I HC NNG TRNG I HC BCH KHOA KHOA IN T - VIN THNG

TI:

MT S K THUT NNG CAO CHT LNG DCH V QoS TRONG MNG IPNGI THC HIN LP NGI HNG DN : NG TH TRANG : 06DT3 : GVC. ThS. NGUYN DUY NHT VIN

NNG, NM 2011

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NI DUNG

Gii thiu v QoS M hnh cht lng dch v Mt s k thut hng i iu khin tc ng Thut ton lp lch hng i Thut ton qun l hng i M phng trn NS2

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GII THIU V QoS Cht lng dch v l c ch, cng c m bo cho cc mc dch v tha mn cc yu cu v: Bng thng (BW) tr (Delay) trt (Jitter) mt gi (Packet Loss)

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M HNH CHT LNG DCH V Dch v tch hp Intergratd Service(IntServ). Cung cp cc ng dng thi gian thc trn mng IP. Hot ng theo tng lung. S dng giao thc d tr ti nguyn RSVP. u: Cung cp dch v tt nht. Nhc: Phc tp, t tin. Khng c kh nng m rng.

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DCH V PHN BIT (DIFFSERV) Dch v phn bit Differentiated Service (DiffServ): Trng m dch v phn bit DSCP

u im : n gin v c kh nng m rng.5

MT S K THUT HNG I IU KHIN TC NGHN Mt s thut ton lp lch hng i: - Lp lch hng i phn phi cc gi vo cc hng i u tin khc nhau v lp lch cho chng. Bao gm: Hng i vo trc ra trc FIFO. Hng i u tin PQ. Hng i tun t CQ. Hng i cn bng trng s WFQ. Mt s thut ton qun l hng i: - Qun l hng i a ra phng php nh rt gi tin. Gm: Thut ton loi b ui drop-tail. Thut ton loi b sm ngu nhin RED. Thut ton CHOKe. Thut ton Blue.6

THUT TON LP LCH HNG I Hng i vo trc ra trc FIFO (First In First Out).

u: n gin, nhanh. Nhc: Phn phi bng thng khng cng bng.7

THUT TON LP LCH HNG I Hng i u tin PQ (Priority Queuing).

u: - Dch v cn c u tin c phc v tt nht. Nhc: - Cc gi hng i u tin thp c th khng bao gi c phc v.8

THUT TON LP LCH HNG I Hng i tun t CQ (Custom Queuing) :

u: - Cc hng i u c phc v. Nhc: Phn trm bng thng c chia khng chnh xc. jitter cao. Cu hnh khng t ng.

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THUT TON LP LCH HNG I Hng i cn bng trng s WFQ (Weighted Fair Queuing)

u: - Cu hnh t ng. - Cp bng thng cng bng v c u tin. - Tn dng bng thng. Nhc: - Kh phc tp.

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THUT TON QUN L HNG I Thut ton b ui (Tail drop):

u: n gin. Nhc: - Mt s lung chim gi hng i ngn cc lung khc i vo hng i. - Gy ng b trn cc lung TCP.

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THUT TON QUN L HNG I Thut ton loi b sm ngu nhin (RED).

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THUT TON QUN L HNG I Thut ton loi b sm ngu nhin (RED) Da trn tnh ton kch thc hng i trung bnh nh gi tc nghn v gi thng bo phn hi. - Pht hin sm, trnh tc nghn. - Trnh ng b trn cc lung TCP. - iu khin c kch thc hng i trung bnh. - Tnh ton phc tp v nhiu thng s cn cu hnh ph hp vi tng mng khc nhau.

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THUT TON QUN L HNG I Thut ton CHOKe:

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THUT TON QUN L HNG I Khi c nghn th: Cc lung lu lng p ng khi nhn c thng bo nghn s gim tc gi d liu. Cc lung lu lng khng p ng vn tip tc gi d liu nh bnh thng. => Cc lung khng p ng chim bng thng nhiu hn. CHOKe: Chn v gi nhng lung lu lng p ng. Chn v loi b nhng lung khng p ng. => Hot ng tng t RED nhng vi mt iu chnh thng minh m phn phi bng thng cng bng hn.15

THUT TON QUN L HNG I Thut ton Blue :Da trn mt gi : if ((now-last_update) > freeze_time) then Pm = Pm + 1 Last_update = now Da trn kt ni ri : if ((now last_update) > freeze_time) then Pm = Pm 2 Last_update = now Trong : Pm : xc sut nh du gi freeze_time: thi gian ng bng 1 : lng tng Pm 2 : lng gim Pm16

THUT TON QUN L HNG I Thut ton Blue : - Thut ton RED s dng kch thc hng i trung bnh nh gi tc nghn v gi thng bo phn hi l khng hiu qu v kch thc hng i trung bnh thay i lin tc. - Blue nh gi tc nghn trc tip trn mt gi v kh dng lin kt, nh tc gi lai thng bo phn hi hiu qu hn. - Blue tnh ton n gin hn so vi RED.

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M PHNG TRN NS2 Mc ch m phng: nh gi hiu qu ca thut ton RED v Blue. M hnh mng m phng:

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M PHNG TRN NS2 S gi rt ca Blue v RED:

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M PHNG TRN NS2Kch thc hng i RED: Kch thc hng i Blue:

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M PHNG TRN NS2 T kt qu m phng nhn thy: S gi rt ca Blue l t hn ca RED. Kch thc hng i ca Blue l nh hn RED. Vic gi cho kch thc hng i nh mang li nhng li ch: Gip b m cn d khong trng tip nhn cc gi tip tc i vo hng i. Gip hng i tip nhn cc lung lu lng bng n thay v loi b chng. Lm gim tr v jitter cho cc gi khi xp hng trong hng i. Nh vy vi mt thut ton n gin hn nhng Blue li hot ng hiu qu hn RED.21

KT LUN Cc c ch hng i tc ng vo cc tham s cht lng dch v. Cc thut ton lp lch nhm cung cp u tin v phn phi bng thng v thi im truyn tin cho cc mc dch v. Cc thut ton qun l hng i a ra cc phng php nh rt gi phng trnh v gii quyt tc nghn nh m nng cao cht lng dch v. Mi thut ton u c u, nhc im v gii quyt nhng kha cnh khc nhau. Vic tm ra mt thut ton n gin v hiu qu l v cng cn thit v cn nghin cu lu di.

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XIN CM N QU THY C V CC BN LNG NGHE !

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