Bai 3 - Kien Truc Phan Tang Va Mo Hinh OSI

5/25/2018 Bai 3 - Kien Truc Phan Tang Va Mo Hinh OSI

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BI GiNG MN H THNG MY TNH V MNG BI 3KiN TRC PHN TNG V M HNH OSI

04/10/2009 Ging vin - V Khi Th 1

Kin trc phn tng Kin trc phn tng Nguyn tc ca kin trc mng phn tng Cc vn cn phi gii quyt khi thit k cc tng

Mt s khi nim Tng Giao din, dch v, n v d liu

M hnh OSI Gii thiu

Chc nng ca cc tng

Trong bi ny nghin cu cc vn sau y:


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I. KiN TRC PHN TNG

1. Kin trc phn tng

gim phc tp ca thit k v vic ci t mnghu ht cc my tnh u c phn tch thit k theoquan im phn tng.

Mi h thng thnh phn ca mng c xem nh mt

cu trc a tng, trong mi tng c xy dng trntng trc n.

S lng cc tng cng nh tn v chc nng ca mitng ty thuc vo nh thit k.

Trong hu ht cc mng, mc ch ca mi tng l cung cp mt s dch v nht nh cho tng cao hn

Mi tng khi s dng khng cn quan tm n cc thaotc chi tit m cc dch v phi thc hin


3/23



Tng N

Tng I+1

Tng I

Tng I-1

Tng 1

Tng N

Tng i+1

Tng i

Tng i-1

Tng 1

Giao thc tng N

Giao thc tng I+1

Giao thc tng I

Giao thc tng I-1

Giao thc tng N

ng truyn vt l

Kin trc phn tng tng qut


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2. Nguyn tc ca kin trc mng phn tng

Mi h thng trong mt mng u c cu trc tng nh nhau (s lng

tng, chc nng ca mi tng).

D liu khng c truyn trc tip t tng I ca h thng ny sang tngth I ca h thng kia (ngoi tr i vi tng thp nht). Bn gi d liucng vi cc thng tin iu khin chuyn n tng ngay di n v c

th cho n tng thp nht. Bn di tng ny l ng truyn vt l, y s truyn tin mi thc s din ra.

i vi bn nhn th cc thng tin nhn c chuyn t tng di lntrn cho ti tng I ca h thng nhn.

Gia hai h thng kt ni ch tng thp nht mi c lin kt vt l cn tng cao hn ch l lin kt logic hay lin kt o.


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3. Cc vn cn phi gii quyt khi thit k cc tng

C ch ni, tch:

Mi tng cn c mt c ch thit lp kt ni (tc l cn c mtc ch nh a ch tt c cc my trong mng) v c mt cch kt thc kt ni khi m s kt ni l khng cn thit na.

Cc quy tc truyn d liu:

Trong cc h thng khc nhau d liu c th truyn theo mt s cch khcnhau nh: Truyn theo mt hng; Truyn theo c hai hng khng ng thi; Truyn hai hng ng thi.

Kim sot li: ng truyn vt l ni chung l khng hon ho, cn phi tha

thun dng m no pht hin, kim tra li v sa li. Pha nhnphi c kh nng thng bo cho bn gi bit cc gi tin no thung, gi tin no pht li.


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di bn tin:

Khng phi mi qu trnh u chp nhn di gi tin l ty , cn phi

c c ch chia bn tin thnh cc gi tin nh.Th t cc gi tin:

Cc knh truyn c th gi khng ng th t cc gi tin do vy cn cc ch bn thu ghp ng th t ban u.

Tc pht v thu d liu:

Bn pht c tc cao c th lm lt bn thu c tc thp. Cn phic c ch bn thu bo cho bn pht bit tnh trng .


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II. MT S KHI NiM C BN

1. Tng - Layer:

Mi qu trnh trao i thng tin gia hai i tng u thc hin qua nhiubc, cc bc ny c lp tng i vi nhau.

Thng tin c trao i gia hai i tng A, B qua ba bc nh sau: Pht tin: Thng tin truyn t tng cao n tng thp Nhn tin: Thng tin truyn t tng thp n tng cao.

Qu trnh trao i thng tin: Trc tip qua ng truyn vt l (thchin tng cui cng).

2. Giao din, dch v, n v d liu

Mi quan h gia hai tng k nhau gi l giao din.

Mi quan h gia hai tng ng mc ca hai h thng khc nhau gi lgiao thc.

Th th - Entity: L thnh phn tch cc trong mi tng, n c th l mttin trnh trong h a x l hay l mt trnh con cc thc th trong cngmt tng cc h thng khc nhau (gi l thc th ngang hng hay thcth ng mc).


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Mi thc th c th truyn thng lntng trn hoc tng di n thng quamt giao din Interface. Giao din

gm mt hoc nhiu im truy nhpdch v (service access point SAP).

Ti cc im truy nhp dch v tngtrn ch c th s dng dch v do tngdi cung cp.

Thc th c chia lm hai loi: Thcth cung cp dch v v s dng dchv.

Tng N

Tng I+1

Tng I

Tng I-1

Tng 1

Tng N

Tng i+1

Tng i

Tng i-1

Tng 1

Giao thc tng N

Giao thc tng I+1

Giao thc tng I

Giao thc tng I-1

Giao thc tng N

ng truyn vt l


Thc th cung cp dch v - Service Provide: L cc thc th tng Ncung cp dch v cho tng N+1.

Thc th s dng dch v - Service User: l cc thc th tng N sdng dch v do tng N-1 cung cp.


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n v d liu s dng giao thc Protocol Data UnitPDU.

n v d liu dch v - Service DataUnitSDU.

Thng tin iu khin ProtocolControl InformationPCI.

Mt n v d liu m 1 thc th tng N ca h thng A gi sang thcth tng N ca 1 h thng B khngbng ng truyn trc tip m phitruyn xung di truyn bng

tng thp nht thng qua ngtruyn vt l.

Tng N

T

ng I+1Tng I

Tng I-1

T

ng 1

Tng N

T

ng i+1Tng i

Tng i-1

Tng 1

Giao thc tng N

Giao thc tng I+1

Giao thc tng I

Giao thc tng I-1

Giao thc tng N

ng truyn vt l



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04/10/2009 Ging vin - V Khi Th 10

D liu tng N-1 nhn c do tngN truyn xung gi l SDU n v

d liu dch v. Phn thng tin iu khin ca mi

tng gi l PCI thng tin iu khin.

tng N-1 phn thng tin iu khin

PCI thm vo u ca SDU to thnhPDU. Nu SDU qu di th ct nhthnh nhiu on, mi on b xungphn PCI, to thnh nhiu PDU.

Bn h thng nhn trnh t din ra

theo chiu ngc li. Qua mi tngPCI tng ng s c phn tch vct b khi PDU trc khi gi lntng trn.

Tng N

Tng I+1

Tng I

Tng I-1

Tng 1

Tng N

Tng i+1

Tng i

Tng i-1

Tng 1

Giao thc tng N

Giao thc tng I+1

Giao thc tng I

Giao thc tng I-1

Giao thc tng N

ng truyn vt l



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04/10/2009 Ging vin - V Khi Th 11

III. M HNH OSI

1. Gii thiu:

M hnh OSI l mt c s dnh cho vic chun ho cc h thng truynthng, n c nghin cu v xy dng bi ISO. Vic nghin cu v mhnh OSI c bt u ti ISO vo nm 1971 vi mc tiu nhm ti vicni kt cc sn phm ca cc hng sn xut khc nhau v phi hp cchot ng chun ho trong cc lnh vc vin thng v h thng thng tin.

Theo m hnh OSI chng trnh truyn thng c chia ra thnh 7 tng vinhng chc nng phn bit cho tng tng. Hai tng ng mc khi lin ktvi nhau phi s dng mt giao thc chung. Trong m hnh OSI c hai loigiao thc chnh c p dng: giao thc c lin kt (connection - oriented)v giao thc khng lin kt (connectionless)


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04/10/2009 Ging vin - V Khi Th 12

Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

Session

Presentation

Application

H thng A H thng BGiao thc tng 7

Giao thc tng 6

Giao thc tng 5

Giao thc tng 4

Giao thc tng 3Giao thc tng 2

Giao thc tng 1

ng truyn vt l

Giao thc c lin kt: trc khi truyn d liu hai tng ng mc cnthit lp mt lin kt logic v cc gi tin c trao i thng qua lin ktny, vic c lin kt logic s nng cao an ton trong truyn d liu.

Giao thc khng lin kt: trc khi truyn d liu khng thit lp lin ktlogic v mi gi tin c truyn c lp vi cc gi tin trc hoc sau n.


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04/10/2009 Ging vin - V Khi Th 13

Nh vy vi giao thc c lin kt, qu trnh truyn thng phi gm 3 giaion phn bit:

Thit lp lin kt (logic)--> Truyn d liu --> Hy b lin kt (logic)i vi giao thc khng lin kt th ch c duy nht mt giai on truyn dliu m thi.

Gi tinca giao thc: Gi tin (Packet) c hiu nh l mt n v thngtin dng trong vic lin lc, chuyn giao d liu trong mng my tnh.Nhng thng ip (message) trao i gia cc my tnh trong mng, cto dng thnh cc gi tin my ngun.

V nhng gi tin ny khi ch s c kt hp li thnh thng ip banu. Mt gi tin c th cha ng cc yu cu phc v, cc thng tin iukhin v d liu.


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04/10/2009 Ging vin - V Khi Th 14

Data

Data

data

Data

Data

Data

Hdr

Hdr

Hdr

Hdr

Hdr Ctrl

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

HdrHdr

Data

Data

data

Data

Data

Data

Hdr

Hdr

Hdr

Hdr

Hdr Ctrl

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

HdrHdr

Data

Data

data

Data

Data

Data

Hdr

Hdr

Hdr

Hdr

Hdr Ctrl

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

HdrHdr

Data

Data

data

Data

Data

Data

Hdr

Hdr

Hdr

Hdr

Hdr Ctrl

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

Hdr

HdrHdr

Phisycal Phisycal

Data link

Network

Transport

Session

Presentation

Application

Data link

Network

Transport

Session

Presentation

Application

Hdr: Phn u gi tin Trl: Phn kim li (tng lin kt d liu ) Data: Phn gi liu ca gi tin

Phng thc xc lp gi tin trong m hnh OSI


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04/10/2009 Ging vin - V Khi Th 15

Trn quan im m hnh mng phn tng tng mi tng ch thc hin mtchc nng l nhn d liu t tng bn trn chuyn giao xung cho tng

bn di v ngc li. Chc nng ny thc cht l gn thm v g b phn u (header) i vi

cc gi tin trc khi chuyn n i. Ni cch khc, tng gi tin bao gmphn u (header) v phn d liu.

Khi i n mt tng mi gi tin s c ng thm mt phn u khc

v c xem nh l gi tin ca tng mi, cng vic trn tip din cho tikhi gi tin c truyn ln ng dy mng n bn nhn.

Ti bn nhn cc gi tin c g b phn u trn tng tng tng ngv y cng l nguyn l ca bt c m hnh phn tng no.

Ch : Trong m hnh OSI phn kim li ca gi tin tng lin kt dliu t cui gi tin


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04/10/2009 Ging vin - V Khi Th 16

2. Chc nng cc tng trong m hnh OSI

2.1. Tng vt l Phisycal Layer

Tng vt l (Physical layer) l tng di cng ca m hnh OSI l. N m tcc c trng vt l ca mng:

Cc loi cp c dng ni cc thit b,

Cc loi u ni c dng ,

Cc dy cp c th di bao nhiu v.v...V d: Tiu chun Ethernet cho cp xon i 10 baseT nh r cc c

trng in ca cp xon i,kch thc v dng ca cc u ni, di ti a ca cp

Khc vi cc tng khc l tng vt l khng c gi tin ring v do vy khngc phn u (header) cha thng tin iu khin, d liu c truyn itheo dng bit.

Mt giao thc tng vt l tn ti gia cc tng vt l quy nh v phngthc truyn (ng b, phi ng b), tc truyn


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04/10/2009 Ging vin - V Khi Th 17

Cc giao thc xy dng cho tng vt l c phn chia thnh hai loi giaothc:

S dng phng thc truyn thng d b (asynchronous) Phng thc truyn thng ng b (synchronous).

Phng thc truyn d b:khng c mt tn hiu quy nh cho s ngb gia cc bit gia my gi v my nhn, trong qu trnh gi tn hiu mygi s dng cc bit c bit START v STOP c dng tch cc xu

bit biu din cc k t trong dng d liu cn truyn i. N cho php mt kt c truyn i bt k lc no m khng cn quan tm n cc tn hiung b trc .

Phng thc truyn ng b:s dng phng thc truyn cn c ngb gia my gi v my nhn, n chn cc k t c bit nh SYN

(Synchronization), EOT (End Of Transmission) hay n gin hn, mt ci"c " (flag) gia cc d liu ca my gi bo hiu cho my nhn bitc d liu ang n hoc n.


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04/10/2009 Ging vin - V Khi Th 18

2.2. Tng lin kt d liu Data Link Layer

Cung cp phng tin truyn thng tin qua lin kt vt l m bo tin

cy: Gi cc khi d liu vi c ch ng b ha

Kim sot li v kim sot lung d liu cn thit

Cc bc tng lin kt d liu thc hin l:

Chia nh thnh cc khi d liu Frame (Vi trm bytes), ghi thm vou v cui Frame nhng nhm bits c bit lm ranh gii giacc Frame.

Trn cc ng truyn vt l lun c li nn tng ny phi gii quytvn sa li (do bn tin b hng, mt v truyn li).

Gi cho s ng b tc gia bn pht v bn thu. Tm li: Tng lin kt d liu chu trch nhim chuyn khung d liu

khng li t my tnh ny sang my tnh khc thng qua tng vt l. Tngny cho php tng mng truyn d liu gn nh khng phm li qua linkt mng.


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04/10/2009 Ging vin - V Khi Th 19

2.3. Tng mng Network Layer

Lp a ch cc thng ip, din dch a ch v tn logic thnh a ch vt

l.

Kim sot v iu khin ng truyn: nh r cc b tin c truyn itheo con ng no t ngun ti ch. Cc con ng c th l cnh i vi nhng mng t thay i, cng c th l ng ngha l cc con

ng ch c xc nh trc khi bt u cuc ni chuyn. Cc conng c th thay i ty theo trng thi ti tc thi.

Qun l lu lng trn mng: Chuyn i gi, nh tuyn, kim sot stc nghn d liu (nu c nhiu gi tin cng c gi i trn ng

truyn th c th xy ra tc nghn). Kim sot lung d liu v ct hp d liu (nu cn).

Ch : Trong mng phn tn nhim v ca tng rt n gin thm ch cth khng tn ti


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04/10/2009 Ging vin - V Khi Th 20

2.4. Tng giao vn Transport Layer

Thc hin vic truyn d liu gia hai u nt (End ToEnd).

Thc hin kim sot li, kim sot lung d liu t my n my. mbo gi tin truyn khng phm li, theo ng trnh t, khng b mt mthay sao chp.

Thc hin vic ghp knh, phn knh ct hp d liu (nu cn). ng

gi thng ip, chia thng ip di thnh nhiu gi tin v gp nhiu ginh thnh mt b.

Tng ny to ra mt kt ni cho mi yu cu ca tng trn n. Khi cnhiu yu cu t tng trn vi thng lng cao th n c th to ra nhiu

kt ni v cng mt lc c th gi i nhiu b tin trn ng truyn.


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04/10/2009 Ging vin - V Khi Th 21

2.5. Tng phin Session Layer

Cung cp phng tin truyn thng gia cc ng dng: cho php ngi

s dng trn cc my tnh khc nhau c th thit lp, duy tr, hy b vng b ha cc phin truyn thng gia h vi nhau.

Nhim v chnh ca tng ny l:

Qun l th bi i vi nhng nghi thc: Hai bn kt ni truyn thng

tin khng ng thi thc hin mt s thao tc. gii quyt vn nytng phin cung cp mt th bi, th bi c th c trao i v ch bnno gi th bi mi c th thc hin mt s thao tc quan trng.

Vn ng b: Khi cn truyn i nhng tp tin di tng ny chn thm

cc im kim tra (check point) vo lung d liu. Nu pht hin thy lich c d liu sau im kim tra cui cng mi phi truyn li


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04/10/2009 Ging vin - V Khi Th 22

2.6. Tng trnh din Presentation Layer

Quyt nh dng thc trao i d liu gia cc my tnh mng. Ngi ta

c th gi y l b dch mng. bn gi, tng ny chuyn i c phpd liu t dng thc do tng ng dng gi xung sang dng thc trunggian m ng dng no cng c th nhn bit. bn nhn, tng nychuyn cc dng thc trung gian thnh dng thc thch hp cho tng ngdng ca my nhn.

Tng trnh din chu trch nhim chuyn i giao thc bin dch d liu,m ha d liu, thay i hay chuyn i k t v m rng lnh ha.

Nn d liu nhm lm gim s bit cn truyn.

tng ny c b i hng hot ng i hng cc hot ngnhp/xut gi n cc ti nguyn trn my phc v.

BI 3 KiN TRC PHN TNG V M HNH OSI


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04/10/2009 Ging vin V Khi Th 23

2.7. Tng ng dng Application Layer

Cung cp cc phng tin ngi s dng c th truy nhp c vomi trng OSI, ng thi cung cp cc dch v thng tin phn tn.

Tng ny ng vai tr nh ca s dnh cho hot ng x l cc trnh ngdng nhm truy nhp cc dch v mng. N biu din nhng dch v htr trc tip cc ng dng ngi dng, chng hn nh phn mm chuyntin, truy nhp c s d liu v email,

X l truy nhp mng chung, kim sot li v phc hi li.

Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

Session

Presentation

Application

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Phisycal

Data link

Network

Transport

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Presentation

Application

H thng A H thng BGiao thc tng 7

Giao thc tng 6

Giao thc tng 5

Giao thc tng 4

Giao thc tng 3

Giao thc tng 2

Giao thc tng 1

ng truyn vt l

Ht

Documents

Bai 3 - Kien Truc Phan Tang Va Mo Hinh OSI