Cac Thuat Toan Va Dinh Tuyen Trong Mang 5201

7/31/2019 Cac Thuat Toan Va Dinh Tuyen Trong Mang 5201

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TRNG I HC BCH KHOA H NI

VIN IN T VIN THNG

********** **********

BI TP L NMN HC: TCH C V QUY HOCH MNG VIN THNG

ti:Cc Thut Ton V Phng Thc nh Tuyn Trong Mng

Ging vin h ng dn: Nguyn Vn Thng

Nhm sinh vin thc hin:

Hv tn SHSV L p

H NI 4/2012


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M c L c I. M u ..................................................................................................................... 3 II. Ni dung.............................................................................................................. 4

1.

Gi i thiu v nh tuyn: ............................................................................... 4

2. Cc khi nim trong l thuyt graph:........................................................... 5 3. Phn loi nh tuyn : .................................................................................... 8

3.1. nh tuyn tnh:......................................................................................... 8 3.2. nh tuyn ngu nhin (random routing):.............................................. 9

3.2.1. nh tuyn ngu nhin lan trn gi (flooding): .................................... 9 3.2.2. nh tuyn ngu nhin (random walk): .............................................. 11 3.2.3. nh tuyn ngu nhin (hot potato): ................................................... 11

3.3. nh tuyn ng (dynamic routing):..................................................... 12 3.3.1. nh tuyn ng (minimum spanning tree): ....................................... 13 3.3.2. nh tuyn ng (shortest path tree): ................................................. 13

4. Cc thut ton dng nh tuyn: ........................................................... 14 4.1. Thut ton Prim: ..................................................................................... 14 4.2. Thut ton Kruskal:................................................................................ 17 4.3. Thut ton Dijkstra:................................................................................ 19

4.4. Thut ton Bellman Ford:...................................................................... 20 5. Mt sgiao thc nh tuyn ng hin nay:.............................................. 21 5.1. Giao thc nh tuyn RIP (Routing Information Protocol):.............. 22 5.2. OSPF (Open Shortest Path First):......................................................... 23 5.3. EIGRP (Enhanced Interior Gateway Routing Protocol):.................... 25

III. Kt lun ............................................................................................................. 27 IV. Ti liu tham kho ........................................................................................... 28


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I. M uMt trong nhng hot ng ca mng ni chung l vic truyn d liu t ngun t i

ch. nh tuyn l mt chc nng khng thtch r i ca mng khi truyn d liuh tngunti ch v c ngha c bit quan trng trong vic thit kv ti u mng. Cu trc mng,gii php cng ngh v phng php nh tuyn l 3 vn lin quan mt thit v i nhau vquyt nh cht l ng hot ng ca mng. Chnh v vy, bi ton nh tuyn cn c quantm nghin cu nhm ti u ha hiu sut sdng ti nguyn mng.

Trn thgii c nhiu nghin cu vcc phng php nh tuyn, v i mc chchyu l tm ra nhng phng php nh tuyn thch hp p dng vo thc tmng

l i. Trong th i gian gn y, xuhng nh tuyn theo gitrn mng tr thnh mtch nghin cu quan trng. Thng th ng, l i ch mang li trn mng c ti a bngvic ti u ha cc hm mc tiu. Ty thuc vo cu trc v cc ng truyn trn mngm cc hm mc tiu v rng buc i theo skhc nhau.


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II. Ni dung

1. Gi i thiu v nh tuyn:

nh tuyn l qu trnh tm ng i truyn ti thng tin trong lin mng tngunn ch. N l mt chc nng c thc hin tng mng. Chc nng ny cho phprouternh gi cc ng i sn c ti ch. nh gi ng i, nh tuyn sdng cc thngtin vTopology ca mng. Cc thng tin ny c th do ng i qun tr thit lp. Qu trnhnh tuyn cn tha mn cc yu cu cho tr c bao gm: ng i ngn nht hoc c bngthng rng nht. ng i th ng phi ti utheo mt trong hai tiu ch.cc gi tin c th

c gi i theo ng ny. Nhng cng c th chng c gi i ng th i trn nhiu ng . Vic nh tuyn c s dng cho nhiu loi mng: mng vin thng, lin mng,internet, mng giao thng.

Hnh 1: Tm ng i tip theo

nh tuyn c th c chia ra lm 3 phng php nh tuyn: nh tuyn tnh, nhtuyn ngu nhin v nh tuyn ng. Trong mi tr ng mng th ng xuyn c s thayingu nhin nn nh tuyn tnh ch c ngha cc gateway v cc mng nh.

Trong nh tuyn ng, c hai phng thc nh tuyn: tm ng theo ng ingn nht v tm ng i ti u.


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Vn tm ng i ngn nht c t ra: ta c th tm ng i ngn nht tmtnt n tt ccc nt khc hoc tm ng i ngn nht tmt nt n mt nt cth. Cchgii quyt ny c s dng trong giao thc OSPF(Open Shortest Path First) v i vic s

dng cc thut ton Dijikstra, Bellman-Ford.Ngoi ra ta c th cc nt mng t ng tm ra ng i ti u. Vic tim ra tuyn

i c thc hin mt cch phn tn ti cc nt chkhng do mt nt trung tm tnh ton.Cc nt ch ng trao i thng tin lin quann cu hnh mng v i nhau. Tcc thng tinthu thp c mi nt t tm ra ng i ti u n cc nt khc ri lp ra bng nh tuyna ra quyt nh nh tuyn. Bng nh tuyn thng xuyn c cp nht mi khi c thay

i cu hnh mng. Thut ton c sdng l Prime v Kruskal nhm to ra cy bc cuti thiu.

2. Cc khi nim trong l thuyt graph:

Phn ny gii thiu cc thut ng v cc khi nim c bn nhm m t cc mng, grapv cc thuc tnh ca n. L thuyt graph l mt mn hc xut hin t lu, nhng l thuyt nc mt s thut ng c chp nhn khc nhau dng cho cc khi nim c bn. V th c th s

dng mt s thut ng khc nhau lp m hnh graph cho mng. Cc thut ng c trnh bdi y ny l cc thut ng c cng nhn v c s dng thng xuyn chngny.

Mtgraph G, c nh nghi bi tp hp cc nhV v tp hp cc cnh E . Cc nhthng c gi l ccnt v chng biu din v tr (v d mt im cha lu lng hoc mtkhu vc cha thit b truyn thng). Cc cnh c gi l cclin kt v chng biu din phng tin truyn thng. Graph c th c biu din nh sau:

G=(V, E)


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Hnh 2 l mt v d ca mt graph.

Hnh 2: Mt graph n gin

Mc d theo l thuyt,V c th l tp hp rng hoc khng xc nh, nhng thng

thngV l tp hp xc nh khc rng, ngha l c th biu din V={v i | i=1,2,......N}

Trong N l s lng nt. Tng t E c biu din:

E={e i | i=1,2,......M}

Mt lin kt,ej, tng ng mt kt ni gia mt cp nt. C th biu din mt lin ktej gia nti vk bi

e j=(v i ,vk )

hoc bi

e j=(i,k)

Mt lin kt gi l i ti mt nt nu nt l mt trong hai im cui ca lin kt. Nti vk gi lk nhau nu tn ti mt lin kt (i, k ) gia chng. Nhng nt nh vy c xem lcc ntlng ging. Bc ca nt l s lng lin kt i ti nt hay l s lng nt lng ging. Hakhi nim trn l tng ng nhau trong cc graph thng thng. Tuy nhin vi cc graph cnhiu hn mt lin kt gia cng mt cp nt, th hai khi nim trn l khng tng nTrong trng hp , bc ca mt nt c nh ngha l s lng lin kt i ti nt .

Mt lin kt c th c hai hng. Khi th t ca cc nt l khng c nghi. Ngli th t cc nt c ngha. Trong trng hp th t cc nt c ngha, mt lin kt c thc xem nh l mtcung v c nh ngha

a j=[v i ,vk ]


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hoc n gin hn

a j=[i,k]

k c gi lcn k hng ra i vii nu mt cung [i,k ] tn ti vbc hng ra cai l s lng cc cung nh vy. Khi nimcn k hng vov bc cn k hng vo cngc nh ngha tng t.

Mt graph gi l mtmng nu cc lin kt v cc nt c mt trong lin kt c cc thuctnh (chng hn nh di, dung lng, loi...). Cc mng c s dng m hnh cc vncn quan tm trong truyn thng, cc thuc tnh ring bit ca nt v lin kt th lin quan cc vn c th trong truyn thng.

S khc nhau gia cc lin kt v cc cung l rt quan trng c v vic lp m hnh chomng ln qu trnh hot ng bn trong ca cc thut ton, v vy s khc nhau cn phi luc phn bit r rng. V mt hnh hc cc lin kt l cc ng thng kt ni cc cp nt cc cung l cc ng thng c mi tn mt u, biu din chiu ca cung.

Mt graph c cc lin kt gi lgraph v hng, tuy nhin mt graph c cc cung gi lgraph hu hng. Mt graph hu hng c th c c cc lin kt v hng. Thng thng ,

cc graph c gi s l v hng, hoc s phn bit l khng c ngha. C th c kh nng xy ra hin tng xut hin nhiu hn mt lin kt gia cng mt

nt (iu ny tng ng vi vic c nhiu knh thng tin gia hai chuyn mch). Nhng lin knh vy c gi l cclin kt song song. Mt graph c lin kt song song gi l mtmultigraph.

Cng c kh nng xut hin cc lin kt gia mt nt no v chnh nt . Nhng li

kt c gi l ccself loop. Chng t khi xut hin v thng xut hin do vic xem hai ntnh l mt nt trong qu trnh lp m hnh graph cho mt mng hoc pht sinh trong qu trnhthc hin mt thut ton c vic hp nht cc nt. Hnh 4.2 minh ho mt graph c cc lin ksong song v cc self loop. Mt graph khng c cc lin kt song song hoc cc self loop gi lmtgraph n gin. Vic biu din v vn dng cc graph n gin l tng i d dng, vvy gi thit rng cc graph c xem xt l cc graph n gin. Nu c s khc bit vi gthit ny, chng s c ch ra.


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3. Phn loi nh tuyn:

Hnh 3: Phn loi nh tuyn

3.1. nh tuyn tnh:

i vi nh tuyn tnh cc thng tin v ng i phi do ng i qun tr mng cpnht cho cc router. Khi cu trc mng c bt k thay i no th chnh ng i qun trmngphi xa hoc thm cc thng tin v ng i cho cc router.Nhng loi ny gi l ngi c nh. i v i h thng mng nh, t c thay i th cng vic ny mt cng hn.Chnh v nh tuyn i hi ng i qun tr mng phi cu hnh mi thng tin v ng icho cc router nn n khng c c tnh linh hot nh nh tuyn ng. Trong nhng h thng mng l n, nh tuyn tnh th ng c s dng kt h p v i giao thc nh tuynng cho mt smc ch c bit.

Hot ng ca nh tuyn tnh c th chia lm 3 bc nh sau:

- u tin, ng i qun trmng cu hnh cc ng c nh cho cc router

- Router ci t cc ng i ny vo bng nh tuyn

- Gi dliu c nh tuyn theo cc ng i c nh ny


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Sau y l demo cu hnh ca mng nh tuyn tnh

Hnh 4: Demo cu hnh mng nh tuyn

3.2. nh tuyn ngu nhin (random routing):

3.2.1. nh tuyn ngu nhin lan trn gi (flooding):

Mt dng mnh hn ca nh tuyn ring bit l lan trn gi. Trong phng thcny, mi gi i n router s c gi i trn tt c cc ng ra tr ng m n i n.Phng thc lan trn gi ny hin nhin l to ra rt nhiu gi sao chp (duplicate). Trnthc t, s gi ny l khng xc nh tr khi thc hin mt s bin php hn chqutrnh ny. Mt trong nhng bin php l sdng b m b c nhy trong phn tiu ca mi gi. Gi tr ny sb gim i mt ti mi b c nhy. Gi sb loi bkhi b mt gi tr khng. Vmt l t ng, b m b c nhy sc gi tr ban u tng ng vi di tngun n ch. Nu nh ng i gi khng bit di ca ng i, nc th t gitr ban u ca b m cho tr ng h p xu nht. Khi gi tr ban u s c t bng

ng knh ca mng con. Mt k thut khc ngn slan trn gi l thm s th tvo


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tiu cc gi. Mi router scn c mt danh sach theo nt ngun ch ra nhng stht tngun c xem xt. trnh danh sch pht trin khng gi i hn, mi danh schs tng ln b i s m k ch ra rng tt ccc s th t n k c xem. Khi mt gi

i t i, rt ddng c thkim tra c gi l bn sao hay khng. Nu ng gi l bn saoth gi ny sb loi b. Tc l khi nhn c mi gi tin,nt mng sgi i tt cccnt kcn,tr nt g i gi cho n.Lan trn gi c u im l lan trn gilun lunchn ng ngn nht. C c u im ny l do v phng din l thuyt n chn ttc cc ng c th do n schn c ng ngn nht. Tuy nhinnhc imca n l s l ng gi g i trong mng qu nhiu. Sdng lan trn gi trong hu ht ccng dng l khng thc t. Tuy vy lan trn gi c thsdng trong nhngng dng sau.

Trong ng dng qun s , mng s dng phng thc lan trn gi gi cho mng lunlun hot ng tt khi i mt vi qun ch.

Hnh 5: nh tuyn lan trn gi

Trong nhngng dng c s d liu phn b, i khi cn thit phi cp nht tt c c s d liu. Trong tr ng hp sdng lan trn gi l cn thit. V dsdng lan trngi gi cp nht bn nh tuyn b i v cp nht khng da trn chnh xc ca bngnh tuyn. 40

Phng php lan trn gi c th c dng nh l n v so snh phng thcnh tuyn khc. Lan trn gi lun lun chn ng ngn nht. iu dn n khng cgii thut no c th tm c trngn hn. Mt bin i ca phng php lan trn gil lan trn gi c chn lc. Trong gii thut ny, router ch gi gi i ra trn cc ng mi theo hng ch. iu c ngha l khng gi gi n nhng ng m r rng nmtrn h ng sai


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3.2.2. nh tuyn ngu nhin (random walk):

Trong phng php nh tuyn ny, router schuyn gi i n trn mt ng ura c chn mt cch ngu nhin. Mc tiu ca phng php ny l cc gi lang thangtrong mng cui cng cng n ch. Vi phng php ny gip cho qu trnh cn bng tigia cc ng. Cng ging nh phng php nh tuyn lan trn gi, phng php nylun m bo l gi cui cng s n ch. So vi phng php tr c th snhn rng gitrong mng s t hn. Nhc im ca phng php ny l ng tngun n ch c th di hn ng ngn nht. Do tr ng truyn s di hn strngn nht thc s tn titrong mng.

- Gi tin c gi n mi u ra v i mt xc xut no - So v i flooding,s l ng gi truyn i nh hn - ng i ngn nht c thkhng nm trong s ng c chn

Hnh 6: nh tuyn ramdom walk

3.2.3. nh tuyn ngu nhin (hot potato):nh tuyn ring bit l loi nh tuyn m routerquyt nh nh tuyn i chd a

vo thng tin bn thn n l m lt c.y l mt thut ton tng thch ring bit (isolated adaptive algorithm). Khi mt

gi n mt nt, router scgng chuyn gi i cng nhanh cng tt bng cch cho nvo hng ch u ra ngn nht. Ni cch khc, khi c gi i n router stnh ton sgi c nm ch truyn tren mi ng u ra. Sau n sgn gi m i vo cui hng

ch ngn nht m khng quan tm n ng s i u. Hnh7 biu din cc hng ch


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u ra bn trong mt router ti mt thi im no . C ba hng ch u ra tng ng v i03 ng ra.Cc gi ang xp hng trn mi ng ch c truyn i. Trong v d y, hng ch n F l hng ch ngn nht v i ch c mt gi nm trn hng ch ny.

Gii thut khoai ty nng do s t gi mi n vo hng ch ny.

Hnh 7: nh tuyn ngu nhin

C thbin i t ng ny mt cht bng cch kt hp nh tuyn tnh v i giithut khoai ty nng. Khi gi i n, router s tnh n cnhng trng s tnh ca ngdy v di hng ch . Mt kh nng l sdng la chn tnh tt nht tr khi di hngch ln hn mt ngng no . Mt kh nng khc l sdng di hng ch ngn nhttrtrng s tnh ca n l qu thp. Cn mt cch khc lsp xp cc ng theo trng s tnh ca n v sau li sp xp theo di hng ch ca n. Sau schn ng ctng v tr sp xp l nhnht. D gii thut no c chn i chng na cng c c tnhl khi t ti th ng c trng s cao nht s c chn, nhng slm cho hng ch cho ng ny tng ln. Sau mt s lu l ng s c chuyn sang ng t ti hn.

3.3. nh tuyn ng (dynamic routing):

L qu trnh m trong giao thc nh tuyn tm ra ng tt nht trong mng vduy tr chng. C rt nhiu cch xy dng ln bng nh tuyn mt cch ng. Nhng ttc u thc hin theo quy tc sau: n skhm tt ccc tuyn ng n ch c thvthc hin mt squy tc c nh trc xc nh ra ng tt nht n ch. u imca dynamic routing l n gin trong vic cu hnh v t ng tm ra nhng tuyn ngthay thnu nh mng thay i. Nhc im ca dynamic routing l yu cu xl ca CPUca router cao hn l static route. Tiu tn mt phn bng thng trn mng xy dng lnbng nh tuyn.


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3.3.1. nh tuyn ng (minimum spanning tree):C thsdng qu trnh trnh duy t tm mt cy bc cu nu c mt cy bc cu

tn ti. Cy tm c thng l cy v h ng. Vic tm cy "tt nht" th ng rt quan trng. Chnh v vy, chng ta c thgn mt "di" cho mi cnh trong graph v t ra yu cutm mt cy c di ti thiu. Thc t, "di" c thl khong cch, gi, hoc l mt ilng nh gi trhoc tin cy. Mt cy c tng gi l ti thiu c gi l cy bccu ti thiu. Ni chung, nu graph l mt graph khng lin thng, chng ta c th tm cmt rng bc cu ti thiu. Mt rng bc cu ti thiu l mt tp h p cc cnh ni ngraph mt cch ti a c tng di l ti thiu. Bi ton ny c th c xem nh l vicla chn mt graph con ca graph gc cha tt ccc nt ca graph gc v cc cnh cla chn. u tin, to mt graph cn nt,n thnh phn v khng c cnh no c. Mi ln,chng ta chn mt cnh thm vo graph ny hai thnh phn lin thng trc cha c kt ni c lin kt li v i nhau to ra mt thnh phn lin thng m i (ch khngchn cc cnh thm vo mt thnh phn lin thng trc v to ra mt vng). V vy, tibt k giai on no ca thut ton, quan h: n=c+e .

lun c duy tr, y n l s l ng nt trong graph,e l s cnh c la chntnh cho t i thi im xt v c l s l ng thnh phn trong graph tnh cho t i thi im xt.cui thut ton,e bng n tr i sthnh phn trong graph gc; nu graph gc l linthng, chng ta s tm c mt cy c(n-1) cnh. Qu trnh duyt cy stm ra mt rngbc cu. Tuy nhin, chng ta thng khng tm c cy bc cu c tng di ti thiu.

tm ra cy bc cu ti thiu ng i ta sdng 2 thut ton:prime v kruskal.

3.3.2. nh tuyn ng (shortest path tree):Bi ton tm cc ng i ngn nht l mt bi ton kh quan trng trong qu trnh thit

k v phn tch mng. Hu ht cc bi ton nh tuyn c th gii quyt nh gii quyt bi ttm ng i ngn nht khi mt " di " thch hp c gn vo mi cnh (hoc cung) tromng. Trong khi cc thut ton thit k th c gng tm kim cch to ra cc mng tho mn tchun di ng i.


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Bi ton n gin nht ca loi ton ny l tm ng i ngn nht gia hai nt chtrc. Loi bi ton ny c th l bi ton tm ng i ngn nht t mt nt ti tt c cc cn li, tng ng bi ton tm ng i ngn nht t tt c cc im n mt im. i

i hi phi tm ng i ngn nht gia tt c cc cp nt. Cc ng i i khi c nhng ghn nht nh (chng hn nh gii hn s lng cc cnh trong ng i).

Tip theo, chng ta xt cc graph hu hng v gi s rng bit di ca mt cungia mi cp nti v j l lij. Cc di ny khng cn phi i xng. Khi mt cung khng tnti th dilij c gi s l rt ln (chng hn ln gpn ln di cung ln nht trong mng).Ch rng c th p dng qu trnh ny cho cc mng v hng bng cch thay mi cnh b hai cung c cng di. Ban u gi s rnglij l dng hon ton; sau gi thit ny c thc thay i.

Loi nh tuyn ny c dng thng dng vi cc thut ton c dng:dijkstra,bellman ford.

4. Cc thut ton dng nh tuyn:

4.1. Thut ton Prim:

Thut ton ny c nhng u im ring bit l khi mng dy c,trong vic xem xt m bi ton tm kimcc cy bc cu ti thiu. Hn na cc thut ton phc tp hn c xydng da vo cc thut ton cy bc cu ti thiu,v mt s thut ton ny hot ng tt hncc cu trc d liu c s dng cho thut ton sau y,thut ton ny c pht biu bi PrCc thut ton ny ph hp vi cc quad trnh thc hin song song bi v cc qu trnh thc hin bng cc ton t vector. Thut ton c miu t nh sau:

- B1: Chn mt nh s bt k ca G cho vo cy T. Khi cy T l mt cy ch cmt nh v cha c cnh no.

- B2: Nu T gm tt c cc nh ca G th T l cy bao trm cn tm. Kt thc.

- B3: Nu G cn c cc nh khng thuc T ,v G lin thng nn c cc cnh nimt nh trong T vi mt nh ngoi T, chn mt cnh c trng s nh nht trong s cho vT.

- B4: Quay li B2.


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V d:

Hnh minh ha U Cnh (u,v) V \ U M t

{}{A,B,C,D,E,F,G}

y l th c trngs ban u. Cc s lcc trng s ca cccnh.

{D}

(D,A) = 5V (D,B) = 9

(D,E) = 15(D,F) = 6

{A,B,C,E

,F,G}

Chn mt cch ty nh D l nh bt u.Ccnh A, B, EvF uc ni trc tip

tiD bng cnh ca th. A l nhgn D nht nn tachn A l nh th haica cy v thmcnh ADvo cy.

{A,D}

(D,B) = 9(D,E) = 15(D,F) = 6V (A,B) = 7

{B,C,E,F,G}

nh c chn tiptheo l nhgn D hoc Anht. B ckhong cch tiD bng9 v tiA bng 7, E ckhong cch ti cy

hin ti bng 15,
http://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_2.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_1.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_0.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_2.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_1.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_0.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_2.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_1.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_0.svg


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vF c khong cch bng 6. F l nh gncy hin ti nht nn

chn nh F v cnhDF.

{A,D,F}

(D,B) = 9(D,E) = 15(A,B) = 7V (F,E) = 8

(F,G) = 11

{B,C,E,G}

Thut ton tip tctng t nh bctrc. Chn nhB ckhong cch ti A bng

7.

{A,B,D,F}

(B,C) = 8(B,E) = 7V (D,B) = 9

chu trnh(D,E) = 15(F,E) = 8(F,G) = 11

{C,E,G}

bc ny ta chngia C, E, vG. C ckhong cch tiB bng8, E c khong cch

tiB bng 7, v Gckhong cch ti F bng11.El nh gn nht,nn chn nh Evcnh BE.

{A,B,D,E,F}

(B,C) = 8(D,B) = 9chu trnh(D,E) = 15chu trnh(E,C) = 5V (E,G) = 9

(F,E) = 8

{C,G}

bc ny ta chngia C vG. C ckhong cch ti E bng5, vG c khong cchtiE bng 9. ChnC vcnh EC.
http://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_5.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_4.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_3.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_5.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_4.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_3.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_5.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_4.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_3.svg


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chu trnh(F,G) = 11

{A,B,C,D,E,F}

(B,C) = 8chu trnh(D,B) = 9chu trnh(D,E) = 15chu trnh

(E,G) = 9V (F,E) = 8chu trnh(F,G) = 11

{G}

nh G l nh cn liduy nht. N c khongcch ti F bng 11, vkhong cch ti E bng

9. E gn hn nn chnnh Gv cnh EG.

{A,B,C,D,E,F,G}

(B,C) = 8chu trnh(D,B) = 9chu trnh(D,E) = 15chu trnh(F,E) = 8chu trnh

(F,G) = 11chu trnh

{}

Hin gi tt c cc nh nm trong cy v cy bao trm nh nht ct mu xanh l cy.Tng trng s ca cyl 39.

4.2. Thut ton Kruskal:

- B1: khi to T lc u l mt th rng.

- B2: nu T gm ng n-1 cnh ca G th t l cy bao trm cn tm. Kt thc.
http://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5thttp://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5thttp://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5thttp://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5thttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_7.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_6.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_7.svghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Prim_Algorithm_6.svghttp://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5thttp://vi.wikipedia.org/wiki/C%C3%A2y_bao_tr%C3%B9m_nh%E1%BB%8F_nh%E1%BA%A5t


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- B3: nu T cn cha n-1 cnh,th v G lin thng, nn G c khng t hn n-1cnh, do cn cc cnh ca G cha thuc T. trong cc cnh ca G cha thuc t c cc cnkhng to ra chu trnh vi cc cnh c trong T, chn cnh v c trng s nh nht trong c

cnh y b sung vo T. Loi b nhng cnh to thnh chu trnh. - B4: quay li B2.

V D:

nh minh ha M t

ADvCE l cc cnh nh nht vi di 5, v tachn AD mt cch ty (t mu xanh).

CE l cnh nh nht khng to thnh chu trnh vi di 5,nn n l cnh th hai c chn.

Cnh th ba DF vi di 6 cng c chn tng t nhvy.
http://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_3.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_2.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_1.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_3.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_2.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_1.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_3.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_2.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_1.svg


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Cc cnh tip theo theo th t trng s tng dn l ABvBE,vi di 7. Chn AB mt cch ty . Cnh BD khng thc chn trong tng lai (t mu ) v c ngni B vD nn nu chn n s to thnh chu trnh ABD.

Tip tc chn cnh nh nht tip theo l BE vi di 7.

Thm mt s cnh c t mu : BC v n s to chutrnhBCE, DE v n s to chu trnh DEBA, vFE v n sto chu trnh FEBAD.

Cui cng, thut ton chn cnh EG di 9, v tm ra cy bao trm nh nht.

4.3. Thut ton Dijkstra:

Cho Graph lin thng G={V,E}, cn tm khong cch ngn nht v ng i t nt s tt c cc nt khc.

B1: thit lp i=0, tp cha cc nt c gi c nh S={uo= s}, gnd(v) bng:

vi vuo

0 vi v=uo

Nu | V|= 1 th kt thc.
http://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_6.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_5.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_4.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_6.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_5.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_4.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_6.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_5.svghttp://vi.m.wikipedia.org/wiki/T%E1%BA%ADp_tin:Kruskal_Algorithm_4.svg


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B2: vi mi v V/S, thay th :d(v)= min{d(v),d(ui)+ d(vui)}. Nu d(v) thay i gi tr,t nhn (d(v),ui) cho v.

B3: trong s cc v va c cp nht gi, tm Ui+1 c gi nh nht. gn S=S(ui+1)

B4: thay th bi i+1. Nu i =|V|-1 kt thc. Nu khng quay v B2.

4.4. Thut ton Bellman Ford:

Cho graph lin thng G={V,E},cn tm khong cch ngn nht v ng i t nt s ntt c cc nt khc.

B1: thit lp hm xc nh nt tin bi cu s l (s)= s v cc gi d(v) bng:

= vi vuo

=0 vi v =uo


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To dng i FIFO Q ca cc nt qut. a s vo Q.

B2: ly ra nh u tin trong hng i h, kim tra gi ca cc nt ln cn U,nu d(u )>d(h)+ d(hu) th a u vo hng i v gn:

d(u)= d(h)+ d(hu)

(u)= h

B3: lp li B2 cho n khi Q={}

5. Mt s giao thc nh tuyn ng hin nay:

qun tr mng d dng hn, ngi ta c gng nghin cu nh tuyn ng theo chng khc nhau nh: tm ng i ngn nht v tm ng i ti u nht. in hnh cho hhng nghin cu l hai giao thc nh tuyn: RIP (tm ng i ngn nht) v OSPF (tmng i ti u nht), ngoi ra ngi ta cn pht trin thm giao thc EIGRP l giao thc ntuyn lai gia hai giao thc trn li dng u im ca mi loi giao thc.


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Hnh 8: Phn loi cc giao thc nh tuyn

5.1. Giao thc nh tuyn RIP(Routing Information Protocol):

Giao thc nh tuyn RIP l giao thc nh tuyn distance vector nh tuyn theokhong cch t nt cho ti mng ch. Hin nay giao thc ny c nghin cu v pht trin version 3, trong vesion 2 c s dng nhiu nht. Chng u s dng hop count l gca ng i ti mng ch, trong mi hop count l mt nt mng c chc nng hot lp 3 trong m hnh OSI. V gi ca ng i c gi tr t 0 n 15. C mi 30 giy th cc

nt mng gi thng tin bng nh tuyn cho nhau cp nht d liu v ng i ti cc mch v duy tr kt ni. Giao thc ny s dng thut ton Bellman-Ford so snh gi ca cc linkt xy dng nn bng nh tuyn v nh tuyn gi tin.

V d trn nt mng R1 ta s dng chng trnh theo di bn tin cp nht d liu bnnh tuyn, sau mi thi gian nht nh nt mng gi yu cu nt mng khc gi thng tin tuyn v xy dng bng nh tuyn ca ring mnh. Trong bng nh tuyn c cha thng

v mng ch, cng i ti mng ch v gi ca ng ti mng ch l bao nhiu.


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Hnh 9: Qu trnh gi thng tin nh tuyn RIP

Nhc im ca giao thc nh tuyn ny l d dn ti gi tin trong mng b lp vn(loop) do thi gian cc nt mng gi thng tin nh tuyn cho nhau l nh k, v trong thi giankh lu trong khi mi trng mng lun c s thay i ngu nhin. ng thi giao thc nkhng phn bit loi gi tin c truyn i trong mng nn vi nhng gi tin l thi gian thvn b x l ging nhng gi tin d liu thng, tc l giao thc khng h tr QoS(Quality of Service). Ngoi ra, v gi c tnh theo s hop count nn c th c trng hp gi ca lin ktth nh trong khi bng thng cng nh th s gy nghn mng, m lin kt c gi ln hn nhn

bng thng ln th li khng c d liu c truyn. Do giao thc ny ch c s dng mng nh, v dung lng mng khng qu ln trnh tnh trng nghn mng gy mt d ldo b lp vng qu nhiu.

5.2. OSPF (Open Shortest Path First):

Giao thc OSPF c pht trin nm 1987 bi IETF (Internet Engineering Task Force).

y l giao thc link -state hot ng da trn thng tin v trng thi cc lin kt trong mng.


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Mi nt mng nhn v gi cc gi tin LSU (Link State Update) ti cc nt mng khc v trnthi lin kt ca n ti cc mng khc nh th no, t xy dng nncy SPF (Shortest PathFirst) bng thut ton Dijkstra. y, gi c s dng bng cch tnh ton t bng thng ca

cc lin kt, bng thng cng ln th gi cng nh, cho thy s ti u v cch tnh gi lin kt vi giao thc RIP. Khi mi nt mng bit c bt k s thay i no v trng thi lin kt tmng khc th n mi gi d liu nh tuyn cp nht ti nt mng khc. Do , bnh thkhng c s thay i no v mng th cc nt mng ch gi nhng gi c kch thc khng nk duy tr lin kt, cn khi c thay i th ch gi thng tin v s thay i , dn ti gilng bng thng cho ton mng.

Trong mng a truy cp OSPF (cc nt mng s dng giao thc OSPF trao i thng tinvi nhau cng ni vo thit b lp 2 m hnh OSI nh Hnh 10 ) c c ch bu chn nt mngch(BDR), nt mng ny chu trch nhim cp nht thng tin nh tuyn cho cc nt khc davo thng tin nh tuyn t cc nt thay i ti n. Do hn ch c tnh trng tn bnthng do cc nt mng trao i thng tin nh tuyn vi nhau hoc gy nghn mng ti thit btrung tm.

Hnh 10: u im ca BDR

u im ca giao thc ny l mng hi t nhanh do ch cp nht khi mng c s thay v ch cp nht nhng lin kt b thay i. ng thi, do gi c tnh ton theo bng thng ccc lin kt nn tng c tc lu thng thng tin trn ton mng.


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5.3. EIGRP (Enhanced Interior Gateway Routing Protocol):

y l giao thc nh tuyn do Cisco IOS Software Release xy dng t nm 1992 v chhot ng trn cc thit b mng do Cisco sn xut. Giao thc ny s dng thut ton Bellma-

Ford hoc Ford-Fulkerson, l hai thut ton nh tuyn theo khong cch. Nhng qu trnh hotng cp nht bng nh tuyn th EIGRP li hot ng ging nh OSPF, tc cp nht tuyn theo trng thi lin kt. Nh vy, ging OSPF, giao thc EIGRP tng dung lng cmng hn hn so vi giao thc nh tuyn RIP. ng thi, gi ca mi lin kt c tnh toda vo bn thng s: bng thng, tr, tin cy v ti. Da vo bn thng s ny, mi thntin nh tuyn trong ng i c tnh ton ti u, m bo cho cc gi tin trong mng luc truyn i vi tin cy cao nht. Ngoi ra, giao thc OSPF cn gip ngi qun tr mngthc hin qun tr mng ti u hn bng cch phn vng t tr cho cc vng ln cn nhau. Mvng t tr l mt AS:

Hnh 11: u im ca phn vng t tr (AS)

Mi AS chy mt nh tuyn EIGRP chung v ch nh tuyn trong AS , mun nhtuyn d liu sang mng khc th cc nt mng phi nh tuyn tnh ti nt mng bi(Gateway). y, ta li thy nh tuyn tnh cng c chc nng c bit trong mng.

Hai giao thc OSPF v EIGRP c h tr xc thc bn tin update nn c tnh bo mt rcao, cng vi update thng tin nh tuyn mi khi c s thay i ca trng thi lin kt nn c uth vt tri so vi giao thc nh tuyn RIP. Nhng b li mi nt mng cn yu cu tc


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l cao, do hai giao thc ny ch yu c s dng trong mng li. Vi mng nh vi s lngi dng t ngi ta s dng nh tuyn RIP chi ph thit b r hn, v d cu hnh s dhn.


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III. Kt lun nh tuyn lu l ng trong mng tri qua nhng giai on pht trin quan trng.

V i spht trin nhanh chng ca cng nghvin thng v my tnh, cc phng php nhtuyn mng ngy cng tr nn linh hot gn lin v i hiu quca hot ng mng l i, k hoch nh tuyn tr thnh mt thnh phn khng th thiu c trong cng tc thit k,xy dng v vn hnh, qun l mng.

Qua qu trnh tm hiu v nh tuyn t sch bo v internet, bi tp l n ca chngem a ra cc vn :

- nh tuyn.

- Phng php nh tuyn (cc loi nh tuyn).- Thut ton nh tuyn v v d.- Giao thc nh tuynng dng cc thut ton.Bi tp l n ca chng em cn nhiu thiu st, rt mong c s ch bo ca thy

gio. Em xin chn thnh cm n thy!


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IV. Ti liu tham kho [1] Rick Graziani - Allan Johnson, Routing Protocols And Concepts. Cisco Press,

2008.[2] Donald Gross, Carl M. Harris, Fundamentals of Queueing Theory , Wiley-

Interscience,1998

[3] Joseph L. Hammond, Peter J.P.O' Reilly, Performance Analysis of Local

Computer Networks , Addison-Wesley, 1988

[4] Slide ging dy mnC s mng thng tin , TS. Nguyn Vn Tin, Vin in

t vin thng, i hc Bch Khoa H Ni.[5] Slide ging dy mnMng my tnh , Ging vin Nguyn Hu Thanh, Vin

in t vin thng, i hc Bch Khoa H Ni.

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