Đại học quốc gia Hà Nội tr-ờng đại học công nghệ Trn Anh Tun NNG CAO CHT LNG DCH V MNG INTERNET Ngành: Công Nghệ Điện tử - Viễn thông Chuyên ngành: Kỹ thuật vô tuyến điện tử thông tin liên lạc Mã số: 2.07.00 LUN VN THC S Ng-ời h-ớng dẫn khoa học: PGS.TS Nguyễn Cảnh Tuấn Hà Nội 2007 C LC CH VIT TT vi DANH MC BNG vii DANH MC HèNH V viii M U x CHNG 1: S PHT TRIN CA MNG INTERNET V YấU CU V CHT LNG DCH V - CC Mễ HèNH CHT LNG DCH V (QoS) 1.1 Gii thiu mng Internet v cht lng dch v IP (IP QoS) 1.2 Lch s cht lng dch v giao thc Internet (IP QoS) 1.3 Cỏc thc o thụng s hnh 1.3.1 Di thụng Error! Bookmark not defined 1.3.2 Tr v Trt gúi tin Error! Bookmark not defined 1.3.3 Mt gúi Error! Bookmark not defined 1.4 Cỏc chc nng QoS Error! Bookmark not defined 1.4.1 ỏnh du v phõn loi gúi tin Error! Bookmark not defined 1.4.2 Qun lý tc lu lng Error! Bookmark not defined 1.4.3 Cp phỏt ti nguyờn Error! Bookmark not defined 1.4.4 Chớnh sỏch trỏnh tc nghn v loi b gúi Error! Bookmark not defined 1.4.5 Giao thc bỏo hiu QoS Error! Bookmark not defined 1.4.6 Chuyn mch Error! Bookmark not defined 1.4.7 nh tuyn Error! Bookmark not defined 1.5 Cỏc mc ca cht lng dch v (QoS) Error! Bookmark not defined 1.5.1 Dch v N lc cao nht (Best-effort service) Error! Bookmark not defined 1.5.2 Dch v cú phõn loi Error! Bookmark not defined 1.5.3 Dch v cú bo m Error! Bookmark not defined 1.6 Dch v cú bo m (Intergrated Service): Giao thc dnh trc ti nguyờn (RSVP) Error! Bookmark not defined 1.6.1 Giao thc dnh trc ti nguyờn (RSVP) Error! Bookmark not defined 1.6.1.1 Vn hnh ca RSVP Error! Bookmark not defined 1.6.1.2 Cỏc thnh phn RSVP Error! Bookmark not defined 1.6.1.3 Cỏc bn tin RSVP Error! Bookmark not defined 1.6.2 Cỏc kiu dnh trc Error! Bookmark not defined 1.6.2.1 Dnh riờng riờng bit Error! Bookmark not defined 1.6.2.2 Dnh riờng chia x Error! Bookmark not defined 1.6.3 Kiu dch v Error! Bookmark not defined 1.6.3.1 Ti kim soỏt Error! Bookmark not defined 1.6.3.2 Tc Bit bo m Error! Bookmark not defined 1.6.4 Tớnh quy mụ ca RSVP Error! Bookmark not defined 1.7 Cu trỳc dch v cú phõn loi (Differentiated Services Architecture) Error! Bookmark not defined 1.7.1 Cu trỳc diffserv Error! Bookmark not defined 1.7.2 im mó dch v cú phõn loi (DSCP) Error! Bookmark not defined 1.7.3 Khi iu ho lu lng biờn mng Error! Bookmark not defined ii 1.7.4 c tớnh truyn theo chng (PHB) Error! Bookmark not defined 1.7.5 Chớnh sỏch phõn b ti nguyờn Error! Bookmark not defined CHNG 2: CC C CH THC HIN INTSERV V DIFFSERV P DNG CHO THIT BI NH TUYN CA CISCO Error! Bookmark not defined 2.1 B iu ho lu lng biờn mng: thit b phõn loi, ỏnh du v qun lý tc lu lng Error! Bookmark not defined 2.1.1 S phõn loi gúi Error! Bookmark not defined 2.1.2 ỏnh du gúi Error! Bookmark not defined 2.1.3 S cn thit ca vic qun lý tc lu lng Error! Bookmark not defined 2.1.3.1 Khng ch lu lng: s dng Tc truy cp cam kt (CAR) Error! Bookmark not defined 2.1.3.2 Ch tiờu phự hp lu lng Error! Bookmark not defined 2.1.3.3 Thit b o lu lng Error! Bookmark not defined 2.1.3.4 Chớnh sỏch hnh ng Error! Bookmark not defined 2.1.4 nh dng lu lng Error! Bookmark not defined 2.1.4.1 Thit b o lu lng dựng cho nh dng lu lng Error! Bookmark not defined 2.1.4.2 nh dng lu lng chung (GTS) v nh dng lu lng phõn b (DTS) Error! Bookmark not defined 2.2 Cỏc c ch xp lch cho gúi tin Error! Bookmark not defined 2.2.1 Xp hng Vo trc trc (FIFO) Error! Bookmark not defined 2.2.2 Nguyờn lý cp phỏt chia x cụng bng Max-Min Error! Bookmark not defined 2.2.3 Xp hng cụng bng (FQ) v Xp hng cụng bng cú trng s (WFQ) da trờn tớnh toỏn s th t Error! Bookmark not defined 2.2.4 Xp hng cụng bng cú trng s theo lung Error! Bookmark not defined 2.2.5 WFQ phõn tỏn theo tng lung (FlowBased Distributed WFQ-DWFQ) Error! Bookmark not defined 2.2.6 WFQ theo loi (Class-Based WFQ) Error! Bookmark not defined 2.2.7 Cỏc c ch xp hng WFQ khỏc Error! Bookmark not defined 2.2.7.1 Xp hng cụng bng cú trng s phõn tỏn DWFQ theo ToS Error! Bookmark not defined 2.2.7.2 Xp hng cụng bng cú trng s phõn tỏn DWFQ theo nhúm QoS Error! Bookmark not defined 2.2.8 Xp hng u tiờn (Priority Queuing PQ) Error! Bookmark not defined 2.2.9 Xp hng tu bin (Custom Queuing-CQ) Error! Bookmark not defined 2.2.10 Cỏc c ch xp lch cho lu lng thoi Error! Bookmark not defined 2.2.10.1 WFQ theo loi vi hng i u tiờn (PQ-CBWFQ) Error! Bookmark not defined 2.2.10.2 Xp hng tu bin vi cỏc hng i u tiờn (PQ-CQ) Error! Bookmark not defined 2.2.11 Xp hng s dng thut toỏn Round-Robin Error! Bookmark not defined iii 2.2.11.1 Round Robin theo trng s ci tin (Modified Weighted Round Robin - MWRR) Error! Bookmark not defined 2.2.11.2 Round Robin khu tr ci tin (Modified Deficit Round Robin MDRR) Error! Bookmark not defined 2.3 Cỏc c ch trỏnh tc nghn v chớnh sỏch loi b gúi tin .Error! Bookmark not defined 2.3.1 Khi ng chm giao thc kim soỏt truyn dn (TCP Slow Start) v Loi tr nghn Error! Bookmark not defined 2.3.2 Hot ng ca lu lng TCP mụ hỡnh loi b cui hng (TailDrop) Error! Bookmark not defined 2.3.3 Phỏt hin sm ngu nhiờn (RED): Qun lý hng i tớch cc trỏnh nghn mng Error! Bookmark not defined 2.3.4 Phỏt hin sm ngu nhiờn cú trng s (WRED) Error! Bookmark not defined 2.3.5 Phỏt hin sm ngu nhiờn cú trng s theo lung (Flow WRED) Error! Bookmark not defined CHNG 3: O KIM MT S C CH HOT NG CA DIFFERENTIATED SERVICE TRấN THIT B NH TUYN CISCO Error! Bookmark not defined 3.1 Kt qu o thụng s Diffserv Error! Bookmark not defined 3.1.1 Bi o Tc truy cp cam kt (CAR) Error! Bookmark not defined 3.1.2 Bi o kớch thc bursts bỡnh thng v vt quỏ Error! Bookmark not defined 3.1.3 Bi o chc nng Xp hng cú trng s theo loi (Class-Based Weighted Fair Queuing - CB-WFQ) Error! Bookmark not defined 3.1.4 Bi o WRED i vi ng truyn nghn nỳt c chai Error! Bookmark not defined 3.1.5 Bi o so sỏnh WFQ v PQ h tr lu lng EF Error! Bookmark not defined 3.2 p dng cỏc bi o Cht lng dch v cú phõn loi tiờu biu vo mng thc t ca Bu in thnh ph H Chớ Minh Error! Bookmark not defined 3.2.1 Mng IP ca Bu in thnh ph H Chớ Minh Error! Bookmark not defined 3.2.2 Bi o c ch Tc truy cp cam kt (CAR) Error! Bookmark not defined 3.2.3 Bi o chc nng Xp hng cú trng s theo loi (CB-WFQ) - cỏch ly lu lng (traffic isolation) Error! Bookmark not defined 3.2.4 Bi o WRED i vi ng truyn nghn nỳt c chai Error! Bookmark not defined 3.2.5 Bi o so sỏnh WFQ v PQ h tr lu lng EF Error! Bookmark not defined KT LUN Error! Bookmark not defined Ti liu tham kho iv M U Mng vin thụng hin i ngy ang phỏt trin mt cỏch mnh m c v quy mụ cng nh cụng ngh Vit Nam, cựng vi mc tng trng chúng mt ca thuờ bao in thoi l t l ngi dựng Internet bng thụng rng Lm vic v gii trớ, giao tip trờn mụi trng mng Internet núi riờng v mng IP núi chung ang l hỡnh thc giao tip hiu qu v thun tin nht Xu hng hi t tt c cỏc dch v vin thụng lờn nn tng IP ó c d oỏn v ang c kim chng ti Vit Nam Cỏc dch v trờn nn IP rt a dng: t gi th in t, truy cp web, thng mi in t n truyn file, mng riờng o, thoi VOIP, truyn hỡnh trc tuyn, truyn hỡnh hi ngh Trc s bựng n v s lng v chng loi dch v thụng tin trờn mng IP, cỏc nh sn xut v cung cp mng ngy cng phi chỳ ý n cht lng dch v Ngoi vic tng cng u t thit b mi cung cp dch v, mt vic ht sc cn thit l s dng h tng mng mt cỏch hiu qu Cỏc k thut Cht lng dch v QoS c a nhm mc ớch ny Thc cỏc k thut v khỏi niờm IP QoS ó xut hin t rt lõu nhng phi n nhng nm gn õy nú mi c thc s chỳ ý n Lý l ban u, lu lng trờn mng Internet rt ớt, ch gm cỏc dch v nh email, truyn file v truy cp web õy l nhng dch v bng hp, dựng ớt di thụng v khụng phi l dch v thi gian thc Ngy nay, s lng dch v ó tng lờn rt nhiu, bao gm c dch v truyn thng v cỏc dch v ũi hi thi gian thc nh VOIP v hi ngh truyn hỡnh Cỏc nh cung cp dch v phi tỡm mi cỏch tho khỏch hng v lu lng thụng tin v cht lng thụng tin Cỏc k thut QoS cú th m nhim vic m bo cht lng thụng tin cng nh s dng hiu qu nht bng thụng ca mng Mt mng dự c trang b bng thụng ln cng cn phi cú nhng chớnh sỏch QoS thớch hp cõn bng nhu cu gia cỏc loi dch v Trc nhng nhu cu ca thc t khai thỏc hnh mng nh vy, tụi ng ký ti nghiờn cu v cỏc k thut m bo cht lng dch v QoS Ni dung ca ti ny l tỡm hiu cỏc mụ hỡnh v QoS mng IP v ng dng trờn mng Vin Thụng Vit Nam, ú l mụ hỡnh N lc cao nht (Best effort), mụ hỡnh Dch v cú bo m (Integrated Service) v mụ hỡnh Dch v phõn bit (Diffrentiated Service) c bit chỳ ý n mụ hỡnh Dch v phõn bit vỡ nú cú th ỏp ng cht lng dch v quy mụ ln Mc tiờu ca ti l: Tỡm hiu tt c cỏc k thut ca mụ hỡnh Dch v cú phõn loi cú th ng dng mụ hỡnh ny mt cỏch tt nht trờn mng li Vit Nam Trờn c s cỏc hiu bit v QoS, ti cng cp n mt s bi o cht lng dch v trờn nn tng Dch v phõn bit cho mng IP ca Bu in thnh ph H Chớ Minh Do thi gian nghiờn cu cũn hn ch nờn mt s cha c cp chi tit , vỡ vy lun chc s khú trỏnh cỏc thiu sút Tụi mong nhn c s quan tõm v úng gúp ý kin ca cỏc thy, cụ v cỏc bn ng nghip hon thin ti ny Xin cỏm n 1 CHNG 1: S PHT TRIN CA MNG INTERNET V YấU CU V CHT LNG DCH V - CC Mễ HèNH CHT LNG DCH V (QoS) 1.1 Gii thiu mng Internet v cht lng dch v IP (IP QoS) Mng IP ln nht l mng Internet ton cu Internet phỏt trin vi tc chúng mt sut vi nm gn õy cựng vi mt s lng ln cỏc ng dng trờn nn tng Internet Khi Internet v cỏc mng intranet tip tc phỏt trin, nhiu ng dng khỏc ngoi d liu truyn thng nh thoi trờn nn IP (VoIP) v hi ngh truyn hỡnh (video-conferencing) cng xut hin theo ú Ngy cng nhiu ng dng v ngi dựng hng n Internet mi ngy, vỡ vy, Internet cn cú chc nng h tr cht lng cỏc dch v hin cú cng nh tng lai Dch v ph bin nht m Internet cung cp hin l dch v n lc cao nht (besteffort) Dch v best-effort khụng bo m gúi c chuyn giao n ni nhn no hoc cú chuyn n hay khụng, ú cỏc gúi thng xuyờn b loi b lỳc nghn mng Trong mt mng, thụng thng cỏc gúi theo tng lung (flow) c phõn bit bi nm trng mo u gúi IP: a ch IP ngun, a ch IP ớch, trng phng thc IP, cng ngun, v cng ớch Mt lung riờng l c to bi cỏc gúi xut phỏt t mt ng dng trờn mt mỏy ngun n mt ng dng trờn mt mỏy ớch, v cỏc gúi thuc mt lung mang cỏc giỏ tr nm trng mo u ging h tr lu lng thoi, v video, v ng dng d liu vi cỏc yờu cu dch v khỏc t mng, cỏc h thng ti mng lừi IP cn phõn bit v ỏp ng cỏc dng lu lng khỏc da trờn c s nhu cu ca chỳng Tuy nhiờn,vi dch v best-effort, khụng th phõn bit s hng nghỡn lung lu lng tn ti mng lừi IP Vỡ vy, khụng cú mc u tiờn hay s m bo cho bt c lung lu lng ng dng no iu ny hn ch c bn kh nng ca mng IP truyn lu lng mng ú ch cú mt ngun ti nguyờn hn ch cựng vi cỏc yờu cu kốm theo v bo m dch v Cht lng dch v IP nhm gii quyt ny Cỏc chc nng IP QoS hng n vic cung cp cỏc dch v c m bo v a dng bng cỏch trao cho nh khai thỏc mng quyn kim soỏt v cỏch s dng ti nguyờn mng Internet QoS l mt hp cỏc yờu cu dch v m mng phi ỏp ng truyn mt lung QoS cung cp s bo m dch v t im u n im cui (end-to-end) v s iu khin cỏc phng phỏp hnh mng IP, nh cỏc c ch cp phỏt ti nguyờn, chuyn mch, nh tuyn, xp lch v loi b gúi Mt s li ớch chớnh ca IP QoS: - Giỳp cỏc mng cú th h tr cỏc yờu cu dch v v ng dng multimedia hin cú cng nh ang xut hin Cỏc ng dng mi nh Voice over IP (VoIP) s cú c cỏc yờu cu QoS rừ rng c th i vi mng - Cho phộp nh hnh mng iu khin ti nguyờn mng v cỏch thc s dng chỳng - Cung cp s m bo dch v v s phõn bit lu lng trờn mng iu ny cn thit hi t lu lng thoi, video v d liu trờn mt mng IP nht - Nú cho phộp cỏc nh cung cp dch v a thờm cỏc dch v cht lng cao cựng lỳc vi cỏc dch v best-effort hin ti Nh cung cp cú th phõn loi cỏc dch v cht lng cao ca h thnh cỏc mc vớ d nh mc Bch kim, Platinum, Vng hay Bc, v t cu hỡnh mng theo ú phõn bit cỏc loi dch v khỏc núi trờn - QoS úng vai trũ ch cht vic a nhng dch v mng mi nh Mng riờng o (VPNs) 1.2 Lch s cht lng dch v giao thc Internet (IP QoS) IP QoS khụng phi l mi xut hin Cỏc nh sỏng ch Internet ó sm nhn thy s cn thit ny v a mt byte cú tờn gi Dng dch v (ToS) mo u IP lm cho QoS tr thnh mt phn c im k thut IP ban u Mc ớch ca byte ToS c miờu t nh sau: Dng dch v th hin nhng thụng s túm tt ca cht lng dch v mong mun Nhng thụng s ny c s dng hng dn la chn cỏc thụng s dch v thc t truyn mt datagram qua mt mngc th [5] Cho n cui nhng nm 1980, Internet cũn mc nghiờn cu v ch cú mt ớt dch v v lu lng thụng tin Vỡ vy, s h tr ToS khụng úng vai trũ quan trng, v hu ht tt c cỏc trin khai mng IP u b qua byte ToS Nhng ng dng IP khụng ỏnh du rừ byte ToS, v cỏc router cng khụng s dng nú iu khin cỏch thc chuyn tip gúi IP Tm quan trng ca QoS trờn Internet ó tng lờn cựng vi s phỏt trin ca Internet t n mc ph bin v thng mi nh hin Mng Internet da trờn c s dch v gúi endto-end khụng kt ni thng cung cp cỏc cụng c truyn ti best-effort (n lc cao nht), dựng b Giao thc iu khin truyn dn/Giao thc Internet (TCP/IP) Mc du thit k khụng kt ni cung cp cho mng Internet tớnh linh hot v mnh m, s linh hot ca gúi tin ca nú cng l nguyờn nhõn ca hin tng tc nghn, c bit ti cỏc router kt ni cỏc mng vi rt nhiu di thụng khỏc Tp hp cỏc chc nng QoS ban u c thit lp cho cỏc host Internet Mt ln i vi nhng kt ni mng din rng (WAN) cú giỏ thnh cao l vic kớch thc mo u quỏ ln so vicỏc gúi TCP nh c to bi nhng ng dng nh telnet v rlogin Thut toỏn Nagle ó gii quyt ny v ngy c h tr bi tt c cỏc ng dng host IP Thut toỏn Nagle bỏo trc s i ca chc nng QoS Internet mng IP [4] Vo nm 1986, Van Jacobson phỏt trin hp tip theo cỏc cụng c QoS Internet ú l c ch trỏnh tc nghn cho h thng u cui, c ch ny ang c s dng nhng ng dung TCP Nhng c ch ny l ng chm v trỏnh tc nghn, v chỳng ó h tr rt ln vic ngn chn s sp mng tc nghn ca Internet hin Chỳng bc u khin cỏc lung TCP cú kh nng ỏp ng nhng tớn hiu bỏo tc nghn (nhng gúi b mt) mng Hai c ch na l tỏi truyn nhanh v khụi phc nhanh c b sung thờm vo nm 1990, cung cp hot ng ti u thi on mt gúi 4 Mc dự nhng c ch QoS h thng u cui l yu t cn thit, chỳng khụng lm nờn QoS end-to-end cho n nhng c ch tng xng c ng dng vo cỏc router truyn ti lu lng d liu gia cỏc h thng u cui Vỡ vy, khong nm 1990, QoS trung vo cỏc router Nhng router ch cú c ch xp hng vo trc, trc (FIFO) thỡ th khụng cung cp c ch phõn loi v cp u tiờn cho lu lng Xp hng FIFO gõy loi b cui hng (tail drop) v khụng bo v c nhng lung ang hot ng chun nhng lung hot ng khụng chun WFQ, mt thut toỏn xp lch gúi, v WRED, mt thut toỏn qun lý xp hng, c chp nhn rng rói lpbự p nhng khim khuyt ca mng ng trc Internet S phỏt trin ca QoS Internet tip tc vi nhng n lc tiờu chun hoỏ vic cung cp QoS end-to-end trờn Internet Nhúm hot ng IETF (Internet Engineering Task Force) v dch v cú bo m hng ti cung cp cỏc cụng c cho cỏc ng dng th hin nhng yờu cu ti nguyờn end-to-end vi nhng c ch h tr cỏc router v nhng cụng ngh mng RSVP l mt giao thc bỏo hiu cho mc tiờu ny Mụ hỡnh dch v cú bo m (inteserv) ũi hi cỏc trng thỏi theo tng lung dc theo tuyn kt ni, ú intserv khụng th m rng quy mụ mng ng trc Internet, ni phc v hng nghỡn lung ti mt thi imbt k Byte ToS IP khụng c s dng nhiu quỏ kh, nhng nú li c tng cng s dng sau ny nh mt cỏch bỏo hiu QoS Byte ToS ó tr thnh mt k thut ban u cho vic cung cp dch v cú phõn loi (diffserv) trờn Internet, v phc v mc ớch ny, nhúm hot ng ITEF diffserv ó tiờu chun hoỏ vic s dng TOS nh l byte dch v cú phõn loi 1.3 Cỏc thc o thụng s hnh S trin khai QoS nhm mc ớch cung cp mt kt ni vi nhng gii hn hot ng no ú t mng rng bng thụng, tr v trt gúi tin, mt gúi l nhng thc o ph bin c s dng mụ t hnh ca kt ni mng Chỳng c miờu t nhng phn sau õy 5 Ti liu tham kho F Faucheur (2001), Mpls support of differentiated services, Internet Draft, IETF Gilbert Held (2000), Managing TCP/IP network: techniques, tools, and security considerations, John Wiley & Sons H Jonathan Chao, Xiaolei Guo (2002), Quality of Service Control in HighSpeed Networks, John Wiley & Sons J Nagle (1984), RFC 896, "Congestion Control in IP/TCP Internetworks" J Postel (1981), RFC 791: "Internet Protocol Specification," K Nichols and others, RFC 2474, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers" Peter Massam (2003), Managing service level quality across wireless and fixed networks, John Wiley & Sons S Shenker, C Partridge, and R Guerin (1997), RFC 2212, "Specification of Guaranteed Quality of Service" Vilho Raisanen (2003), Implementing Service Quality in IP Networks, John Wiley & Sons 10 Cisco.com, Introduction to IP QoS 11 Cisco.com, DiffServ - The Scalable End-to-End QoS Mode 12 Cisco.com, Cisco IOS Quality of Service Solutions Configuration Guide 13 www.Juniper.net, Supporting differentiated service classes in large IP networks 14 http://www.ietf.org/rfc/rfc1633.txt, Integrated Services Architecture 15 http://www.ietf.org/rfc/rfc2001.txt, "TCP Slow Start, Congestion Avoidance, Fast Recovery, and Fast Recovery Algorithms," 16 http://www.ie tf.org/rfc/rfc2210.txt, The use of RSVP for Integrated Services 17 http://www.ietf.org/rfc/rfc2475.txt, An Architecture for Differentiated Services 6 18 http://www.ietf.org/rfc/rfc2597.txt, Assured Forwarding (AF) PHB 19 http://www.ietf.org/rfc/rfc2598.txt, An Expedited Forwarding per-hop behavior (PHB) 20 http://www.cnaf.infn.it/~ferrari/tfng/ds/ [...]... of differentiated services”, Internet Draft, IETF 2 Gilbert Held (2000), Managing TCP/IP network: techniques, tools, and security considerations, John Wiley & Sons 3 H Jonathan Chao, Xiaolei Guo (2002), Quality of Service Control in HighSpeed Networks, John Wiley & Sons 4 J Nagle (1984), RFC 896, "Congestion Control in IP/TCP Internetworks" 5 J Postel (1981), RFC 791: "Internet Protocol Specification,"