hn tin bn Ngocanhwdm ni vQoS, trong bi vit nh ny ti trnh by hiu bit ca mnh v vn QoStrong mng GPON.Thc cht vicQoSngay trong GPON phc tp c th ni kh hn khi so snh vi vic mappingQoSvi cc mng bin v mng li.

GPON quy nh nhiu phn khc nhau nh:ITU-T984.4 OMCI quy inh v vic cnh bo qun l trong GPON, 983.2 quy inh v cc lp vt l ni chung nh in th quang, ngun quang, v.v; 984.1 quy inh v cc c tnh trung GPON,Vn mun cp y chnh l 984.3 quy nh v lp truyn ti, ti u truyn dn trnh cho xung t trong cc mng quang, lin quan mt thit tiQoS.Nh cc bn nghin cu GPON bit, GPON s dng phng thc truyn im a im theo chiu xung t OLT ti ONT.- Theo chiu xung cc gi tin c lc ti ONT nh theo Port ID (PhtBroadcastv lc nh Port ID).- Theo chiu ln th phc tp hn nhiu, vic chuyn gi tin s theo phng thc a im im do vy cn phi c phng thc trnh xung t trong vic truyn ln.ITU-T984.3 quy inh s dng phng thcTDMAcho chiu ln. OLT s quy inh cc ca s truyn tin cho mi ONT, v vic cp pht cc ca s tin ny c thc hin bi OLT theo phng thc t ng da theo vic tin liu lu lng ca nh cung cp dch v v da theo kh nng phn tch bng thng ca thit b tu thuc gii php ca mi hng a ra (ti s quay li phn ny trong bi vit sau).Quay tr li vn QoS, trc tin l nhng khi nim c bn ca GPONGEM l g: y l t vit tt ca GPON Encapsulation Method, phng thc GEM quy inh vic truyn tin cng nh dch v trong mng quang th ng.GEM quy nh nh sau:- n v nh nht ch cc khung tin trong GPON l GEM Port, phn bit cc GEM port khc nhau da trn GEM port ID. Nu bn no cATMri th GEM port ID khng khc g VCs trong ATM- n v ln hn GEM port l T-CONT y l thnh phn c th ni l quan trng nht, T-CONT (Transmission Containers) l n v iu khin nh nht trong mng GPON.

Hnh v di y gip cho cc bn mng tng c GPON, GEM, T-CONT

Nh cp pha trn, GEM Port l thnh phn nh nht chuyn ch thng tin trong GPON, T-CONT l thnh phn iu khin, mt T-CONT cha ng nhiu GemPort ID, nhiu T-CONT s truyn ng thi trn mt si quang.Vy vic cung cpQoScng nh vic cam kt bng thng cho tng thu bao thc hin bng cch no.1. Thc hin bi vic tin liu thu bao v bng thng cam kt vi mi thu bao ca cc Operator.2. Thc hin bi vic cung cp bng thng mm do bi OLT.

Vn u tin, khi cc thu bao ng k dch v cc nh cung cp dch v u cam kt tc cho tng khch hng, cc khi nim CIR,EIR, AIR, delay, c cp ti y. n gin ti khng nh ngha m a ra v d

CIR: Nh cung cp dch v cam kt mt ng leased-line 2 M cho user A (User VIP). CIR (Committed Information Rate). Tc 2M s lun c duy tr trong mi trng hp, ngay c thu bao khng s dng bng thng ny.

Khi nimEIR(Excess Information Rate) Khi nim ny gn ging nh vic cc operators ang c x vi cc thu baoADSL, v d nh dch vInternetnh cung cp cam kt s cung cp cho down 2M v up 1M, nhng tc ny ch t c khi trn mng bng thng v khng phi chia s vi ai, cn nu nh c nhiu thu bao th bng thng cho mi user ch l vi trm Kbps.

Khi nim AIR: thng dng cho cc thu bao cao cp hnADSLmt cht v d cc thu bao cho dch v IPTV chng hn: gi s h thu mt ng 3M nhng h ch s dng c 2 M, vy 1M cn li c th c nh cung cp dch v s dng cho cc thu bao khc

C th cc bn thy ti gii thch di dng nhng y chnh l nhng khi nim u tin xc nhQoStrong GPON.Ngoi cc khi nim quy nh v tc lin quan ti AIR, CIR,EIR, mt khi nim khc cn nhc ti l delay time.V d n gin th ny:Trong cuc gi thoi qua mng GPON, tr khng c di 1ms, tc truyn l 150 Kbps. Do vy trong 1ms, khng c mt 150 kbpsx1ms = 150 byte (thc ra khi nim delay kh phc tp ty thuc vo code, v.v v d trn ch c ngha minh ha).

T cc thng s AIR, CIR,EIR, Delay Time, cc loi T-CONT tng ng c hnh thnh, theoITU-T984.3 c 5 loi T-CONT c quy nh. OLT ca cc hng phi h tr c 5 loi OLT ny.Hnh v tng ng sau: