Tieu Luan-chat Luong DV Tren Mang IP Cuong-Thanh

8/3/2019 Tieu Luan-chat Luong DV Tren Mang IP Cuong-Thanh

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Cc phng php nng cao cht lng dch v trn mng IP---------------------------------------------------------------------------------------------------------------

Mc lcMc lc .................................................................................................................................... 1

Li ni u ...............................................................................................................................2

PHN I .................................................................................................................................... 3MNG IP & CC THNG S NH HNG N CHT LNG DCH V ..........3

I.1. Phn loi lu lng v ng dng trn mng IP ............................................................ 3

I.2. Cc thng s nh gi cht lng dch v ................................................................... 5I.2.1. Tr ............................................................................................................................................................5I.2.2. Thng lng .............................................................................................................................................5

I.3. Vn cung cp cht lng dch v trn mng IP ....................................................... 6

PHN 2 .................................................................................................................................... 7

Cc phng php nng cao cht lng dch v trn mng IP ....................................... 7

II.1. M hnh dch v tch hp (IntServ) .............................................................................. 8II.1.1. Nhng c trng chnh ca m hnh IntServ ...........................................................................................8II.1.2. Giao thc RSVP ....................................................................................................................................10

II.1.2.1. Cc c trng ca RSVP .................................................................................................................10II.1.2.2. M hnh hot ng ca giao thc RSVP ........................................................................................11II.1.2.3. Mt s vn ca giao thc RSVP ...............................................................................................16

II.1.3. Kim sot chp nhn .............................................................................................................................16II.1.4. Phn loi gi tin ........................................................................................................................ ........ .....17II.1.5. Lp lch gi tin ................................................................................................................................ .......17II.1.6. Kin trc dch v tch hp .....................................................................................................................18

II.1.6.1. Dch v ti c kim sot .................................................................................................................20II.1.6.2. Dch v m bo (Guaranteed Service) .........................................................................................22

II.1.7. Cc vn vi m hnh dch v tch hp ............................................................................................. 23

II.2. M hnh dch v phn bit ..........................................................................................24II.2.1. Cc c im chnh ca m hnh DiffServ ...........................................................................................24II.2.2. Kin trc dch v phn bit ...................................................................................................................25II.2.3. nh ngha dch v ................................................................................................................................27

II.2.3.1. Trng DS v cc PHB c bn ......................................................................................................27II.2.3.2. PHB chuyn tip nhanh ..................................................................................................................29II.2.3.3. PHB chuyn tip c m bo .........................................................................................................29

II.2.4. Qun l ng ti nguyn trong m hnh DiffServ .................................................................... ......... ...30II.2.4.1. Tng quan v Bandwidth Broker ....................................................................................................30II.2.4.2. Kin trc ca mt h thng BB ......................................................................................................32

II.2.5. u im v hn ch ca dch v Diffserv .............................................................................................33II.2.5.1. u im ..........................................................................................................................................33

II.2.5.2. Hn ch ca Diffserv .....................................................................................................................33II.3. Multi Switching Label Protocol v Traffic Engineering .........................................34II.3.1. Gii thiu ..............................................................................................................................................34II.3. 2. Kin trc MPLS .......................................................................................................................... ........ ..35

II.3.2.1. Cc thnh phn chnh trong m hnh .............................................................................................36II.3.2.2. Forwarding Equivalent Class .........................................................................................................36II.3.2.3. Label Distribute Protocol ................................................................................................................37

II.3.3. Traffic Engineering vi MPLS ........................................................................................................ ......37II.3.3.1. Gii thiu chung .............................................................................................................................37II.3.3.2. M hnh thc hin ..........................................................................................................................38

II.3.4. Kt lun .................................................................................................................................................39PHN 3 ..................................................................................................................................40

nh gi, kt lun ..............................................................................................................40III.1. nh gi, phn tch cc phng php: ....................................................................40

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III.2. xut, kin ngh .......................................................................................................41

III.3. Phng n thc hin cc xut v kin ngh ........................................................41III.3.1. M hnh Kt hp IntServ v DiffServ ............................................................................................. .....41

III.3.1.1. Li ch ca m hnh kt hp Intserv v Diffserv ...........................................................................41III.3.1.2. Framework cho Intserv/RSVP over Diffserv ...............................................................................42III.3.1.3. Thc thi Framework ................................................................................................................. .....44III.3.1.4. Kt lun ..........................................................................................................................................44

III.3.2. H tr Diffserv trn MPLS ..................................................................................................................44III.3.2.1. Li ch ca kt hp Diffserv v MPLS .........................................................................................44III.3.2.2. Nguyn tc ....................................................................................................................................45III.3.2.3. Cc hot ng ca LSR Diffserv MPLS ........................................................................................45III.3.2.4. Nhng u im v tn ti ca hai m hnh E-LSP v L-LSP ......................................... ........ .....46III.3.2.5. Kt lun ..........................................................................................................................................46

Kt lun ..................................................................................................................................47

Ti liu tham kho ................................................................................................................48

Li ni u

Ngy nay, cc mng dng cng ngh IP, c bit l Internet tr thnh cng c

quan trng trong nhiu lnh vc. Cng vi cc dch v truyn thng (nh email, FTP,

WWW,. . .) cc dch v mi (truyn ting ni, hnh nh hay a phng tin) i hi tnh thi

gian thc cng ngy cng pht trin. Nhu cu truyn cc dch v thi gian thc trong mngIP tng ln nhanh chng trong khi m hnh cung cp dch v truyn thng trong mng IP

da trn vic truyn gi tin vi c gng ti a (best effort) khng p ng c nhng yu

cu cht ch v mt thi gian, tr hay bng thng ca cc dch v thi gian thc i hi

phi c gii php gii quyt vn ny.

p ng c yu cu ca cc ng dng thi gian thc, c hai gii php c bn.

Gii php th nht l b xung thm ti nguyn bng cch nng cp c s h tng truyn

thng. Nhng gii php ny tn km v d ti nguyn mng c tng th cc ng dng tiu

tn ti nguyn cng tng ln v ti nguyn c xem l lun thiu so vi nhu cu. Gii php

th hai hp l hn l b sung cc c ch h tr cht lng dch v vo h tng mng. Do

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t chc Internet Engineering Task Fork (IETF) nghin cu, pht trin v a ra bn

phng php nhm thc hin phng n ny. l cc phng php:

- M hnh dch v tch hp ( Integrated Services IntServ)

- M hnh dch v phn bit (Differentiated Services DiffServ)

- Multiprotocol Label Switching

- Traffic Engineering

Trong tiu lun ny, chng em xin trnh by v 4 phng php h tr cht lng

dch v trn. nh gi u nhc im ca tng phng php v a ra cc kin ngh v

xut ca ring mnh.

Chng em xin cm n thy gio Ng Hng Sn cung cp cc kin thc qu bu chng em hon thnh tiu lun ny.

PHN I

MNG IP & CC THNG S NH HNG N CHT LNG

DCH V

I.1. Phn loi lu lng v ng dng trn mng IPTrn mng IP c hai loi lu lng khc nhau c bn l lu lng thi gian thc v

lu lng d liu (data traffic, lu lng khng c thuc tnh thi gian thc)

3

IP applicationsIP traffic

Real time applicationsReal time traffic

Elastic applicationsData traffic

Hnh 1 . Phn loi ng dng v lu lng trn mng IP


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Lu lng d liu to bi cc ng dng nh telnet, ftp, www, email,. .. . l cc

ng dng mm do (chng lun i d liu n). tr ln s lm gim hiu sut thc hin

ng dng nhng d liu i n u c s dng. Cc ng dng mm do c th tip tc

c phn loi cn c vo i hi tr ca chng. Interactive burst traffic

(nh telnet, NFS) cn tr nh, interactive bulk traffic (nh ftp, www) cn tr trung

bnh, asynchronous bulk traffic (email) khng b nh hng g bi tr.

Lu lng d liu thng l ri rc v khng on trc c. Cc lin kt thng

c tui th ngn v dng truyn mt hay nhiu khi d liu. Cc ng dng gi d liu i

vi kh nng nhanh nht c th c ri dng li. Do lu lng d liu mang tnh bng

n. Lu lng thi gian thc to bi cc ng dng thi gian thc. Cc ng dng thi gian

thc u c c tnh ch chu tr nh. Khc vi cc ng dng mm do, chng rt nhy

cm vi tr v s bin thin tr. Qu trnh truyn d liu ca ng dng thi gian thc

thng u v ko di, lung d liu c tnh iu ho. m t lung d liu thi gian thc,mt phng php thng c s dng l m hnh gi th bi (token bucket model). Mt b

gi th bi c xc nh bi hai tham s : tc th bi rv kch thc gi b .

Trong hnh 2, rl tc th bi xp vo gi, nu gi y cc th bi k tip s b

loi, nh vy gi ch cha c ti a b th bi. Nhng gi i n s c lu vo hng i.

truyn gi i cc th bi c ly ra khi gi vi mt lng tng ng vi kch thc

gi, mi khi mt gi kch thc p c gi i, p th bi s chy ra khi gi. Gi ch c

gi i khi trong gi c th bi. Vi c ch ny lu lng d liu c kim sot (trong

thi gian T, lu lng gi i khng th vt qu rt + b)

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Hnh 2 . Nguyn l hot ng ca m hnh gi th bi

Gi d liu iGi d liu n

Hng i di c nh

Gi ( kch thc b )

Cc th bi i n vitc khng i r


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I.2. Cc thng s nh gi cht lng dch vCht lng dch v l kh nng ca mng cung cp dch v tt hn cho cc lu

lng mng c la chn trn cc cng ngh khc nhau nh Frame Relay, ATM,. .. Nicch khc, l c tnh ca mng cho php phn bit cc lp lu lng khc nhau v x l

chng mt cch ph hp.

Cc thng s quyt nh cht lng dch v l tr, thng lng v mt mt

I.2.1. Tr

Tr ca lu lng dch v l c tnh rt quan trng ca cht lng dch v. Cc kha

cnh khc nhau ca tr c nh hng khc nhau n cc dch v.

- Tr u cui n u cui (end to end)

- Bin thin tr (jitter)

Cc ng dng tng tc thi gian thc (nh truyn thng thoi) nhy cm vi tr u

cui n u cui v bin thin tr. tr di nh hng n tnh tng tc ca qu trnh

thng tin .

Cc ng dng phi tng tc thi gian thc (nh qung b mt chiu) khng nhy

cm vi tr u cui n u cui nhng b nh hng bi bin thin tr. Bin thin tr

thng c iu chnh bng cch dng b m ti u thu, ti cc gi n c gi v

pht li ti thi im thch hp. Thi im pht (im pht li) c xc nh bi bin thin

tr ti a. Cc ng dng c th iu chnh im pht li da trn s thay i gi tr bin

thin tr gi l cc ng dng thch nghi. Cc gi n sau thi im pht li thng khngcn gi tr vi ng dng.

Cc ng dng khng c thuc tnh thi gian thc khng nhy cm vi tr. l do

cc ng dng ny c th dng cc php o tr iu khin tc lu lng (nh TCP) hay

lu tr d liu cho n khi c bo nhn (nh FTP). Tr ln hoc thay i c th nh

hng n cht lng ca nhng ng dng ny .

Cc thnh phn khc nhau ca tr u cui n u cui l :

- Tr pht: l thi gian cn thit a tt c cc bit ca gi tin vo ng truyn- Tr truyn: l thi gian mt bit truyn qua knh

- Tr x l: l thi gian x l mt gi trong phn t mng

- Tr hng i: l thi gian gi tin phi i trong hng i trc khi n c truyn i

Ti u cui, c th c cc tr khc khi nhn gi tin t giao din mng n chng

trnh v cui cng n ngi s dng .

I.2.2. Thng lng

Kha cnh chnh ca thng lng l bng thng dnh cho ng dng. N xc nh lulng m ng dng c th truyn qua mng. Mt kha cnh quan trng khc l li (thng

lin quan n t l li c truyn) v mt mt (thng lin quan n dung lng b m)

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Vi ng dng thi gian thc cng, chng ch c gi tr khi c cung cp mt lng

di thng nht nh. Cc ng dng thch nghi c yu cu thp hn, hiu sut ca cc ng

dng ny tng nhanh khi di thng tng ln, nhng ch n mt mc nht nh, khi di

thng tip tc tng, hiu sut ng dng khng c ci thin. i vi cc ng dng mm

do, hiu sut t ph thuc vo di thng hn nhng khi tng di thng th lun nng cao

c hiu sut ng dng .

Hnh 3 th hin s ph thuc hiu sut ca ng dng vo di thng ca cc loi ng dng

Mt s ng dng c th gim tc truyn thch ng vi du hiu thng lng

thp. Cc ng dng ny c gi l thch ng tc .

Thng lng ph thuc vo cc yu t sau :

- c tnh ng truyn: bng thng, t l li- c tnh nt mng: dung lng b m, nng lc x l

Mt s c tnh ca cc phn t mng khc nhau nh cc thit b u cui / my ch,

chuyn mch / b nh tuyn xc nh cht lng dch v cung cp cho ng dng theo cc

ch tiu v thng lng v tr.

I.3. Vn cung cp cht lng dch v trn mng IPCc mng hin nay cn h tr nhiu kiu lu lng trn cng mt lin kt mng n.

Cc kiu lu lng khc nhau yu cu mng phi x l khc nhau. Lu lng ch c thc phn bit ti cc phn t mng tch cc l b nh tuyn (router), chuyn mch

(switch) v gateway .

V vy, yu cu thit k mng bao gm :

Mng c th truyn nhiu loi dch v, c ngha l chng phi quan tm n cht

lng dch v

Kh nng m rng, ngha l lu lng mng c th tng m khng lm nh hng

n hot ng ca mng

Kh nng h tr cc ng dng quan trng, dng nhiu ti nguyn mng, cc ng

dng ny ng vai tr quan trng trong hot ng kinh doanh ca cc doanh nghip

6

Hiu sut

Di thng

a. ng dng thi gian thccng b. ng dng thch nghi tr

Hiu sut

Di thng

c. ng dng mm do

Hiu sut

Di thng

Hnh 3 . S ph thuc ca hiu sut ng dng vo di thng


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C hai c ch c bn cung cp cht lng dch v thch hp da trn cc tiu

chun tr v thng lng.

Cung cp dung lng

S dng cng ngh qun l lu lng

Khi c dung lng ti nguyn trong mng th khng cn mt c ch c bit no

m bo cht lng dch v. iu bao gm c :

ng truyn tc cao

Cc b x l mnh

B m dung lng ln

C ch ny thch hp cho mi trng cc b c iu khin nh mng LAN ca cc

doanh nghip nhng khng ph hp vi cc mng ln nh mng Internet. Trong khi gi

bng thng, b nh v b x l ang gim i th gi ca cc thit b u cui v ng

truyn vin thng tc cao p ng m hnh ny vn cn kh cao .

C ch cung cp cht lng dch v th hai l s dng cng ngh qun l lu lng.

tng y l lu lng c th c phn bit v cung cp cc mc dch v khc nhau.

Mc phn bit c th l mt tp nh cc lp hay phn bit n tng lung ng dng. Phi

c c ch iu khin mc lu lng ca tng lp c a vo mng tu theo ti nguyn

sn c iu ny c th c thc hin tnh (bng cch cung cp trc) hay ng (bo hiu

vic d tr ti nguyn). Phi c cc c ch chuyn tip lu lng hiu qu trn mng. Hn

na, phn t mng phi qun l vic x l v xp hng i cc gi mt cch thch hp m

bo vic cung cp cc dch v khc nhau tu theo tng gi.

PHN 2

CC PHNG PHP NNG CAO CHT LNG DCH V

TRN MNG IP

IETF a bn phng php cung cp cht lng dch v trong mng IP

Integrated Services IntServ

Differentiated Services DiffServ

Multiprotocol Label Switching

Traffic Engineering

Intserv cho php t trc mt knh xuyn qua mng vi bng thng m bo. N

d tr ti nguyn mng mt cch r rng bng giao thc bo hiu ng v s dng kim sotchp nhn, phn loi gi, lp lch thng minh t c cht lng dch v mong mun

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DiffServ phn loi cc gi thnh mt s nh cc kiu dch v v dng c ch u tin

cung cp cht lng dch v thch hp cho lu lng. y khng s dng d tr ti

nguyn hay kim sot chp nhn, mc d cc nt c s dng c ch hng i thng minh

phn bit lu lng.

MPLS khng phi l m hnh nh Intserv v Diffserv, n l mt chun kt hp cng

ngh chuyn mch nhanh tng hai v nh tuyn tng ba cho php dn ng hiu qu.

MPLS thm mt nhn ngn vo gi tin IP v thc hin chuyn tip packet da trn nhn ny

trnh nhng phc tp do phi x l header ca gi tin IP.

Traffic Engineering c s dng t c mc tiu hiu nng nh ti u ti

nguyn mng v sp t lu lng vo cc ng truyn c th. Bng cch s dng mt

cng ngh nh MPLS, traffic engineering cho php gim tc nghn lu lng trn mng .

Sau y chng ta s xem xt cc phng php ny .

II.1. M hnh dch v tch hp (IntServ)Integrated Service l m hnh QoS u tin c IETF pht trin vo u nhng nm

1990 v mt s phn ca m hnh ny ngy nay vn ang c hon thin. Khi nhm

Integrated Service bt u, World Wide Web cha xut hin v trao i a phng tin

c xem l ng dng tng lai. Do , IntServ l mt chun ph hp nht vi truyn thng

ng di vi bng thng m bo.

Trong IntServ nhiu lp lu lng c cc phn t mng m bo cc loi cht

lng dch v khc nhau . y cc ng dng cn bit trc cc c tnh lu lng cachng v bo hiu cho cc phn t mng trung gian t trc cc ti nguyn nht nh

nhm p ng tnh cht lu lng ca n. Tu theo s kh dng, mng c th dnh ti

nguyn v gi v mt bo nhn tch cc hoc khng p ng yu cu .

tng chnh ca IntServ l h tr ng k tng lung. InteServ cho php ng k

trn ton tuyn trc khi thc s gi d liu.

Trung tm ca Integrated Service l giao thc ng k ti nguyn RSVP. Khi mt

sender mun truyn lu lng ti mt receiver (thng qua unicast hay multicast), sender gi

mt thng ip PATH ti receiver. Mt thng ip PATH chuyn thng tin ti receiver vngun lu lng, c im ca ng i mng v cui cng n ci t trng thi cn thit

thng ip RESV c th tm n sender t receiver. Khi receiver nhn c thng ip

PATH, n tr li mt thng ip RESV dc theo ng m thng ip PATH i qua.

Thng ip RESV thc s t trc bng thng cn thit trong router dc theo ng i.

Khi sender nhn c thng ip RESV, n mi bt u truyn d liu .

II.1.1. Nhng c trng chnh ca m hnh IntServ

a) Lung (flow)

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Lung l mt dng cc gi sinh ra t cng mt hnh ng ca ngi s dng v d

mt phin ng dng n. C th xc nh lung bng cc c ch khc nhau .V d IP V6

dng a ch ngun v nhn lung cn IP V4 dng a ch ngun, a ch ch v cng ch .

b) Cc loi dch v

IntServ nh ngha cc loi dch v c th cung cp, da trn cc yu cu v tr v

mt mt, c th l :

* Dch v m bo : cung cp s m bo tuyt i v tr v mt mt gi m lung phi

chu (dng cho cc ng dng thi gian thc khng thch nghi). Cc gi tun theo s d

tr s khng b mt hay tr qu gii hn xc nh. S m bo cht ch i hi mc d

tr ti nguyn cao

* Dch v ti c kim sot : cung cp dch v tng c vi mng khng qu ti (dng

cho cc ng dng thch nghi hot ng tt trong iu kin mng ti nh) . Phn ln gi

tin s khng b mt hay tr hng i. Nhng y khng cung cp mc m bo mangtnh ng lng c th

* c im lu lng (Traffic Specification Tspec)

Lu lng lung c c trng bi c im lu lng (Tspec). Tspec cha cc

tham s tc th bi r, kch thc gi b (gi th bi), tc nh p (peak rate), n v

x l nh nht m v kch thc gi ti a M

- Tc th bi r xc nh tc truyn d liu lin tc khng i, kch thc gi b

xc nh mc m tc truyn d liu c th vt qu tc cho php trong mt

khong thi gian ngn- Tc nh p l tc ti a m ngun v cc im inhj dng lu lng c th gy

ra bng n lu lng trn mng

- n v x l nh nht m (minimum policed unit), xc nh s byte c tnh khi

kim tra lu lng v s ph hp vi Tspec. Cc gi c kch thc m khi kim tra

u c coi l c kch thc bng m

- Kch thc gi ti a M l kch thc ln nht ca gi tun theo Tspec. M phi nh

hn hoc bng MTU ca lin kt v cc gi s dng dch v khng c phn on.

Lung s b loi b (khng c s dng dch v yu cu) nu kch thc gi ti a

yu cu ln hn M .

c) c im dch v c yu cu

Lung c tr m bo c th xc nh thm bng c im dch v c yu cu

(Requested Service Specification Rspec) yu cu mc dch v c th. Rspec c cc

tham s sau :

- Tc yu cu R, xc nh tc mong mun m lu lng c gi trong lung,

n phi ln hn r

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- S hng vi chnh S, xc nh s trnh lch gia tr mong mun v tr thu c

khi gi tc R. N cho php mng iu chnh tc c phn b p ng

yu cu tr

d) c im ng (Path Characterization)

gii thch cc cht lng dch v c cung cp dc theo mt chng ng c

th, c ch d tr ti nguyn cng thng bo mt s c tnh ca ng, chng bao gm

- Kh nng cung cp IntServ: ch ra xem c nt no trn ng khng c kh nng

cung cp dch v tch hp

- S chng IntServ: ch ra s nt c kh nng cung cp dch v tch hp trn ng

- Bng thng ng sn c: ch ra bng thng ti thiu

- tr ng ti thiu: ch ra tr ti thiu ca mt gi, bao gm tr truyn, tr x

l nhng khng tnh n tr hng i.- MTU ca ng: ch ra kch thc n v truyn cc i trn ng

- Cc tham s tr: ch ra tr tch lu trn ng truyn ca mt lung c th, bao gm

cc s hng ph thuc tc v s hng ph thuc tc D.

e) D tr ti nguyn

Phi d tr ti nguyn cho cc lung c th cung cp cht lng dch v theo yu

cu. iu c th thc hin thng qua giao thc d tr ti nguyn ng, qua cu hnh bng

tay hay qua mt giao thc qun l mng. M hnh tch hp dch v khng gn lin vi mtc ch c th no. Tt nhin, n xc nh tng qut cc lu lng v c tnh ng truyn

thng qua mng. Vic d tr ti nguyn c thc hin bng giao thc d tr ti nguyn

(Resource ReSerVation Protocol RSVP)

II.1.2. Giao thc RSVP

RSVP l giao thc c th c thit k cho c thit k cung cp vic d tr ti

nguyn. N c thit k cho mi trng dch v tch hp, nhng ngoi ra n cn c th

dng vi cc m hnh dch v khc.

II.1.2.1. Cc c trng ca RSVP

Mi trng qung b (multicast): RSVP c thit k lm vic tt trong mi trng

qung b bi v cc ng dng yu cu d tr ti nguyn l hng qung b (multicast

oriented), v d nh ng dng hi ngh. Giao thc cung cp qu trnh truyn thng n gin

gia tpcc bn gi v tp cc bn nhn, vi ng truyn thc s s dng cc cy truyn

b.

Hng bn nhn (receiver oriented): c th m rng p ng mi trng qung

b ln, giao thc yu cu bn nhn thc hin vic d tr. Bn nhn yu cu d tr tinguyn da trn c tnh lu lng ca bn gi v c im ca ng truyn

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S khng ng nht ca bn nhn: RSVP h tr cc bn nhn khng ng nht bng

cch cho php mi bn nhn thc hin vic d tr ring ca mnh, c th khc nhau, thm

ch nu lu lng nhn t cng mt ngun. Cc nt trung gian s tp hp cc yu cu d tr

Trng thi mm (soft state): trng thi d tr phi c cc bn lm ti nh k,

nu khng chng s ht hn. iu ny lm cho giao thc hot ng tt v thch ng vi cc

iu kin mng v cc yu cu d tr thay i .N cng hn ch yu cu cn c c ch bo

hiu tin cy

Khng c c ch i km nh ng hay lp lch cho gi tin, RSVP ch l mt

giao thc bo hiu. N ph thuc vo qu trnh nh ng IP thng thng tnh ng

d tr. Tt nhin, n mun bao gm yu cu v ti nguyn trong qu trnh tm ng nhng

hin nay cha c giao thc tm ng chun no trong mng IP xem xt yu t cht lng

dch v. RSVP cng khng quan tm n cch cc nt mng thc hin yu cu d tr

RSVP truyn ti v duy tr cc tham s iu khin lu lng v chnh sch qun tr,nhng nhng tham s ny li trong sut i vi RSVP. RSVP hot ng trong sut qua cc

b nh tuyn khng h tr RSVP

II.1.2.2. M hnh hot ng ca giao thc RSVP

Qu trnh ng k c thc hin theo trnh t sau

- Bn gi gi i thng bo PATH ti cc bn nhn thit lp trng thi ng i ti

cc b nh tuyn trn ng i

- Sau khi nhn c thng bo PATH, bn nhn gi li bn gi thng bo RESV chayu cu ng k (theo ng ng m thng bo PATH i qua) thit lp trng

thi ng k ti cc b nh tuyn trn ng i

11

Nt gi

Nt nhn Nt nhn

B nh tuyn

B nh tuyn

PATH (1)

Ressv (2) Ressv (2)

Hnh 4. Qui trnh t ch


12/49


a) Thit lp trng thi ng i

Mi nt gi truyn cc thng bo RSVP PATH xui dng tho cc l trnh pht

n/qung b nhm c cung cp bi cc giao thc dn ng, theo l trnh ca dng d

liu. Thng bo PATH lu trng thi ng i ti mi b nh tuyn trn ng i.

Trng thi ng i bao gm cc thnh phn :

- PHOP (Previous Hop) : a ch IP pht n ca nt trc , dng dn ng cho

thng bo RESV i theo chiu ngc li

- Sender Template : m t khun dng gi m nt s gi i

- Sender Tspec : xc nh cc c t lu lng ca dng d liu m nt gi s to ra.

Sender Tspec dng ngn chn ng k tha

- AdSpec : mang d liu OPWA (One Pass With Advertisement). Thng tin ny c

chuyn ti module iu khin lu lng ti mi nt, v c tr v gi tr cp nhtri c chuyn tip xung di trong thng bo PATH. Cc thng tin ny c bn

nhn s dng c lng kh nng phc v ca mng t chn la dch v v

xc nh cc tham s ng k cho ph hp .

Cc thng tin chnh bao gm :

Tng tr ng i ti thiu (khng tnh tr hng i). Trong trng hp

dch v m bo, bn nhn cng thm gi tr ny vo tr hng i c tr

tng cng Di thng ti thiu trn ng i : di thng ca lin kt hp nht

Mt bit c : ban u c xo v c t khi gp mt b nh tuyn khng

h tr RSVP

PATHMTU : kch thc gi ln nht c chp nhn (gi tr nh nht trong

s MTU ca cc lin kt trn ng i)

Cc break bit cho tng dch v : ban u c xo v c t khi gp mt

b nh tuyn khng h tr dch v tng ng. V d, c mt s b nh tuyn

ch h tr dch v Ti c iu khin nhng khng h tr dch v m bo . Gi tr tng hp cc s hng li C v D.

Mi nt trn ng i nhn thng bo PATH v x l to lp trng thi ng i.

Cui cng n ti ng dng trn cc nt nhn, tuy nhin n khng quay tr v nt nhn trong

cng tin trnh vi nt gi .

b) Thit lp trng thi ng k

Mi nt nhn khi nhn c thng bo PATH s s dng cc tham s (v d, trong

trng hp Dch v m bo th cc tham s l : r, b, p, m t Sender Tspec , tr ng i

nh nht, PATHMTU, Ctot, Dtot, di thng ti thiu t Adspec) to lp thng bo RESV

cha yu cu ng k chuyn ti cc nt gi.

12


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Thng bo RESV bao gm :

Yu cu kiu ng k (WF, SE hay FF)

RSVP c mt s tu chn ng k, gi l kiu ng k nhm phc v cc loi

ng dng khc nhau, s dng ti u ti nguyn ng k. Cc kiu ng k c xc

nh da trn hai yu t : c la chn nt gi hay khng v dng chung ng k hay

dng ring. C 3 kiu ng k nh sau :

La chn bn gi ng kPhn bit Dng chung

C Fixed Filter(FF) Shared Explicit(SE)Khng (khng nh ngha) Wilcard Filter (WF)

o Wildcard Filter (WF) : To mt ng k dng chung cho cc lung t tt c cc

nt gi. C th hnh dung nh l phn ti nguyn c ng k to thnh mt

ng dng chung vi kch thc l yu cu ti nguyn ln nht t tt c cc

nt nhn, khng ph thuc vo s lng nt gi s dng n

o Shared Explicit (SE) : To mt ng k dng chung cho cc lung t mt s

nt gi c la chn

o Fixed Filter (FF) : To mt ng k cho lung d liu t mi nt gi, khng

chia s vi lung d liu ca cc nt gi khc trong cng phin

Kiu ng k ti nguyn dng chung (WF, SE) ph hp vi cc ng dng qung b

nhm trong nhiu ngun d liu khng truyn ng thi. V d, vi cc ng dnghi ngh audio, ti mi thi im ch c mt s hu hn ngi cng ni, ngha l ch

c mt s hu hn nt gi ng thi. Do mi nt nhn c th yu cu kiu WF

hay SE vi di thng gp i cho mi nt gi. Cn kiu FF, to nhng ng k ring

bit cho cc lung t nhng nt gi khc nhau, ph hp vi cc ng dng video.

Filter Spec (vng mt nu kiu ng k l WF), dng nhn dng nt gi, khung

dng ca Filter Spec thng tng t nh khun dng ca Sender Template trong

thng bo PATH

Flow Spec : gm c Tspec v Rspec (Rspec vng mt nu yu cu dch v Ti ciu khin). Tspec thng bng Sender Tspec, ngoi tr tham s M c t bng

PATHMTU ly t Adspec

Mt s i tng tu chn, nh i tng RESVCONF ch ra rng nt nhn cn

xc nhn ng k, i tng policy, cha thng tin v chnh sch qun tr. ..

Thng bo RESV i chnh xc theo chiu ngc li l trnh m d liu i n. N

to lp v duy tr mt trng thi ng k ti cc nt dc theo l trnh. Cui cng thng bo

RESV n cc nt gi, do cc nt ny c th thit lp cc tham s iu khin lu lng

cho ph hp vi chng u tin. a ch IP ch ca thng bo RESV l a ch pht n cant gi trn, ly t trng thi ng i. a ch IP ngun l a ch ca nt gi thng bo

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14/49


c) Trn cc yu cu ng k

Thng bo RESV c chuyn ti nt trn mang theo c t lung ln nht trong s

cc c t lung yu cu bi nt di. Nh th gi l cc c t lung c trn .

Thng thng c t lung l vector a chiu, n c th cha c hai thnh phn

Tspec v Rspec, v bn thn mi thnh phn li l nhng vector a chiu .Do c nhiu

trng hp khng th so snh hai c t lung. Chng hn, nu mt ci yu cu di thng

cao hn v ci kia yu cu tr nh hn. Khi thay v ly ra ci ln hn, th tc trn phi

cho ra c t lung th ba m cc gi tr bng gi tr nh nht ca cn trn (Least Upper

Bound LUB) v ln nht ca cn di (Greatest Lower Bound GLB). Trong trng hptrn, c t lung th ba phi c yu cu di thng ca c t lung th nht v tr ca

c t lung th hai.

Lut trn cc c t tu thuc vo kiu ng k ca chng. Cc c t lung ch

c trn khi chng c cng kiu ng k v cng n mt giao din ca b nh tuyn

(trong trng hp giao din ny ni vo mt mng LAN, n c th nhaanj c nhiu c t

lung t nhiu nt nhn). Cc c t lung cng ch c trn khi chng thuc cng mt

phin. Hnh 6 minh ho c ch trn cc c t lung vi cc kiu FF, SE v WF vi gi s

cc c t lung l cc vector mt chiu v c so snh bng o B.

Mi khi trng thi ng k hin ti thay i, b nh tuyn s to ra thng bo RESV

mi v chuyn tip ln trn ngay tc th (khng cn i n ht khong thi gian lm ti).

C ch trn yu cu ng k l mt u im c bn ca RSVP, kh nng m rng,

vi mt s lng ln ngi s dng tham gia vo mt nhm qung b nhm, lu lng trn

mng tng ln khng nhiu .

d) Duy tr trng thi ng k

RSVP theo cch tip cn trng thi mm qun l trng thi ng k trn cc b

nh tuyn v cc trm u cui .Cc trng thi RSVP c to lp v nh k lm ti bicc thng bo PATH v RESV. Trng thi b xo nu sau khong thi gian nht nh m

14

H

H

H

H

R RNt gi

Nt nhn

Nt nhn

Nt nhn

R : b nh tuynH : H thng cui

Hnh 5. Trn cc yu cu tch


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khng c lm ti. Trng thi cng c th b xo b bng thng bo hu b. Sau mi

khong thi gian lm ti ( refresh timeout) hoc sau khi trng thi thay i, tin trnh

RSVP qut trng thi ca n to v y cc thng bo PATH v RESV ti cc nt tip

theo.

Khi ng i thay i, thng bo PATH tip theo s khi to trng thi ng i trn

l trnh mi v cc thng bo RESV sau s thit lp trng thi ng k trn

RSVP gi thng bo RSVP di dng cc gi IP vi tin cy khng m bo. V

th cn phi kim sot c tnh hung cc thng bo lm ti b mt. Nu nh thi hn xo

b trng thi ng k bng K ln thi hn lm ti th RSVP c th i ph vi kh nng

K-1 thng bo lm ti b mt m khng lm hu b trng thi ng k. Mt khc, c ch

kim sot lu lng ca mng cn cung cp c nh mt di thng ti thiu cho cc thng

bo RSVP trnh mt thng bo do tc nghn.

Trng thi duy tr bi RSVP l ng, thay i mt tp cc nt gi Si hoc thay i

yu cu cht lng dch v, nt ch cn gi i cc thng bo PATH/RESV sa i. Kt qu

l nhng trng thi ca cc nt trn ng i s c iu chnh, trng thi c b hu b.

Khi trng thi nhn c khc vi trng thi lu trc , trng thi ang lu s

c cp nht. Nu vic cp nht ny lm thay i trng thi c chuyn tip trong cc

thng bo lm ti, nhng thng bo lm ti s c sn sinh v chuyn tip ngay tc th.

Tuy nhin ,s lan truyn ny s dng khi n ti mt im trn m sau khng gy ra thay

i no. iu ny lm ti thiu ho lu lng trn mng do s thay i trng thi gy ra vlm cho RSVP c th p ng c vi nhm qung b nhm ln.

e) Hu b trng thi

Khi cn hu b trng thi ng i hoc trng thi ng k, tin trnh RSVP gi i

thng bo hu b. Mc d trng thi s b hu b khi ht thi hn cleanup timeout nhng

cc nt u cui nn gi cc thng bo hu b ngay khi ng dng kt thc .

C hai loi thng bo hu b l PATHTEAR v RESVTEAR. Thng bo

PATHTEAR i xui dng xung tt c cc nt nhn t ni n c khi to v xo trng

thi ng i cng nh trng thi ng k km theo ti cc nt trn ng. Thng bo

RESVTEAR c chuyn ngc ln cc nt gi t ni n c khi to v xo cc trng

thi ng k. C th hiu PATHTEAR v RESVTEAR c ngha ngc li so vi cc

thng bo PATH v RESV .

f) Hot ng qua cc b nh tuyn khng h tr RSVP

RSVP phi hot ng c khi hai b nh tuyn RSVP ni vi nhau bi mt m

my cc b nh tuyn khng h tr RSVP .

RSVP c thit k hot ng chnh xc qua m my cc b nh tuynkhng h tr RSVP. D nhin l mt m my khng h tr RSVP th khng th thc hin

15


16/49


ng k ti nguyn, nhng nu c ti nguyn, n vn c th m bo tr gi theo yu

cu. Cc b nh tuyn RSVP v khng RSVP u chuyn tip thng bo PATH ti a ch

ch dng bng dn ng pht n/qung b nhm cc b ca chng. Do , vic dn

ng ca thng bo PATH s khng b nh hng bi cc b nh tuyn khng RSVP trn

ng i. Khi thng bo PATH i qua m my khng RSVP, n mang theo ti nt c h

tr RSVP k tip a ch IP ca b nh tuyn RSVP cui cng trc , trc khi vo m

my. Thng bo RESV s c chuyn tip ng ng ti b nh tuyn RSVP ngay bn

trn ng i ln nt ngun

g) Bo mt

Vi kh nng cho php ng k trc ti nguyn, RSVP to ra cc loi hnh tn

cng mi nh n cp dch v, treo ti nguyn dn n dch v b t chi. RSVP ngn chn

nhng tn cng nh trn bng c ch xc thc qua tng chng s dng hm bm m ho,thng qua i tng INTEGRITY(tu chn) trong cc thng bo RSVP

II.1.2.3. Mt s vn ca giao thc RSVP

Vi kh nng bo mt hn ch, RSVP cha thc s an ton trc cc loi hnh ph

hoi nh n cp ti nguyn hoc treo ti nguyn. RSVP s dng lc m ho MD5

xc thc thng bo. Tuy nhin c ch ny i hi mt h thng phn b kho. V trc khi

mt h thng phn b kho nh vy c s dng rng ri, vic phn b kho phi c

thc hin th cng

Cc vn v chnh sch qun tr v qun l chnh sch cng cha c m t y

. RSVP cung cp cc c ch thc hin chnh sch, nhng n cha nh ngha mt chnh

sch no c th

Cui cng l vn m rng, khi s dng RSVP trn qui m ln s ny sinh cc vn

sau : lu lng iu khin trn mng qu ln ,cc trng thi ng k cng rt ln i hi

ti nguyn rt ln v phi c c ch iu khin lu lng cho nhiu ng k

II.1.3. Kim sot chp nhn

M hnh IntServ da vo vic kim sot chp nhn gii hn thng tin c nhnvo mng, do c th c ti nguyn cung cp cht lng dch v cho cc lung ang

16

Nt gi Nt nhn

m my cc b nh tuyn khng h tr RSVP

R RSVPR RSVP

Hnh 6 . Hot ng ca RSVP qua cc b nh tuyn khng h tr RSVP


17/49


tn ti. Cc yu cu d tr ti nguyn c cc nt x l xem xt mt yu cu mi c th

c chp nhn hay khng m khng nh hng n cc lung ang tn ti. Module kim

sot chp nhn ti cc b nh tuyn ra quyt nh da vo cc thut ton o ti cc b ca

mnh ti thi im ra quyt nh, phng php ny c gi l kim sot chp nhn da trn

php o (measurement based admission control). Cch tip cn truyn thng c ngh

l cc router cn ghi nh cc thng s dch v ca cc yu cu trc v tnh ton da

trn gii hn xu nht ca mi dch v Cch tip cn ny an ton nhng hiu qu khng cao

do rt him khi cc dch v ng thi t n gii hn xu nht. Cch tip cn c ngh

gn y c v gip s dng ng tryn hiu qu hn l router nh gi s s dng ng

truyn thc t ca cc lung packet ang tn ti v s dng thng tin ny lm c s cho vic

chp nhn hay khng yu cu dch v ca lung mi. Cch tip cn ny c ri ro ln hn

nhng lm tng hiu qu s dng bng thng

II.1.4. Phn loi gi tin

Cc gi tin i n trc khi c lp lch s c phn thnh lp nh b phn lp

gi Cc gi thuc cng mt lp s nhn c cng mt cch i x nh nhau t b lp lch

gi : chng cng c a vo mt hng i vi mc cht lng dch v no .

Vic phn lp ny da vo mt s d liu trong gi (v d trong phn u ca n v

thng tin tng mng hay tng giao vn. Trong IP V4 c th dng a ch IP ngun v ch

cng nh s Port tng giao vn. Trong IP V6, c th dng a ch IP ngun v nhn lung).

Mt lp c th tng ng vi mt phm vi rng cc lung, v d tt c cc lungvideo, hoc ch mt lung n l.

Vic phn lp ch c ngha cc b : mt gi c th thuc cc lp khc nhau ti cc

b nh tuyn khc nhau dc theo ng i. V d, cc b nh tuyn trn mng trc

(backbone) c th gp nhiu lung vo mt s lp, cn cc b nh tuyn gn u cui,

ni c rt t lung c th phn mi lp vo mt lung

II.1.5. Lp lch gi tin

Lp lch cho gi tin l chc nng nn tng ca h thng, l c s m bo kh

nng cung cp dch v thi gian thc ca phn t mng. Lp lch gi tin da trn vic xpxp li hng i u ra. C nhiu cch thc hin vic ny .

Cch n gin nht l s u tin trong cc packet c xp th t theo mc

u tin. Cc packet c mc u tin cao nht s c gi i u tin. Nhng s ny c th

dn n cc packet c mc u tin thp c gi i qu chm hoc thm ch khng c gi

i nu c nhiu packet c mc u tin cao.

Mt s lp lch gi khc l c ch phc v quay vng (round robin) hoc mt s

s ci bin t s ny (tiu biu l Weighted Fair Queuing). N cho php cc lp

packet khc nhau chia s mt ng truyn chung.

Ngoi ra cn nhiu s phc tp cho php qun l hng i tu thuc vo mt s

mc tiu dch v i vi mt s lung ring bit .

17


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II.1.6. Kin trc dch v tch hp

Thng thng trong mng IP c mt s cch tu chn ci t mt chc nng trong

mng. Vi dch v tch hp cn phi trao i thng tin gia cc h cui vi cc phn t

mng (b nh tuyn hay mng con). S la chn l gc cho trng hp ny l s dng

giao thc RSVP, nhng khng phi l kh nng duy nht. C th dng mt s giao thc

thit lp khc tng ng v mt chc nng cng nh th tc qun l thc hin vic .

Giao thc thng c s dng trong dch v tch hp l RSVP nhng RSVP v m hnh

IntServ c lp vi nhau .

Hnh 7 trnh by mt phn ca kin trc h thng dch v tch hp. Trong RSVP

l giao thc duy nht mang yu cu ca chc nng cht lng dch v. N c gi n cc

khi chc nng thc s cung cp cht lng dch v trong b nh tuyn / mng con. RSVP

truyn ti cc i tng nhng cc i tng ny li trong sut i vi RSVP. Hnh 10 minh

ho mi quan h gia cc khi chc nng. V d chc nng kim sot thu nhn skhng ch

dng i tng chnh sch ca RSVP chuyn m cn dng cc i tng dng gi chc

nng cht lng dch v v thm ch c i tng nh danh v k ton

Mt im cn lu l vic yu cu v cung cp cht lng dch v l khc nhau, hn

na giao thc RSVP khng cung cp cht lng dch v m cung cp dch v truyn thng.

Do vic cung cp dch v tch hp (v c dch v DiffServ) l c lp vi RSVP.

Hnh 7 m t cc i tng d liu trong tin bo PATH. Nh trnh by trn trong

RSVP, tin bo PATH c truyn t bn gi n bn nhn v cha thng tin v lu lng

xut pht t bn gi.

Dng lu lng m t trong Tspec ca bn gi. Tspec khng thay i cc c trng

ca dng lu lng trong qu trnh gi m ch bo hiu chng n tt c cc nt trung gian

trong mng v ch. Adspec c sinh ra bi my ch gi hoc b nh tuyn u tin trn

ng, n cha cc tham s tng qut c trng cho ng , xc nh bi vic tnh tontrn tng chng, cng nh cc tham s c trng cho cht lng dch v c th c phn t

18

Acct

Auth

Policy

D liu

RSVP RSVP

Chc nngkim sotchnh sch

X l itng kimsot QoS

X l ingnh danh

X l itng kton

Chc nng ng d liuKim sot QoS

Hnh 7 . Kin trc ca m hnh dich v tch hp

B nh tuyn hoc mng conMy ch


19/49


mng h tr. V d v cc tham s tng qut : kch thc MTU ca ng truyn, bng

thng, tr ti thiu trn ng. ..

Hnh 8 cho thy b m t lung (flow description) trong RSVP. M t lung bao

gm hai phn : flow spec v filter spec. M t lung c gi trong thng bo RESV, truyn

t bn nhn n bn gi .

Filter spec ch lm nhim v phn bit cc gi mt cch logic. Cn c vo nhn ca

lung (trong IP v6) hay a ch ch, cng ch (trong gi IP v4), vic la chn dng con

thch hp vi dch v trn c thc hin.Flow spec cha ba phn : kiu dch v c yu cu, cc tham s dch v (Rspec) v

cc tham s lung yu cu dch v (Tspec).

Hnh 9 m t chi tit hn v chc nng ng d liu kim sot cht lng. Thng

tin t giao thc RSVP c a vo cc khi chc nng khc nhau trong b nh tuyn, ti

chng c x l a ra quyt nh cung cp cht lng dch v tng ng. B phn

loi gi xc nh cch x l cc gi. B lp lch gi p dng cc c ch xc nh vi cc gi

cung cp cht lng dch v c yu cu. Chc nng kim sot chnh sch v kim sot

chp nhn xc nh mt lung c th c c php yu cu mt dch v nht nh ti thi

im hay khng (chnh sch) v c ti nguyn trong phn t mng h tr dch v

c yu cu (chp nhn). Kt qu ca cc hot ng nh hng n quyt nh ca b

phn loi gi. Hn na, cc thng tin ca RSVP cng nh hng ti cc gii thut chn

ng ca phn t mng (chn ng c xem xt n cht lng dch v).

19

AdSpec TSpec

Hnh 8 . Cc i tng trong tin boPATH

Lpdch v

RSpec TSpec a chngun

FlowSpec Filter Spec

Hnh 9 . Cc i tng trong tin boRESV

M t lung

RSVP

Chnng

Kim sotchp nhn

Kim sotchnh sch

Phn loi gitin

Lp lch gitin

i tng chnhsch

TSpecRSpec

TSpec

FilterSpec

Hnh 10. Quan h gia thng tin RSVP v vic xl gi trong b nh tuyn


20/49


Sau y chng ta x xt hai dch v c th ca m hnh IntServ .

II.1.6.1. Dch v ti c kim sot

Dch v ti c kim sot c p dng cho mt lp ng dng c c tnh thi gian

thc nhng c th thch nghi vi iu kin mng khng qu ti. Dch v ti c kim sot c

gng to ra iu kin mng khng ti cho cc ng dng nhng khng cung cp m

bo dch v. Cc dch v ny c th l audio hoc videoDch v ti c kim sot quan tm n hai tham s cht lng dch v : tr v mt

gi. Mc tiu ca dch v ny l t l mt gi v tr trn mng t ti thiu v xp x

dch v thng thng khi mng khng qu ti .

Kin trc dch v.

Hnh 11 m t mt phn t mng cung cp dch v ti c kim sot, trong phn

quan trng nht l chc nng x l gi. Ti y, tt c cc lung gi u i qua b phn loi

gi trong b nh tuyn. N xc nh gi no thch hp vi dch v ny gi no khng.

u ra ca b phn loi gi l thng th bi. C ch thng th bi c dng xc nh gino nhn dch v ti c kim sot. Trong thit k hnh 11 c hai hng i. Hng i trn

20

Lp lch / x l giPhn loigi

Thng thbi

Chc nng ng d liu kim sot cht lng

B nh tuyn

Hnh 11 . Dch v ti c kim sot


21/49


c u tin v cc cc gi tun theo c ch thng th bi ca lung c a vo hng i

u tin cao hn ny. Hng i thp hn c dng chung cho cc gi khng tun theo c

ch thng th bi v cc gi ch nhn c dch v c gng ti a. Hng i di li c th

phn thnh hai hng i nh hn.

y, c mt s vn cn xem xt. Trc ht l cch x l lu lng khng tun

theo yu cu dch v. RFC 2211 ngh i x vi chng nh vi lu lng c gng ti a.

Do trn hnh 6, ta thy phn vt qu c a vo hng i c gng ti a. Tt nhin

lu lng vt qu khng c nh hng nhiu n dch v c gng ti a bnh thng, v

d n khng c gy ra s suy gim cht lng dch v ng kt vi dch v thng thng.

Vn l khi c nhiu lu lng ti c kim sot khng tun th, chng c th lm dch

v thng thng b dng li do b mt nhiu gi trong hng i. Do cn c c ch x l

lu lng vt qu t dch v ti c kim sot. Mt s gii php c ngh nh dng mt

mc hng i u tin khc cho phn lu lng ny hay dng c ch hng i WFQ hayCBQ m bo lu lng c gng ti a khng b nh hng bi lu lng vt qu .

Vn th hai l phn b ti nguyn trong hng i u tin cao (lu lng ti c

kim sot), c ngha l cch cc lung ti c kim sot chia s hng i ny v cch kim

sot chp nhn vi cc lung ny .

C ch thc hin dch v ti c kim sot

gi dch v ti c kim sot cho mt lung, ng dng dng giao thc

SENDER_TSPEC vi yu cu dch v ti c kim sot trong tin bo PATH . RSVP cnggi ADSPEC trong tin bo PATH, cha thng bo rng dch v ny c c ci t trn mi

chng ca ng hay khng, kch thc MTU ti thiu v cc tham s c trng ca ng

i ca cc gi trong lung. Cc nt trung gian c th sa i ADSPEC nhng khng th sa

i SENDER_TSPEC. Khi bn nhn thy tin bo PATH cho dch v ti c kim sot, chng

ch bo dch v c c h tr hay khng bng cch t bit gy (break bit). Bit ny

bo cho mi ngi bit rng c t nht mt nt trn ng khng h tr dch v ny.

Mt im ch quan trng l khng c nh ngha mang tnh nh lng chnh xc

ca dch v ti c kim sot. Mi phn t mng cn quyt nh mt cch c lp xem n c

th cung cp dch v ny da trn mc ti hin ti ca n cng nh mc ri ro c th c

(do cung cp qu mc tng ca Tspec ca cc lung ti c kim sot).

Khi lung c chp nhn, chc nng ng d liu bt u lm vic. Chc nng

ny quan tm n vic x l v lp lch gi. y chng ta cn xem xt mt kha cnh trong

p ng ca thng th bi : gi s lung t n s gi m thng th bi cho php v sau

gi vi tc th ghi trong Tspec. Nu nt chn phc v lung vi tc th th s c

ng (backlog) c nh cc gi ti hng i ca nt . V vy RFC 2211 khuyn ngh

nn c c ch cho php dn dp backlog lm gim thi gian xp xp hng i cho

lung. Mt cch tng t, nh chng ta bit, lu lng gi qua nhiu nt khng duy trc hnh dng v c tnh ban u ca n, nu mt nut t kch thc b m ti a bng

21


22/49


kch thc chm ch ra trong Tspec th s c mt mt gi (khng cn thit) do lu lng

khng c nh dng li ti mi nt trong mng. RFC cng khuyn ngh dng s phn

b b m mm do c th cung cp thm b m cho cc chm .

Nt xc nh s tng thch ca lung bng c ch thng th bi (c tham s ho

trong Tspec). Vic x l cc gi khng tng thch khng qu cht ch, nhng khng c

lm gim dch v cung cp cho cc lung ti c kim sot khc v dch v c gng ti a.

Tt nhin, mt tu chn trong vic x l lung vi lu lng khng tng thch l lm gim

dch v ca c lung (ch khng ch cho cc gi khng tng thch). Mt kh nng khc l

nh dng li lung cc gi khng tng thch i n khi chng tng thch hoc n

mt thi hn xc nh no . Mt cch x l khc l a chng vo hng i cng vi lu

lng c gng ti a (hoc sau lu lng ). iu lm cc gi trong lung b chuyn

khng theo th t v gy tr cho cc giao thc tng cao hn

II.1.6.2. Dch v m bo (Guaranteed Service)

Mc tiu ca dch v ny l cung cp l cung cp tr c gii hn v m bo vic

truyn tt c cc gi c xc nh cho ng dng cn n n. Phn ny xem xt cc tham

s ca dch v m bo, cch s dng v c ch cung cp dch v. Phn c bn ca dch v

m bo l tham s t tt c cc phn t mng trong ng c th phi c kh nng t hp

vi nhau mt cch n gin d on (gii hn) cht lng dch v m cc gi trong lung

s tri qua

Do qu trnh d tr l mt chiu nn i vi truyn thng hai chiu, phi c hai d tr .M hnh dch v

V dch v m bo l nh lng n c gii hn tr xc nh nn n cn da trn

c hai m hnh : p ng ca ngun v cch phn t mng x l lung. Mc ch ca cc m

hnh ny l gii hn tr hng i. Mt thnh phn khc ca tr u cui n u cui l tr

truyn, c kim sot bng cc gii thut nh ng dng khi thit lp lung. Cc m hnhc m t di y.

22

X

Hnh 12 . M hnh dch v m bo

R

M hnh thng th bi M hnh m dng cht lng

r th bi /s

B

p

b


23/49


Bn tri l m hnh thng th bi, dng cho bn ngun. C ngha l dng bn ngun

lun phi nm trong gii hn do thng th bi qui nh. Bn phi l m hnh ca mt lin kt

trong b nh tuyn. N ch ra ti nguyn (b m v bng thng) m b nh tuyn phi

phn b cho lung c m bo. M hnh c s dng l m hnh dng cht lng

(fluid model). Ngun sinh ra dng cht lng vi tc r (l tc th bi c to ra)

nhng i khi n c th to ra lung c tc nhanh hn r. Phn vt qu s c gi li

ngun v a ra vi tc r. Nu ngun khng pht trong mt thi gian, th bi c gi

n gii hn b, bt k lung no n s c truyn ngay lp tc khi cn th bi. Tc

truyn s l p .

Khi dng d liu n phn t mng, n c phc v vi tc R v dng b m

kch thc B. Cn c b m v tc truyn p c th ln hn nhiu so vi R

Kt qu l thuyt cho thy tr ca lung mng c gii hn b/R (vi iu kinr


24/49


T cc vn trn, ngi ta rt ra kt lun IntServ l m hnh thch hp cho mng

nh, trong ch c t lung v vn an ton v chnh sch c th qun l mt cch d

dng. Cng c th trin khai cc IntServ trong cc mng ln (chng hn mng ca cc nh

cung cp dch v) vi mt s hn ch cc lung. Ngoi phm vi , cc mng trc ln cn

nhng c ch kh dng hn phn bit lu lng v cung cp cc dch v khc nhau cho

chng. DiffServ l mt c ch nh vy .

II.2. M hnh dch v phn bitYu cu t ra vi cc nh cung cp dch v mng l cn c cc c ch kh dng v

thc t cung cp cc mc dch v khc nhau cho khch hng xut pht t nhng mi quan

tm mang tnh thng mi. Ngoi ra, cc doanh nghip s khng a cc s liu quan trng

ca h ln mng nu khng c cc c ch m bo dch v. S pht trin ca cc ng dng

nh thoi trn IP (VOIP) v mng ring o (VPN) gn lin vi kh nng ca h tng mng

trong vic cung cp cc loi dch v phn bit cho cc ng dng nh vy.

II.2.1. Cc c im chnh ca m hnh DiffServDo nhng vn tn ti ca m hnh IntServ nh trnh by trn, m hnhDiffServ c nghin cu nhm cung cp mt c ch n gin kh dng hn cho vic

phn bit cc dch v. Nhng c im chnh ca m hnh ny nh sau:

Mc phn bit th hn

Cc b nh tuyn trc chnh chuyn mt s lng ln cc lung n. Vic duy tr trng

thi d tr cho tng lung l rt kh khn v kch thc mng tng rt nhanh. V vy,

trong m hnh DiffServ, lu lng khng c phn bit theo lung, thay vo , c mt

s nh cc lp c nh ngha trc, cung cp cc dch v khc da trn tr v

mt mt thng tin.

Khng phn loi gi trong mng

24


25/49


RSVP ch ra rng, mi b nh tuyn u thc hin chc nng phn loi gi nhm cung

cp cc mc dch v khc nhau, do cn kim tra nhiu trng trong phn u gi (v

d vi IP v4, cn kim tra a ch IP ngun v ch, ch danh giao thc, cng ngun v

ch). Thao tc ny rt tn km, v vy trong m hnh DiffServ vic phn loi c thc

hin bin ca mng, ni c t gi phi x l hn. Cc b nh tuyn bin phn loi v

nh du cc gi tin mt cch tng ng. Cc b nh tuyn bn trong ch x l cc

gi theo du ca chng. Nh vy, cc b nh tuyn bn trong khng lm vic vi tng

lung n m ch lm vic vi cc lp tp hp. iu ny lm cho gii php kh dng

hn .

Cc m hnh cung cp khc nhau

RSVP iu khin vic d tr ti nguyn ng. iu ny c th to ra nhiu gi tin kim

sot v i hi kim sot thu nhn ng mi b nh tuyn. M hnh DiffServ a vic

kim sot thu nhn ra bin ca mng. Hn na, n khng yu cu vic d tr ng. Thayvo , n s dng vic cung cp tnh, di hn tho thun dch v vi ngi s dng

mng, m lu lng ca h c th c kim sot im vo mng. Cng c th dng

cng ngh kim sot lu lng nh ng cc gi t cc ngun nht nh theo cc

ng xc nh trc trnh cc im tc nghn trong mng (m gi c th i qua nu

dng cc giao thc nh ng khng quan tm n cht lng dch v thng thng)

Khng c m bo dch v tuyt iDch v tr c m bo trong m hnh IntServ cung cp gii hn cht ch v tr ti a

m cc gi c th tri qua. N thc hin c iu nh d tr ti nguyn trn ng

truyn. Tri li, DiffServ khng cung cp s m bo cht ch tr phi c mt lung tnh

c cung cp c bit cho lung c th. Trong m hnh ny, b nh tuyn bn trong

khng phn bit cc lung n m lm vic vi tp hp lung, do n khng th i

x mt cch u tin i vi mt lung c th.

Mc tiu ca DiffServ l theo di lu lng i vo mng nt vo v kim tra tnh

tng thch vi mt s profile dch v nh trc. Da trn , cc gi c th c nh dul trong (tho mn) hay ngoi (khng tho mn) cc profile ca chng. Bn trong mng,

b nh tuyn s u tin loi b cc gi c gn nhn ngoi.

Bn cnh u tin loi b, c cc thng tin trong phn u gi cho bit kiu dch v

mong mun ca gi. V d, dch v hng nht (premium service) l tng ng vi CBR.

Tng t dch v m bo c p ng chm v c cung cp dung lng mong mun.

II.2.2. Kin trc dch v phn bit

tng ca dch v phn bit kh n gin: mt lung mt chiu i vo mng qua

b nh tuyn bin u vo, n c nh dng v gi i bng p ng theo chng (Per

Hop Behaviour PHB), theo dch v tng ng c cung cp cho lung. Ti cc b

25


26/49


nh tuyn tip theo, PHB c p dng cho lung cho n khi n n b nh tuyn bin

u ra, lung c th c nh dng li trc khi gi n my ch hoc mt min dch

v phn bit khc .

Mt vng dch v phn bit l mt mng DiffServ. Li vo ca vng ny c gi

l nt vo (ingress node), li ra c gi l nt ra (egress node), cc nt ny cn c gi l

nt bin. Mt min DS bao gm mt hoc nhiu vng DiffServ, mi vng gm nhiu nt

trong (interior) v t nht hai nt bin (border) m lu lng i vo v i ra khi vng. Mt

nt bin l mt router hay mt my tnh thc hin phn loi packet n chuyn tip trong

min DS. Cc packet c th c phn loi ti my tnh gi hay ti nt bin ca mng DS.

Cu trc ca mt nt cung cp dch v phn bit c th khc nhau cn c vo v tr

ca n trong mng ( bin mng hay trong mng) v da vo s la chn ca ngi

qun tr mng khi ci t tho thun mc dch v v chnh sch .

Nt bin c ni chung c nhiu chc nng hn nt bn trong v c th m rng cc

dch v nh nh du, nh dng gi cho cc my ch hay min khng c kh nng t cungcp cc dch v . Nt bn trong c th gi thit rng lu lng i qua cc nt bin h

tr dch v phn bit v do vy c nh du v iu chnh chnh xc. Cc chc nng

ny c th c b qua cc nt bn trong .

Tho thun mc dch v (Service Level Agreement SLA) l mt khi nim quan

trng trong dch v phn bit. SLA xc nh mt min dch v phn bit x l cc gi. SLA

thng cha tho thun iu kin lu lng (Traffic Conditioning Agreement TCA), trong

m t s phn lp ca lung, cch nh du v b du i vi cc gi trong lung, cc

tham s thng th bi v tho thun v cch x l cc gi ngoi profile (ngha l khng p

ng mt s c tnh tho thun). Chc nng ny c thc hin trong mt s thit b

logic nh trong hnh 13 .

Profile lu lng xc nh mt s tnh cht ca lung vi mc dch v nht nh.

l cc c tnh hay thit b cho php b nh tuyn xc nh mt cch r rng mt gi l

trong hay ngoi profile. Hn na trn c s ca SLA/TCA hay trn c s ca chnh sch

min, cc gi ngoi profile c th c i x khc vi cc gi trong profile.

Thit b u tin chng ta xem xt trong cu trc nt l thit b phn loi gi (packet

classifier). Thit b ny dng chn cc lung nhn mc dch v nht nh. C hai loi

thit b phn loi gi : mt kiu da trn vic ch s dng trng DS trong phn u gi tinIP. Kiu ny gi l thit b phn loi tp hp p ng (behaviour aggregate BA). u im

26

Phn loigi o

nh dugi

inh dnghoc loi bgi

CchPHB

nh dng lu lng

Nt DS

Hnh 13 . Cu trc nt dch v phn bit


27/49


ca kiu phn loi ny l tnh n gin v ch c mt s hu hn cc trng thi cn c b

nh tuyn duy tr. Kiu thit b khc gi l thit b phn loi nhiu trng (multi field

MF) v n c th dng nhiu nhiu trng trong phn u gi xc nh xem gi c thuc

lung hay khng. u im ca kiu phn loi ny l cc gi thuc v cc lung cng n

mt giao din nhng c SLA khc nhau c xc nh v phn bit. Nhc im ca kiu

phn loi ny l thng tin trng thi c th rt ln .

Trn hnh 13, mt s thit b logic tp hp vi nhau to nn b iu chnh lu lng

(traffic conditioner). B iu chnh lu lng hu ch nht khi s dng ti cc b nh tuyn

bin u vo hay u ra ca mng dch v phn bit. Tt nhin chng c th c ngun

thng tin hoc b nh tuyn bn trong mng. Trong mt nt hay mt giao din c th, mt

s (hay tt c) chc nng m t tr hnh c th khng tn ti.

Thit b logic tip theo l thit b o (meter), dng theo di lung xc nh bi

thit b phn loi gi. N c cha c ch logic nh thng th bi v c kh nng xc nhxem gi tin trong hay ngoi profile. Tu theo SLA v chnh sch ca mng, thng tin t thit

b o c th c thit bnh du v nh dng / loi b gi s dng .

Thit b nh du gi (packet marker) cho php cc gi c x l theo SLA/TCA.

Cc vn c nu ra trong SLA nh lung no nhn dch v no, cch x l cc gi

ngoi profile c b nh tuyn bin thc hin bng cch nh du trng DS vi cc gi

tr c th. Cc gi tr ca trng ny v ngha ca chng c trnh by phn trn.

Thit b nh dng (shaper) m bo lung tun th chnh xc cc tham s cho

trong profile lu lng nht nh. N c th lm mt s gi b tr. Nu dng gi thc s rtkhc so vi profile lu lng, n c th gy ra loi b gi v thit b ng dng khng c b

m v hn (hoc rt ln)

Thit b loi b (dropper) loi b cc gi khi lung m bo s tng thch vi

profile lu lng. SLA/TCA hay chnh sch min xc nh thit b loi b p dng cho tt c

hay ch mt phn ca lung (chng hn cc gi ngoi profile) hay tt c cc lung. Thit b

ny c th dng thng tin t thit b phn loi, o v nh du ra quyt nh loi b gi.

II.2.3. nh ngha dch v

C mt s nh ngha khc nhau cho mng dch v phn bit. Ta s xem xt cc

PHB c bn, c thit k tng thch vi vic s dng trng IP Precedence (trc kia

l mt phn ca trng TOS). Ta cng m t PHB chuyn tip nhanh

(Expedited Forwaring EF) v PHB chuyn tip c m bo (Assured ForwardingAF)

II.2.3.1. Trng DS v cc PHB c bn

Byte DS l nh ngha li ca byte TOS trong phn u IP v4 v lp octet lu lng

trong phn u IP v6. Byte ny c chia thnh hai trng : mt m (codepoint) DS 6 bit v

mt trng (hin khng dng) 2 bit. Mi quan h gia m v PHB ci t trong nt v mngl cu hnh c. duy tr s tng thch ngc vi trng IP Precedence (3 bit) hin

27


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ang s dng, mt tp m c nh ngha, gi l m chn lp (Class Selector), c nh x

vi tp chun cc p ng ti thiu tng thch vi cc p ng IP Precedence ang s

dng.

Cu trc trng DS :

PHB c bn c cc nt dch v phn bit h tr gi l PHB mc nh v l p

ng truyn c gng ti a bnh thng ca IP. PHB ny chu s hn ch ti nguyn ca nh

qun tr mng v cc gi c truyn khi nt mng khng phi phc v cc lp dch vkhc. M chn PHB mc nh l 000000 (nh phn). Cc m khc c th nh x n PHB

ny v cc m cha nh ngha c th chn PHB ny l cch x l mc nh chung. PHB

mc nh tng thch vi cch cc gi tin c cng gi tr trng TOS c x l hin nay.

Bng 1 : Bng nh x gia DSCP v PHB

C 8 m chn lp, trong c mt m chn p ng mc nh. Cc PHB do 7 m

cn li chn phi tho mn cc yu cu sau : cc m chn lp phi c trt t theo gi tr ca

chng. Qui lut chung cho cc PHB chn lp l di iu kin ti tng ng, PHB gn

vi m gi tr cao hn phi c p ng tt hn so vi PHB gn vi m gi tr thp hn.

tho mn yu cu ti thiu, phi c t nht hai p ng phn bit r rng .Mt p ng phiu tin cho cc gi mang m DS 11x000 so vi cc gi nhn PHB mc nh tng

28

2 3

DSCP

0 1 75 64

CU

Codepoint

000000

001000

001111

111000

111001

111101

PHB

PHB_number PHB_semantic

PHB_1

PHB_2

PHB_3

Best - Effort

EF

AF


29/49


thch vi cc lp IP Precedence 111v 110 ang dng cho lu lng nh ng. PHB

chn lp cung cp c s cho mt tp cc PHB chun c cc dch v phn bit cung cp .

64 m d tr c chia thnh 3 phn.

- xxxxx0 : dng cho cc PHB chun, c 32 m c th gn cho cc PHB chun

- xxxx11 : dng cho cc PHB thc nghim hay cc b, chng c nh ngh v ch

dng trong mt trng DS n

- xxxx01 : dng cho cc PHB thc nghim hay cc b, 16 m ny trong tng lai c

th c dng cho tp chun nu 32 m khng

II.2.3.2. PHB chuyn tip nhanh

Mc tiu ca PHB EF l xy dng kiu dich v ng thu ring o . Cc c

trng dch v ny l : t l mt gi nh, tr v bin thin tr thp v thng lng m bo.nh ngha ca EF tp trung vo cc c ch trong ng truyn vi gi thit rng lu lng

c x l ti cc nt bin ca min DS v c chc nng kim sot chp nhn bn

trong min.

tng chnh ca EF l i vi lung tp hp EF, tc ra c gi mt tc

cho (cu hnh c) hoc cao hn, khng quan tm n ti trn nt ti bt k thi im

no v cng khng quan tm n c trng ca bt k dng lu lng khc m nt nhnh

thy. L do ca yu cu cht ch ny l cung cp dch v vi nhng c im k trn,

hng i phi lun gi mc thp. Cc r rng t c iu l gi tc vo thphn tc ra. thc hin iu , tc ra phi c nh hoc t nht l khng di mt

ngng cho.

C mt s c ch ci t PHB EF, bao gm hng i u tin n gin, lp lch theo

vng trn (round robin) c trng s. .. . Mc d cc c ch ny c th thc hin chc nng

c bn ca EF, chng khng c cng c tnh. Mt s tnh cht ca dch v nh bin thin

tr c th khc nhau rt nhiu trong cc ci t khc nhau ca cng dch v .

II.2.3.3. PHB chuyn tip c m bo

Mc tiu ca nh ngha dch v ny l cho php mng cung cp cc mc m bo

truyn khc nhau v c th cc mc tr v bin thin tr khc nhau. Tt nhin, hai tnh cht

sau khng phi l mi quan tm chnh ca AF. Khng c mc tiu c th v tr v bin thin

cho AF, mc d trong iu kin no (v d nh ph thuc vo vic phn b ti nguyn v

c ch ci t PHB ny), lung c gn PHB AF cao hn c th t c cc c tnh v

tr v bin thin tt hn.

M c gn cho nhm PHB AF cho trong bng sau :

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Bng 2 Byte m DS cho AF

Yu cu ca PHB AF c pht biu bng nhng iu kin v p ng truyn, phn

b v sp xp li ti nguyn. C 4 lp AF v 3 mc u tin loi b trong mi lp. 6 bit ca

byte DS c chia thnh hai trng : trng th nht (3 bit) l s lp AF (gi tr thp phn

2, 3, 4 hoc 5) v trng th hai (3 bit) l mc u tin loi b (gi tr thp phn 0, 2 hoc 4).

Th t ca byte DS (gi tr s lp AF) ch ra trt t ca dch v. Nu m (x) < m (y) th lp

(y) c lng ti nguyn (b m v bng thng) c cp t nht bng lp (x). Tng t, th

t ca trng u tin loi b ch ra trt t ca t l loi b. Cui cng, trong cng mt lp

AF, nt khng c php sp xp li cc gi ca lung bt k mc u tin loi b .

Trong dch v ny, cc nt ci t c 4 lp AF v cc lp ny khng c kt hp

vi nhau : c ngha l cac gi thuc cc lp khc nhau phi c truyn c lp vi nhau.

i vi 3 mc u tin loi b, phi c t nht hai mc t l loi b phn bit. Nu mng ch

cung cp hai mc, hai gi tr u tin loi b cao hn s c nh x vo t l loi b cao

hn v gi tr thp nht s c nh x vo t l loi b thp hn.

Cui cng, c th dng iu chnh lu lng gii hn lu lng AF i vo mng.

Cc gi c th b loi b do hnh ng iu chnh lu lng nhng chng c th nng cp

hoc gim cp trong mc u tin loi thm b, ch gn vo lp AF

II.2.4. Qun l ng ti nguyn trong m hnh DiffServ

C hai phng php qun l ti nguyn l qun l ti nguyn ng v qun l ti

nguyn tnh, ti nguyn c th c cung cp ng theo nhiu phng php. Trong m hnh

dch v tch hp, vic cung cp ng ng ti nguyn ch yu nh giao thc RSVP. Trong

m hnh dch v phn bit, phn trn ta xem xt m hnh DiffServ vi s cung cp tnh

ti nguyn. Vic cung cp tnh ti nguyn c u im l khng to ra nhiu cc gi tin bo

iu khin cho vic d tr ti nguyn nh trong cung cp ng v khng i hi vic kimsot thu nhn ng, nh th m hnh s n gin hn. Tuy nhin, vic cung cp tnh ti

nguyn cng c mt s hn ch, l tnh km linh hot v c bit l khng s dng ti u

ti nguyn. Chnh v th, gn y, qun l ti nguyn ng trong m hnh DiffServ ngi

ta s dng mt phn t mi l Bandwidth Broker.

II.2.4.1. Tng quan v Bandwidth Broker

Mc tiu cui cng ca h tr QoS cho mng l cung cp cc dch v phn phi d

liu vi cht lng khc nhau cho cc user v cc ng dng khc nhau. Tuy nhin t quan

im nh tuyn, h tr QoS gm ba phn c bn :

nh ngha cc lp

30

AF1 AF2 AF3 AF4u tin loi b thp 010000 011000 100000 101000u tin loi b trung bnh 010010 011010 100010 101010u tin loi b cao 010100 011100 100100 101100


31/49


Xc nh lng ti nguyn cho mi lp

Phn loi cc gi vo cc lp tng ng

N lc DiffServ gii quyt vn th nht v vn th ba, n xc nh cc lp lu

lng cng nh cung cp mt c ch phn lp gi n gin m khng cn bit cc gi thuc

lung no hay thuc vo ng dng no. Bandwidth Broker gii quyt vn th hai bng

cch theo di s cp pht ti nguyn hin ti cho cc lu lng c nh du v xem xt

cc yu cu mi da trn cc chnh sch v s cp pht hin ti.

bn trong vng DS, BB kim tra yu cu v QoS t cc user v cc ng dng ring

bit v phn phi ti nguyn trong vng tu thuc vo cc chnh sch s dng ti nguyn

ca vng. bn ngoi, mt BB s chu trch nhim thit lp v duy tr tho thun dch v

song phng vi BB ca cc min ln cn m bo x l cc lu lng d liu i qua

bin ca vng .C ch hot ng ca Bandwidth Broker : yu cu cp pht ti nguyn cho mt

lung c th c gi ti BB. Yu cu bao gm loi dch v, tc , burst ti a v thi

gian yu cu dch v, yu cu ny c th do mt user hay mt BB ca vng khc a ra.

u tin BB s tin hnh chng thc yu cu, sau kim tra xem ti nguyn cha c

phn phi c p ng yu cu khng. Nu mt yu cu qua c hai kim tra ny, bng

thng kh dng s gim i mt lng bng bng thng yu cu v c tnh lung (flow

specification) c lu li.

BB cu hnh cc router l thch hp vi thng tin v lung c cp dch v ti thiim dch v bt u. S cu hnh ny l trng thi mm (soft state), c BB lm ti

nh k .

BB l mt phn ca kin trc DiffServ, n ng vai tr quan trng trong vic qun l

ti nguyn dch v khc bit .Hai kha cnh quan trng l :

- Qun l ti nguyn trong vng

- Qun l ti nguyn gia cc vng

a) Qun l ti nguyn trong vngQun l ti nguyn trong mt vng gii quyt vn cp pht ti nguyn trong mt

mng hay mt vng (domain) .

Trong mt mng gc, SLA c tho thun vi khch hng v yu cu cp pht bng

thng c p ng hay t chi da trn vo lng ti nguyn kh dng. Ngoi ra, thng tin

v DSCP c thit lp, c chuyn cho cc router l v thng tin v thit lp lp c

chuyn ti egress router cn c vo yu cu .

Trong mng chuyn tip, qun l ti nguyn c yu cu ch yu h tr lung

thng tin i qua min. Khi mt BB nhn c thng tin qun l ti nguyn gia cc min,

thng tin bao gm : thng tin v lung tp hp i vo vng ti mt im vo c th v DSCP

c yu cu cho lung . Lung tp hp hin ti c update profile thng tin lung ra vo.

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BB theo di lu lng DS i vo v ri khi vng qua bin ca n, m bo rng tho thun

song phng vi cc min ln cn c m bo

b) Qun l ti nguyn gia cc vng

Qun l ti nguyn gia cc vng cp n vic cung cp v phn phi ti nguyn

ti bin mng gia hai vng. Mt SLA song phng xc nh s lng v loi lung, m

mi bn ng gi v/hoc nhn, phi c thit lp trn bin gia hai min

Thng ip bo hiu c gi gia cc BB ca cc vng ln cn yu cu BB ln

cn ti nguyn cn thit trong mng ln cn v truyn t thng tin v ti nguyn c

yu cu trn ng ni cc vng.

Trong mt mng gc, mt BB qun l ti nguyn trn ng ni mng gc vi mng

chuyn tip k vi n. Trong mng chuyn tip, BB theo di lu lng DS n v i khi

vng qua bin vng, m bo rng tho thun song phng vi vng ln cn c gi vng.BB thng tin vi router bin i vo v i ra cu hnh b iu khin lu lng

trong router da trn cc tho thun.

II.2.4.2. Kin trc ca mt h thng BB

Mt BB bao gm 4 thnh phn nh sau Bandwidth Broker Database

Bandwidth Broker Server

Bandwidth Broker Command Line Interfaces

o Service Level Agreement Client.

o Bandwidth Allocation request Client.

Bandwidth Broker router configuration client

Trong :

BB SLA Client dng theo di cc user, ti nguyn v topology ca vng. BB SLAClient cha d liu SLA, d liu cp pht ti nguyn v d liu topology ca vng .

32

BB

Database

BB SLA

Client

BB BARClient

BB RouterClient

BBServer

Hnh 14 . Kin trc h thng BandwidthBroker


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BB Server x l tt c tin tc truyn thng gia cc thnh phn ca BB, tin hnh

chng thc v cu hnh thit b

Bandwidth Broker Command Line Interfaces cung cp chc nng yu cu v thay

i dch v user

BB Router Configuration Client cu hnh cc router l trong min x l d liu t

mt user ring bit

Hnh di y minh ho m hnh dch v phn bit s dng Bandwidth Broker, trong

BB l phn t ng vai tr qun l ti nguyn trong dch v phn bit

II.2.5. u im v hn ch ca dch v Diffserv

II.2.5.1. u im

Tnh d m rng (scalability)

y l u im quan trng nht ca Diffserv. Trn mng trc c th c rt nhiu

lung lu lng, bt k giao thc no yu cu duy tr trng thi tng lung hay tnh ton

phc tp u dn n kh khn trong vic m rng dch v. Diffserv thc hin gp nhiu

lung v do c th x l mt s lng lung ln. Thm na, Diffserv a nhng cng

vic phc tp (phn loi, qui nh lu lng) ra cc b nh tuyn bin nn cc PHB trong

Diffserv n gin, cho php hot ng vi tc cao.

D qun tr

Trong mt DS framework, cc vng DS khc nhau c th ci t cc PHB tu

min l tho mn SLA . Do cc nh cung cp dch v c th t do la chn ci t, v

vy h c th chn cch cung cp Diffserv vi nhng thay i ti thiu trong c s h tng

ca h.

II.2.5.2. Hn ch ca DiffservTrong kin trc Diffserv c hai hn ch c bn.

33

Hnh 15 . M hnh dch v phn bit x dng BB


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Diffserv cung cp cht lng dch v cho lung lu lng trn c s tng chng, thng

khng m bo cht lng dch v t u cui n u cui

Diffserv khng c kh nng x l li ng truyn. Chng hn, khi mt ng truyn

mang lu lng EF trong min Diffserv hng, nh cung cp dch v khng c cch no

gi nhanh lu lng qua mt ng truyn khc v m bo mt gi l ti thiu.

Hn na s dng c ch chn ng ngn nht, mt s ng trong min Diffserv c

th b tc nghn trong khi cc ng khc li khng c s dng.

C th thy Diffserv ch thch hp vi mng trc, ni c nhiu lung i qua, kt hp

cc lung gim bt ti cho thit b. Nhng ngay c trn mng trc, cng cn c nhng c

ch h tr Diffserv trong vic chn ng nng cao hiu qu s dng dch v . MPLS vi

kh nng traffic engineering c th p ng yu cu ny .

II.3. Multi Switching Label Protocol v Traffic EngineeringII.3.1. Gii thiu

Trong mng IP truyn thng, gi d liu c chuyn tip c lp ti mi router cn

c vo header ca gi v bng thng tin nh tuyn. Thut ton chuyn tip da trn so khp

di nht, ngha l prefix so khp cng di cng c u tin. Tuy nhin thut ton ny kh

chm. ng thi chn ng theo qui tc ng dn ngn nht cng gii hn kh nng qun

l ti nguyn mng .

MPLS l mt cng ngh mi c gng gii quyt nhng vn v nh tuyn trong

mng IP truyn thng . Vi MPLS, mt nhn c chiu di ngn v c nh c gn cho mi

packet v qu trnh chuyn gi trong mng da trn nhn ny. Vic phn tch ton b

header ca gi d liu c thc hin ch mt ln ti nt vo ca mng MPLS, nh vy tin

trnh nh tuyn n gin hn v nhanh hn.

Cc dch v trong mng IP truyn thng c c trng khng th d on trc. im

mnh ca MPLS l cung cp kh nng Traffic Engineering. V d nh vic s dng cc

tuyn ng r rng dn n kh nng qun l ti nguyn mng v h tr cc dch v mi.

Sau y, chng ta s xem xt kin trc ca MPLS v Traffic engineering vi MPLS

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II.3. 2. Kin trc MPLS

tng ca MPLS l khi mt packet n mt ingress LSR (Label Switching

Router). LSR xc nh FEC (Forwarding Equivalent Class) ca packet v gn nhn cho

packet tng ng vi FEC da vo nh x trong Incoming Label Map (LIM). LIM c th

c t ti mi nt bng tay hoc bng giao thc bo hiu nh LDP, CR LDP v RSVP

TE (c IETF nh ngha). Cc LSR tip theo trong ng i ca packet ra quyt nh

chuyn tip da trn nhn ca packet v thc hin hnh ng tng ng vi nhn (c qui

nh trong LIM) .Nt cui cng trong min MPLS, egress LSR s b nhn router k tip

nhn c packet ging nh khi packet i vo min MPLS .

S chuyn tip gi MPLS nh sau :

35

Tonhn

inhn i

nhn

LSR

inhn

inhn

Bnhn

Bn nhn

Bn nhn

Bn nhn

Bn nhn

Ntbin

Ntbin

Mngkhng

phiMPLS

MngMPLS Mng

khngphiMPLS

Lung khng c gnnhnLung c gn nhn l trnh1Lung gn nhn l trnh 2

Hnh 16 . C ch chuyn tip gi MPLS


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II.3.2.1. Cc thnh phn chnh trong m hnh

Nhn

Nhn c s dng trong MPLS c chiu di ngn v c nh. Mt nhn ch c

ngha cc b v n i din cho mt FEC m packet c gn vo. Mt packet c th c

nhiu nhn v chng c t chc thnh stack (Last In First Out).

Label Switching Router (LSR)

LSR l mt nt c kh nng chuyn tip packet t nhin ca tng mng v cng cho

php cc giao thc iu khin MPLS. C th phn LSR thnh LSR ngc hng v LSR

xui hng .LSR chuyn packet theo hng ca lung d liu l LSR xui hng cn LSR

nhn packet l LSR ngc hng. Label Switching Path (LSP)

LSP ca mt packet l mt dy cc router < R1 ;. .. ; Rn > vi R1 l LSP ingress v

Rn l LSP egress. LSP ingress gn nhn vo packet mc m no , cc router gia nt vo

v nt ra chuyn packet da vo nhn ny, nt ra chuyn tip packet s dng nhn mc m

k vi k > 0 hoc s dng mt s th tc chuyn tip khc.

Next Hop Label Forwarding Entry (NHLFE)

NHLFE c s dng khi mt packet gn nhn c chuyn tip v pha trc

NHLFE cha thng tin v chng tip theo ca packet v hot ng c thc hin trnchng nhn ca packet. Mt nhn c th c thay th bng mt nhn mi hay c th b b

i. Mi nhn ca mt packet vo c th c lin kt mt NHLFE. chia lu lng ra

thnh cc ng khc nhau c th c vi NHLFE cho mt label .

Incoming Label Map (ILM)

ILM m t nh x gia nhn ca mt packet vo v mt tp NHLFE. LSR chuyn

tip packet c xc nh bi NHLFE. C th so snh ILM vi bng nh tuyn ca router

IP truyn thng.

Label MappingKt hp nhn l kh nng ca LSR chuyn tip cc packet c ngun hoc nhn khc

nhau ti mt FEC vi mt nhn. Thng tin m cc packet c khi chng ti t cc interface

khc nhau vi nhn khc nhau, s b mt trong th tc kt hp nhn .

II.3.2.2. Forwarding Equivalent Class

Thng tin t mt s giao thc dn ng truyn thng (nh OSPF) c gi li

trong nh tuyn tng mng bit cn chuyn tip packet nh th no v chia khng

gian chuyn tip thnh thnh cc FEC. FEC bao gm cc packet c chuyn tip trn cng

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ng dn v c i x nh nhau. Nhn ca mt packet nh x packet ti mt FEC.

Packet c gn vo FEC ch mt ln

Forwarding granularity cp n mc tp hp c s dng trong quyt nh

chuyn tip. MPLS h tr nhiu kiu forwarding granularity. Cc packet c th c gn

vo cng FEC da trn nt ra, a ch IP ch hoc lung ng dng. Phn loi da vo nt ra

l mc th nht ca granularity v ph hp vi mng ln. Trong khi phn loi cn c vo

lung ng dng l mc tinh vi nht nhng n kh nng m rng khng cao .

II.3.2.3. Label Distribute Protocol

Label Distribute Protocol c s dng trong tin trnh thit lp ng dn, vi

LDP, mt LSR thng bo cho LSR khc v nh x label/FEC m n thc hin. Quyt

nh gn mt label ti mt FEC c thc hin bi LSR xui hng. LSR ny c th thchin kt ni nhn theo hai cch. Cch th nht, LSR ngc hng yu cu LSR ln cn kt

gn mt nhn ti mt FEC. Cc th hai, LSR xui hng gn trc tip m khng cn yu

cu .Label Distribute Protocol cng c s dng trao i thng tin v kh nng MPLS

gia hai Label Distribute peer. MPLS cho php nhiu Label Distribute Protocol. Ba Label

Distribute Protocol l LDP, CR LDP v RSVP TE c chun ho .

II.3.3. Traffic Engineering vi MPLS

II.3.3.1. Gii thiu chung

Traffic Engineering c s dng t c mc tiu hiu nng nh ti u ti

nguyn mng v xp t lu lng vo cc ng truyn c th. iu ny c ngha l tnh

ton ng i t ngun n ch da vo mt tp rng buc v chuyn tip lu lng dc

theo ng i ny. Chuyn tip lu lng theo mt ng nh vy l iu khng th i vi

IP, bi v quyt nh chuyn tip IP c a ra c lp ti mi chng v ch da trn ach ch IP ca packet

MPLS c th d dng chuyn tip lu lng trn mt ng i tu . Kh nng dn

ng r rng ca MPLS cho php ngi khi to LSP tnh ton ng i, thit lp trng

thi chuyn tip MPLS dc theo ng i v nh x cc packet ti nhng LSP ny. Khi mt

packet c nh x vo mt LSP, vic chuyn tip c thc hin da trn nhn v khng

hop trung gian no thc hin bt c quyt nh chuyn tip c lp da trn a ch ch IP

ca packet. MPLS TE a ra khi nim LSP priorities. Mc ch ca priorities l nh du

mt s LSP bo hiu rng chng quan trng hn cc LSP khc v cho php chng ly ti

nguyn t nhng LSP t quan trng hn. Lm nh vy s m bo rng :

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- Khi khng c cc LSP quan trng, ti nguyn c th c dnh cho cc LSP t quan trng

hn.

- Mt LSP quan trng lun thit lp dc theo ng i ti u nht (ngn nht)

- Khi mt LSP cn nh tuyn li, cc LSP quan trng c c hi tm thy mt ng i ln

hn .

Mc tiu ca traffic engineering l tm ra mt ng i trong mng tho mn mt tp

cc rng buc. Do , nhng rng buc ny cn c a vo tnh ton khi tnh ton cc

ng i kh thi ti ch. Cc rng buc c th l bng thng yu cu cho mt LSP c

th, s lng hop m lu lng c php i qua, mc u tin ca LSP so vi cc LSP

khc. v. v. .

Vic tnh ton mt ng dn tho mn nhng iu kin rng buc ny c th cthc hin ti nt vo s dng mt thut ton tnh ng (v d nh CSPF).

Cui cng khi ng i c tnh ton thnh cng, trng thi chuyn tip MPLS

c thit lp dc theo ng i bng cch s dng RSVP TE nh mt giao thc phn b

nhn. Khi ng i c thit lp, ti nguyn kh dng c update ti mi nt v cc nt

khc c thng tin v s thay i ny

II.3.3.2. M hnh thc hin

thc hin traffic engineering, ngui ta a ra hai phng php l Overlay Model

v Peer Model .

a) M hnh Overlay

Mng backbone thng s dng cng ngh ATM v s dng n theo cch thng

thng xy dng mch qua la chn ng i qua mt mng. Thay v cho php mi

router quyt nh ng i xuyn qua mng, iu hnh vin c th xy dng ng i haycc mch i qua vi router m khng nhng router ny a ra bt k quyt nh no v

dn ng, iu ny c ngha l bng nh tuyn c xy dng bng tay. i vi mng IP,

MPLS c th thc hin nhim v ny.

Chc nng tch cc ca mt mng nh vy l lu lng c th c chuyn mt

cch r rng, cho php lu lng i qua mt s ng truyn tc thp, gii phng dung

lng trn cc ng truyn khc nhm nng cao hiu nng truyn lu lng. Vic ny c

th c thc hin bng cch nhp vo bng tay mt s tuyn hoc bng cch thit lp t

ng mt mng full mesh (mng m mi li vo /ra u c ng i trc tip n mi li

vo khc). Mc d m hnh Overlay c nhiu thun li v ang c s dng rng ri hin

nay nhng n c vn v m rng khi thit lp mng full mesh. l vn N square

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m i vi mi LER c thm vo mng, phi thm vo mt ng i t LER ny ti

mi LER khc trong mng. Nh vy s c N 1 ng i mi cho mi LER mi. Khi mng

tng ln, s lng ng i tng ln rt ln, thm vo s phc tp v chi ph thng ip

ng k. c bit l khi mt ng truyn hng, phi thc hin mt s lng ln hot ng

update.

b) M hnh peer

Trong m hnh ny iu khin lu lng cn bng c th t c bng cch thay

i weight ca ng truyn trong giao thc dn ng OSPF. Vi phng php ny, mi

ng truyn c cho mt gi tr phn nh mc s dng ca ng truyn . Nu l

mt ng truyn chm, t nh ng truyn v tinh hay ng hay b tc nghn, ng

truyn ny c th c cho mt gi tr weight cao, bo cho router chn ng truyn

khc. Theo cch ny, cc weight c tnh ton v thit lp ch mt ln , c th gip mngcn bng vi t hoc khng c ng truyn tc nghn v lu lng overhead t hn so vi

m hnh Overlay .

II.3.4. Kt lun

c thit k cho php IP over ATM nhng MPLS c nhng kt qu tch cc nu

c ci t trn mng IP thng thng. MPLS l mt gii php a nng cho nhiu vn

ca mng hin nay: tc , scalibility, qun l cht lng dch v v traffic engineering.

Bng cch gn mt header c bit vo mt packet, cc router trong mng s khng cn mpacket, trch ra a ch IP v da vo quyt ng i. MPLS ch n gin m header

c bit v cn c vo header ny, gi packet n ng k tip xc nh.

Bng cch s dng mt cng ngh nh MPLS, traffic engineering cho php gim tc

nghn lu lng trn mng. Vi traffic engineering, c th a mt s lu lng vo mt

ng v mt s lu lng vo ng khc, chng hn nh trn mt ng truyn v tinh

v trn mt ng truyn khc r hn. MPLS header s bo cho router ng gi packet

thay v lu chn packet gn nht

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PHN 3NH GI, KT LUN

III.1. nh gi, phn tch cc phng php:

C bn phng php cung cp cht lng dch v cho mng IP l Intserv, Diffserv,

MPLS v Traffic engineering u c nhng u v nhc im ring.

(1) M hnh dch v tch hp (Intserv)

u im:

o C kh nng cung cp cht lng dch v end-to-end.

o Cho php p trc mt knh xuyn qua mng vi bng thng m bo

Nhc im:

o Kh nng m rng km, ch thch hp vi mng nh.

(2) M hnh dch v phn bit (Diffserv)

u im:

o D m rng: y l u im quan trng nht ca Diffserv. Trn mng trc

c th c rt nhiu lung lu lng, bt k giao thc no yu cu duy tr

trng thi tng lung hay tnh ton phc tp u dn n kh khn trong vic

m rng dch v. Diffserv thc hin gp nhiu lung v do c th x l

mt s lng lung ln. Thm na, Diffserv a nhng cng vic phc tp

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(phn loi, qui nh lu lng) ra cc b nh tuyn bin nn cc PHB trong

Diffserv n gin, cho php hot ng vi tc cao

o D qun tr: Trong mt DS framework, cc vng DS khc nhau c th ci

t cc PHB tu min l tho mn SLA . Do cc nh cung cp dch v

c th t do la chn ci t, v vy h c th chn cch cung cp Diffserv

vi nhng thay i ti thiu trong c s h tng ca h.

Nhc im:

o Diffserv cung cp cht lng dch v

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