSVP-TE c hiu mt cch ng cch

l Mrng ng hm hn l kthut iu khin lu lng. Cng v th, cc k hiu

khc nhau tn ti lin quan ti giao thc c nh ngha trong [RSVP]; lun vn

ny theo cc thut ng ca [RSVP-TE] v gi RSVP gc l RSVP chun.

RSVP-TE hot ng trn cc router c kh nng RSVP ni m mrng ng

hm cho php to cc LSP c nh tuyn hin, cung cp kh nng nh tuyn li

d dng, v pht hin lp. Vi im khc bit cbn gia giao thc RSVP chun v

RSVP-TE gm :

o RSVP chun cung cp bo hiu gia cc cp host; RSVP cung cp bo hiu

gia cc cp LERs.

o

RSVP chun ng dng cho cc lung n host-ti-host; RSVP-TE to trngthi cho lung lu lng. Mt LSP ng hm thng tp hp ton th cc

a lung host-ti-host v v th gim s lng trng thi RSVP trong mng.

o RSVP chun s dng giao thc nh tuyn chun hot ng da vo a ch

ch; RSVP-TE s dng IGPs mrng v nh tuyn rng buc.

Nhng cng ging nh RSVP chun, RSVP-TE cng h trcc m hnh dch

v IntServ phong ph v cch phn phi cc tham siu kin lu lng nh tc

trung bnh, tc nh v kch thc bng n cho dch v ti iu khin. Nhngc im ny cho php mng vi MPLS-TE v RSVP-TE cung cp cc dch v phong

ph vi i hi QoS cht ch. Mt thiu st ca gii php ny l khng c qu trnh

loi b gi. Mt cng ngh quan tm ti vn ny v cung cp cch thc khc

m bo QoS c ni ti phn 3.

3.3 MPLS vi DiffServ

3.3.1. MPLS h trDiffServ

By gikhi m c MPLS v DiffServ c xem xt, chng ta c th tholun mt cng ngh m kt hp hai gii php m bo QoS. Chng ta hy nhli l

DiffServ cung cp cc c x QoS vi ton th lu lng. l mt gii php linh hot

v vn hnh n gin v n khng i hi bo hiu v trng thi mi lung. Tuy nhin

n khng thm bo QoS, bi v n khng chi phi tuyn mi gi, v v th trong

sut qu trnh li hoc nghn, thm ch gi u tin cao cng khng c m bo bng

thng.

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Mt khc, MPLS c thy gi theo nhng tuyn nh v kt hp vi nh

tuyn rng buc-c th m bo bng thng cho cc FEC. Nhng dng c bn

MPLS khng xc nh cc c x da trn cp mi lung.

Kt hp phn loi da trn DiffServ v PHB vi MPLS da trn TE dn ticht lng dch v thc s trong mng chuyn mch gi ng trc. Cc qu trnh

MPLS h trDiffServ c miu t trong RFC3270[MPLS-DiffServ].

[MPLS-DiffServ] nh ngha hai loi LSP : E-LSP v L-LSP. Trong E-LSP,

mt nhn c s dng ch th FEC ch, v 3 bit trng Exp c s dng ch

th cp ca lung chn PHB ca n, bao gm sp xp v loi bu tin. Ch

rng DiffServ s dng 6 bit nh ngha cc BA v tng ng vi cc PHB, trong

khi E-LSP ch c 3 bt cho chc nng trn.

Trong L-LSP, nhn c s dng ch th c FEC ch v k hoch u tin.

Trng Exp trong L-LSP chc s dng ch th vic loi bu tin.

nh x gia tiu IP vi DiffServ v tiu chn MPLS cho E-LSP v L-

LSP c ch ra trong hnh 13 v 14 mt cch tng ng.Trong nhng hnh ny thut

ng 5 tuple lin quan ti 5 trng trong tiu IP, bao gm a ch ngun, a ch

ch IP, cng ngun v ch TCP hay UDP, v giao thc c thc s dng cho FEC

ang nh ngha. Tt c cc thut ng da vo kin trc DiffServ

BA

OA

5-tuple (FEC) ECN

Label( LSP = vi OA) EXP

PSC Drop

BA

OA

5-tuple (FEC) ECN

Label( LSP = mt OA) EXP

PSC Drop

Hnh 14 : nh x gia tiu IP v tiu chn MPLS vi L-LSP

DSCPHnh 13 : nh x gia tiu IP v tiu chn MPLS vi E-LSP

DSCP

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Kho lun tt nghip

Ch rng hnh 13 v 14 biu din nh x mt phn ca tiu gi IP t

nhin v nhn v phn EXP ca tiu chn MPLS. Chng khng t l v khng biu

din ton b cu trc ca tiu

Mi loi LSP c u im v nhc im ca n. E-LSP d vn hnh v linhhot hn bi v n bo v nhn v s dng trng EXP cho thnh phn DiffServ.

Nhng thc t bo hiu MPLS dnh sn bng thng trn csmi LSP, bng thng

dnh cho ton b LSP v khng c m bo da trn PSC, v c th thiu bng thng

trong phc v hng i mt vi PSC no .

Mt khc, L-LSP c qu nhiu vn vi vic d tr, bi v cn thit c nhiu

nhn gn cho tt c cc PSC ca tt c FEC. Nhng (bi v nhn mang thng tin v sp

xp) khi bng thng c dnh sn cho mt LSP cho, n kt hp vi hng i u

tin m LSP thuc v.

Hai hnh tip theo biu din lm sao nh tuyn v QoS ci thin cht lng

nh tuyn mng bng vic s dng MPLS cbn v sau MPLS c h trDiffServ.

E-LSR

LSR 5

LSR 4

LSR 3

LSR 2

LSR 1

I-LSR

(2)MPLS TE khng c CoS

(1)ng ngn nht khng c MPLS-TE

Hnh 15 : Lung gi trong MPLS khng c DiffServ

Hnh 15 biu din s khc nhau gia mt tuyn bi cc gi m theo con ng

ngn nht (1) v tuyn c iu khin lu lng (2). Tuyn (2) c thc chn

bi v n c bng thng phc v mt FEC nh, nhng bng thng ny li

khng c kt hp vi bt k cp dch v no, v th lu lng u tin (v d

VoIP) khng th c bng thng cho hng i nht nh ca n.

Hnh 16 biu din mt ci tin trong kin trc so vi hnh 15. Tuyn (1) v (2)

ca hnh trc c v nhng t qung. Trong m hnh kin trc ny MPLS h

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tr cng ngh DiffServ c trin khai, v c th dnh sn bng thng ng vi cc

hng i u tin nht nh. Chng ta hy tha nhn rng lu lng VoIP s dng hng

i 0, l hng i hng u trong mi LSP.

LSR 5

E-LSR

LSR 4

LSR 3

LSR 2

LSR 1

I-LSR

(2)MPLS TE khng c CoS

(1)ng ngn nht khng c MPLS-TE(3)MPLS TE viDiffServ(L-LSP)

Hnh 16 : Lung gi d liu qua MPLS vi DiffServ

LSR-4 c th c bng thng qua tt c cc hng i ca n, nhng n

khng c bng thng trong hng i 0 v v th , tuyn (2) khng cung cp QoS li

thch hp cho lu lng VoIP. l v sao chng ta li qua hng i VoIP LSR-4.

Nhng nu mt L-SLP c s dng hng i 0 vi bng thng dnh sn xc nh,

sao lu lng c thi qua tuyn (3) qua LSR-2 v LSR-3, v VoIP c th nhn

c vi sm bo QoS.

Tm li MPLS h trDiffServ tho mn c hai iu kin ca QoS : m bo

bng thng v c x vi cc dch v hng i c phn bit. MPLS tho mn iu

kin th nht : v d n thc y cc lung ng dng theo cc tuyn vi bng thng

m bo; v dc theo nhng tuyn DiffServ tho mn iu kin th hai bng vic

cung cp dch v hng i c phn bit i x.

Ch rng MPLS h trDiffServ vn cn n gin hn v linh hot hn

IntServ vi RSVP chun. IntServ i hi bo hiu mi vi lung v trng thi mi vi

lung trong mi router. Ngc li, cc LSP c th bn thn n l ton th cc vi lung

v v thi hi bo hiu t hn. Thm vo , router khng lu gi trng thi mi vi

lung. Thay vo cc LSR gi thng tin ton th v bng thng kh dng cho tt c

cc LSP hay cho mi hng i u tin.

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Kho lun tt nghip

3.3.2. Kthut iu khin lu lng DiffServ-Aware MPLS

Trong phn trn ta miu t hot ng ca MPLS trong mng ni cc LSR

c cho php DiffServ. Nhng thu c cc chc nng ny v dn ti QoS- Cc

mng ny phi c thit k cn thn vi TE c p dng vo trn csmi cp ngc vi TE ton th.

Mc tiu cn thit ca DS-TE l m bo bng thng tch bit cho mi loi

lu lng ci thin v ti u ho ng theo cc yu cu QoS ca n. M hnh DS-

TE ci tin m hnh TE ton th, ang tn ti bng vic cho php CoS da trn TE, ni

m CoS c nh ngha bi m hnh nh l mt tp hp th t ton th (OA) suy

rng ra t mc tuyn ti mc mng. Trong m hnh DS-TE, m bo bng

thng da trn CoS thu c bng hai chc nng mng:

1. Tch bit dnh sn bng thng cho tp hp cc cp lu lng khc nhau

2. Qu trnh qun l c p dng trn mi cp cs

miu t hai chc nng trn, m hnh DS-TE a ra hai khi nim:

1. Kiu cp (CT) l mt nhm cc tuyn lu lng (TT) da trn gi tr

CoS ca chng m chng cng chia s s dnh sn bng thng, v mt CT

c th biu din ca nhiu cp

2. Bng thng rng buc (BC) l gii hn phn trm bng thng ca tuyn mmt CT c th hay mt nhm CT c th ly.

Cc mi quan h gia cc CT v cc BC c nh ngha trong m hnh bng

thng rng buc ( Bandwidth Constrain model-BC). Hin ti, TE-WG nh ngha hai

m hnh BC:

1. M hnh cp pht ti a (MAM) gn mt BC ti mi CT ( nh biu din

hnh 17)

2. M hnh bp b Lin X (RDM) gn BC ti cc nhm CT theo cch m CT

vi cc yu cu QoS cht ch nht (v d : CT7, VoIP) nhn s dnh sn

bng thng ring, BC7, mt CT vi yu cu QoS nghim ngt nht, CT6

chia s dnh sn bng thng BC6 vi CT7 (BC6 > BC7); v c th cho ti

CT0 (v d : lu lng Best Efford) chia s BC0 (v d : ton b bng thng

ca tuyn) vi tt c cc loi lu lng khc (nh hnh 18 )

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Hnh 17 : M hnh cp pht bng thng ti a (MAM)

Hnh 18 : M hnh bp b Lin X (RDM)

M hnh DS-TE cng nh ngha mt qu trnh cho php gii phng bng

thng chia s b chim gi bi cc lu lng u tin thp hn khi lu lng u tin

cao hn ti. N a ra khi nim cp iu khin lu lng (TE-class), mt TE-

class c nh ngha bi hai tham s: Kiu cp (CT) v mc u tin (p). Hai

hay nhiu TE-class c th bao gm cng CT vi cc gi tr p khc nhau, hay cc CT

khc nhau vi cng gi tr p, v th cho php u tin v phc v trc cc LSP trong

v gia cc CT.

trin khai DS-TE, cc IGP(OSPF-TE v ISIS-TE) v LDP(RSVP-TE) phi

c mrng theo cc mrng da trn MPLS-TE c nh ngha mang thmthng tin nh miu t trong [DSTE-PRO]. Ch rng [DSTE-PRO] khng lp li

cc nh ngha, cc TLV v cc i tng c nh ngha trong [OSPF-TE], [ISIS-

TE], v [RSVP-TE] m cha ra cc thnh phn v ci tin mi.

m rng IGPs, n nh ngha thm cc TLV ph mang gi tr ca BC v

bng thng khng c phc v cho mi cp TE. Cng nh vy, RSVP-TE c

m rng bng vic nh trong thng i p tuyn mt i tng CLASSTYPE mi

bao gm mt trng CT. V th cc giao thc c m rng cho php LSR qun l

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Kho lun tt nghip

vic nh gi v ra quyt nh trn c smi cp . V d LSR c th tnh bng

thng c tn dng bi tt c cc tuyn lu lng trn csmi mc quyn u tin,

to quyt nh mi khi nhn mt TT mi m c thit lp bi thng ip tuyn, v

tnh ton bng gi tr thng khng c phc v s dng bi IGPs.

M hnh DS-TE cung cp nhiu s linh hot cho vic thc hin iu khin lu

lng. V d n cho php gn cc CT vo k hoch hng i LSR v khi k hoch i

bng thng, k hoch siu chnh cc tham s bng thng ca mi hng i vi trng

thi dnh sn ca nhm lu lng dch v. Siu chnh ca k hoch c th l ng,

khi s dnh sn bi cc LSP da trn cp mi tng hay gim , hay khng i, bng

vic iu chnh cu hnh k hoch vi ti liu trc mt cch chnh xc.

C v vn l do c th p dng vic thit lp cp pht bng thng ti a cho

cc loi lu lng khc nhau. V d cung cp iu khin bin thin tr tt hn vi

cc ng dng thi gian thc m chia s mt tuyn vi nhiu lu lng d liu bng

n, phn trm tuyn c s dng bi lu lng thi gian thc c gimc thp

(thng di 50%). Phn trm ti a ny l ci sau BC sc kt hp vi CT thi

gian thc. Trong khi vic s dng ca BC qu v trn mc d tr bng thng cp

nhy cm l tu trong DS-TE, ngi vn hnh mng m cu hnh trc cc thng s

m bo bng thng trong k hoch hng i ca n c th quyt nh gn cc BC ti

tt c cc CT n mang. Mc ch ca vic ny l iu khin vic dnh sn lulng ca cc CT thch ng vi cc thng sm bo bng thng c cu hnh

trc.

nh ngha mi quan h gia CoS v CT cng rt ngi vi vic thc hin

ca ngi iu hnh mng. Mt cp lu lng no c th khng khc bit

vici khc bo m s tch bit cc PSC v bng thng m bo. Mt v d ly

bi cnh khi hai loi gi thoi, VoIP v VoATM khng nn, c mang qua mng

MPLS. Hai cp lu lng thi gian thc c thc gn cc k hoch c x khc

nhau mt cch hp l, by gip dng gii hn phn trm bng thng n l cho c

hai. Chng ri sc i x mt cch thch hp nh mt CT. Tuy nhin, c th nn

t chng vo hai cp TE khc nhau m c hai c cng gi tr CT nhng khc nhau

gi tr quyn u tin p.

V th mc ch m hnh DS-TE cung cp kh nng iu khin linh hot v

m bo ti nguyn mng trn csmi cp v cho php QoS mc li cao.

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3.4. Thc hin qun l hng i thc t trong MPLS-DiffServ

Trong [MPLS-DiffServ] v d tho MPLS, IETF vch ra kin trc ton th

cho MPLS h trDiffServ, v cc nh cung cp dch v phi phn tch kin trc ny

chn cc gii php ti u vi mi trng ca h.Din n MPLS cho mt vi phn tch v cc quy tc qun l hng i

trong node mng m h trE-LSP v L-LSP. [QMgmt] a ra mt tha nhn thc t

rng mc d hng i c thc qun l trc v sau c cu chuyn mch LSR,

nhng c kh nng xp t cc LSP sao cho s bt ng vi ccu chuyn mch

c ti thiu v hng i s din ra sau c cu chuyn mch v trc giao din bin

li ra, nhc ch ra trong hnh 19

Hnh 19 : Kin trc LSR vi hng i v k hoch.

Trong hnh 19 gi ti mt trong N giao din bin li vo. N c phn loi

v c chuyn tip ti giao din bin li ra thch hp khi chng c t vo mt

hng i u tin tng ng. Hnh 19 ch ra hnh nh mrng ca giao din bin li ra

1. Giao din h trbn hng i u tin, t 0 ti 3. v k hoch y gi ra t mi hng

i da trn u tin ca n.

Hnh 19 biu din hnh nh n gin ca hng i bin li ra, nhng cc E-

LSP v L-LSP phc tp hn nh miu t trong [Qmgmt]. V d hng i c th cp

pht mi CoS cho mi LSP. Trong bi cnh , nu mt E-LSP h trbn k hoch

c x khc nhau v nu c hai E-LSP nh th, LSR s c tm hng i u tin khc

nhau, mi ci cho mi CoS ca LSP. S sp xp ny s rt kh qun l v khng linh

hot.

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Mt cch sp xp thay th l c mt tp hp nh hng i cho mi giao din

bin li ra. Gi ti nhng hng i ny thng biu din cc LSP khc nhau, nhng

hng i c qun l vi kha cnh loi b v sp xp nh l chng biu din mt

lung n. [QMgmt] khuyn co cch thc ny cho cc giai on u tin ca MPLS

h trDiffServ. Vi cch ny, L-LSP biu din mt mc u tin n l v s phn

chia ti nguyn cho mt L-LSP dn ti m bo bng thng nh tho lun trn.

Mt khc, LSP c th biu din vi k hoch u tin; cp pht ti nguyn cho mt E-

LSP khng thc hin vic mi CoS s dnh ti nguyn hng i nht nh. Trong

mng hon thin hn, c th c nhiu cc hng i nhn v cc mc u tin, v E-LSP

cng c thc s dng cho dch v bo m.

3.5. Cc thnh phn QoS trong MPLS-UNI

Cc tho lun trn v rt nhiu phng php c phn tch cung cp

QoS trong mng MPLS. Nhng trong kin trc mng thc t, mng MPLS c cung

cp trong min nh cung cp v khng mrng phn khch hng. Mt l do khc cho

iu ny l bo hiu LSP truyn thng c x l bi cc LER, v nu cc LERc

t ti phn khch hng, nh cung cp s phi mang cho khch hng mt vi chc

nng iu khin qua mng ng trc ca h. L do khc l khch hng c cc cp

dch v khc nhau v s phc tp v ti nguyn, v h c th khng mong phi lin

quan ti vic qun l mng.Nhng, nh ni trong [E2E-QoS], c thm bo QoS u cui-u

cui, cc qu trnh QoS phi c cung cp tt c cc phn h p thnh mng, v

chng phi c nh x mt cch thch hp giao din gia cc mng khc nhau.

Thc t, nh chng ta tho lun trong phn gii thiu, phn truy cp ca mng c

th l tuyn yu nht trong gii hn ca QoS, v phi c thit k cn thn cho kh

nng hot ng QoS.

Din n MPLS tha nhn vai tr hng u trong nh ngha giao din datrn MPLS gia phn khch hng v nh cung cp dch v mng da trn MPLS. Giao

din gi l giao din ngi dng ti mng MPLS (MPLS-UNI) v n c miu t

trong [MPLS-UNI]

[MPLS-UNI] miu t bo hiu qua UNI nh hnh 20

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Hnh 20 : MPLS UNI

Trong hnh 20 chc nng Ru v Rd biu din cc router lung ln v lung

xung nhc nh ngha trong [MPLS-Arch]. K hiu nh cung cp bin (PE) v

khch hng bin (CE) c k tha t [VPN] lm cho r rng khi lin h ti nh

cung c p v khch hng. Xem rng mt LSP lun theo mt hng duy nht, theo

hng lung d liu t PE ti CE th PE l Ru v CE l Rd; theo hng lung d liu

t CE ti PE th PE l Rd v CE l Ru.

Phn quan trng trong nh ngha MPLS UNI l mc ch ti thiu chcnng CE v thc t rng cc LSP c nh ngha qua UNI khng m rng trong

mng nh cung cp, nhng l lin kt cho PE vi LSP ca nh cung cp. [MPLS -

UNI] s dng mt giao thc LSP mrng cho bo hiu da trn phng php lung

xung theo yu cu. Qu trnh bo hiu bt u vi vic thit lp kt ni TCP gia PE

v CE. Sau PE gi ti CE yu cu nhn cho LSP PE ti CE. y CE l node

lung xung, v khi n nhn c yu cu, n cung cp rng buc nhn cho tt c

thuc tnh m c xc nh trong yu cu nhn. Ti thi im ny, bo hiu LSP

CE-ti-PE, CE phi gi yu cu ti PE, s dng chnh xc thuc tnh nh c

cung cp trong yu cu ca PE. V th hnh vi ca CE l kh n gin v t do quyt

nh. Qu trnh bo hiu c hon thnh khi PE p li vi rng buc nhn cho LSP

CE-ti-PE.

Phin bn hin ti ca [MPLS-UNI] ch quan tm ti hng PVC (kt ni o

cnh) c c trng bi s d phng ca nh cung cp v tnh thng CE. Cng

vic tng lai s m rng kin trc ny thnh MPLS UNI SVCs (Switched Virtual

Connection) ni CE s c th yu cu bo hiu cho vic thit lp hay kt thc LSP.

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Trong khi [MPLS-UNI] miu t bo hiu qua MPLS UNI dn ti thit lp cc

LSP hai chiu, cng vic ang pht trin Lin minh MPLS/ Frame Relay cng

nghin cu cc kt ni dch v m c th chy trn nh ca nhng LSP ny. Cc kt

ni dch v MPLS UNI s cung cp cho khch hng mt truy cp MPLS vo dch v

mng ring o qua nh cung cp dch v mng cng nh cc dch v khc ca nh

cung cp, nh Internet, cng VoIP, v nhng th khc na. Cc dch v ny c th t

ng cung cp bi nh cung cp ti khch hng, vi mt s lin quan khch hng ti

thiu. Chc nng MPLS UNI tng t nh kt ni ATM v Frame Relay ni cc kt

ni o khch hng c kt hp vi LSP v khng phi vi cc giao din, v v th v

d vi VPN c thc h trqua mt giao din dn. Hnh 21 biu din khi nim

ny

Hnh 21 : VPNs phc v thng qua MPLS UNI

Trong hnh 21 PE bn tri h trhai CE khc nhau thuc v hai VPN khc

nhau. PE di c mt giao din n vi mt CE, nhng CE ny lin quan ti c hai

VPN m c phn bit bi cc LSP c nh ngha qua UNI ny.Lin minh MPLS/ Frame Relay l vic trn cc dch v UNI cng s miu t

cc thuc tnh dch v phong ph m c thc cu hnh bi PE CE. Mt trong cc

thuc tnh s l Profile QoS bao gm cp QoS (v d : thi gian thc), nh du

QoS, bng thng, tr v dnh sn rung pha, cc yu cu kh dv cc tham s khc.

Profile s cho php SP cung cp QoS cn thit cho cc lung qua UNI, cng nh

nh x n ti mng cc LSP. V th QoS sc phc v trc v nh x thch hp

giao din gia khch hng v nh cung cp mng.

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Trong khi mi trng dch v MPLS PVC UNI c qun l ton b bi cc

PE, th MPLS SVC UNI cng s cho php CE yu cu ci tin dch v.

3.6. Tm tt chng

Chng 3 a ra cc m hnh dch v c th cung cp QoS nh Dch vtch hp (IntServ), Dch v khc bit (DiffServ) hay MPLS vi MPLS-TE v RSVP-

TE. Vi cc u im ca DiffServ nhn gin, linh hot kt hp vi cng nghiu

khin lu lng (TE), MPLS-TE kt hp vi DiffServ c xem l m hnh mng h

trQoS thc s trong mng ng trc.

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Kho lun tt nghip

KT LUN

S ra i ca mng th h sau (Next Generation Network-NGN) gn lin vi

nhng thay i cbn trong quan nim, t chc, v cng ngh. MPLS c coi l mt

cng ngh tim nng cho mng NGN trong thi gian ti. Tuy nhin pht trin lnNGN th cn phi p ng c cc yu cu cht lng dch v ngy cng cao ca cc

ng dng trong tng lai nh thoi, multimedia, hay hi ngh t xa

Phng php ban u c QoS trong mng chuyn mch gi tp trung ch

yu vo vic a thm vo bng thng gic thay th vi cc qu trnh phc tp m

cho php cc nh cung cp d tr v vn hnh mng thm chnh xc. Qu trnh ny

c thc y bi hai ng lc chnh : (1) gim CAPEX i hi thm ch thm bng

thng v (2) sinh v thm thu nhp bng vic cung cp cc dch v gi tr gia tng vi

tho thun cp dch v (SLA) nghim ngt hn.

Vi cc dch v mng tin tin, nh VoIP, i hi m bo bng thng cng.

Trong khi kin trc IntServ ch cung cp mt s linh hot thay th nhng n c hn

ch l khng cung cp sm bo. V vy vic kt hp DiffServ v cng ngh MPLS

trong mng chuyn mch gi dn ti cho php m bo QoS cng; v nhng sm

bo ny vi s linh hot cao hn v gim s phc tp so vi IntServ. Nhng s ci

tin ny l kt qu ca c tnh phn cp ngn xp v FEC ton th ca mng MPLS

cng nh trng thi ton th duy tr bi cc node h trDiffServ.

Mt lnh vc chnh khc c quan tm xem xt trong phm vi ti l s m

rng ca mng bin MPSL ti phn khch hng m khng cn mt mt iu khin qua

cung cp v vn hnh mng ca h. MPLS UNI cung cp mt gii php quan trng

cho vic m rng MPLS ti giao din PE-TE [MPLS-UNI] v kch hot QoS v cc

dch v phong ph qua giao din ny. MPLS UNI cho php QoS gia khch hng v

min nh cung cp, v th h trcc i tung QoS u cui- u cui.

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TI LIU THAM KHO

[1] [DSTE-PRO] F. Le Faucheur, Protocol Extensions for Support of DiffServ-aware

MPLS Traffic Engineering draft-ietf-tewg-diff-te-pro-03.txt, Feb 2002

[2] [E2E-QoS] V.FineBerg, A Practical Architecture for Implementing End-to-End inan IP Network, IEEE Communications Magazine, Jan 2002.

[3] [MPLS-arch] Rosel et al. Multiprotocol Label Switching Architechture work in

progress (draft ietf-mplsframework-05) March 2000

[4] [MPLS-DiffServ] F. Le Faucheur, et al, MPLS Support of Differentiated

Services RFC3270, May 2002

[5] [MPLS-UNI] A, Malis, D. Sinicrope, MPLS PVC UNI Implemetation

Agreement: Baseline Text MPLS Forum draft, mplsforum2002.035, Mar. 5,2002.

[6] [Qmgmt] P, Schicker, Class of Services Queue Management in

Switches/Routerss MPLS Forum draft, mplsforum2002.035, Mar. 5,2002.

[7] [RSVP-TE] D. Awduche, et al, RSVP-TE: Extensions to RSVP for LSP Tunnels

RFC3209, Dec. 2001.

[8] [TE-RQ] D. Awduche, et al, Requirements for Traffic Engineering over MPLS

RFC2702, Sep.1999.

[9] [VPN] Eric C.Rosen, et al, BGP/MPLS VPNs, dratf-ietf-ppvpn-rfc2547bis-

03.txt, Oct.2002.

[10] MPLS and IP Quanlity of Service In Service Provider ATM Network. Cisco

Systems White Paper.

[11] Multiprotocol Label Switching. http://www.iec.org Web Tutorials.

[12] QoS protocols and Architectures. Qosforum.com White Paper.

[13] Quanlity of Service (QoS). http://www.cisco.com Web Technology Document.

[14] Victoria FineBerg, Consultant. QoS support in MPLS Network. MPLS/ FrameRelay Alliance White Paper

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