Quan Li Chat Luong Dich Vu QOS

8/3/2019 Quan Li Chat Luong Dich Vu QOS

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n tt nghip i hc Mc lc

MC LC

THUT NG VIT TT .................................................................iii

LI NI U .....................................................................................5CHNG I - MT S VN TNG QUAN V MNG IP 2

1.1 Khi nim v mng IP ................................................................................................. 21.2 M hnh phn lp TCP/IP ........................................................................................... 21.3 Cu trc tiu IPv4 v IPv6 .....................................................................................6

1.3.1 Cu trc tiu gi tin IPv4 ...........................................................................61.3.2 Cu trc tiu gi tin IPv6 ...........................................................................81.3.3 a ch IPv4 ................................................................................................. 10

1.4 Cc mc QoS end to end....................................................................................12

1.4.1 Dch v n lc ti a.....................................................................................121.4.2 Dch v tch hp (Intergrated Service) ......................................................... 131.4.3 Dch v khc bit (Differentiated Service) ................................................... 14

CHNG II - CHT LNG DCH V TRONG MNG IP . 172.1 Khi nim QoS .......................................................................................................172.2 Tr ............................................................................................................................192.3 Nghn .......................................................................................................................192.4 Jitter ..........................................................................................................................202.5 Mt gi ......................................................................................................................21

CHNG III - KIN TRC CQS ..............................................223.1 Vn nh tuyn trong mng IP ............................................................................. 22

3.1.1 Khi nim v nh tuyn ................................................................................223.1.2 Cc phng php nh tuyn......................................................................... 23

3.1.2.1 nh tuyn tnh ............................................................................ 233.1.2.2 nh tuyn lun phin ....................................................................243.1.2.3 nh tuyn ng ............................................................................25

3.1.3 Mt s giao thc nh tuyn ........................................................................ 263.1.3.1 nh tuyn vect khng cch.........................................................263.1.3.2 nh tuyn trng thi lin kt .........................................................283.1.3.3 nh tuyn phn lp.......................................................................30

3.1.3.4 nh tuyn khng phn lp. ..........................................................313.1.3.5 nh tuyn trn c s QoS.............................................................32

3.2 Cu trc router .......................................................................................................... 333.3 Kin trc CQS ............................................................................................................36

CHNG IV - NG DNG KIN TRC CQS CHO QUN LNGHN TRONG MNG IP ............................................................40

4.1 Ti sao phi qun l nghn........................................................................................ 404.2 Cc chin lc qun l nghn s dng kin trc CQS.............................................. 41

4.2.1 Cc chin lc qun l nghn s dng hng i ........................................... 414.2.1.1 Chin lc hng i FIFO ............................................................. 414.2.1.2 Chin lc hng i cn bng trng s (WFQ) .............................414.2.1.3 Chin lc hng i khch hng (CQ) .......................................... 57

Nguyn Hu Lim, Lp D2001VT i


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4.2.1.4 Chin lc hng i u tin (PQ) .................................................604.2.1.5 So snh cc chin lc s dng hng i ...................................... 62

4.2.2 Cc chin lc trnh nghn............................................................................634.2.2.1 Random Early Detection ................................................................644.2.2.2 Weighted Random Early Detection .............................................. 66

4.2.2.3 Random Early Detection cho cc gi trong v ngoi h s ...........674.2.2.4 Adaptive Random Early Detection ................................................. 684.2.2.5 Flow Random Early Detection ........................................................69

KT LUN ........................................................................................ 71

TI LIU THAM KHO ................................................................ 72

Nguyn Hu Lim, Lp D2001VT ii


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n tt nghip i hc Thut ng vit tt

THUT NG VIT TT

AVB Available Bit Rate Tc bt kh dng

BGP4 Border Gateway Protocol version 4 Giao thc cng bin phinbn 4

CIDR Classess Inter Domain Routing nh truyn lin vng khngphn lp

CL Controlled Load iu khin truyn ti

CQS Classification, Queuing, Sheduling Phn loi, hng i, lp lch

DCEF Distributed Cisco Express

Forwarding

Chuyn tip phn phi nhanh

ca Cisco

DiffServ Differentiated Servervice Dch v khc bit

DWFQ VIP-Distributed Weighted FairQueuing

Hng i cn bng trng sphn phi theo VIP

FIFO First In, First Out Vo trc ra trc

FIP Forwarding Information Base C s thng tin chuyn tip

GS Guaranteed Service Dch v m bo

IGRP Interior Gateway Routing Protocol Giao thc iu khin cngbn trong

LLC Logical Link Control iu khin lin kt logic

LLQ Low Laytency Queuing Hng i tr thp

LSA Link State Advertisements Thng bo trng thi lin kt

MTU Maximum Transmission Unit Khi truyn dn ln nht NCP Network Control Protocol Giao thc iu khin mng

NP Net Performance Hiu nng mng

OSPF Open Sortest Path First Thut ton tm ng ngnnht u tin

PVC Permanent Virtual Circuit Knh o c nh

RED Random Early Detection Tch sm ngu nhin

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n tt nghip i hc Thut ng vit tt

RTP Real-Time Transport Protocol Giao thc truyn ti thigian thc

SLA Service Level Agreement Hp ng mc dch v

SVC Switched Virtual Circuit Knh o chuyn mch

TCP/IP Transfer Control Protocol/InternetProtocol

Giao thc iu khin truynti / Giao thc lin mng

VBR Variable Bit Rate Tc bt bin thin

VIP Versatile Interface Procesor B x l giao din a nng

WFQ Weighted Fair Queuing Hng i cn bng trng s

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n tt nghip i hc Li ni u

LI NI U

Ngy nay mng li vin thng v ang ngy cng pht trin mnh m vrng khp trn th gii. iu t ra mt bi ton l qun l mng vinthng nh th no n hot ng mt cch hiu qu v m bo c chtlng dch v ca mng. i vi mng Internet trc y do nhu cu khchhng cha cao, ch yu l s dng cc dch v truyn thng nh truyn file, thin t, dch v telnet v.v... Do vy m dch v Best Effort l rt hiu qu vm bo c cht lng dch v. Nhng hin nay vi nhu cu truyn a

phng tin ang ngy cng pht trin nhanh chng, iu lm xut hincc dch v Intergrated Service v Differentiated Service. Khi cc dch v ny rai th yu cu v vn nh tuyn v tc cc router cng phi c nngcao. iu cn thit phi c mt c ch qun l mi v mt kin trc mi qun l router tt hn. p ng yu cu , Kin trc CQS ra i vc ng dng trong mng Internet ngy nay. Ni dung n s nghin cu nkin trc mi ny v mt s ng dng ca kin trc CQS trong vn qun l nghn trong mng IP. n cng thc hin lp trnh m phng xcnh lng bng thng cung cp cho cc lung lu lng IP u tin s dng

thut ton WFQ. B cc ca n gm nm chng nh sau:Chng I: Mt s vn tng quan v mng IP Trnh by m hnhgiao thc TCP/IP v cc dch v Best Effort, Intergrated Service,Differentiated Service.

Chng II: Cht lng dch v trong mng IPTrnh by cc thng scht lng dch v nh: tr, nghn, jitter, mt gi.

Chng III: Kin trc CQS Trnh by vn nh tuyn trong mng IP v

kin trc CQS trong router.

Chng IV: ng dng kin trc CQS cho qun l nghn trong mng IPTrnh by cc phng php qun l nghn c s dng kin trc CQS.

Ngoi ra n cng thc hin lp trnh m phng xc nh lng bngthng cung cp cho cc lung lu lng u tin IP s dng thut ton WFQ.Phn ny khng c a vo ni dung n m c a ra mt phnring.

Nguyn Hu Lim, Lp D2001VT 5


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n tt nghip i hc Li ni u

Trong qu trnh thc hin n, vi nng lc c hn nn chc chn khngtrnh khi nhng thiu st. Rt mong c s ng gp kin ca cc thy cgio, ca cc c gi quan tm ti vn c trnh by trong n nc hon chnh hn.

Ti xin chn thnh cm n thy gio Thc s Nguyn Vn t ht sc tntnh gip v hng dn ti trong qu trnh thc hin n.

Nguyn Hu Lim, Lp D2001VT

H ni 10/2005

Sinh vin Nguyn Hu Lim

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n tt nghip i hc Mt s vn tng quan v mng IP

CHNG I - MT S VN TNG QUAN V MNG IP

1.1 Khi nim v mng IP

Tin thn ca mng Internet l mng ARPANET ca B quc phng M.Mng ARPANET ra i vi mc ch l kt ni cc trung tm nghin cu camt s Vin nghin cu v trng i hc nhm chia s, trao i ti nguynthng tin. Ban u giao thc truyn thng c s dng l NCP (NetworkControl Protocol) nhng sau c thay th bi b giao thc TCP/IP (TransferControl Protocol/ Internet Protocol). B giao thc TCP/IP gm mt tp hp ccchun ca mng, c t chi tit cch thc cho cc my tnh thng tin lin lc vinhau, cng nh quy c cho u ni lin mng v nh tuyn cho mng.

Trc y, ngi ta nh ngha Internet l mng ca tt c cc mng sdng giao thc IP. Nhng hin nay iu khng cn chnh xc na v nhiumng c kin trc khc nhau nhng nh cc cu ni giao thc nn vn c th ktni vo Internet v vn c th s dng y cc dch v Internet. Internetkhng ch l mt tp hp cc mng c lin kt vi nhau, Internetworking cnc ngha l cc mng c lin kt vi nhau trn c s cng ng vi nhau vcc quy c m cho php cc my tnh lin lc vi nhau, cho d con ng linlc s i qua nhng mng m chng khng c u ni trc tip ti. Nh vy,k thut Internet che du chi tit phn cng ca mng, v cho php cc h thng

my tnh trao i thng tin c lp vi nhng lin kt mng vt l ca chng.1.2 M hnh phn lp TCP/IP

TCP/IP l mt b giao thc c pht trin bi cc cc d n nghin cu cpcao (ARPA) ca b quc phng M. Ban u n c s dng trong mngARPANET. Khi cng ngh mng cc b pht trin, TCP/IP c tch hp vomi trng iu hnh UNIX v s dng chun Ethernet kt ni cc trm lmvic vi nhau. n khi xut hin cc my PC, TCP/IP li c chuyn sang mitrng PC, cho php cc my PC chy DOS v cc trm lm vic chy UNIX cth lin tc trn cng mt mng. Hin nay TCP/IP c s dng rt ph bin

trong mng my tnh, m in hnh l mng Internet.TCP/IP c pht trin trc m hnh OSI, do cc tng trong TCP/IP

khng tng ng hon ton vi cc tng trong m hnh OSI. Chng giao thcTCP/IP c chia thnh bn tng: giao din mng (network interface), linmng (internet), giao vn (transport) v ng dng (application) c cho nhhnh v 1.1:



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ng dng

Trnh din

PhinGiao vn

Mng

Vt l

Lin kt d liu

M hnh OSI

ng dng

Giao vn

Lin mng

Giao din mng

M hnh TCP/IP

Hnh 1.1: M hnh giao thc TCP/IP v m hnh OSI

Tng ng dng

Tng ng dng cung cp cc dch v di dng cc giao thc cho ng dngca ngi dng. M s giao thc tiu biu ti tng ny gm:

FTP (File Transfer Protocol): y l mt dch v hng kt ni v tin cy,s dng TCP cung cp truyn tp gia cc h thng h tr FTP.

Telnet (Terminal Network): Cho php cc phin ng nhp t xa gia ccmy tnh. Do Telnet h tr ch vn bn nn giao din ngi dng thng dng du nhc lnh tng tc. Chng ta c th nh lnh v cc thng bo tr lis c hin th.

HTTP (Hyper Text Transfer Protocol): Trao i cc ti liu siu vn bn h tr Web.

SMTP (Simple Mail Transfer Protocol): Truyn th in t gia cc mytnh. y l dng c bit ca truyn tp c s dng gi cc thng bo ti

mt my ch th hoc gia cc my ch vi nhau.POP3 (Post Office Protocol): Cho php ly th in t t hp th trn my

ch.

DNS (Domain Name System): Chuyn i tn min thnh a ch IP. Giaothc ny thng c cc ng dng s dng khi ngi dng ng dng ny dngtn ch khng dng a ch IP.

DHCP (Dynamic Host Configuration Protocol): Cung cp cc thng tin cuhnh ng cho cc trm, chng hn nh gn a ch IP.

SNMP (Simple Network Managament Protocol): c s dng qun tr txa cc thit b chy TCP/IP. SNMP thng c thc thi trn cc trm ca



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ngi qun l, cho php ngi qun l tp trung nhiu chc nng gim st viu khin trong mng.

Tng giao vn

Tng giao vn chu trch nhim chuyn pht ton b thng bo t tin trnh -ti - tin trnh. Ti tng ny c hai giao thc l TCP v UDP, mi giao thccung cp mt loi dch v giao vn: hng kt ni v phi kt ni.

Giao thc TCP

TCP thc hin mt s chc nng nh sau: Chc nng u tin l nhn lungd liu t chng trnh ng dng; d liu ny c th l tp vn bn hoc l mt

bc nh. Vic u tin TCP lm l chia lung d liu nhn c thnh cc ginh c th qun l. Sau gn mo u vo trc mi gi. Phn mo u nyc cha a ch cng ngun v cng ch. Ngoi ra n cn cha s trnh t

chng ta bit c gi ny nm v tr no trong lung d liu.Sau khi nhn c mt s lng gi nht nh, TCP s gi xc nhn. V d,

nu chng ta pha nhn, v s lng gi c quy nh l 3 th chng ta s gixc nhn cho pha gi sau khi nhn c 3 gi. u im ca vic lm ny lTCP c kh nng iu chnh vic gi v nhn cc gi tin.

Giao thc UDP

UDP (User Datagram Protocol) l mt giao thc truyn thng phi kt ni vkhng tin cy, c dng thay th cho TCP trn IP theo yu cu ca ng dng.

UDP c trch nhim truyn cc thng bo t tin trnh - ti - tin trnh, nhngkhng cung cp c ch gim st v qun l.

UDP cng cung cp c ch gn v qun l s cng nh danh duy nhtcho cc ng dng chy trn mt trm ca mng. Do t chc nng phc tp nnUDP c xu th hot ng nhanh hn TCP. N thng dng cho cc ng dngkhng i hi tin cy cao.

Tng lin mng

Tng lin mng trong chng giao thc TCP/IP tng ng tng mng trong

m hnh OSI. Chc nng chnh ca tng lin mng l nh a ch logic v nhtuyn gi ti ch. Giao thc ng ch nht tng lin mng l giao thc linmng IP (Internet Protocol). Ngoi ra cn c mt s giao thc khc nh ICMP,ARP, RARP.

Giao thc IP

IP l mt giao thc phi kt ni v khng tin cy. N cung cp dch v chuyngi n lc ti a. N lc ti a y c ngha IP khng cung cp chc nngtheo di v kim tra li. N ch c gng chuyn gi ti ch ch khng c sm bo. Nu tin cy l yu t quan trng, IP phi hot ng vi mt giaothc tng trn tin cy, chng hn TCP.



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Giao thc ICMP

Nh trnh by trn, IP l giao thc chuyn gi phi kt ni v khng tincy. N c thit k nhm mc ch s dng hiu qu ti nguyn mng. IPcung cp dch v chuyn gi n lc ti a. Tuy nhin n c hai thiu ht: thiu

ht iu khin li v thit lp cc c ch h tr; IP cng thit lp c ch truyvn. Mt trm i khi cn xc nh xem router hoc mt trm khc c hot ngkhng. Mt ngi qun l mng i khi cn thng tin t mt trm hoc routerkhc.

Giao thc thng bo iu khin lin mng ICMP (Internet Control MessageProtocol) c thit k b p hai thiu ht trn. N c i km vi giaothc IP.

Giao thc ARP

Giao thc phn gii a ch (ARP: Address Resolution Protocol) chuyn ia ch lgic thnh a ch vt l.

Khi mt trm hoc router cn tm a ch vt l ca mt trm hoc mt routerkhc trn mng, n gi gi yu cu ARP. Gi ny cha a ch vt l v a chlgic ca ngun v a ch IP ca ch. Do ngun khng bit a ch vt l cach nn yu cu ny c gi qung b.

Mi trm v router trn mng u nhn v x l yu cu ARP ny, nhng chc trm ch nhn ra a ch IP ca n v gi tr li ARP li cho ngun. Gi trli cha a ch lgic v a ch vt l ca ch. Gi tr li ny c gi thng(gi unicast) ti trm yu cu (ngun) s dng a ch vt l c trong gi yucu ARP

Giao thc RARP

Giao thc phn gii a ch ngc (RARP: Reverse Address ResolutionProtocol) chuyn i a ch vt l thnh a ch lgic. N c s dng trongtrng hp mt my bit a ch vt l ca mnh nhng li khng bit a ch IP.Khi my c bt, yu cu RARP c to ra v c gi qung b trn mngcc b. Mt my khc trn mng bit v mi a ch IP s tr li yu cu bng

bn tin tr li RARP. My yu cu RARP phi chy chng trnh RARP khchv my tr li RARP phi chy chng trnh RARP ch.

Tng giao din mng

Tng giao din mng tng ng vi tng lin kt d liu v tng vt l trongm hnh OSI. Tng ny cung cp giao tip vi mng vt l. N bao gm tt ccc thnh phn phn cng ca c s h tng mng, v thc hin vic kim sotli d liu phn b trn mng vt l, to cc kt ni vt l n h thng cptrong thi gian thch hp, to khung thng tin. Tng ny khng nh ngha mt

giao thc ring no c m h tr tt c cc giao thc chun v c quyn. V dnh: Ethernet, Token Ting, FDDI, X25, wireless, Async, ATM, SNA



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1.3 Cu trc tiu IPv4 v IPv6

1.3.1 Cu trc tiu gi tin IPv4

Tiu IP c thm vo sau khi n nhn c thng tin ca tng chuynvn hoc tng ng dng, sau n c a xung tng lin kt d liu truyn i trn mt phng tin nht nh. Chiu di ca tiu IP c th t 20

bytes n 60bytes trn cc ng i nu nhng chc nng l chn c sdng. Cu trc tiu c ch ra trn hnh 1.2 nh sau :

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Version IHL ToS Total Length

Fragment offsetFlagsIdentification

TTL Protocol Header Checksum

Source IP Address

Destination IP Address

Options and Padding

..

Hnh 1.2: Tiu IPv4

Version: Ch ra phin bn ca giao thc hin hnh IPv4, c s dng my gi, my nhn, cc b nh tuyn cng thng nht v nh dng lc dliu.

IHL (Identifed Header Length): Trng xc nhn di tiu cung cpthng tin v di tiu ca gi tin, thng thng tiu c di 20 octets.

TOS (Type Of Service): Trng kiu phc v di 8 bit n gm 2 phn.Trng u tin v kiu phc v. Trng u tin gm 3 bit dng gn mc utin cho cc gi tin, cung cp c ch cho php iu khin cc gi tin qua mng.Cc bit cn li dng xc nh kiu lu lng gi tin khi n chuyn qua mng,nh c tnh tr, thng qua v tin cy. Vo khong cui nm 1990, IETF nh ngha li ngha ca cc bit trong trng TOS, th hin mt tp hp

cc dch v khc bit. Thng qua 6 bit u tin thit lp 64 im m (codepoint) nh x vo mt s dch v c s, 2 bit cn li trng. Tuy nhin trng d



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liu ny c s dng nh th no th cn tu thuc rt nhiu vo kin trcmng, v chnh bn thn mng Internet khng m bo cht lng phc v QoS,nn y n thun ch l tiu ch yu cu ch khng phi l tiu ch i hi ivi cc b nh tuyn.

TL (Total length): trng hin th tng di gi tin di 16 bit, n s dng xc nh chiu di ca ton b gi IP. Chiu di ln nht mt gi IP cho phpl 65535 octets.

Identification: Trng d liu nhn dng ny di 16 bit. Trng ny cmy ch dng pht hin v nhm cc on b chia nh ra ca gi tin. Cc bnh tuyn s chia nh cc gi tin nu nh n v truyn tin ln nht ca gi tinMTU (Maximum Transmission Unit) ln hn MTU ca mi trng truyn (Mitrng m gi tin c truyn dn trn ). MTU ca mi trng truyn cnh ngha nh l kch c ca gi IP ln nht m n c th c mang i trong

mt khung lin kt d liu (Tng lin kt d liu truyn cc khung thng tinc ghp knh v thng tin ny c cha ng trong cc khe thi gian TS).Vic hp li cc on tin c thc hin ti my ch ch.

S chia ct gi tin to thm cng vic cho cc b nh tuyn v cc my chu cui. Mt k thut c tn l tm tuyn ng cho n v truyn gi tin lnnht (Path MTU Discovery) c a ra, to kh nng cho mt my ch gi tinc th tm ra mt MTU rng nht c th, theo con ng t ngun ti ch mkhng cn bt k qu trnh chia ct gi tin no khc.

Flags: Trng c cha 3 bit c s dng cho qu trnh iu khin phnon, bit u tin ch th ti cc b nh tuyn cho php hoc khng cho phpphn on gi tin, 2 bit gi tr thp c s dng iu khin phn on, kt hpvi trng nhn dng, trng phn on xc nh gi tin nhn c sau qutrnh phn on.

Fragment Offset: Trng phn on mang thng tin v s ln chia mt gitin, kch thc ca gi tin ph thuc vo mng c s truyn tin, tc l di gitin khng th vt qu MTU ca mi trng truyn.

TTL (Time-to-live): Trng thi gian sng ca gi tin c s dng ngn

cc gi tin lp vng trn mng. N c vai tr nh mt b m ngc, trnh hintng tr gi tin qu lu trn mng. TTL cng s dng xc nh phm vi iukhin, qua vic xc nh xem mt gi c th i c bao xa trong mng. Bt kgi tin no c vng TTL t gi tr bng 0 th gi tin s b b nh tuyn hu

b v thng bo li s c gi v trm pht gi tin.

Protocol : Trng ny c dng xc nhn giao thc tng k tip mccao hn ang s dng dch v IP di dng con s.

H-Check sum: trng kim tra tng di 16 bit, c tnh ton trong tt c cc

trng ca tiu IPv4 (ToS, HL, TL...). Mi khi gi qua b nh tuyn, cctrng la chn c th b thay i v trng TTL s b thay i. Cho nn mt



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gi tin khi qua cc b nh tuyn th trng kim tra tng cn phi c tnhton v cp nht li m bo tin cy ca thng tin nh tuyn.

Source Address- Destination Address: Trng a ch ngun v a ch chc cc b nh tuyn v cc gateway s dng nh tuyn cc n v s liu,

lun lun i cng vi gi tin t ngun ti ch.Options v Padding: C di thay i, dng thm thng tin tu chn v

chn y m bo s liu bt u trong phm vi 32 bit.

Ngoi ra, tiu IP cng c th cha cc chc nng m n cn c x ltrn mi b nh tuyn dc theo ng truyn. Tuy nhin, cc chc nng nykhng c s dng qu nhiu bi v bt k ci g thm vo phn tiu ca gitin, u yu cu mt qu trnh x l ph i vi mi b nh tuyn trung gian.Thng thng, cc bn ghi tuyn ng s c thm vo trong trng la

chn.1.3.2 Cu trc tiu gi tin IPv6

Din n IP phin bn 6 c bt u vo thng 7-1999 bi 50 nh cung cpInternet hng u vi mc ch pht trin giao thc IPv6, n s ci thin chtlng v bo mt ca Internet, thit lp mt c cu cho th k mi. IPv6 c

bit quan trng khi cc thit b tnh ton di ng tip tc gia tng trong thp kti.

Do s thay i v bn cht ca Internet v mng thng mi m giao thclin mng IP tr nn li thi. Trc y, Internet v hu ht mng TCP/IP cungcp s h tr cc ng dng phn tn kh n gin nh truyn file, mail, truynhp t xa qua TELNET, song ngy nay Internet ngy cng tr thnh a phngtin, mi trng giu tnh ng dng, dn u l dch v WWW (World WideWeb). Tt c s pht trin ny b xa kh nng p ng cc chc nng v dchv ca mng IP. Mt mi trng lin mng cn phi h tr lu lng thi gianthc, k hoch iu khin tc nghn linh hot v cc c im bo mt m IPv4hin khng p ng c y . Cu trc tiu gi tin IPv6 c cho nhhnh v 1.3:



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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

V ersion Traffic C lass F low Labe l

Hop L imi t Next HeaderPayLoad Leng th

Source A ddress(128bit)

Destination Address(128bit) ..

Da ta ..

Hnh 1.3: Khun dng tiu IPv6

Version: Ch ra phin bn IPv6 (4 bits).Traffic Class: Lp lu lng (8 bits), s dng phn phi mc u tin lu

lng Internet.

Flow Label:Nhn lung (20 bits), c dng xc nh cch x l c bitt ngun ti ch theo th t gi.

Payload Length: di ti tin (16 bits). Xc nh di ca s liu tronggi. Khi thit lp v 0 th l cch chn ti ln khi chuyn theo tng chng .

Next Header: Tiu k tip (8 bits). Xc nh giao thc ng gi tip theo.

Cc gi tr tng thch vi cc gi tr dng trong trng giao thc IPv4.Hop Limit: Gii hn bc nhy (8 bits), mi b nh tuyn, khi chuyn gi

gi tr ny s gim i 1, nu gi tr ca trng ny l 0 th gi s b loi b.Trng chc nng gii hn bc nhy thay cho trng TTL trong tiu IPv4.

Source address: a ch ngun IPv6 (128 bit).Destination address: a ch ch IPv6 (128 bit).

Th gii ang i mt vi vic thiu a ch IP cho cc thit b mng, a chdi 32 bit khng p ng c s bng n ca mng. Thm na, IPv4 l giao

thc c, khng p ng nhng yu cu mi v bo mt, s linh hot trong nhtuyn v h tr lu lng, IPv6 c thit k bao gm nhng chc nng v nh



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dng m rng hn IPv4 gii quyt vn ny. Tt c cc a ch s dngtrong Internet u phi duy nht. Vi phng thc nh a ch hin nay th victhiu a ch s xy ra sm hn. IPv6 l mt giao thc thay th c kh nng duytr s pht trin ca Internet, gii quyt vn khng gian a ch IP: 3,4x1038 so

vi khong 4 t a ch IPv4 v nhng thuc tnh khc ca Internet.IPv6 khng ch c kh nng m rng a ch m cn h tr kin trc mng

hnh thang, pht trin bo mt v tnh ton vn d liu, nng cao cht lng dchv QoS v tnh bo mt, nh tuyn n gin v c tnh t ng nh cu hnh.

Vi khng gian a ch v cng ln n cho php cc nh thng mi trinkhai cc h thng thit b mng bn v di ng mt cch hiu qu. S linhhot trong nh tuyn vi cc a ch ca nt, thit b nh v theo cu trc cyv kh nng t nh cu hnh v pht hin cc thit b xung quanh.

1.3.3 a ch IPv4Mi trm trong mng Internet u c c trng bi mt s hiu nht nhgi l a ch IP. a ch IP c s dng trong lp mng nh tuyn cc gitin qua mng. Do t chc v ln ca cc mng con trong lin mng khcnhau nn ngi ta chia a ch IP thnh cc lp A, B, C, D.

Lp A: cho php nh danh ti 126 mng, vi ti a 16 triu host trn mimng. Lp ny c dng cho cc mng c s trm cc ln.

Lp B: cho php nh danh ti 16384 mng vi ti a 65534 host trn mimng.

Lp C: cho php nh danh c khong 2 triu mng vi ti a 254 hosttrn mt mng. Lp ny c dng cho cc mng c t trm.

Lp D: c dng gi cc IP datagram ti mt nhm cc host trong linmng.

Cc lp ny c th hin nh hnh v 1.4:



16/77


0 N N N N N N N H o s t I D H os t ID H o st ID

1 0 N N N N N N Network ID H os t ID H o st ID

1 1 0 N N N N N Network ID N e tw o rk ID H o st ID

1110NN NN M ultica s t M u lticas t M u ltica st

0 7 15 23 3 1

Lp A

L p B

Lp C

Lp D

Hnh 1.4: Phn lp a ch IP

Phn mng l mt cng ngh c s dng chia mt a ch mng IP nra thnh mt s cc mng con. y l mt hnh thc m rng m hnh a ch.iu ny cho php mt di a ch IP ln c chia ra thnh cc di a ch nh

hn v c phn n nhiu v tr khc nhau m khng gp kh khn g so vivic yu cu mt a ch lp mng ring cho mi v tr. Cch x l phn mngny c thc hin bng cch phn chia phn my ch ca lp a ch IP chotng mng con. Cng nh a ch phn lp c in, ranh gii gia phn mng(tin t mng + mng con) v cc phn my ch th c xc nh bi mt mtn mng con. Khi cn c thm mt vng nhn dng phn mng subnetID(subnet Identifier) nh danh cc mng con . Vng subnetID s nm trongvng nhn dng my ch hostID c. Vn mng con s gp phn gii quytcho cc bng nh tuyn trong cc b nh tuyn thc hin n gin hn trong

qu trnh tm kim a ch.S phn mng chia mt a ch IP n thnh cc mng con. Mt mng siu

nh c to thnh bi vic tng hp nhiu mng con, to thnh mt a chchung cho cc mng . Vic tng hp ny to ra hai u im sau:

Gim kch c ca cc bng nh tuyn c duy tr bi cc b nh tuyncng vi vic gim s lng cc u vo mng trn lp ring bit.

To ra kh nng s dng hiu qu khng gian a ch IP cha c sdng bng cch ch cp a ch cho mt mng khi n cn.



17/77


Khi cc a ch lp con gn nhau th c biu din li bng mt k hiutin t mang v khi ny c gi l khi nh tuyn lin vng khng phnlp CIDR (Classess Inter Domain Routing).

CIDR c tc dng :

- Gim tc cp pht cc a ch IP ca mng Internet cho cc mngcon.

- Gim s ng vo cc b nh tuyn ca mng ton cu.

Cc t chc gi y mong mun rng mt a ch Internet s c phn chiathnh cc khi CIDR hn l cc a ch c chia lp nh truyn thng cm t trn.

1.4 Cc mc QoS end to end.

Ni n cc mc dch v l ni n cc kh nng QoS end to end thct, ngha l kh nng mt mng thc hin nhu cu dch v bi lu lng mngring end to end hoc edge to edge. Cc dch v khc nhau mc QoSchnh xc ca chng. C ba mc QoS end to end c th c cung cp thngqua mng hn hp: Dch v n lc ti a, dch v khc bit v dch v tch hp.

1.4.1 Dch v n lc ti a.

Dch v Best Effort hon ton ph hp vi cc ng dng khng yu cu chtch v thi gian v s phn phi gi c kh nng d on trc. Nh l cc ngdng c khuynh hng pht sinh bng n d liu hoc t nht c th chu c

s bng n. Vi TCP, mng c th x l nhiu ng dng khi khng ch bng nm cn chu ng s mt gi.

Cy ng dn ngn nht thit lp kt ni ch ra. Ngay c khi tham s cagiao thc nh tuyn l mt c tnh c y ngha nh tr tng chng hay

bng thng kh dng th mng cng khng m bo tnh sn sng thc t ca tinguyn (nh bng thng kt ni v kh nng router) dc ng dn ti mt thiim cho trc. Bi v m hnh edge/core tch ri, cc giao thc nh tuyn IPkhng th tc ng ti nhu cu thay i nng ng cc lung lu lng end to

end bng n trn mng. Trong mng IP thng thng, bng thng kh dng

thc t hoc tr trn mt s chng cho ph thuc vo ln trn s linh ngca tng lung lu lng qua mng ti mt thi im.

Mt router IP thng thng phn nh bn cht nh ngha dch v n ginca mng IP Best Effort. Nhim v c bn ca mt router IP l chuyn mt gim n nhn c ra khi mt giao din, thc hin tm kim bng chuyn tipda trn a ch ch ca gi v chuyn gi ti router chng k tip nh chra. Router c gng thc hin cng vic nhanh ti mc n c th. Tuy nhinrouter quan tm ti ni gi gi m t khi quan tm ti vic khi no gi gi.iu n gin l n thc hin theo nguyn l hng i FIFO.



18/77


1.4.2 Dch v tch hp (Intergrated Service)

ng trc nhu cu ngy cng tng trong vic cung cp cc dch v thi gianthc (thoi, video) v bng thng cao (a phng tin) dch v tch hp IntServ ra i. y l s pht trin ca mng IP nhm ng thi cung cp dch v

truyn thng n lc ti a v cc dch v thi gian thc (minh ho trn hnh1.5). ng lc thc y m hnh ny ch yu do nhng l do c bn sau y:

o Dch v n lc ti a khng cn tt na: ngy cng c nhiu ng dngkhc nhau c nhng yu cu khc nhau v c tnh lu lng c trinkhai, ng thi ngi s dng ngy cng yu cu cao hn v cht lngdch v.

o Cc ng dng a phng tin ngy cng xut hin nhiu: mng IP phi ckh nng h tr khng ch n dch v m phi h tr tch hp a dch v

ca nhiu loi lu lng khc nhau t thoi, s liu n Video.o Ti u ho hiu sut s dng mng v ti nguyn mng: m bo hiu

qu s dng v u t. Ti nguyn mng s c d tr cho lu lng c u tin cao hn, phn cn li s dnh cho s liu n lc ti a.

o Cung cp dch v tt nht: m hnh dch v IntServ cho php nh cungcp mng cung cp c dch v tt nht khc bit vi cc nh cung cpcnh tranh khc.

n g d n g Se tu p

Lp l chP h n l o i

SetupGi ao t h c n h

tuy n/Da t ab ase

Lp l chP h n l o i

i u k h i nch p n h n/C n g b c

Data

IP Data

Cc bn tin Setup t trc

Hnh 1.5 : M hnh dch v tch hp

Trong m hnh ny c mt s thnh phn tham gia nh sau:

o Giao thc thit lp: Setup cho php cc my ch v cc router d tr ngti nguyn trong mng x l cc yu cu ca cc lung lu lngring, RSVP, Q.2931 l mt trong nhng giao thc .

o c tnh lung: xc nh cht lng dch v QoS s cung cp cho lung

ring bit. Lung c nh ngha nh mt lung cc gi t ngun nch c cng yu cu v QoS. V nguyn tc c th hiu c tnh lung



19/77


nh bng tn ti thiu m mng bt buc phi cung cp m bo QoScho lung yu cu.

o iu khin lu lng: trong cc thit b mng (my ch, router, chuynmch) c thnh phn iu khin v qun l ti nguyn mng cn thit

h tr QoS theo yu cu. Cc thnh phn iu khin lu lng ny c thc khai bo bi giao thc bo hiu nh RSVP hay nhn cng. Thnh

phn iu khin lu lng bao gm:

- iu khin chp nhn: xc nh thit b mng c kh nng h tr QoStheo yu cu hay khng.

- Thit b phn loi (Classifier): nhn dng v la chn lp dch v - datrn ni dung ca mt s trng nht nh trong mo u gi.

- Thit b lp lch (Scheduler): cung cp cc mc cht lng dch v

QoS trn knh ra ca thit b mng.Cc mc cht lng dch v cung cp bi IntServ bao gm:

o Dch v bo m GS: bng tn dnh ring, tr c gii hn v khng btht thot gi tin trong hng i. Cc ng dng cung cp thuc loi ny cth k n: hi ngh truyn hnh cht lng cao, thanh ton ti chnh thigian thc v.v...

o Dch v kim sot ti CL: khng m bo v bng tn hay tr nhng khcn lc ti a im khng gim cht lng mt cch ng k khi ti

mng tng ln. Ph hp cho cc ng dng khng nhy cm lm vi trhay mt gi nh truyn multicast audio/video cht lng trung bnh.

1.4.3 Dch v khc bit (Differentiated Service)

Vic a ra m hnh IntServ c v nh gii quyt c nhiu vn linquan n QoS trong mng IP. Tuy nhin trn thc t, m hnh ny khng thcs m bo c QoS xuyn sut (end-to-end). c nhiu c gng thay iiu ny nhm t c mt mc QoS cao hn cho mng IP v mt trong nhngc gng l s ra i ca DiffServ. DiffServ s dng vic nh du gi v xphng theo loi h tr cc dch v u tin qua mng IP. Hin ti IETF cmt nhm lm vic DiffServ a ra cc tiu chun RFC v DiffServ.

Nguyn tc c bn ca DiffServ nh sau:

o nh ngha mt s lng nh cc lp dch v hay mc u tin. Mt lpdch v c th lin quan n c tnh lu lng (bng tn min - max, kchc burst, thi gian ko di burst)

o Phn loi v nh du cc gi ring bit ti bin ca mng vo cc lpdch v.

o Cc thit b chuyn mch, router trong mng li s phc v cc gi theoni dung ca cc bit c nh du trong mo u ca gi.



20/77


Vi nguyn tc ny, DiffServ c nhiu li th hn so vi IntServ:

+ Khng yu cu bo hiu cho tng lung.

+ Dch v u tin c th p dng cho mt s lung ring bit cng mt lp

dch v. iu ny cho php nh cung cp dch v d dng cung cp mts lng nh cc mc dch v khc nhau cho khch hng c nhu cu.

+ Khng yu cu thay i ti cc my ch hay cc ng dng h tr dchv u tin. y l cng vic ca thit b bin.

+ H tr rt tt dch v VPN.

Tuy nhin c th nhn thy DiffServ cn vt qua mt s vn nh:

+ Khng c kh nng cung cp bng tn v tr m bo nh GS caIntServ hay ATM.

+ Thit b bin vn yu cu b Classifier cht lng cao cho tng gi gingnh trong m hnh IntServ.

+ Vn qun l trng thi classifier ca mt s lng ln cc thit b binl mt vn khng nh cn quan tm.

+ Chnh sch khuyn khch khch hng trn c s gi cc cho dch vcung cp cng nh hng n gi tr ca DiffServ.

M hnh DiffServ ti bin v li c m t trong hnh 1.6 sau y:

Phn loia byte Chnh sch

nh dugi

Hng i, qunl lp lch

Phn loi DSbyte

Hng i, qun lLp lch

Router bin

Router li

Hnh 1.6: M hnh DiffServ ti bin v li ca mng

M hnh DiffServ bao gm mt s thnh phn nh sau:

o DS-Byte: byte xc nh DiffServ l thnh phn ToS ca IPv4 v trngloi lu lng IPv6. Cc bit trong byte ny thng bo gi tin c mongi nhn c thuc dch v no.



21/77


o Cc thit b bin (router bin): nm ti li vo hay li ra ca mng cungcp DiffServ.

o Cc thit b bn trong mng DiffServ.

o

Qun l cng bc: cc cng c v nh qun tr mng gim st v okim m bo SLA gia mng v ngi dng.

Cc mc cht lng dch v cung cp bi dch v DiffServ bo gm: Expedited forwording Assured forwording

Trng dch v khc bit

Trong mng DiffServ octet ToS ca gi tin IPv4 tr thnh trng dch vkhc bit (Differentiated servervice Field). Trong 6 bit ca octet ToS c to

nn mt im m ho DiffServ mi (DSCP) nh ch ra trn hnh 1.7. V nhvy v mt l thuyt cho php phn loi ti 26 trng hp khc nhau.

DSCP CU

0 5 7

Hnh 1.7: Trng dch v khc bitDSCP: Differentiated Services Code-Point.CU: Currently unused.



22/77

n tt nghip i hc Cht lng dch v trong mng IP

CHNG II - CHT LNG DCH V TRONG MNG IP

2.1 Khi nim QoS

Khuyn ngh ca CCITT l E800 a ra mt tnh cht chung ca QoS(Quanlity of Service): Hiu ng chung ca c tnh cht lng dch v lxc nh mc hi lng ca ngi s dng i vi dch v.

Khuyn ngh ETR300 003 ca ETSI chia v ci tin nh ngha ca ITUthnh cc nh ngha nh hn, n ph hp vi cc yu cu v quan im cacc nhm khc nhau trong vin thng. Cc nh ngha l:

o Yu cu QoS ca ngi s dng/khch hng.

o ngh QoS ca nh cung cp dch v.

o Vic thc hin QoS bi cc nh cung cp dch v.

o S cm nhn QoS ca ngi s dng/khch hng.

o Yu cu QoS ca nh cung cp dch v.

Nh vy mt cch tng qut QoS mang ngha l kh nng ca mng mbo v duy tr cc mc thc hin nht nh cho mi ng dng theo nh cc yucu c ch r ca mi ngi s dng. Mt trong nh ngha ny chnh lcha kho hiu c QoS l g t gc nhn ca nh cung cp dch v mng.

Nh cung cp dch v mng m bo QoS cung cp cho ngi s dng, v thc

hin cc bin php duy tr mc QoS khi iu kin mng b thay i v ccnguyn nhn nh nghn, hng hc thit b hay li lin kt v.v QoS cn ccung cp cho mi ng dng ngi s dng c th chy ng dng , v mcQoS m ng dng i hi ch c th c xc nh bi ngi s dng, bi v chngi s dng mi c th bit c chnh xc ng dng ca mnh cn g hotng tt. Tuy nhin, khng phi ngi s dng t ng bit c mng cn phicung cp nhng g cn thit cho ng dng, h phi tm hiu cc thng tin cungcp t ngi qun tr mng v chc chn rng, mng khng th t ng t raQoS cn thit cho mt ng dng ca ngi s dng.

Cc nh cung cp dch v mng a ra thng tin c t v gi tr thc t cacc thng s QoS theo mt trong hai cch sau. Vi mi trng knh o c nh(PVC: Permanent Virtual Circuit), cc gi tr ca cc tham s QoS c th chn gin c ghi bng vn bn v trao li cho i din ca nh cung cp dchv mng. Khch hng vi nh cung cp dch v tho thun vi nhau v cchthc s dng. QoS c hiu lc trn PVC khi PVC sn sng. Vi mi trngknh o chuyn mch (SVC: Switched Virtual Circuit), cc gi tr ca thng sQoS c gi cho nh cung cp dch v trong bn tin bo hiu thit lp cucgi, n l mt phn ca giao thc bo hiu c s dng cung cp dch v

chuyn mch trn mng. C hai phng php u c s dng trong mng.Phng php PVC cho php QoS c cung cp trong mt min ln hn, trong



23/77


khi phng php SVC i hi QoS trn mt kt ni cho trc v c thit lplin tc.

Nu mt mng c ti u hon ton cho mt loi dch v, th ngi s dngt phi xc nh chi tit cc thng s QoS. V d, vi mng PSTN, c ti u

cho thoi, khng cn phi xc nh bng thng hay tr cn cho mt cuc gi. Ttc cc cuc gi u c m bo QoS nh c quy nh trong cc chunlin quan cho in thoi. m bo cht lng mng trong mt mi trng dchv hp ng thng c biu hin theo hnh thc tho thun mc dch v(SLA: Service Level Agreement) c thit lp gia khch hng v nh cungcp dch v. SLA c th l mt phn ca hp ng dch v hay l mt ti liuc lp hon ton. SLA a ra cc yu cu ca khch hng v cc hnh pht ivi nh cung cp trong trng hp xy ra s c. SLA cng cung cp mt

phng php thun tin cho khch hng so snh cc dch v do cc nh cung

cp dch v khc nhau a ra.Vy trong tt c nhng iu nu v phn cp QoS, m bo cht lng v

SLA, iu no phi c thc hin cc dch v thi gian thc trn mi trngIP, v d nh VoIP? Vn l bn cht nh hng IP l mt mng n lc ti ado "khng tin cy" khi yu cu n m bo v QoS. Cch tip cn gn nht cc nh cung cp dch v IP c th t ti m bo QoS hay SLA gia khchhng v ISP l vi dch v mng IP qun l c. Thut ng qun l c yl bt c ci g m nh cung cp dch v qun l thay mt cho khch hng.

Hnh v 2.1 sau y biu din mt m hnh QoS tng quan.

` `

A PA P

Q o S

M n g M n g

N P N P N P

Hnh 2.1 M hnh QoS tng qutTrong hnh v, NP (Net Performance: hiu nng mng) l nng lc v hiu

qu ca mt mng c th. N bao gm kh nng ng x ca mng, tnh hiu quca mng v cht lng phc v m mng cung cp. Trnh nhm ln gia NP vQoS. AP (Access Point) l im truy nhp mng.

Cc thng s xc nh QoS l cc c tnh tr, nghn, Jitter, mt gi,v.v Sau y chng ta s tm hiu tng c tnh .



24/77


2.2 Tr

Tr (latency, delay) l c tnh ch lng thi gian cn thit mt gi tindi chuyn t ngun ti ch (tr end to end). Tr end to end l kt hpca ba loi tr: tr truyn lan, tr qu trnh, v tr xp hng.

Tr truyn lan

Tr truyn lan do tc truyn tn hiu trong mng gy nn. V d tc ccin t truyn truyn lan trong cp ng l 125000 mile/giy. Nh vy mtmng cp ko di lin tc na vng tri t c tr truyn lan mt chiu vokhong 70ms. Loi tr ny l c th d on trc.

Tr qu trnh

Tr qu trnh l tr gy ra bi qu trnh x l ca cc thit b trong mng(nh cc thit b chuyn mch, router), v nhiu yu t khc nh qu trnh nggi, nnTr qu trnh nh hng rt ln ti mng chuyn mch gi trong c mng IP.

V d, trong sn phm Cisco IOS VoIP, b x l tn hiu s (DSP) pht ramu thoi sau mi 10 ms khi dng G.729. Hai mu thoi ny (c hai u tr 10ms) c t vo mt gi. Do vy gi b tr 20 ms. Mt khong thi gian tinx l 5 ms l cn thit khi dng G.729, dn n tr ban u l 25 ms cho framethoi u tin.

Cc nh ch to c th quyt nh s lng mu m h s gi vo trong mt

gi. Bi G.729 dng cc mu thoi 10 ms, nn mi mt s gia tng mu l lmcho thi gian tr ca frame tng ln 10 ms. Trn thc t Cisco cho php ngidng t la chn s mu t vo trong mi frame.

Tr xp hng.

Trong mng chuyn mch gi vic s dng cc hng i s gy ra mt loitr l tr hng i. S d c loi tr ny l do trong qu trnh xp vo hngi cc gi phi ch x l c ra khi hng i. Trong trng hp lulng mng thp (hng i khng b y) th cc gi c th c x l ngay.

Nhng khi mng xy ra nghn (hng i b y) th cc gi s phi ch mt thigian x l mi c th c truyn i v qu trnh i ny c th rt lu tu votnh trng nghn ko di hay khng.

Tr gy ra qu trnh xp hng ny l khng th d on trc v thng giaong theo mt m hnh nghn.

2.3 Nghn

Chng ta bit rng router l im quy t v phn chia lu lng ca hngchc, hng trm, thm ch hng nghn lung gi. Lu lng cc lung gi n llun lun thay i. Nu nh cc lung lu lng n ng thi cng mt lc m

n cng nh hng ti mt u ra, m kh nng x l v tc giao din u



25/77


ra khng p ng kp thi, tc l tc n ln hn tc i th s c nghnxy ra.

V d, lu lng hi t t nhiu ng lin kt Ethernet 100 Mbps c th ddng vt qu kh nng ca cc lung OC 3/STM 1,55 Mbps, hoc lu

lng t mt ng kt ni T3/E3 c th ng thi yu cu chuyn tip ra cngnhiu ng lin kt T1/E1 nh hn. x l nhng iu , tt c cc routerkt hp cc b m (hng i) ni b trong chng lu gi cc gi d ra chon khi chng c th gi tip v pha trc. Vic ny s gy ra tr cng vo.

2.4 Jitter

Mt cch n gin jitter l s thay i khong thi gian gia cc gi. Jitter lmt vn ch tn ti trn cc mng gi. V d c mt lng gi c truyn i(gi s l gi thoi) trong mi trng IP. Ngi gi mong i cc gi ny c

chuyn i mt cch tin cy v cch nhau mt khong thi gian khng i (chnghn 20ms). Thc t cc gi ny c th b tr hon khi i qua mng v khng thn ch vo cc thi im cch u nhau nh khi gi i. V d, chng c thkhng nhn c sau mi 20 ms nh ch ra trn hnh 2.2. lch gia thi immong i v thi im nhn c gi thc s c gi l jitter.

` `

A

A

B C

B C

D1 D2 = D1 D3 D2

My ngunMy ch

My ch truyn

Khe nhn

Mng

Hnh 2.2: Hin tng jitter.

Trn hnh v cho thy thi lng cn phi gi gi A v gi B l bng nhau(D1 = D2). Gi C vp phi mt thi gian tr trn mng v nhn c vo thiim tr hn so vi thi gian d nh. y l l do tn ti b m jitter, b mny che i s thay i thi gian tr.

iu cn lu l jitter v tr khng phi l mt s vic, cho d c nhiujitter trong mng gi c th lm tng tng thi gian tr trong mng. Bi v cngc nhiu jitter th cng phi tng b m jitter b vo bn cht t nhin khngth d on c ca mng gi.



26/77


Nu mng s liu ca chng ta tt v c phng nga thch hp th jitter trongmng khng phi l tr ngi ln v b m jitter khng ng gp lng ng kvo tng tr.

Cc tem thi gian RTP c dng trong phn mm Cisco IOS xc nh

mc jitter no xut hin trong mng.B m jitter i khi cn c gi l hng i ng (dynamic queue). Hng

i ny c th tng ln hay gim xung theo hm m tu vo khong thi giangia cc gi.

2.5 Mt gi

Mt vn khc l mt gi. Nh chng ta bit cc router thng ch cmt kh nng m gii hn, giai on duy tr nghn c th lm cho b m tti gii hn ca chng. Khi cc gi i vo b m m khng gian b m ht

th cc gi phi b thi hi cho n khi b m tr li kh dng. iu ny s lmcho pha thu khng nhn c gi. N cng gy nn tr cng vo khi thc hintruyn li.



27/77

n tt nghip i hc Kin trc CQS

CHNG III - KIN TRC CQS

3.1 Vn nh tuyn trong mng IP3.1.1 Khi nim v nh tuyn

nh tuyn l qu trnh tm ng i t mt ngun n mt ch cho trc.Ngun v ch y c th l mt my tnh, c th l my fax, hay ni chung lbt k mt thit b no tham gia vo qu trnh vn chuyn v truyn nhn thngtin trong mng. nh tuyn m bo cho thng tin c truyn i trn mng tic ch cn n ca n. Qu trnh ny cn phi thc hin theo mt tiu chnht nh chn ra c mt ng i ti u (chng hn nh ng i ngnnht).

Thit b thc hin vic nh tuyn l router (hay b nh tuyn). Trongmi b nh tuyn s c mt bng nh tuyn ghi li trng thi ca mng vcc thng tin hnh mng t router c quyt nh chn ng i ti unht theo tiu ch nh trc. Cn thng tin v a ch s c ghi trong tiu gi tin.

Hnh v 3.1 sau y biu din mt qu trnh truyn tin c thc hin trongmng t mt my tnh X n mt my tnh Y thng qua cc router. M hnh

phn lp di biu din qu trnh truyn gi tin trong cc lp theo m hnhOSI.

` `

Application

Presenlation

Session

Transport

Network

Data Linhk

Physical

Network

Data Linhk

Physical

Network

Data Linhk

Physical

Network

Data Linhk

Physical

Application

Presenlation

Session

Transport

Network

Data Linhk

Physical

X

A B C

Y

X

A B

C

Hnh 3.1: Qu trnh truyn tin trong mng.



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3.1.2 Cc phng php nh tuyn.

3.1.2.1 nh tuyn tnh

L phng php nh tuyn khng s dng cc giao thc nh tuyn. Ccnh tuyn n mt mng ch s thc hin mt cch c nh khng thay itrn mi b nh tuyn. Mi khi thc hin mt vic thm bt cc mng phi thchin thay i li cu hnh trn mi b nh tuyn. To hng c nh l phngthc n gin nht, trong mi b nh tuyn ca mng cha cc bng tohng c nh. Cc bn to hng ny cung cp cho chng tt c cc thng tincn phn hng cho cc gi qua mng. Hnh v 3.2 l mt v d v nhtuyn c nh:

F

`

`

`

`

`

`

BC

D

E

R1

R2

R3

R4

1

2

3

4

1

2

3

Hnh 3.2: Nguyn tc nh tuyn tnh.

m t s lm vic ca n ta xc nh bng nh tuyn cho b nh tuynR2, R3 theo phng php nh tuyn tnh nh sau:

Thit bu cui

Tuyn

A

B

C

D

E

F

3

3

3

4

2

1

Thit bucui

Tuyn

A

B

C

D

E

F

3

3

4

1

2

2

R2 R3

Bng 3.1: Bng nh tuyn tnh cho R2 v R3.

u im ln nht ca nh tuyn c nh l cu hnh mng chm, c ngha ltnh chu n hi ca mng s tt hn dn ti vic on hiu nng mng v sa



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li nhanh hn. Trong nh tuyn tnh cc b nh tuyn khng cn trao i ccthng tin tm ng cng nh c s d liu nh tuyn. Do n c s dngtrong trng hp cn che du mt phn ca lin mng (v l do an ton). Trongtrng hp mng ch c mt ng dn duy nht tip cn vi n (mng ny

cn c gi l stub network) th cng ch cn mt tuyn tnh l . Hnh 3.3biu din mt mng nh vy:

`

`

Mng ct

R1

R2

ng kt niduy nht

Hnh 3.3: S dng nh tuyn tnh cho mng ct.

3.1.2.2 nh tuyn lun phin

Phng php nh tuyn lun phin c biu din trong hnh v 3.4 diy. Gia bt k hai nt mng no cng c nhiu hn mt tuyn. Nguyn tcnh tuyn lun phin nh sau: khi tt c cc mch thuc tuyn u tin bn thtuyn th hai c chn; nu tuyn th hai bn th tuyn th ba c chn v cnh vy cho ti khi tm c tuyn ri hoc s mt cuc gi .

Phng php ny rt hiu qu trong vic ti u ho s dng cc knh trungk v thng c p dng gia cc tng i in t s SPC.



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`

`R1

R2

R3 R4

R5Tuyn th1

Tuyn th2

Tuyn th3

Hnh 3.4: Nguyn tc nh tuyn lun phin.3.1.2.3 nh tuyn ng

nh tuyn ng l nh tuyn da trn thng tin v trng thi hin thi camng. Thng tin trng thi c th d on v tuyn ng c th thay i khicu hnh mng hoc lu lng mng thay i. Thng tin nh tuyn cp nhtvo trong cc bng nh tuyn ca cc node mng trc tuyn v p ng tnhthi gian thc nhm trnh tc nghn cng nh ti u hiu nng mng. C hai

phng php nh tuyn ng c s dng l: nh tuyn ng theo thi

gian v nh tuyn ng theo trng thi mng.nh tuyn ng theo thi gian c p dng trong nhng vng mng c lu

lng thay i theo thi gian trong ngy v s thay i theo mt quy lutnht nh. Phng php nh tuyn ny m bo tnh linh hot v hiu qu chovic s dng s dng knh trung k di tc ng ca s thay i lu lngmng thc t theo thi gian trong ngy.

nh tuyn ng theo trng thi mng c s dng rng ri trong mngvin thng. Vi phng php ny vic chn tuyn s hon ton t ng theotrng thi lu lng mng hin thi. Vic chn tuyn ny c iu khin bi

mt trung tm iu hnh mng.u im ln nht ca nh tuyn ng l n c th thit lp tuyn ng ti

tt c cc thit b trong mng, t ng thay i khi tuyn ng cu hnh mngthay i, chng hn nh khi:

- Thm thit b v a ch mng mi.

- Loi b thit b v a ch khi mng.

- T ng cu hnh ph hp vi s thay i mng.

Hnh 3.5 cho chng ta thy c mt trong nhng u im ca nh tuynng. y qu trnh nh tuyn t ngun ti ch c th c la chn mt



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trong hai ng. C th i theo ng X -> R1 -> R2 -> R4 -> Y hoc X -> R1-> R3 -> R4 -> Y. Gi s ban u n ang i theo ng th nht. Nu trongqu trnh truyn thng tin th mng b li tuyn . Lc ny Router R1 s tng cp nht v thay i li bng nh tuyn v chuyn hng truyn tin theo

ng th hai m khng lm gin on qu trnh tuyn tin. iu ny l khngth c trong nh tuyn tnh. Trong nh tuyn tnh nu xy ra s c trn ngtruyn th qu trnh truyn tin s b gin on cho ti khi s c c khc phc.

`

`

X

R2

R3 R4

Y

Hnh 3.5: Kh nng thay th tuyn ca nh tuyn ng

nh tuyn ng s dng cc giao thc nh tuyn thc hin xy dng nn

cc bng nh tuyn trn cc b nh tuyn. Cc giao thc nh tuyn ng cchia thnh hai nhm chnh l: Giao thc nh tuyn vector khong cch v giaothc nh tuyn trng thi lin kt. Ngoi ra cn c mt s giao thc lai ghpnh: Giao thc nh tuyn phn lp, giao thc nh tuyn khng phn lp vgiao thc nh tuyn trn c s QoS. Sau y chng ta s nghin cu cc giaothc nh tuyn .

3.1.3 Mt s giao thc nh tuyn

3.1.3.1 nh tuyn vect khng cch.

Theo giao thc ny, cc router s nh k chuyn thng tin c trong bngnh tuyn n cc router ln cn ni trc tip vi n v cng theo nh k nhncc bng nh tuyn t cc router ln cn. Sau khi nhn cc bng nh tuyn tcc router ln cn n s so snh vi bng nh tuyn hin c v quyt nh vvic xy dng li cc bng nh tuyn theo thut ton ca tng giao thc haykhng. Trong trng hp phi xy dng li, router sau s gi bng nhtuyn mi cho cc router ln cn v cc router ln cn li thc hin cc cngvic tng t. Cc router t xc nh cc router ln cn trn c s thut ton vcc thng tin thu c t mng.

T vic cn thit phi gi cc bng nh tuyn mi cho cc router ln cn vcc router ln cn li phi gi bng nh tuyn mi ca n, nh tuyn lp vng



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c th xy ra nu s hi t v trng thi bn vng ca mng din ra chm trnmt cu hnh mi. Cc router s dng k thut b m nh thi m bokhng ny sinh vic xy dng mt bng nh tuyn sai. C th din gii iu nh sau:

- Khi mt router nhn c mt cp nht t ln cn ch rng mt mng c thtruy xut trc y nay khng th truy xut c na, router nh du tuynkhng th truy xut v khi ng mt b nh thi.

- Nu ti bt k thi im no m trc khi b nh thi ht hn mt cp nhtc tip nhn cng t ln cn ch ra rng mng c truy xut tr li,router nh du mng c th truy xut v gii phng b nh thi.

- Nu mt cp nht n t mt b nh tuyn ln cn khc vi gi tr nhtuyn tt hn gi tr nh tuyn c ghi cho mng ny, router nh du mng

c th truy xut v gii phng b nh thi. Nu gi tr nh tuyn ti hn th cpnht c b qua.

- Khi b nh thi m v khng th gi tr nh tuyn mi c xc lp,router c bng nh tuyn mi.

Vic tnh ton tuyn trong giao thc vector khong cch s dng thut tontm ng ngn nht theo k thut phn tn m in hnh l thut ton chnng Ford & Fulkerson. K thut chn ng ny cho php ta tm tt c cccon ng i ngn nht t tt c cc nh ti mt nh cho trc. Gii thut nyc thc hin bng cc bc lp, sau k bc, mi nh c nh du bi mt

cp gi tr (nk(v), Dk(v)), trong :Dk(v) l gi tr cc tiu t nh v n ch ti bc th k.

Nk(v) l nh tip theo trn con ng t v n ch ti bc th k.

Qu trnh lp s dng li khi cp nh du ca mi nh c gi nguynkhng thay i na. Thut ton Ford & Fulkerson c m t nh sau:

- u vo:

th c hng G = (V, E) vi n nh.

a(u,v) l ma trn trng s khng m.s l nh ch.

- u ra:

N(v) ghi nhn nh trc v trn ng i n ch.

Dk(s) ghi li ng i ngn nht.

Gii thut:

Bc 0 (khi to):

D0(s) = 0;



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Bc k (tnh v cp nht):

Vi mi v khc s (ch), cp nht li Dk(v) nh sau:

Dk(v) = min[Dk 1(w) + l(v,w)]

Vi w thuc Nv

, trong Nv

l tp cc nt ln cn ca v.Cp nht nk(v) nh sau:

nk(v) = w1;

vi w1 tho mn biu thc:

Dk 1(w1) + l(v, w1) = min[Dk 1(w) + l(v, w)]

Kim tra iu kin lp:

Nu tn ti Dk(v) khc Dk 1(v) th tip tc bc k+1. Ngc li th

kt thc qu trnh tnh ton.3.1.3.2 nh tuyn trng thi lin kt

Cc gii thut nh tuyn trng thi lin kt cn c gi l nh tuynng dn ngn nht OSPF (Open Shortest Path First). N duy tr mt c s dliu phc tp cha thng tin v cu hnh mng. Trong khi gii thut vectorkhong cch khng c thng tin c bit g v cc mng xa v cng khng bitcc router xa, gii thut trng thi lin kt bit c y v cc router xav bit c chng lin kt vi nhau nh th no. Giao thc nh tuyn trngthi lin kt s dng:

- Cc thng bo v trng thi lin kt LSA (Link State Advertisements).- Mt c s d liu v cu hnh mng.- Gii thut OSPF v cy OSPF sau cng.- Mt bng nh tuyn lin h cc ng dn v cc cng n tng mng.

Hot ng tm hiu khm ph mng trong kiu nh tuyn trng thi lin ktc thc hin nh sau:

- Cc router trao i cc LSA cho nhau. Mi router bt u vi cc mng

c kt ni trc tip ly thng tin.- Mi router ng thi vi cc router khc tin hnh xy dng c s d liuv cu hnh mng bao gm tt c cc LSA n t lin mng.

- Gii thut OSPF tnh ton ng i mng c th t n. Router xy dngcu hnh mng lun l nh mt cy, t n l gc, gm tt c cc ng dn cth n mi mng trong ton b mng ang chy giao thc nh tuyn trng thilin kt. Sau n sp xp cc ng dn ny theo chin lc chn ng dnngn nht.



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- Router lit k cc ng dn tt nht ca n v cc cng dn n mngch trong bng nh tuyn ca n. N cng duy tr cc c s d liu khc vcc phn t cu hnh mng v cc chi tit v hin trng ca mng.

Khi n thay i v cu hnh mng, router u tin nhn bit c s thay i

ny gi thng tin n cc b nh tuyn khc hay n mt router nh trcc gn l tham chiu cho tt c cc router trn mng lm cn c cp nht.

- Theo di cc ln cn ca n, xem xt c hot ng hay khng, v gi trnh tuyn n ln cn .

- To mt gi LSA trong lit k ca tt c cc router ln cn v gi trnh tuyn i vi cc ln cn mi, cc thay i trong gi tr nh tuyn v cclin kt dn n cc ln cn c ghi.

- Gi gi LSA ny i sao cho tt c cc router u nhn c.

- Khi nhn mt gi LSA, ghi gi LSA vo c s d liu sao cho cp nhtgi LSA mi nht c pht ra t mi b nh tuyn.

- Hon thnh bn ca lin mng bng cch dng d liu t cc gi LSAtch lu c v sau tnh ton cc tuyn dn n tt c cc mng khc sdng thut ton OSPF. C hai vn cn lu vi giao thc nh tuyn trngthi lin kt l:

Hot ng ca cc giao thc nh tuyn trng thi lin kt trong hu htcc trng hp u yu cu cc router dng nhiu b nh v thc thi nhiu

hn so vi giao thc nh tuyn theo vector khong cch. Cc yu cu nyxut pht t vic cn thit phi lu tr thng tin ca tt c cc ln cn, cs d liu mng n t cc ni khc v thc thi cc thut ton nh tuyntrng thi lin kt. Ngi qun l mng phi m bo rng cc b nhtuyn m h chn c kh nng cung cp cc ti nguyn cn thit ny.

Cc nhu cu v bng thng cn phi tiu tn khi ng s pht tngi trng thi. Trong khi khi ng qu trnh khm ph tt c cc routerdng cc giao thc nh tuyn trng thi lin kt gi cc gi LSA n ttc cc b nh tuyn khc. Hnh ng ny lm trn ngp mng khi m cc

router ng lot yu cu bng thng v tm thi lm gim lng bngthng kh dng dng cho lu lng d liu thc c nh tuyn. Sau khikhi ng pht tn ny, cc giao thc nh tuyn trng thi lin kt thngch yu cu mt lng bng thng ti thiu gi cc gi LSA kch hot skin khng thng xuyn nhm phn nh s thay i cu hnh mng.

Vic tnh ton tuyn trong giao thc nh tuyn trng thi lin kt s dngthut ton chn ng ngn nht theo k thut chn ng tp trung m inhnh l thut ton Dijkstra. Thut ton a ra tm ng i ngn nht t nhs n tt c cc nh cn li trong th c hng da trn c s gn cho cc

nh cc nhn tm thi (khc vi thut ton Ford & Fulkerson tm ng i ttt c cc nh n mt ch).



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Thut ton Dijkstra c m t nh sau:

- u vo:

th c hng G = (V, E) vi n nh.

s thuc V l nh xut pht.a[u, v] l ma trn trng s.

d(v) l khon cch t nh xut pht s n v.

- u ra:

Truoc[v] ghi nhn nh i trc v trong ng i ngn nht t s n v.

Bc 0 (khi ng):

N0 = {s};

D0(v) = l(s, v); vi v khng thuc N0.Bc k (tnh v cp nht):

Nk = Nk 1 + {w};

Trong w tho mn biu thc:

Dk 1 (w) = min[Dk 1 (v)]

vi v khng thuc Nk 1

Cp nht:

Vi mi v khng thuc Nk:

Dk(v) = min[Dk 1 (v), Dk 1 (w) +l(w, v)]

Kim tra iu kin lp:

Nu Nkkhc vi V th lp bc k + 1 ngc li th dng qu trnh tnhton.

3.1.3.3 nh tuyn phn lp.

Giao thc nh tuyn phn lp thc hin tun t cc phng php vector

khong cch tnh ton tuyn. Cc mt n nh tuyn khng pht hnh trnmng theo chu k.

Khi s dng giao thc nh tuyn phn lp, tt c cc mng con trn cngmt mng chnh (lp A,B,C) cng dng chung mt mt n mng. Tu thuc vocc gi tin cp nht nh tuyn, b nh tuyn chy giao thc nh tuyn phnlp theo mt trong cc phng php sau:

Nu thng tin nh tuyn trong cng mt mng v c cu hnh trn cngmt giao tip nhn tin, b nh tuyn t mt n mng c cu hnh trn mt n

nhn. Nu thng tin nh tuyn nm trn mng khc cng c cu hnh trnmt nhn, b nh tuyn s p dng mt n ngm nh (theo lp a ch). Cc



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giao thc nh tuyn phn lp nh RIPv1 v IGRP, chuyn i tuyn trn mngcon trong cng mt mng. iu ny l c th v tt c cc mng con trong mtmng ln l c cng mt mt n mng v cng mt mt n nh tuyn.

Khi tuyn c trao i vi mng ln cn, cc thng tin v mng con cng s

c chuyn theo, v mt n nh tuyn ca cc mng khc s khng c bit.Kt qu, cc thng tin v mng lm vic t mng ny c th tng kt(sumerized) thnh ng bin phn lp nh s dng mt n nh tuyn ngmnh cp nht vo bng nh tuyn. To ra tuyn tng kt (sumary) ti ng

bin ca mng chnh c x l t ng bi cc giao thc nh tuyn phn lp.Tng kt ti cc im khc trong mng khng c thc hin bi cc giao thcnh tuyn phn lp.

Khi thc hin phn lp mng con ti im chuyn tip vi cc giao thc nhtuyn phn lp, cn phi ch ci t cc mt n mng con ti tt c cc giao

tip trong vng nh tuyn phn lp. iu ny yu cu cc b nh tuyn mngcon phi c pht hnh chnh xc.

S dng mt n mng con c nhng nhc im t gc ch nh vng ach hiu qu. Vi 27 bit mt n, ch ra s host khong 30 trm trn mi mt phnon Ethernet, khng phi tt c 30 host cng c s dng trn ng lin ktni tip (S0,S1).

3.1.3.4 nh tuyn khng phn lp.

Cc giao thc nh tuyn khng phn lp gm cc mt n nh tuyn vi cc

hng pht hnh (advertisement).Giao thc nh tuyn khng phn lp c coi nh l cc giao thc nh

tuyn th h tip theo ca cc giao thc nh tuyn phn lp, v n c thit k nh a ch nhm gii hn ca cc giao thc nh tuyn phn lp. Mt trongnhng gii hn c bn nht ca nh tuyn phn lp l mt n nh tuyn khngc trao i trong qu trnh x l cp nht nh tuyn, yu cu cng mt mtn nh tuyn cho tt c cc mng lm vic.

Cc gii hn khc ca giao thc nh tuyn phn lp tip cn nh mt nhu

cu tng kt cc mng phn lp. Vi cc mt n nh tuyn ngm nh ti ngbin mng. Trong mi trng khng phn lp, x l tng kt c iu khinnhn cng v c th xc nh bt c mt v tr bit no trn mng. Cc giao thcnh tuyn khng phn lp s dng cp nht lp tc hc cc s thay i topomng. iu khin ni dung bng nh tuyn, cc hng tng kt c th cto ra. Thit k phn cp s dng OSPF cho php tng kt ti bt k bit no,nhng gii hn cu hnh tng kt trn mt s loi thit b c bit, nh cc bnh tuyn ng bin vng. V cc hng mng con c chun b qua vngnh tuyn, cc tng kt c yu cu gi kch thc bng nh tuyn.



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3.1.3.5 nh tuyn trn c s QoS.

Giao thc nh tuyn trn c s QoS c gng to nhiu php o vo tinguyn khi xy dng bng chuyn tip ca mng. Giao thc ny tng cnghin cu trong nhiu nm v thng bt u bng mt s tha nhn rng

mng c xy dng t cc router IP n lc ti a. Bt u t s tha nhn nynh tuyn n thng s dng nh c mt s hn ch khi tha nhn p ngnhu cu QoS c nh ca mi trng a dch v.

Mt thng s c th c xem l mt loi gi tr v mi kt ni (chng) cmt gi tr tng ng. Giao thc nh tuyn n lc tm kim nhng ng dnvi tng gi tr ca tt c cc kt ni t ngun n ch c th l nh nht. Tuynhin gi tr ny khng th l i din ng quan tm v cn thit cho tt c ccloi lu lng. Phi chng n i din cho tr ca ng lin kt, bng thng,kh nng mt gi hoc c th l chi ph hin ti cho vic gi gi qua ng lin

kt . Chn la mt trong s chng ta s t c mt s la chn ph hpvic tm kim lu lng, trong khi s la chn lu lng khc l lng ph tinguyn.

Chng hn, mt mng xem tr l mt thng s. ng dn ngn nht lc nyph hp vi cc ng dng c yu cu thi gian thc cht ch. Nhng chngkhng n l. Mng cng hon ton c th c s dng cc ng dng d liu

bng n truyn thng m s quan tm ti n t hn l tr. Lu lng t cc ngdng khc ny cng i theo cc ng dn ngn nht vi tr nh nht, thm titrng vo cc router n lc ti a dc theo ng dn. Mt tc ng khngthun li l lu lng bng n chim cng khng gian hng i c s dng

bi lu lng thi gian thc, s tng ln ca jitter v tr trung bnh bi tt c cclu lng qua cc router. Cch tip cn ny cng gy nh hng n s chnhxc ca gi tr tr m giao thc nh tuyn s dng quyt nh ng dnngn nht.

nh tuyn trn c s QoS to nhiu cy ng dn ngn nht bao gm hnh hin thi ca cc router v cc ng lin kt vi mi cy s dng mt thp tham s khc nhau nh n v kt ni. Mc tiu l gim thiu s cng tnti khng cn thit trong router ca lu lng vi yu cu QoS m rng khc.Cc gi vi yu cu tr nghim ngt sau c chuyn tip bng cch s dngcy c xy dng vi tr nh l mt thng s. Cc gi khng yu cu thi gianthc c th xy dng cy theo kiu khc (chng hn nh gim gi tr cui cngca ng dn ti mc cc tiu). Mt vi vn thc t tn ti trong vic nhtuyn trn c s QoS l:

- Mi router cn c nhiu bng chuyn tip (hoc chc nng tng t)trn biu din ch dn chng tip theo trn c s a ch ch ca migi. Mi ch dn c mt loi cy ngn nht. Cc trng thm vo trong

tiu gi c s dng chn mt chng tip theo c th kt hp vi



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a ch ch ca gi. iu ny gy kh khn cho vic thit k c chtruyn dn chng tip theo.

- Mt s tng ln trong giao thc nh tuyn trn xut hin bi v cngvic ca router phi chu ng mt c th ca mi giao thc cho mi cy

ngn nht duy nht. Yu cu lm cho thi gian tp trung gi ca routertrong mng tng ln mt khong thi gian ngn no (chng hn khi cckt ni n hoc i hoc gi tr ca chng thay i) thi gian tp trungtng ln nhiu hn nu giao thc nh tuyn c yu cu tnh ton cyda trn nhiu thng s cng mt lc.

- Cc thng s nh tr hoc bng thng kh dng ph thuc nhiu volu lng hin thi i qua mng. Mt cy ng dn ngn nht xy dngvi gi tr tr c nh hnh mt cch c nh c th tr nn li thi khilu lng bt u chy qua mng. Khng c quy c cho vic cp nht

gi tr mi kt ni vi cc s o thi gian thc hp l, to ra mt s lo sl thuyt iu khin thc - mi gi tr cp nht c th l kt qu tnh tonli cy ng dn ngn nht kt hp dn n vic tip tc x l ti trngtrn tt c cc router.

iu th v l s pht trin ca cc router vi kin trc CQS mt mc no lm gim nhu cu nh tuyn trn c s QoS. V d s dng tr nh mtthng s gi tr. By gi ch rng vi mi router c t nht hai hng i trnmt giao din u ra. Mt cho lu lng nhy cm vi tr, mt cho tt c cclu lng cn li. Tt c cc lu lng u c nh tuyn theo ng dn vitr thp nht. Tha nhn cc router phn loi lu lng ph hp vo hai hngi , dch v nhn c vi lu lng nhy cm vi tr khng ph thuc vos bng n ca tt c cc loi lu lng khc. iu chng t mt s quy cv giao thc nh tuyn IP n thng s khi kt hp vi cc router da vo kintrc QoS c th chu ng c nhiu mc khc nhau ca dch v. iu ch yuc ni y l kh nng thch ng tn ti dc theo mt cy n cung cptt c nhng ngi tham gia.

3.2 Cu trc routerMt router thng thng c cc khi ch nng c bn sau (xem hnh 3.6):

- Khi a giao din.

- Khi chuyn tip.

- Khi qun l.



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Khi chuyn tip

Khi qun l S liu thng k, bntin t cc router khc

Cc cp nht ni bbn tin ti cc router

khc

,

In putOut put

In put

In put

In put

Out put

Out put

Out put

Hnh 3.6: Cu trc chung ca router

Giao din vo nhn cc gi n t cc router khc, v khi chuyn tipchuyn cc gi ti giao din ra ph hp (da vo a ch ch ca mi gi). Migiao din sau s dng cc c ch kt ni ring truyn dn cc gi ti ccrouter (hoc host) k tip dc theo ng dn. Khi mt router cho rng nghnni ang tng ln mt cch tht thng, cc gi c th b loi b hoc b nhdu nh l mt iu kin ch r trng thi ny ti cc mng xung quanh n. Hot

ng ca tng gi trong khi chuyn tip (chn giao din u ra v p ngnghn) ch yu c iu khin bi khi qun l.

Khi chuyn tip da vo mt bng FIB (Forwording Information Base) chuyn cc gi ti u ra ph hp. Vi mi a ch ch c th, mt s tm kimxc nhn tin t di nht c nh dng qua FIB. Nu mt xc nhn c tmthy, li vo tng ng ch cho khi chuyn tip bit giao din u ra no c thnhn gi. Nu khng tm thy c ngha l gi b rt. Ni dung ca FIB phn nhtrng thi hin ti ca cu trc mng IP xung quanh router, c xc nh bicc giao thc nh tuyn IP chng hn nh Giao thc OSPF (Open Sortest

Path First) v Giao thc cng bin phin bn 4 (BGP4: Border GatewayProtocol version 4) - chy trn khi qun l.

Ch : vic bit cu trc mng xung quanh cho php mt FIB ca chng ktip nhn c t vic tnh cy ng dn ngn nht v t bit tt c ccch/tin t.

R rng hnh 3.6 l mt m hnh c tnh tru tng cao. Cc router in hnhban u thng c mt CPU trung tm ring iu khin tt c cc chc nngqun l v chuyn tip gi. T khi cc router pht trin theo hng cu trc

phn tn, tt c cc thit k u nhm loi b hoc gim nh hng ca hintng tht nt chai. Trong cc router backbone, khi chuyn tip c phn



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phi gia cc mu card giao din ni lin vi nhau bi c cu chuyn mch tc cao hoc mt mt bng pha sau [KLS98][KESH98][DSRTER]. Tuy nhin,tt c cc router c trnh t cc bc chung m mt gi phi i qua trong khi xl gi.

Ngy nay, QoS tr nn quan trng, qu trnh chuyn tip c thit k linhm mang li thut li hn khi router gi gi. Hnh 3.7 cho ta mt ci nhntng quan v qu trnh x l xy ra trong khi chuyn tip trong hnh 3.6. Thngthng, mt gi phi tri qua ba giai on chnh sau:

- Phn loi v tm kim FIB (thit lp nhn dng gi v tm giao dinu ra).

- Kim sot v nh du (phn nh li trong trng hp gi khng ntrong mt khung thi gian ph hp).

- Xp hng v lp thi gian biu (chuyn tip gi ti cc kt ni chia shay quy tc nh hnh lu lng hoc loi b n khi quy tc iu khinnghn).

Giai on phn loi gi s dng router thit lp trng hp tng qut chocc gi n sau. Mc d hu ht trng hp c s dng thit lp ctnh iu khin thi gian (kim sot, nh du, xp hng v lp lch), mt vitrng hp thm vo c th c s dng thay i quyt nh chuyn tip.Chng hn, mt router tin tin c th h tr nhiu FBI (i din cho cy ngdn ngn nht da trn n v khc) v la chn gia chng, bng cch s dng

cc thng tin khc trong phn tiu ca gi (nh a ch ngun chng hn).Mt cch tng t hay ti thiu mt mi quan h ng thng tn ti gia mttrng hp ca mt gi (thit lp qua mt phn loi gi) v cc loi ca n.

OutputInterface

InputInterface

Policing &Marking

SwitchFabric

Queuing &Scheduling

ForwardingTable (s)

FBI

FBIFBI

PacketClassification

IP header

FBI

IP payload

Tnh hung gi nh hng n qu trnh sau

Hnh 3.7: Qu trnh x l gi trong khi chuyn tip.



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3.3 Kin trc CQS

Trn y chng ta tm hiu mt kin trc chung ca router, kin trc ny tng c s dng rng ri trong mng vin thng ni chung v mngInternet ni ring. Tuy nhin vi s pht trin mng li vin thng nhanh

chng v rng khp hin nay i hi phi tng cng kh nng x l, v tngtc cho cc router, cng nh cn phi a thm vo cc c tnh mi nhmqun l lu lng mt cch linh hot v mm do hn ng thi p ng cy yu cu QoS ca cc loi lu lng dch v mi. y chng ta cpn mt kin trc l kin trc CQS. y l mt kin trc mi c a vorouter nhm nng cao kh nng qun l ca router ng thi tng kh nng giiquyt vn tc nghn xy ra router v n ch c trong mng dch v khc

bit. Kin trc ny c cho nh hnh v 3.8:

Queue

Queue

Queue

Queue

Classify

Port1

Port N

Schedule

Hnh 3.8: Kin trc CQS.

Theo kin trc ny, cc gi n c phn loi theo u tin hoc theomt tiu ch no ri chng c cho vo cc hng i tng ng khc nhau.Cui cng, cc hng i phi chia s tt c kh nng ca kt ni u vo mchng a vo. Nhu cu ny bao hm vic thm vo mt c ch lp lch xencc gi t mi hng i v nh vy cc kt ni truy cp vo mt cch c kh

nng d on v iu khin c.Phn loi

C ch phn loi gi ca mt router nh hng trc tip n nhn t m nc th tch cc lp hoc cc loi lu lng IP khc nhau. Trong thc t, tnhtrng ca mt gi tin ph thuc vo c hai thng tin c mang bi chnh bnthn gi v thng tin tnh hnh mng nhn c t giao din ca n (c th lchng tip theo ca n c quyt nh t vic tm kim FIP). Vic phn loida trn cc kho phn loi v cc quy tc phn loi. Kho phn loi m mtnhm N bit trong tiu gi tin. N bit ny c th phn bit c 2N loi (hoclp) gi khc nhau. Qu trnh kt hp cc kho phn loi i hi phi da trn



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nhng quy tc nht nh. Cc quy tc ch r s kt hp cc kho c gi lquy tc phn loi. Mt kha khng th di tu - b nh ca mt router bt

buc phi gii hn s lng thng tin trng thi m n c th lu gi nhnbit lp. (Tuy nhin ngha ca cc bit tn ti trong trng phn loi c th t

hn nhiu so vi 2N

trng hp gii quyt). Thi gian x mi gi kt hptrong tng bc phn loi cng tng ln theo chiu di kha (mc d khng philun theo ng thng), iu c th lm gim hiu sut ca router. Mt khcmt kho khng th qu ngn 2N phi bng hoc ln hn gi tr cc tiu calp lu lng yu cu bi mng c thit k.

Ngoi tr cc trng c phn loi, giai on phn loi phi c kh nnggi c tc nhn gi nh [KLS98]. Cho n khi trng thi ca gi cthit lp, th hng i c th khng c cung cp. Khi m giai on phn loichm hn tc nhn gi th hng i FIFO xut hin trc giai on phn loi.

Hu ht cc s phn loi hn hp in hnh s dng mt kho bao gmnhiu trng trong tiu gi IP c ch gii nh l phn loi a trng (MF).Kho ny c th thm mt vi hoc tt c cc trng thng nh ngha mtlung IP thng thng l a ch ngun v a ch ch, trng giao thc, vch s cng TCP/UDP ngun v ch. Phn loi MF cung cp s lng ln nhtcc trng hp cho cc giai on x l k tip ca router. Tuy nhin, khi mtngi thit k mng tin rng ch mt s lp lu lng nh cn phn bit ti mtvi chng cho trc, gii php thng c n nh cho mt nhm bit ti mt vtr c nh trong tiu gi c phn loi. Octet ToS ca IPv4, octet TC ca

IPv6 v trng dch v khc bit hon ton ph hp trong trng hp ny.Qun l hng i

Mi lp lu lng c yu cu c im lp lch ring phi c t trongchnh hng i ca n vi mi gi trc tip ti hng i thch hp s dngthng tin tnh hung thu thp c t tng phn loi trc . Khng c cchng i ring bit n khng th c kh nng cho tng lp lch sau phn bitgia nhiu lp lu lng cnh tranh mt ng kt ni n. Mt chc nng bqun l hng i l chu trch nhim thit lp v duy tr hng i v phngthc hng i trong router. Chc nng ny bao gm bn hot ng c bn:

- Thm mt gi vo hng i c ch r bng tnh hung ca gi (nhc thit lp trong tng phn loi) nu hng i khng y.

- Loi b mt gi nu hng i y.- Loi b mt gi khi c yu cu bi b lp lch.

- Gim st la chn s chim dng hng i (s gi hoc byte chimdng hng i) v da vo mt trong cc bc thc hin sau gi mcchim dng thp:

+ Loi b mt gi (hoc khng chn thm mt gi) khi hng i y+ nh du mt gi khi hng i bt u y.



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Ti mt vi im mi hng i cng b y (thm ch trong khi khng gianc sn cho hng i khc tng ln) m bo rng khng mt lp lu lngno dng tt c khng gian nh hn ch ca router to hng i.

Tuy nhin, phi m bo khng mt hng i no b b i. Thm vo

mt vi chim dng trung bnh ca hng i c th c gi mc thp.Vic qun l hng i tch cc c thi hn thng p dng phng php gimst v iu khin chim dng hng i trung bnh. chim dng trung bnhthp c hai li ch:

- Tn ti cc hng i tiu th s bng n lu lng khng th trnhkhi m khng lm mt gi. Hot ng vi mt chim dng trung bnhcao lm gim khng gian sn c tiu th s bng n.

- Tr trung bnh c b qua bi s phn chia lu lng mt hng i

cho trc tng ln cng vi s tng chim dng hng i. Gi cho chim dng gim gip gi cho tr end to end gim.

Lp lch

Lp lch iu khin c trng thi gian ca vic lu thot gi khi mi hngi - thng ti giao din u ra hng ti router hoc host tip theo, nhngcng c th l ti cc im hng i trong mt router. Cc router truyn thngch c mt hng i n trn mt giao din kt ni u ra. Nh vy lp lch cnhim v n gin l li cc gi ra khi hng i nhanh bng kh nng kt nic th chuyn c. Trong cc router c kin trc CQS, mi giao din c mt

tng b lp lch chia s kh nng cha ca kt ni u ra gia s kt hp cchng i trong giao din. Chia s kt ni t c mt s sp xp lch bi khino v xy ra nh th no, cc gi c ko ra khi hng i v truyn i.

Bi v tnh hung ca mt gi (hoc mt lp lu lng) iu khin hng ino m n c t trong , b lp lch ch yu cng ch quyn u tin tngi, hn ch tr, hoc bng thng ch nh gia cc lp lu lng khc nhau.Mt b lp lch c th thit lp bng thng kh dng nh nht cho mt lp c

bit bng cch m bo rng cc gi c ly ra khi hng i c quan h vicc lp mt cch thng thng. Mt b lp lch cng c th cung cp nh

hng tc (li dng bng thng c php cc i cho lp c bit). Bngcch gii hn tn s trong hng i ca lp no c phc v ph thuc vothit k ca mt b lp lch, n c th p t hai gii hn bng thng di vtrn trn mi hng i hoc p t gii hn trn cho mt s hng i v gii hndi cho mt s hng i khc.

Cc thut ton lp lch thng tho thun gia s thc hin n gin v ctrng thi gian mong mun. Tt c cc thit k b lp lch c nhng kiu dchv c trng ca ring n cch m n la chn hng i dch v. B lp lchn gin nht tp trung vo hng i phc v trong mt s hng i d ontrc, vic tp trung vo dch v khong cch hn l cng sut thu c. Cc b



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lp lch tin tin hn cho php tng i hoc ton b bng thng thit lpcho mi hng i v chng tip tc lp rp vo cc kiu dch v ca chng m bo bng thng trung bnh hoc tr t c bi mi hng i gii hntrong cu hnh.

Phn tip theo chng ta nghin cu cc chin lc qun l hng i s dngkin trc CQS. V mc nhin t y chng ta tha nhn cc router u c kintrc CQS.



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n tt nghip i hc ng dng kin trc CQS cho qun l nghn trong mng IP

CHNG IV - NG DNG KIN TRC CQS CHO QUNL NGHN TRONG MNG IP

4.1 Ti sao phi qun l nghn.

Cc mng hn hp thm vo nhiu giao thc khc nhau s dng bi cc ngdng, vic tng nhu cu lu lng u tin theo th t cc ng dng thi giancht ch thch hp trong khi vn s dng cc nhu cu ca cc ng dng phthuc thi gian t hn nh dch v truyn file. Cc loi lu lng khc nhau chias mt ng d liu qua mng c th nh hng ln nhau theo cch m n tcng ti s thc hin ng dng ca chng. Nu mng c thit k h trcc loi lu lng khc nhau nhm chia s mt ng d liu n gia cc

router chng ta phi ch vic s dng k thut qun l nghn m bo ix cng bng gia cc loi lu lng.

Sau y l mt s nhn t m rng cn ch xc nh c hoc khng nhhnh QoS qun l nghn:

Mc u tin lu lng c bit quan trng cho cc ng dng tc v, nhycm vi tr - v d hi ngh truyn hnh nhiu bn Cc ng dng nyyu cu mc u tin cao hn cc ng dng truyn file. Tuy nhin, sdng WFQ m bo rng tt c cc lu lng c i x mt cch cng

bng theo trng s ca n v trong mt cch linh ng. Chng hn, WFQ

s dng nhu cu ca ng dng tc ng ln nhau m khng k n ngdng truyn file.

Mc u tin c hiu qu tt nht trn cc kt ni WAN m t hplu lng bng n v tc thp hn tng i c th dn nghn ngnhn.

Ph thuc vo kch thc gi trung bnh, mc u tin c hiu qu tt nhtkhi p dng cho cc kt ni T1/E1 hoc cc kt ni c tc thp hn.

Nu ngi dng cc ng dng ang chy qua mng thy rng khng

thi gian p ng, chng ta phi ch s dng c tnh qun l nghn.c tnh qun l nghn l rt linh ng. Tuy nhin, cn phi ch numt kt ni WAN b nghn lin tc th mc u tin lu lng c thkhng gii quyt c vn . Thm bng thng vo c th l gii php

ph hp.



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4.2 Cc chin lc qun l nghn s dng kin trc CQS.

4.2.1 Cc chin lc qun l nghn s dng hng i

4.2.1.1 Chin lc hng i FIFO

Trong mt dng n gin hng i FIFO (cn c bit n nh l hng ifirst-come, first-served: FCFS) bao hm vic m v chuyn tip cc gi theoth t khi chng n.

FIFO khng a ra khi nim v mc u tin hay loi lu lng v do khng to ra quy nh v mc u tin gi. Ch c mt hng i v tt c cc gic i x nh nhau. Cc gi c gi ra khi giao din theo th t chngn.

Khi FIFO c s dng, cc ngun i x km (ill-behaved) c th dng ttc bng thng, ngun bng n c th gy ra tr trong lu lng nhy cm vithi gian hoc lu lng quan trng v lu lng quan trng c th b loi b

bi lu lng quan trng hn chim y hng i.

Khi khng c hng i khc c cu hnh th tt c cc giao din ngoi trgiao din serial E1 (2,048 Mbps) v thp hn s dng FIFO mt cch mc nh(giao din serial E1 v thp hn s dng WFQ mt cch mc nh).

FIFO l mt phng php hng i nhanh nht v n c hiu qu cho cc ktni ln c t tr v nghn ti thiu. Nu kt ni rt t b nghn th ch cn dnghng i FIFO l .

4.2.1.2 Chin lc hng i cn bng trng s (WFQ)Phn ny trnh by ba loi hng i WFQ sau:

Flow-Based Weighted Fair queuing (WFQ) VIP-Distributed Weighted Fair queuing (DWFQ) Class-Based Weighted Fair Queuing (CBWFQ)

Phn ny cng trnh by cc c trng lin quan sau:

IP RTP Priority Frame Relay IP RTP Priority Hng i tr thp (Low Latency Queuing)

Flow-Based Weighted Fair Queuing

WFQ l mt phng php lp lch linh hot cung cp s phn phi bngthng cn bng ti tt c lu lng mng. WFQ p dng quy tc u tin hoctrng s nhn dng cng nh phn loi lu lng cc cuc thoi v xc nhlng bng thng bao nhiu cp cho mi cuc thoi sao cho n cn i vicc cuc thoi khc. WFQ l mt thut ton trn c s lung lp lch ng thi

lu lng tng tc trc hng i gim thi gian p ng v chia s cnbng bng thng cn li cho cc lung bng thng cao. Ni mt cch khc,



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WFQ cho php c lu lng dung lng thp, nh cc phin Telnet, v u tinlu lng dung lng cao, nh cc phin FTP. WFQ cho php truyn file ngthi s dng dung lng kt ni cn bng; ngha l khi truyn nhiu file xy ra,th vic truyn c cp bng thng c kh nng so snh c. Hnh 4.1 biu

din qu trnh lm vic ca WFQ.

Cc gi vo

Phn loi

S lng cu hnhca hng i

Hng itruyn dn

Cc gi ra

Cc ti nguyn bm hng i

Flow-base Classification : a ch ngun v a

ch ch Giao thc B nhn dng phin

(cng/socket )

Xc nh trng s bng : QoS yu cu (IP Precedence ,RSVP )

Nghch o thng qua mclung

Frame Relay FECN , BECN , DE(cho lu lng Frame Relay )

Lp lch cnbng trng s

Hnh 4.1: Weighted Fair QueuingWFQ khc phc mt lot cc hn ch ca hng i FIFO. Khi FIFO c hiuqu, lu lng c gi i theo th t n nhn c m khng k vic tiu th

bng thng hay tr kt hp. Kt qu l truyn file v cc ng dng mng dunglng cao khc thng to ra chui cc gi d liu kt hp. Cc gi lin quanny c bit n nh l cc dng gi. Cc dng gi l cc nhm gi c khuynhhng cng nhau i qua mng. Cc dng gi ny c th chim tt c bng thngkh dng, v ly i bng thng ca cc lung lu lng khc.

WFQ cung cp vic qun l mc u tin lu lng mt cch nng ng vo

bn tin cho mt cuc thoi. WFQ lm t dng gi trong mt cuc thoi mbo rng bng thng c chia s mt cch cn bng gia cc cuc thoi ringv lu lng dung lng thp c truyn i trong mt thi gian c hiu lc.

WFQ phn loi lu lng vo cc lung khc nhau da vo a ch tiu gi, bao gm cc c tnh nh a ch mng ngun v mng ch hay a chMAC, giao thc, cng ngun, cng ch, ch s phin bn, gi tr nhn dng ktni data-link Frame Relay v gi tr ToS. C hai loi lung lu lng: phin

bng thng cao v phin bng thng thp. Lu lng bng thng thp c mcu tin hiu qu trn lu lng bng thng cao, v lu lng bng thng cao

chia s dch v truyn dn cn xng theo trng s c n nh. Lung lulng bng thng thp gm phn ln lu lng, dch v u i nhn c, cho



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php ton b ti trng c php i vo c gi trong thi gian thch hp.Lung lu lng dung lng cao chia s dung lng cn li mt cch cn bng.

WFQ t cc gi ca cc cuc thoi khc nhau vo cc hng i cn bngtrc khi truyn dn. Th t di chuyn t cc hng i cn bng c xc nh

bi thi gian thc s ca gi tr bit cui cng ca mi gi n.Cc bn tin mi cho cc lung bng thng cao c loi b sau khi ngng

bn tin tc nghn c xc nh. Tuy nhin, cc lung bng thng thp bao gmcc bn tin iu khin cuc thoi, th c tip tc xp vo d liu. Kt qu lhng i cn bng i khi c th cha nhiu bn tin hn theo l thuyt theo chs ngng.

WFQ c th qun l cc lung d liu kp, nh l cc lung d liu gia cccp ng dng, v lung d liu n nh voice hay video.

Thut ton WFQ cng nhm vo vn tnh cht tr quay vng bin thin.Nu nhiu cuc thoi dung lng ln cng hot ng, th tc truyn v thigian n c to ra nhiu kh nng d on. WFQ nng cao cc thut ton nhl cc kin trc mng h thng (SNA: Systems Network Architecture), iukhin kt ni logic (LLC: Logical Linhk Control) v iu khin nghn TCP vc trng bt u chm.

Flow-Base WFQ c s dng nh mt phng thc hng i tu chn trnhu ht cc giao din serial c cu hnh hot ng hoc thp hn tc lung E1.

WFQ cung cp gii php cho tnh hung mong mun cung cp thi gian png ph hp cho cc ngi dng mng khc nhau m khng thm lng bngthng d tha. WFQ t ng thch nghi vi iu kin lu lng mng thay i.

Hn ch

WFQ khng h tr tunneling v mt m ho bi v c tnh ny lm thay ithng tin ni dung gi m WFQ yu cu cho vic phn loi.

WFQ v u tin IP

WFQ nhn bit mc u tin IP. N c th nhn ra cc gi u tin cao cnh du quyn u tin bi b chuyn tip IP v c th lp lch cho chng nhanhhn, cung cp thi gian p ng cao hn cho lu lng ny. V nh vy khimc u tin tng ln, th WFQ cp nhiu bng thng hn cho cuc thoi trongsut thi gian nghn.

WFQ n nh mt trng s cho mi lung, n xc nh th t truyn dn chocc gi c xp hng trong hng i. Trong s ny, cc trng s thp hnc phc v trc. Vi chun WFQ Cisco IOS, mc u tin IP phc v nh lmt b chia cho tha s trng s ny.

Ging nh CQ, WFQ gi mt s byte nht nh t mi hng i. Vi WFQ,mi hng i ph hp vi mt lung khc nhau. Trong mt chu k qua tt c



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cc lung, WFQ gi i mt s byte ngang bng vi mc u tin ca lung cngvi mt.

S ny ch c s dng nh mt t s xc nh bao nhiu byte/gi gii. Tuy nhin, vi mc ch hiu c WFQ, vic s dng s ny nh l s

m byte c kh nng. V d, lu lng c gi tr trng u tin IP l 7 nhnmt trng s thp hn lu lng c gi tr trng u tin IP l 3, l, mc utin trong th t truyn dn. Cc trng s l nghch o ca gi tr trng utin IP.

xc nh bng thng phn phi cho mi hng i, ta chia tng ch s mbyte ca tt c cc lung cho ch s lung. Chng hn, nu c mt lung th mi mc u tin, mi lung s nhn thm mc u tin + 1:

1+2+3+4+5+6+7+8 = 36

Nh vy lu lng c mc u tin 0 s nhn 1/36 ca bng thng, lu lngc mc u tin 1 s nhn 2/36, v lu lng c mc u tin 7 s nhn 8/36.

Tuy nhin, nu c 18 lung mc u tin 1 v cc mc u tin cn li u lmt th tng ch s lc ny l:

1+2(18)+3+4+5+6+7+8 = 70

Lu lng mc u tin 0 s nhn 1/70, mi lung mc u tin 1 s nhn2/70, v c nh vy.

Khi mi lung c thm vo hay bt i th bng thng phn phi thc t s

thay i mt cch lin tc.WFQ vi giao thc dnh trc ti nguyn (RSVP)

RSVP s dng WFQ phn chia khng gian b m, lp lch cc gi vm bo bng thng cho cc lung dnh trc. WFQ lm vic vi RSVP gip cung cp cc dch v QoS m bo v khc bit.

RSVP l giao thc chun Internet IETF cho php mt ng dng dnh trcbng thng mng mt cch linh ng. RSVP cho php cc ng dng yu cumt QoS ring cho mt lung d liu. Thc hin y Cisco cho php RSVP

c khi u trong mng s dng nh hnh proxy RSVP.RSVP l giao thc bo hiu chun duy nht c thit k m bo bng

thng mng t u cui n u cui cho cc mng IP. Cc host v cc router sdng RSVP thc hiu yu cu QoS cho cc router dc ng dn ca lungd liu v duy tr trng thi router v host cung cp dch v c yu cu,thng l bng thng v tr. RSVP s dng mt tc d liu trung bnh, slng d liu ln nht m router s duy tr trong hng i, v QoS cc tiu xc nh s dnh trc bng thng.

WFQ hoc Weighted Random Early Detection (WRED) hot ng nh lmt s chun b ca RSVP, iu chnh phn loi v lp lch gi yu cu cho cc



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lung dnh trc. S dng WFQ, RSVP c th to ra mt dch v m bo ccdch v tch hp.

WFQ v Frame Relay

Trng s WFQ c thc hin bi bit loi b thch hp Frame Relay, cc bitkhai bo nghn tng minh chuyn tip (FECN) v cc bit khai bo nghntng minh phn hi khi lu lng c chuyn mch bi module chuyn mchFrame Relay. Mi ln nghn c nh du, cc trng s c s dng bithut ton c bin i cuc thoi bt gp nghn gi i khng thngxuyn.

Nhng iu cn lu :

Mc d WFQ thch nghi mt cch t ng vi iu kin lu lng mng thayi, n khng a ra mc iu khin r rng trn s phn phi bng thng

m CQ v CBWFQ a ra.VIP-Distributed Weighted Fair Queuing

DWFQ l phin bn tc cao ring ca WFQ hot ng trn VIP. N ch tr trn cc router sau vi mt VIP2-40 hoc mt b x l giao din ln hn:

Cc dy Cisco 7000 vi RSP7000

Cc dy Cisco 7500

Mt b x l giao din VIP2-50 c gii thiu khi tc dng tp hp ca

b thch ng cng trn VIP ln hn DS3. Mt card VIP2-50 c yu cu chocc tc OC-3.

s dng DWFQ, th chuyn mch DCEF (Distributed Cisco ExpressForwarding) phi c cho php trn giao din. Nhiu thng tin trn CEF ca vo ch dn cu hnh dch v chuyn mch Cisco IOS v tham kho lnh ccdch v chuyn mch Cisco IOS.

Ch : Vic thc hin VIP-Distributed WFQ khng ging nh WFQ thchin trn tt c cc nn tng khc.

C hai dng ca DWFQ l: Flow-Based DWFQ v Class-Based DWFQ

Flow-Based DWFQ

Vi flow-based DWFQ, cc gi c phn loi bi lung. Cc gi c cnga ch ngun, a ch ch, cng TCP hoc UDP ngun, cng TCP hoc UDPch, giao thc, v trng ToS thuc cng mt lung (Tt c cc gi khng phigi IP c xem nh lung 0).

Mi lung tng ng vi mt hng i u ra ring bit. Khi mt gi cn nh ti mt lung, n c t vo hng i ca lung . Trong sut thigian nghn, DWFQ phn phi s chia s bng thng ngang bng nhau cho mihng i hot ng.



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Flow-based DWFQ cng c gi l hng i cn bng bi v tt c cclung c nh trng s mt cch cn bng v c phn chia bng thng cn

bng. Trong chiu hng thc hin ca DWFQ, cc trng s khng c nnh cho cc lung. Vi DWFQ, cc host i x tt c bo v t cc host i

x km.Class-Based DWFQ

Trong class-based DWFQ, cc gi c n nh ti cc hng i khc nhauda trn nhm QoS ca chng hoc mc u tin IP trong trng ToS.

Cc nhm QoS cho php tu chn chnh sch QoS. Mt nhm QoS l mtphn loi ni ca cc gi c s dng bi router xc nh nhng gi noc i x bi cc c tnh QoS nht nh, nh l DWFQ v CBR (CommittedAccess Rate). S dng vic truyn b mt chnh sch CAR hoc chnh sch QoS

qua BGP n nh cc gi ti cc nhm QoS.Nu mun phn loi cc gi ch da vo hai bit u tin IP cp thp, th sdng ToS-based DWFQ.

nh r mt trng s cho mi lp. Trong giai on nghn, mi nhm ccp mt phn trm bng thng u ra ngang bng vi trng s ca lp. V d,nu mt lp c n nh mt trng s l 50, cc gi t lp ny s c cp tnht 50% bng thng trong sut giai on nghn. Khi giao din khng b nghnth cc hng i c th s dng mt lng bng thng kh dng.

Chnh sch loi b

DWFQ duy tr du hiu ca s gi trong hng i v tng s gi trong cchng i.

Khi tng s gi di mc gii hn chung, th cc hng i c th m nhiugi hn gii hn hng i ring.

Khi tng s gi t ti gii hn chung th giao din bt u cng p giihn cc hng i ring. Mt s gi mi n khi mt hng i vt qu giihn hng i ring ca n th s b loi b. Cc gi trong hng i s khng

b loi b, ngay c khi nu hng i vt qu gii hn ring.

Trong mt s trng hp, tng s gi trong tt c cc hng i a ra cngnhau c th vt qu gii hn chung.

Nhng hn ch

S dng DWFQ vi lu lng IP. Tt c lu lng khng phi IP c ix nh l mt lung n v trc c t trong cng hng i.

DWFQ c mt s hn ch sau:

C th c cu hnh trn giao din nhng khng th cu hnh trn giao

din con.


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