Gio trnh mn mng my tnh

Chng 1: Gii thiu tng quan v mng

1.1 Gii thiu v mng my tnh

1.1.1 nh ngha

Mng my tnh l s kt ni gia cc my tnh vi nhau nhm mc ch trao i d liu. Cc d liu trao i l tt c nhng g ngi s dng yu cu nh:

+ D liu (data)

+ Ting ni (Voice)

+ Hnh nh (Video)

1.1.2 Phn loi

C nhiu cch phn loi mng c th l phn loi theo phm vi, theo cu trc hay theo phng thc x l thng tin bn trong mng

1.1.2.1 Phn loi mng theo phm vi

Theo cch ny th c th phn loi thnh

Mng LAN : C phm vi bn knh nh hn 1K - thng c lp t trong mt vn phng, cng ty, trng hc....

Mng MAN: Phm vi nh hn 50Km Thng lp t trong mt khu vc nh thnh ph, th x,...

Mng WAN: Mng din rng bao trm ln c mt khu vc, lnh th , quc gia, quc t

1.1.2.2 Phn loi theo Cch thc kt ni mng: C cc cu hnh

Dng BUS Hnh v Trong dng ny tt c cc thit b trong mng u s dng chung mt ng truyn dn. Nh vy nu BUS truyn hng hay t th mng cng ngng lm vic

Hnh 11 Mng Bus

Dng Sao (Star) Hnh v

Tt c cc trm ni v mt trung tm chuyn mch chung gi l HUB. Trong trng hp cp hng th ch ring mt tram khng hot ng cn nu trung tm chuyn mch b hng th ton mng cng s b hng

Hnh 12: Dng Sao

Dng vng nhn RING

Cc trm ni vi nhau thnh vng trn khp kn. Thng tin truyn trong mng i theo mt hng. u pht ca trm ny s l u thu ca trm tip theo. Nh vy trng hp nu mch vng b t hoc mt trm b li th mng vng Ring cng s khng hot ng

Hnh 13: Mng vng RING

V dng hn hp: L s kt hp ca nhiu kiu mng khc nhau to thnh mt mng din rng

1.1.2.3 Phn loi theo phng thc x l thng tin bn trong mng

C hai phng thc l: X l tp chung v x l phn tn

1.1.2.3.1 Phng thc x l tp trung

Tt c thng tin d liu ton mng tp trung vo mt hoc mt vi my ch. Cc my ch thng l cc my ln chy h iu hnh a nhim v cho php nhiu ngi s dng cng mt lc. Cc trm lm vic ch c chc nng hin th v a ra cc yu cu ti my ch. My ch thc hin tt c cc cng tc x l v lu tr v qun l thng tin cng nh ngi s dng

1.1.2.3.2 Phng thc x l phn tn

Cc Thng tin d liu phn tn n c x l v lu tr ti cc my trm lm vic. Cc trm lm vic l c lp v ch trao i thng tin cho nhau thng qua mng di s qun l ca my ch va ngi iu hnh mng

1.2 Cc phng php kt ni my tnh

C nhiu phng php kt ni my tnh nhm mc ch truyn thng d liu

1.2.1 Phng tin kt ni.

+ Cp thng

+ Cp xon i

+ Cp ng trc

+ Cp quang

+ Giao din v tuyn (wireless)

........

1.2.2 Kt ni my tnh qua cng thng tin

My tnh c 2 loi cng thng tin ni tip v song song

Cng ni tip COM : Gm c 4 cng l COM1, COM2, COM3, COM4

Cng song song LPT: Gm c 4 cng l LPT1, LPT2, LPT3, LPT4

Khi kt ni ch n gin dng mt si cp (cp link) ni t mt cng ca my nyti mt cng ca my khc. Ch l hai cng ny khng nht thit phi ging nhau. V d ta c th ni cho gia cng COM v LPT

c im ca phng php ny l n gin. Vi tc truyn dn khong vi chc n vi trm Kbit/s. Nhng ch thc hin kt ni gia hai my vi khong cch khng ln hn di cp. Vi cc cp link di ti a khng qu 5 m

1.2.3 Kt ni my tnh bng MODEM

Trong khi phng php trn gii hn khong cch kt ni l 5m th phng php ny khong cch gia cc my tnh l khng hn ch- ch yu cu c my in thoi v Modem. Vic kt ni thc hin nh hnh v bn di

Hnh 11: Kt ni my tnh bng Modem

c im phng php ny l khng gii hn v khong cch nhng cng ch kt ni trc tip gia hai my tnh. Tc truyn thp khong vi chc Kbit/s v cn ph thuc vo cht lng truyn dn tn hiu thoi

1.2.4 Ni mng my tnh Mng LAN

Tuy c phc tp hn nhng em li hiu qu s dng cao. C th kt ni c nhiu my tnh v truyn thng d liu tc ln hng chc n trm Mbit/s. Cc my tnh mun ni mng cn lp t thm card giao tip mng (NIC: Network Interface Card) v cn c cp ni v cc thit b mng khc nu cn thit.

1.2.5 Ni mng my tnh- Kt ni mng rng

Kt ni my tnh s dng Modem l mt hnh thc ca kt ni mng rng. Trong thc t kt ni mng rng c nhiu cch.

Kt ni thng qua mng truyn s liu chuyn mch gi. X25 Lc ny my tnh ca ta s l mt thu bao ca mng truyn s liu

Kt ni s dng mng s a dch v bng hp ISDN v bng rng B-ISDN nu c

............

1.3 H iu hnh v qun l mng

C nhiu h iu hnh mng nh

UNIX

Novell Netware

Windows, Window NT

OS/2

............

Vic s dng v qun l mng lin quan ti vic qun l ti nguyn, v qun l ngi s dng cng nh cc cng vic vn hnh bo dng v sa cha gim st mng

1.4 Cc loi mng v cc th tc thng tin

Nhn chung trong thc t tn ti rt nhiu loi mng v cc hnh thc thng tin khc nhau. Nh mng in thoi, mng truyn s liu, mng Internet, mng pht thanh truyn hnh......Nhng tt c cc mng thng tin d rt phc tp v c nhiu thnh phn u c c im chung l phc v cho mt cng vic no . Vi d nh khi ta ni vo ng nghe in thoi th s dao ng m thanh to thnh tn hiu in tng t trong ng nghe v mng thng tin thoi bng cch no chuyn c phn ln ni dung tin hiu ti u kia mng. Hay trong mng my tnh th khi ta g v gi mt bc th in t th h thng mng chuyn c bc th ca ta ti ng a ch.

Khi nghin cu v bt k mt loi mng thng tin no - th iu ct yu nht l ta cn hiu r qu trnh thng tin c thc hin nh th no? di y ch trnh by s qua v qu trnh truyn tin trong mt s mng c th

1.4.1 Mng in thoi c nh

Chng 2: M hnh phn lp mng

2.1 Khi nim

Tt c cc h thng thng tin u rt phc tp, gm nhiu thnh phn v cc h thng nh lin kt li vi nhau to thnh mt h thng truyn thng hon chnh. V d Bn c th hnh dung:

Trong mng thng tin thoi qu trnh truyn thng tin t ngi ni n ngi nghe c thc hin nh sau:

4Ni 0,3-3,4 Khz

Nghe

3Bin i A/D(64Kbit/s-Ly mu

Bin i D/A ( tn hiu tng t

-Lng t ho

-M ho

2Ghp knh

Mng truyn dn v chuyn mch tng i

Phn knh

1

Hnh 21: Cc bc truyn tn hiu trong mng thoi

Trong v d v mng thoi, ta c th coi mng thoi c phn thanh 4 lp. Ban thn trong mt lp li c th chia thnh nhiu lp con. V d lp 2 bin i tn hiu tng t s theo phng php PCM gm 3 bc l: Ly mu - Lng t ho - M ho

Trong mng my tnh Qu trnh gi mt bc th t ngi gi n ngi nhn nh sau:

Chy chng trnh v vit th. Sau bm gi

(Ht nhim v ngi s dng)

Thc hin kt ni vi my tnh xa

ng gi(Nu th ln qu th chia thnh nhiu gi nh-cho vo phng b). Vit a ch bn gi v nhn vo trong gi (trn phong b)

Chuyn cc gi i. Bng cch t vo cc khung truyn dn trn ng truyn vt l

Bn thu tip nhn khung- Bc d gi - c a ch ngun-ch trn gi Tch b gi ly d liu ra

Chuyn d liu ti ngi c qu chng trnh nhn th

(

(

(

(

(

Hnh 22 : Qu trnh gi th in t

Qua v d trn ta c th xem thng tin l vic thc hin mt loi cc bc x l tn hiu. T vic to ra tn hiu n vic truyn n ti ch m vn m bo c nguyn dng d liu hoc ti thiu l ni dung thng tin nh ban u l qu trnh gm nhiu bc. Mi bc tng ng vi mt - ta coi nh l mt lp (layer) lm nhim v x l tn hiu. Nh vy mt h thng thng tin c th c t hoc nhiu lp Ni dung phc tp ca mi lp Bn thn trong mt lp c th li phn chia thnh nhiu lp nh hn tt c cc ci l tu thuc vo nh thit k. Tuy nhin do s a dng ca th gii v mt con ngi, khu vc pht trin, tnh cnh tranh, v t tng thit k phong ph nhng li c xu hng ton cu ho v ho trn hp nht cc h thng thng tin nn vic thit k v xy dng h thng cng khng th tu tin m cn c nhng yu cu v qui tc nht nh.

T chc chc tiu chun ho quc t ISO a ra mt m hnh phn lp mng chun cho tt c cc h thng thng tin ni chung gi l m hnh lin kt cc h thng m OSI (Open System Interconnection)

M hnh lin kt mng c thit k trn nguyn tc

M hnh c th c n lp nhng chc nng ca cc lp phi r rng- khng chng cho, khng lp li v tun theo chun quc t

Ti thiu ho lng thng tin i qua gia hai lp lm tng tnh c lp trong vic thit k h thng nhng khng lm gim hiu nng s dng mng

S lng cc lp khng qu nhiu h thng khng tr nn phc tp v chc nng ca cc lp tr thnh vn vt v cng khng gp li qu t chc nng ca mi lp tr nn cng knh

2.2 M hnh OSI

Sau khi tho lun v i n thng nht. T chc ISO a ra m hnh phn lp mng gm c 7 lp nh hnh v

8User

Ngi s dng

7Application

ng dng

6Presentation

Trnh by

5Session

Phin

4Transport

Truyn ti

3Network

NetworkNetwork

Mng

2Datalink

DLDL

Lin kt d liu

1Physical

PhyPhy

Vt l

Hnh 21: M hnh OSI

Nguyn tc trao i thng tin ca m hnh l: i vi bn pht, thng tin chuyn t lp trn xung lp di va ti bn thu th din ra theo chiu ngc li.

Tm tt ngha cc lp trong m hnh

Lp ng dng: C chc nng giao tip vi ngi s dng- cung cp n ngui dng cc dch v m mng thng tin c th lm

Lp trnh by: th hin khun dng d liu, m ho, gii m thng tin

Lp phin: Thc hin thit lp hay kt thc kt ni cc chng trnh ng dng

Lp truyn ti: thit lp knh thng tin to ra gia cc ng dng lp trn, to ra mt kt ni u cui ti u cui phc v cho vic truyn ti d liu

Lp mng: Thc hin cc chc nng lin quan ti mng nh nh a ch cc my, thc hin cng tc chn ng

Lp lin kt d liu: Lin kt thng tin d liu nhn c t lp trn chuyn i trn ng truyn vt l. D liu nhn c thng c ghp vo khung chuyn i

Lp vt l: c chc nng ng truyn gi i dng bt thng tin t im ny ti im kia ca mng

Theo m hnh Trao i thng tin ngang mc gia my gn v my xa. Cc hm dch v gia cc lp.

SAP: Service access point

Hnh 22: Trao i thng tin ngang mc

Thng tin trao i gia cc lp thng qua im truy nhp dch v. im truy nhp dch v cung cp cc dch v ca lp cho lp bn trn. C 4 hm c bn nht ca trao i l : Request(Yu cu), Indication (Ch th), Response (tr li), Confirm (Xc nhn). Lp trn yu cu lp di phc v bng hm Request yu cu ny c lp di chuyn qua mng c bin thnh ch th cho lp ngang mc vi n trn my xa. V tr li ca my xa c chuyn qua mng xc nhn yu cu ca my a phng c c p ng hay khng.

Nguyn tc trao i thng tin gia cc lp. Xem hnh di

Hnh 23: Trao i thng tin trn di

Thng tin trao i gia cc lp l cc khi d liu theo nguyn tc t trn xung di.

SDU (Service Data Unit): n v d liu dch v l n v d liu cn c x l m lp n nhn c t lp n+1 bn trn n

PCI (Protocol Data Unit): n v d liu th tc - y chnh l khi thng tin d liu m lp n thm vo khi x l khi thng tin d liu n nhn c t lp bn trn (SDUn)

PDU=PCI+SDU (Protocol Data Unit): y l khi d liu hon chnh ti lp n sau khi x l xong. N s c chuyn xung cho lp bn di v tr thnh SDU ca lp di . Nh vy PDUn=SDUn-1. PDUn s c chuyn cho lp n ngang vi n trn my xa. (Ch : PCI khng nht thit phi gn vo u khi d liu n co th gn vo bt k v tr no trong SDU)

ICI (Information Control Interface): Thng tin iu khin giao din - iu khin vic chuyn ccPDU t lp bn trn xung lp bn di.

IDU (Interface Data Unit): n v d liu giao din : L ton b lng thng tin i qua giao din gia hai lp bao nh vy IDUn=PDUn+ICIn

Ta c th hnh dung qu trnh truyn thng tin t lp 7 xung lp 1 nh hnh v

8User

User Data(PDU8

7A

PCI7SDU7(PDU7

6P

PCI6SDU6(PDU6

5S

PCI5SDU5(PDU5

4T

PCI4SDU4(PDU4

3N

PCI3SDU3(PDU3

2DL

H

T ..H

T( Frames

1Phy

Dng bt trn ng truyn vt l

Hnh 24: Thng tin truyn t trn xung

Trn hnh 25, Khi ngi s dng (Lp 8) mun gi khi d liu (user Data tng ng vi PDU8). H s truyn khi d liu cho lp 7 lc ny khi d liu thnh SDU7. Lp 7 s x l v gn thm phn thng tin iu khin th tc lp 7 vo SDU7. Ton b khi thng tin tr thnh PDU7 v n li tip tc c truyn xung lp bn di. Qu trnh c tip tc nh vy n lp 2. y PDU3 khi chuyn xung lp 2 c x l bng cch ct ra thnh nhiu on d liu nh, mi on d liu c gn thm phn tip u H (Header) v phn tip ui T (Trailer). Ta c th coi (PCI2 chnh bng tng ca H va T H+T=PCI2). Ti lp ny cc khi d liu gi l cc khung truyn. v n s c truyn trn ng truyn vt l.

Chng 3: Mng Lan v cc chun

3.1 Mng LAN

Khi ni v mng cc b, ngi ta ngh ngay rng l s kt ni cc my tnh gn nhau trong mt khu vc a l hp. iu ny ch ng v mt a l nhng cha ng v mt bn cht. V d nh hai my tnh c th cnh nhau nhng li kt ni vi nhau thng qua thu bao mng truyn s liu hay ISDN hoc qua MODEM ca mng in thoi th li hon ton l kt ni mng din rng v s trao i thng tin gia cc my tnh ny da trn mng din rng ch khng phi l kt ni LAN mc d chng ngay cnh nhau. Nh vy hiu thc cht ca kt ni mng LAN th cn hiu l kt ni gia cc my tnh trong mt phm vi a l hp (trong mt phng lm vic, mt cng ty, mt trng hc) v truyn dn tc cao c th ln n hng trm Mbit/s. S khc nhau gia kt ni mng rng v LAN l bn cht ca kt ni l: thit b kt ni, ng truyn dn, v cch thc lm vic ca h thng.

Nhng tiu chun mng cc b c hip hi cc k s in t v in my IEEE nh ngha trong cc chun 802.x v n tr thnh chun quc t trong vic thit k ci t mng cc b.

Cc tiu chun 802.x c so snh vi m hnh OSI nh hnh 1

Application

Presentation

Session

Transport

802.1

Network

Data-Link

LLC 802.2

802.3

CSMA/CD802.4

Token Bus802.5

Token Ring802.6

Physical

Hnh 31: V tr cc chun IEEE

802.1 : Chun v giao tip vi lp cao hn bn trn (Lp mng)

802.2 : LLC Logical Link Control

802.3 : CSMA/CD

802.4 : Token Bus

802.5 : Token Ring

802.6 : MAN

802.7 : Broadband Technical Advisory Group

802.8 : Fiber Optic Technical Advisory Group

802.9 : Intergrated Data and Voice Network

802.10 Standard for Interoperable LAN Security

802.11 Wireless LAN

802.12 100VG-Any LAN

3.2 Cc Chun LAN

3.2.1 LLC - iu khin kt ni Logic.

3.2.1.1 Cc dch v LLC

Hot ng lp 2, LLC c chc nng iu khin trao i d liu gia hai im ca mng thng qua ng truyn vt l peer to peer (Ch y l trao i gia hai im trn ng truyn vt l ch khng phi l gia hai u cui mng).

Vi chc nng ca mnh LLC cung cp 3 dch v cho cc lp bn trn c tiu chun ho thng qua im truy nhp dch v ca n l LSAP.

-Dch v kt ni khng lin kt v khng c bo nhn (UCS: Unacknowledged Connectionless Service)

-Dch kt ni c lin kt (CMS: Connection Mode Service)

-Dch v kt ni khng lin kt nhng c bo nhn (UCS: Acknowledged Connectionless Service)

Cc trm lm vic trn mng c th c cung cp 1 hay tt c cc dch v trn. S kt hp cc lp dch v ta c bng chc nng sau

Cc lp LLC

IIIIIIIV

Kiu hot ng1XXXX

2

X

X

3

XX

Bng 31:

Kiu hot ng 1dng cho tt c cc lp (t I-IV) iu ny m bo cho tt c cc trm co chung 1 dch v s dng cho cng tc hot ng qun l. Phn cn li, cc trm ch c h tr dch v khi cn thit nhm mc ch ti u ho hot ng ca mng.

3.2.1.2 Cc n v th tc LLC

Cc n v th tc LLC cng c mt dng PDU nh hnh 2.

DSAPSSAPControlInformation

8bit8 bit8 or 16 di thay i

(a) Khun dng LLC-PDU

Information0N(S)P/FN(R)

Supervisory10S S0000P/FN(R)

Unnumbered11M MP/FM M M

(b) Khun dng trng iu khin

I/GDSAPC/RSSAP

I/G=0 Individual DSAP

C/R=0 Command

I/G=1 Group DSAP

C/R=1 Response

P/F: Poll/Final Bit

(c) Trng a ch LLC

Hnh 31: Khun dng LLC-PDU ngha cc trng trong LLC-PDU nh sau (C 4 trng )

DSAP v SSAP c 7bt a ch. Bt th 8 ca DSAP ch ra l a ch ring hay a ch nhm. Bt th 8 ca SSAP ch ra l lnh hay tr li t mt lnh.

Trng iu khin khai bo cc loi PDU khc nhau thng qua cc bit u v cc bit M. N c di l 8 hay 16 bit tu thuc vo kiu PDU. (Ch rng PDU c gi l lnh khi n c pht i a ra cc yu cu v i cu tr li cn PDU c pht i tr li li yu cu th l PDU tr li). Vic nhn bit l lnh hay tr li c th thng qua nhn bit bit P/F. Khi PDU l lnh, ta coi l bit P. Nu P=1 th bt buc bn nhn phi tr li. i vi PDU tr li th coi l bit F. Nu F=1 th chnh l tr li t yu cu ca mt lnh c P=1. C 3 kiu PDU ng vi cc trng iu khin khc nhau

PDU-Thng tin (Khung I: information): Dng mang d liu. Trng iu khin loi PDU ny c bt u bng bit 0. C 7 bit N(S) v 7 bit N(R) dng nh s th t cc PDU gi v nhn

PDU- Gim st (Khung S: Supervisory) dng cho iu khin lung v li. 2 bit u ca trng ny l 10. Tip l 2 bit SS dng ch ra 3 dng khung iu khin khc nhau Xem bng 3-2

Khung khng nh s (Khung U: Unnumbered): C 5 bit M ch ra 32 dng khung iu khin khc nhau

SSKiu khung

00

01

10

11RR : Sn sng nhn

RNR :Khng sn sng nhn

REJ : T chi

Reserved D tr

Bng 31 gi tr cc bt SS

Ngoi ra cn c 7 bit N(R) ch ra s th t khung nhn c

TnChc nng ngha

(a) Dch v UCS

Khung U

UI :Thng tin khng nh s

XID: Nhn bit trao i

TestC

C/R

C/RTrao i d liu ngi s dng

Kiu thng tin v thng tin v kch thc ca s

Loopback Test

(b) Dch v CMS

Khung I

Khung S

+RR

+RNR

+REJ

Cc khung khng nh s (U)

SABME: Thit lp ch cn bng khng ng b m rng

DISC: Kt thc kt ni

UA- Nhn bit khng nh s

DM-Ch kt thc kt ni

FRMR: T chi khungC/R

C/R

C/R

C/R

C

C

R

R

RTrao i d liu ngi s dng

Nhn bit tch cc- sn sng nhn

Khng tch cc cha sn sng nhn

T chi

Yu cu kt ni

Kt thc kt ni

Lnh nhn bit khng nh s

T chi kt ni

Bo co khng chp nhn khung

(c)Dch v ACS

Khng nh s

AC: Thng tin nhn bit kt ni khng lin ktC/RTrao i thng tin ngi s dng

3.2.1.3 Hot ng ca LLC kiu 1: (UCS)

ch hot ng ny, cc PDU c dng truyn d liu ngi s dng m khng cn c nhn bit bo nhn hay cc th tc iu khin lung v li. Tuy nhin vn c s pht hin li v hu b khung lp vt l.

Trong ch ny, n ch s dng 2 kiu PDU

3.2.1.4 Kiu hot ng 2 LLC- (CMS)

S dng tt c 3 dng PDU thc hin 3 qu trnh trong mt kt ni thng tin l: Qu trnh thit lp kt ni Trao i d liu Kt thc cuc ni.

3.2.1.4.1 Thit lp kt ni

giai on ny mt kt ni lin kt d liu c thit lp gia hai im LLC-SAP dng cho vic trao i d liu. LLC-thc hin vic ny mi khi c yu cu DL-Connect request t lp bn trn. Khi LLC gi i khung SABME PDU ti mt LLC khc yu cu mt kt ni. Nu kt ni c chp nhn th LLC ch (a ch DSAP) s tr li li bng khung UA-PDU v kt ni ny l mt khai bo duy nht gia hai im LLC-SAP. Nu LLC ch t chi n s tr li li bng DM-PDU Xem hnh 3-3 (a)

3.2.1.4.2 Giai on trao i d liu

Khi yu cu kt ni c chp nhn v xc nhn th kt ni c thit lp. C hai bn u c th gi thng tin cho nhau qua PDU thng tin (Khung I). Bt u qu trnh gi N(S) v N(R) c gi tr bng 0. V ch c 7 bit nn s gi gi ti a m cha c tr li nhn c (bng kch thc ca s) l 128. Cc gi gi i c nh s theo th t t 0-127 nm trong trng N(S) v c quay vng nh vy. Cc gi tr li s l s th t ca gi m bn nhn cha nhn c v ang i nhn trng N(R) - Gi tr ca trng N(R) trong gi m bn nhn nhn c ni cho bn nhn bit rng bn kia nhn c ca n N(R)-1 gi v ang i gi N(R).

Cc S-PDU c dng cho c ch iu khin lung v li

RR-PDU nhn c thng bo cho LLC gi bit rng LLC ch nhn c N(R)-1 gi v ang i gi th N(R)

RNR-PDU nhn c thng bo cho LLC gi bit rng LLC ch nhn c N(R)-1 gi nhng n cha sn sng nhn tip. Khi no sn sng th bn nhn s pht cho bn gi RR-PDU.

REJ-PDU dng trong c ch go back N. khi bn gi nhn c tr li REJ-PDU th c ngha l bn nhn t chi tt c cc PDU t N(R) v n cn phi pht li tt c cc PDU t N(R) tr v sau.

Thc th LLC cng c th yu cu khi ng li hoc p ng yu cu khi ng li DL-RESET-Request. Yucu khi ng li ch n gin bng cch pht i khung SABME vi cc a ch SSAP v DSAP thch hp. LLC xa cng c th chp nhn hay t chi cc yu cu ny bng cch gi UA-PDU hay DM-PDU. Khi thc hin thit lp li, c hai LLC u thit lp li cc gi tr v 0

3.2.1.4.3 Kt thc kt ni

LLC kt thc kt ni t yu cu DL-DISCONNECT. Lc n pht i DISC-PDU ti LLC xa. LLC xa chp nhn kt thc kt ni bng cch gi tr li khung UA v pht ra ch th DL-DISCONNECT Indication ti lp trn n

(a) Thit lp kt ni v hu kt ni

(b) Trao i d liu 2 hng(c) Xy ra bn

(d) T chi pht li(e) Qu thi gian v pht li

Hnh 31 V d v hot ng ca LLC

Trong hnh 3-4 minh ho s trao i cc LLC-PDU vi cc gi tr N(S) v N(R). Nu c bit P v F th coi nh P/F c gn gi tr bng 1 cn khng c th coi nh bng 0.

+ Trn hnh (a) l qu trnh thit lp v hu kt ni. Khi mun thit lp lin kt, LLC mt pha s pht lnh SABME. Nu LLC bn kia tr li bng UA v khi to bin m th kt ni c thit lp v hai bn c th trao i PDU. Nu sau khi gi SABME mt khong thi gian bng timeout m vn cha nhn c tr li th LLC gi li tip tc gi li SABME ln th 2 nhng vi tham s bit P=1 bt buc bn nhn phi tr li bng UA hay DM. Nu sau mt vi ln nh vy na m vn khng nhn c tr li (V d trong X.25 l 20 ln) th n s thi khng kt ni v bo co vi phn qun l mng (lp cao hn). Khi mun kt thc kt ni LLC pht lnh DISC v LLC nhn cng s tr li bng UA.

+Trn hnh (b) m t qu trnh trao i d liu hai chiu gia hai thc th LLC. Cc I-PDU c nh s theo th t v trao i vi nhau. N(S) l s th t cc gi bn gi gi i cn N(R) l s th t cc gi m bn nhn nhn c.

+Trn hnh (c) minh ho hot ng LLC trong trng hp bn V d nh khi n khng x l kp cc thng tin nhn c- Cc I-PDU n qu nhanh lc ny b m s b y v phi dng lung d liu vo. Lc LLC pht lnh RNR dng vic pht d liu ca bn pht. Bn pht sau khi nhn c RNR s dng vic pht thng tin v pht lp li theo chu k lnh RR vi P=1 sn sng pht tip khi trng thi bn c gii to.

+ Hnh (d) Minh ho qu trnh x l li thng tin trong trng hp truyn b li. Trng hp ny khi bn A pht ti goi th 5 nhng gi 4 b li, bn nhn nhn c gi th 5 m khng nhn c gi 4 lin tr li li bng lnh REJ,4 c ngha l n khng nhn c 4 v yu cu bn gi gi li tt c cc gi t 4 tr i.

+Hnh (e) Minh ho li truyn v mt thi gian. Bn A pht i mt gi tin nhng sau mt thi gian timeout n vn cha nhn c tr li ca bn nhn hoc nhn c yu cu truyn gi ca bn nhn th n s phi truyn li

3.2.1.5 Hot ng ACS

Ch ny khng c HDLC. Mi PDU pht i phi c bo nhn t bn nhn m bo khng mt d liu

3.2.1.6 Hot ng iu khin lung v iu khin li LLC

3.2.1.6.1 iu khin li (error control)

iu khin li l cch thc pht hin li v x l khi d liu b li. C cc trng hp

Li nh c th t sa c

Li khng th t sa c Yu cu truyn li

3.2.1.6.2 iu khin lung (Flow control)

iu khin lung l iu khin lu lng thng tin trao i gia cc my sao cho ti u ho tc trao i m thng tin khng b mt. LLC c mt s phng php iu khin lung l Dng v i Phng php ca s c nh Phng php ca s trt. Xem thm trong iu khin lung ca TCP

3.2.1.6.2.1 Phng php dng v i

Theo phng php ny, bn gi gi i mt gi thng tin ri dng li v i bn nhn tr li nhn c v yu cu truyn tip th n mi truyn tip gi th 2. c nh vy. c im l phng php ny n gin

3.2.1.6.2.2 Phng php ca s c nh (Fixed Window)

Theo phng php ny, bn gi gi i n gi tin bng kch thc ca s. Sau i bn nhn tr li l nhn ht n gi tin th sau n mi tip tc truyn i n gi tin khc. i vi phng php ny. khi bn nhn tr li cho mt gi th m ( tng ng vi t lp 5 n lp 7 ca m hnh

5.1 Repeater

Chc nng tng ng vi lp th nht trong m hnh OSI nh hnh di

User A

User B

7App

A

6Pre

P

5Sesion

S

4Trans

T

3Net

N

2Datalink

Repeater

DL

1Physical

PhyPhy

Phy

Hnh 51 Repeater

Tng ng vi lp vt l nn Repeater c kh nng kt ni cc mng c cng kiu cu hnh v cng cu trc khung lp vt l. V d mng Bus vi Bus. N thng c dng nh l cc b khuych i lp trong trng hp cn m rng khong cch trong mt mng n.

WS

WS

WS

Repeater

WS

WS

WS

Hnh 52: Kt ni mng dng Repeater

Ch : Khng th c m rng mng mi bng Repeater (thng khng qu 5 repeater) v n c lin quan ti tr pht thng tin gia hai u cui ca mng v kch thc khung d liu trong tiu chun 802.3. Xem chun 802.3 v CSMA/CD.

5.2 Cu ni - Bridge

Chc nng tng ng lp 2 m hnh OSI nh sau

User A

User B

7App

A

6Pre

P

5Sesion

S

4Trans

T

3Net

Bridge

N

2Datalink

DLDL

DL

1Physical

PhyPhy

Phy

Hnh 51 Bridge

Theo chc nng ca mnh, Bridge c th x l cc khung d liu lp 2. Chnh v vy n c kh nng kt ni gia cc mng c cu trc khung khc nhau nh mng BUS v RING. v s dng cc phng tin truyn dn vt l khc nhau. Hnh di l kt ni gia cc mng s dng cu ni

Hnh 52 Kt ni mng bng Bridge

Cu hot ng nh mtb lc a ch lp 2. N bin i cc khung d liu ca mng LAN ny thnh khung d liu ca mng LAN khc (V d 802.3 802.5) Nhng khng lm thay i ni dung phn d liu m khung cha (d liu lp bn trn).

V d: Khi tram WS1 trn mng BUS mun gi d liu cho trm WS6 trn mng RING th n s gi khung d liu qua mng BUS theo chun 802.3. Cu tip nhn khung ny thng qua cng kt ni vi mng BUS A. Sau cu s lm nhim vuh bin i khung d liu ny thnh dng ph hp vi mng RING C theo chun 802.5 v chuyn khung ti tram WS6. Qu trnh truyn d liu t tram 6 v 1 din ra theo chiu ngc li

Di con mt ngi s dng th ton b mng ging nh l mt mng duy nht- ngha l khng phn bit trm no trn mng no. Cu hot ng trong sut (transparent) v t ng chuyn cc khung t mng ny sang mng khc theo cc qui tc c nh ngha trc. Cc qui tc ny chnh l cc thut ton chn ng i vi cu. C 3 thut ton thng dng i vi cu l:

TLB (Transparent Learning Bridge) Cu hc trong sut

STB (Spanning Tree Bridge)

SRB (Source Route Bridge)

5.2.1 Cu hc trong sut TLB

y l mt thut ton n gin, n cho php cc mng kt ni vi nhau m khng cn n s can thip ca ngi s dng. Nguyn tc hot ng ca cu nh sau:

Mi khung thng tin trong mng u phi i qua cu v cu s kim tra a ch ngun v ch ca tt c cc khung (a ch lp 2 -MAC). Thng qua cc a ch ngun (SA) ca khung ny cu c th nhn bit trm pht khung nm trn mng no. Tip theo n s so snh thng tin nhn c vi ni dung bng chn ng ca mnh (Forwarding table --> ch cho bit cc trm c a ch MAC no th thuc v mng no). Nu i ch ca trm pht c mt trong bng chn ng th thi cn nu cha c th n s ghi nh li dng cho ln sau. Sau cu s kim tra a ch ch (DA) ca khung. Nu a ch ch bit -ngha l c mt trong bng chn ng th n ch n gin pht khung v pha mng c cha trm ch. Cn nu trong trng hp n khng a ch trm ch trong bng ngha l n khng bit trm ch nm trong mng no th Cu s lm mt bn copy khung v gi ti tt c cc mng m n ni n vi hy vng rng khi trm ch nhn c khung tin v tr li li th qua n s hc c mt a ch mi.

V d trong hnh trn Khi trm 1 mun truyn d liu ti trm 6 th n s gi khung 802.3 c a ch ngun (SA) v ch (DA) qua mng BUS A. Khi cu nhn c khung ny th lp tc c a ch ngun v so snh n vi bng chn ng ca mnh. Nu cha c a ch ny th n s ghi nh li. Tip theo cu kim tra a ch ch ca khung. Nh vy xy ra hai trng hp l

Cu bit a ch trm ch trn mng Ring C. Vy cu ch n gin lm nhim v bin i khung 802.3 thnh khung 802.5 v pht khung vo mng Ring C

Cn nu cu khng bit trm ch nm trn mng no B hay C,.... th n s Copy khung bin i v pht khung ti tt c cc mng khc. Ti trm ch 6 c a ch MAC trng vi a ch ch (DA) ca khung s tip nhn khung d liu v tip n s pht khung tr li li bn gi. Nh vy thng qua khung tr li cu s bit c v tr ca trm 6 u v n ghi nh li s dng cho ln sau.

5.2.2 STB

y l thut ton c to bi Digital Equipment Corporation dng trong cc mng c nhiu kt n bng cu hin c nh ngha trong chun 802.1d. Mc ch ca thut ton ny gii quyt nhng vn thng hay xy ra trong mt h thng mng phc tp gm nhiu cu ni nh vic pht thng tin qung b trong ca nhiu cu s gy tc nghn mng (flooding) hay vic pht quay vng thng tin (Bridge loop).... Thut ton ny cho php ngi thit k mng loi b cc ng i d tha trong mng,xy dng mng thnh dng hnh cy trong ch c mt ng i duy nht gia 2 im hoc nhiu ng nhng c chn theo th bc u tin khc nhau da trn cc thng s v gi thnh v khong cch.

5.2.3 SRB

Thut ton ny thng s dng trong cc mng vng RING.

5.3 Thit b chn ng Router

Chc nng tng ng lp 3 m hnh OSI nh sau

User A

User B

7App

A

6Pre

P

5Sesion

S

4Trans

Router

T

3Net

NN

N

2Datalink

DLDL

DL

1Physical

PhyPhy

Phy

Hnh 51 Router

Tng ng vi lp 3 Router c kh nng x l cc gi d liu, c kim tra a ch, bin i gi cho ph hp vi mng v chn ng i ngn nht trong mng cho gi. Nguyn tc hot ng ca Router nh sau:

Dir: Direct

Hnh 52: V d v s dng Router trong mng

Trong mng ton cu rng, mi nt mng c mt a ch duy nht. a ch nm lp 3 trong gi IP. V d trn hnh v mi trm c gn mt a ch nh A1, A2, B10, B5, C2, D3, D5..... a ch ny l duy nht trn ton mng (a ch Internet bao gm a ch mng v a ch nt mng y ta coi A,B,C,D l phn ia ch mng cn cc con s tip theo l a ch nt mng). Ngoi ra mi trm trong mt mng li c thm a ch phn cng ca card giao tip mng - y chnh l a ch lp 2 - a ch MAC l c con s ghi bn di cc a ch lp 3 (101,102,105,110,.....) a ch MAC ny c th ging nhau trn cc mng khc nhau nhng l duy nht trn mt mng vt l.

Ta ly v d vic truyn d liu t trm c a ch Internet lp 3 l B10 - a ch MAC ca n lp 2 l 110 n trm c a ch D5 v a ch MAC =105. Qu trnh truyn c th c chia thnh 3 bc

Bc 1: u tin khi B10 mun gi thng tin n D5 n to gi tin lp 3 cha a ch bn gi l B10 v bn nhn l D5. Qua b phn tch a ch B10 bit rng trm D khng nm cng trong mng vi n, bi vy n quyt nh phi chuyn gi d liu cho Router R1 l cng ra ca ton mng B. Vic chuyn gi cho R1 (c a ch lp 3 l B5 v MAC=105) c B10 thc hin bng cch chuyn gi ny cho lp 2 bn di cho vo khung (802.3 ca mng BUS). Khung ny s gn a ch MAC bn gi ca B10 l 110 v MAC nhn l 105. Xem hnh di. Trong trng hp B10 khng bit a ch MAC ca B5 l bao nhiu th n s triu gi th tc phn gii a ch ARP ca mnh tm a ch MAC ca B5.( Xem thm phn ARP).

Gi tin lp 3

Source Add:B10

Dest Add:D5

IP Data.....

MAC Source Add:110

MAC Dest Add:105

Hnh 53: Khung Ethernet 802.3 chuyn gi t B10 ti R1

Bc 2: Khi R1 nhn c khung d liu thng qua a ch MAC 105 ca B10 t cng B5. N tch b gi ra khi khung sau s phn tch a ch ca gi. Qua phn tch a ch n bit rng cn phi chuyn gi cho trm D5. Nhn vo bng chn ng ca mnh (Routing Table) R1 hiu rng mun gi tin ti D5 phi gi gi ra cng c a ch C1 l cng kt ni vi mng Ring C ti cng ra R2 ca mng Ring c a ch C2. C1 c a ch MAC l 101 v C2 c MAC=102. Nh vy R1 s cho gi d liu ca B10 vo khung 802.5 chuyn qua mng Ring C nh hnh di

Gi tin lp 3

Source Add:B10

Dest Add:D5

IP Data.....

MAC Source Add:101

MAC Dest Add:102

Hnh 54: Khung Ethernet 802.5 chuyn gi t R1 ti R2

Bc 3: Khi R2 nhn c khung d liu do R1 gi, n s tch b phn khung ly ra gi d liu. c a ch ch trn gi R2 hiu rng cn phi chuyn gi cho trm D5. Nhn vo bng chn ng ca mnh (Routing Table) R1 thy rng n c th chuyn trc tip gi tin ti D5. Bi vy R2 cho gi vo khung 802.3 chuyn ti D5. nh hnh di

Gi tin lp 3

Source Add:B10

Dest Add:D5

IP Data.....

MAC Source Add:103

MAC Dest Add:105

Hnh 55: Khung Ethernet 802.3 chuyn gi t R2 ti D5

5.4 Gateway

Chc nng c th tng ng c 7 lp m hnh OSI nh sau

User A

User B

7App

AA

A

6Pre

PrePre

P

5Sesion

SeSe

S

4Trans

TT

T

3Net

NN

N

2Datalink

DLDL

DL

1Physical

PhyPhy

Phy

Hnh 51 Gateway

Gateway h tr cc th tc phin dch gia cc mng c kin trc khc nhau nhm cung cp mtt dch v chung ti ngi s dng.

Chng 6: Chn ng trong mng6.1 L thuyt v GRAPH6.1.1 Cc khi nim v l thuyt Graph

6.1.1.1 nh ngha:

Mt Graph G(V,E) bao gm mt tp cc i tng gi l Nt (node or vertice) v cc cnh (edge or link). Mi cnh l mt ng ni gia hai nt. Xem hnh v di l Graph v ma trn m t n. y :

V l tp hp cc nt {V1,V2,V3,V4,V5,V6}

v E l tp hp cc link {(V1,V2), (V1,V3), (V1,V4), (V2,V4), (V2,V3), (V3,V4), (V3,V5), (V3,V6), (V4,V5), (V5,V6)}.

aj l cc phn t ca ma trn

Gi tr bng 1: Nu (i,j)( E--> C kt ni trc tip gia hai nt

Gi tr bng 0: cn li --> Khng c kt ni trc tip gia hai nt

V2 V3

V6

V1

V4

V5

V1V2V3V4V5V6

V1011100

V2101100

V3110111

V4111010

V5001101

V6001010

Hnh 61: Graph vi ma trn m t n

Nu hai cnh ca cng mt cp hai nt th gi l cc cnh song song. Mt cnh ch lin quan ti mt nh n gi l vng lp. Mt Graph khng c cnh song song v vng lp th gi l graph n gin.

ng i (Path): l mt ng ni t nh i ti nh j qua mt chui cc cnh v nt bt u t nt i v kt thc nt j. Trong mt graph n gin, khng c cnh hay nt no li xut hin nhiu hn mt ln trong ng i. V d ng i t V1 n V6 c th l mt trong cc tp hp ng sau: (V1,V2,V3,V4,V5,V6), (V1,V2,V3,V5,V6), (V1,V2,V3,V6), (V1,V2,V3,V3,V5,V6), (V1,V3,V6) ......

Khong cch (Distance): khong cch gia hai nt l s nh nht cc cnh to thnh ng kt ni gia chng. Trong s cc ng i t V1 n V6 th ng i (V1,V3,V6) l ng i ngn nht. Khong cch n ch l hai nt.

ng vng (cycle): l ng m bt u v kt thc nt l nh nhau. V d: (V1,V3,V4,V1) to thnh mt ng vng

Cui cng: Graph c gi l kt ni nu c ng ni gia hai nt bt k ca n.

6.1.1.2 Digraphs v Weighted Graphs

Digraph (Direct graph) G(V,E) : trn mi cnh ca n ch hng truyn thng tin i. Mt ma trn lin k c th c s dng m t digraph

V2 V3

V6

V1

V4

V5

V1V2V3V4V5V6

V1025100

V2303200

V3860315

V4723010

V5001102

V6008040

Hnh 61:Weighted Graph

- Trng lng ca graph - Weighted graph or weighted digraph: L gi tr s (gi thnh ng ni) kt hp vi mi cnh. Ma trn trn ch ra gi tr cc ng ni

aj l cc phn t ca ma trn

Gi tr bng wij: Nu (i,j)( E--> C kt ni trc tip gia hai nt

Gi tr bng 0: cn li --> Khng c kt ni trc tip gia hai nt

Trong weighted graph- di ng i bng tng gi tr cc cnh nm trn ng . Trong v d v ng i t V1 n V6 th ng (V1,V3,V2,V4,V5,V6) c gi thnh ln nht bng 16- cn ng i (V1,V4,V5,V6) c gi thnh nh nht bng 4.

6.1.1.3 Cy Tree :

Cy l khi nim hay dng v s dng nhiu trong mng. Cc nh ngha v cy nh sau:

1- Cy l mt graph n gin tho mn: Nu i,j l hai nt trong cy th tn ti mt ng i duy nht t i n j

2- Mt graph n gin N nt l mt cy nu n ch c N-1 cnh v khng c vng lp

3- Mt graph n gin N nt l mt cy nu n ch c N-1 cnh v c kt ni

Hnh di v d v mt cy.

V1

V2 V3

V4

V5V6

Hnh 61: V d v cy

Mt nh ca cy gi l gc (root)- mc 0. Cc nh khc ni trc tip vi gc gi l cp 1, nu ni trc tip vi cp 1 gi l cp 2,.... nh m khng cn c nt no tip theo n na (nt con child) goi l l (leaf).

6.1.1.4 Spanning Tree

Graph con - Subgraph: nm trong Graph G c to thnh t mt s cnh v nt trong G. Cho G(V,E), G(V,E) l con ca G khi :

1. V(V v E(E v

2. cho mi cnh e(E, nu e l ng ni v v w --> v, w (V

Cng cy (Spanning tree) : Mt Graph con T ca G gi l mt Spanning tree ca G nu T l cy v bao gm tt c cc nh ca G. Ni cch khc spanning tree l Graph G khi b i tt c cc vnd trn nhng kt ni vn c duy tr. Hnh di v d v spanning tree

V2 V3

V6

V1

V4

V5V2 V3

V6

V1

V4

V5

Hnh 61: Spanning tree

+ Kim tra rng ca Spanning tree

i vi Graph, ta cn tm Spanning tree cho n. iu ny c th thc hin mt cch t ng bng cch p dng mt thut ton l BFS (Breadth First Search)

tng ca thut ton ny l x l tt c cc nt trong cng mt mc trc khi dch chuyn xung mc tip theo. trong qu trnh x l, ta phn chia cc nt ca Graph thnh tp hp cc nt cc mc khc nhau. Bt u t mt nh bt k v gn cho n mc 0. Tt c cc nt gn k n c gn mc 1 t tn Vi1, Vi2, ..... Vin l cc nh thuc mc i. Coi tt c cc nh gn k Vi1 l khng thuc mc 0,1,2,...i v gn cho nhng nh mc i+1. Tip tc coi tt c cc nh gn k Vi2 khng thuc mc 0,1,2,.....i,i+1 v cng gn cho nhng nh ny mc i+1. Tip tc qu trnh ny cho n khi tt c cc nt a c kim tra.

V d: Vi Graph trn

u tin mt th t cc nt s c chn- V1,V2,V3,V4,V5,V6

Chn nh u tin v t lm gc (Root), Tp T cha nt gc {V1} vi khng cnh.

Thm vo T mi cnh (V1,x) x l gn k v khng nm trong T, nh vy s khng sinh ra vng trn. T V1 cc cnh (V1,V2) , (V1,V3), (V1,V4) c thm vo v cc nh V2,V3,V4 c thm vo T Ta hon thnh bc th nht

Lp li th tc ny cho tt c cc nh thuc mc 1 theo th t v thm cc nh mi mc 2 vao T. Trong trng hp ny

V2: Khng thm

V3: thm vo cnh (V3,V5), (V3,V6) v cc nt V5,V6

V4: Khng thm

Lc ny tt c cc nt c mt trong T. Ta c th dng li , cn nu khng th li tip tc vi mc 3 v c nh vy n ht.

6.1.2 Quyt nh ng i ngn nht

ng di ngn nht c chn vi gi thnh ti thiu. Mt trong nhng thut ton ni ting hay dng nht l Dijkstra v Bellman-Fort

6.1.2.1 Thut ton Dijkstra

Ni dung thut ton ny nh sau: Tm ng i ngn nht t mt nt ti tt c cc nt khc bng cch pht trin dn dn t gc lan sang cc nt khc bn cnh. T bc th k, ng i ngn nht ti nt k (khng quan tm n gi c) gn vi nt ngun nht c quyt inh. Cc nt ny c t trong tp T. bc k+1, nt khng thuc T c ng i ngn nht t nt ngun c thm vo T. Thut ton c th m t nh sau

N=tp cc nt trong mng

s=nh ngun

T=Tp cc nt cha kt hp trong thut ton

w(i,j)= Gi thnh ng ni gia hai nt i v j. w(i,j)=0; w(i,j)=( nu hai nt khng ni trc tip w(i,j)0 nu hai nt ni trc tip

L(n)= gi thnh ng i thp nht t ngun s ti nh n ti thi im tnh ton. thi im kt thc, n chnh l kt qu

Thut ton c tin hnh theo ba bc. Bc 2 v 3 lp li cho n khi T=N

Bc 1: Khi to

T={s}

Bt u tp hp ch c duy nht nt ngun

L(n)=w(i,j) cho n(s

Gi thnh khi to ban u ch n gin l gi ng

ni trc tip ca nt bn cnh ti nt ngun

Bc 2:

Tm cc nt gn k khng trong T c gi thnh ng ni ti s l thp nht v a n vo trong tp T. Cng kt hp cc cnh t cc nt ti cc nt trong T

Din gii:

Tm x(T nh vy L(x)=minj(T L(j)

Thm x vo T, thm vo T cc cnh gn vi x c gi thnh ng i ti x l thp nht

Bc 3: Cp nhp li gi thnh

L(n)=min[L(n),L(x)+w(x,n)] cho tt c n(M

L(x)+w(x,n) ngha l gi thnh t s ti x cng gi t x ti n

Thut ton kt thc khi tt c cc nt thm vo T. Khi kt thc L(x) l gi thnh ng i thp nht t s ti x v ng thi T l spanning tree ca graph gc.

Thut ton Dijkstra (s=1)

Ln lpTL(2) PathL(3) PathL(4) PathL(5) PathL(6) Path

1{1}2 1-25 1-31 1-4( ----( ----

2{1,4}2 1-24 1-4 31 1-42 1-4-5( ----

3{1,2,4}2 1-24 1-4-31 1-42 1-4-5( ----

4{1,2,4,5}2 1-23 1-4-5-31 1-42 1-4-54 1-4-5-6

5{1,2,3,4,5}2 1-23 1-4-5-31 1-42 1-4-54 1-4-5-6

6{1,2,4,5,6}2 1-23 1-4-5-31 1-42 1-4-54 1-4-5-6

Ti mi bc lp, T s thm vo n mt nt x v gi tr L(x) ti thi im l gi thnh ti thiu t s n x. Thm vo ng i duy nht t s dn x cng c nh ngha. ng ny ch i qua cc nt c trong T

6.1.2.2 Thut ton Bellman-Fort [FORT62]

Ni dung thut ton ny nh sau: Tm ng i ngn nht t mt nt ngun cho trc vi s bt buc ng i ch qua mt cnh. Tip tc tm ng i ngn nht vi s bt buc ch i qua 2 cnh ri c tip tc nh vy. Thut ton din gii nh sau

- s=nt ngun

- w(i,j)= Gi thnh ng ni gia hai nt i v j. w(i,j)=0; w(i,j)=( nu hai nt khng ni trc tip w(i,j)0 nu hai nt ni trc tip

- h=S ti a cc cnh trong ng i thi im hin thi

- Lh(n)= gi thnh ng i thp nht t ngun s ti nh n Vi khng hn h cnh

Cc bc thc hin

Bc 1: Khi to

L0(n)=( cho tt c n(s

Lh(s)=0 Cho tt c h

Bc 2: Cp nht

Vi mi h k tip (0:

Cho mi n(s, tnh:

Lh+1(n) =minj [Lh(j) +w(j,n)]

Kt ni nt n vi nt j cp trn n -xc nh gi tr ti thiu v hn ch bt k kt ni ca n vi cc nt cp trn khc m n khng ni n.

i vi mi bc lp, h=K cho mi nt n, thut ton so snh gi ng i t s ti n qua K+1 cnh vi ng i tn ti trong ln lp trc. V n s chn ng c gi thnh b hn. Khi kt thc thut ton th spanning tree cng hon thnh.

Thut ton Bellman-Fort (s=1)

h

Lh(2) PathLh(3) PathLh(4) PathLh(5) PathLh(6) Path

0

( -----( -----( -----( -----( ----

1

2 1-25 1-4 31 1-4( -----( ----

2

2 1-24 1-4-31 1-42 1-4-510 1-3-6

3

2 1-23 1-4-5-31 1-42 1-4-54 1-4-5-6

4

2 1-23 1-4-5-31 1-42 1-4-54 1-4-5-6

6.2 Th tc chn ng Routing Protocol

Chng 7: Thc hnh vi mng my tnh7.1 Kt ni my tnh bng cp Link

7.1.1 Chun b phn cng

C hai my tnh

Mt cp Link ni gia hai my. Ty theo loi cp m ta c th kt ni gia hai my qua cc cng ni tip vi ni tip, hoc song song vi song song hoc ni tip vi song song. Yu cu ca cp Link nh sau:

Cu hnh chn ca cp link

9 - 9 Serial

2 ======= 3

3 ======= 2

4 ======= 6

5 ======= 5

6 ======= 4

7 ======= 8

8 ======= 7

9 - 25 Serial

2 ======= 2

3 ======= 3

4 ======= 6

5 ======= 7

6 ======= 20

7 ======= 5

8 ======= 4

25 - 25 Serial

2 ======== 3

3 ======== 2

4 ======== 5

5 ======== 4

6 ======== 20

7 ======== 7

20 ======== 6

Pin layout of the parallel cable.

1 ======= 7

2 ======= 15

3 ======= 13

4 ======= 12

5 ======= 10

6 ======= 11

7 ======= 1

8 ======= 14

9 ======= 16

10 ======= 5

11 ======= 6

12 ======= 4

13 ======= 3

14 ======= 8

15 ======= 2

16 ======= 9

17 ======= 17

18 ======= 18

19 ======= 19

20 ======= 20

21 ======= 21

22 ======= 22

23 ======= 23

24 ======= 24

25 ======= 25

7.1.2 S dng phn mm

7.1.2.1 Dng chng trnh NC

Chy NC t du nhc h iu hnh C:\>NC\NC

mn hnh NC xut hin

n F9 : vo menu ca NC ==> Chn mc hoc ==> Chn

Tip theo mn hnh NC s c hin ln ca s yu cu bn ch ra cp Link c ni trn cng thng tin no ca my bn v la chon cho my l Master hay Slave.

Ch rng nu ta chn 1 my l master th my kia phi l Slave

Nu kt ni thnh cng th trn my chn Master s xut hin a ca my Slave v ta c th thao tc vi a my Slave nh trn my ca mnh vy

Hnh 71: Mn hnh NC

7.1.2.2 S dng Window

C th s dng window kt ni. Vo mc v t cc tham s cho n

7.1.2.3 Vit chng trnh truyn s liu qua cng thng tin ca my tnh. Khuyn khch

7.2 Kt ni my tnh qua MODEM

7.2.1 Phn cng

Chun b hai my tnh mi my tnh ni ti mt MODEM v MODEM Ni vo mng in thoi nh hnh v 1-1

7.2.2 Phn mm

7.2.2.1 S dng chng trnh NC

7.2.2.2 S dng Window

7.2.2.3 T vit chng trnh truyn s liu qua MODEM

7.3 Xy dng mng LAN. 7.3.1 Cc thit b cn thit Ti thiu hai my tnh PC

Lp t Card giao tip mng cho tng my Kt ni cp c th l mng BUS hoc Sao tu thuc nhu cu7.3.2 Ci t phn mm

La chn h iu hnh mng Window311, Window 95-2002, Unix, Window NT,.....

i vi Unix, Window2000, Window NT khi ci t th ch la chn.

Nu l mng ngang hng th ci t tt c cc my ging nhau

Nu mng c t my ch th khi ci t cn ch t tham s cho my ch

7.3.3 Ci t cu hnh cho cc my

7.3.3.1 Ci t card giao tip mng

Cc my tnh sau khi c lp t Card giao tip mng cn c khai bo vi my tnh. iu ny c th thc hin n gin nh sau:

+ Cho a mm hoc a CD cha chng trnh iu khin Card vo a

+ Vo Control Panen --> Vo mc Network --> Chn Add --> Chn Adapter --> chn Have disk sau ch ra th mc trn a c cha chng trnh iu khin card -->OK

Ch : Sau khi ci t card xong c th kim tra xem card hot ng ng cha bng cch vo Control Panen > mc System --> Chn Device Manager --> chn Network Adapter Nu thy tn card mng khng b nh du vng ngha l Card c my tnh tip nhn

7.3.3.2 Ci t th tc thng tin

Ta c th thy rng

1. My tnh khng c ni mng Ging nh mt k n c b tch ri ra khi th gii

2. My tnh c lp t v ci xong card mng: - My c gia nhp th gii thng tin. Nhng vn l mt k cm ic- khng c kh nng giao tip (nghe ni) vi cc thit b khc.

3. Cn dy cho my tnh bit ni v bit nghe hiu cc lung thng tin trn mng : y chnh l bc th 3: Ci t th tc thng tin cho my tnh: Cc th tc thng tin ca my tnh ging nh ngn ngcon ngi giao tip vi nhau hng ngy thi. hai my tnh mun trao i thng tin vi nhau th cn dng chung mt th tc (Ging hai ngi cn ni vi nhau cng mt ngn ng). trong thng tin cng nh trong cuc sng c rt nhiu th tc (Cng nh c nhiu ngn ng). V mi mt my tnh ch cn ci t cho mnh ti thiu l mt th tc. Th n mi c kh nng giao tip vi cc my tnh khc. Ci cho my cng nhiu th tc th cng nh con ngi bit nhiu ngn ng - anh ta s c kh nng giao tip c vi nhiu h thng thng tin khc. Tt nhin phi tr gi l tc x l thng tin s b chm i. Cc th tc trn my tnh thng dng nht

+ TCP/IP: Th tc chun cho tt c cc my hot ng trn mng Internet

+ SPX/IPX: Th tc chun trong mng Novell Netware

+ .......

C l ch khc vi con ngi - hc mt ngn ng con ngi phi mt n hng nm th ch cn mt vi thao tc cha y mt pht bn c th ci t xong mt th tc cho my tnh. Cc bc nh sau

Chn Control Panen --> Chn Network --> Chn Add --> Chon Protocol --> Chn tn th tc bn mun ci t.

Thng thng vi my chy Window ci TCP/IP th chn manufacture l Microsoft- v Network Protocol l TCP/IPBn hon ton c th thm vo bao nhiu th tc tu thch nhng iu ny khng cn thit nu tt c cc my khc trong mng dng cng mt th tc

7.3.3.3 Cc thng s vi TCP/IP

Khi chn th tc TCP/IP l th tc chun trn mng Internet th cn phi t cho n cc thng s. Trn ca s Network chn TCP/IP v chn Properties Xem hnh 1

Hnh 1Hnh 2

Tip theo phi gn a ch Internet cho mi my. a ch ny phi l duy nht trong mng.

V d hnh 2.

Ngoi ra cn mt s thng s khc nh DNS Configuration, Gateway, WINS Configuration,... cng cn c chi ra.

Nu l mng Intranet- l mng cc b nhng c cng ni ra ngoi vo Internet th cho my c th truy nhp ra ngoi vo Internet th cn ch ra a ch cng ra khi mng cc b trong mc Gateway.

7.4 Kim tra hot ng v S dng mng

Mng sau khi ci t xong bn c th kim tra thng qua mt s th tc v chng trnh lm vic trn mng sau

7.4.1 Kim tra thng mng Lnh PingV d sau khi hon thnh vic ci t v gn a ch cho cc my tnh cng nh cc thng s cnf thit. Ta c th kim tra s trao i thng tin gia cc my trn mng bng lnh Ping. V d a ch IP my bn l 193.105.210.65 v bn mun kim tra s kt ni ti my bn cnh (hng xm) c a ch 193.105.210.76

Ti du nhc h iu hnh ca Window g

C:\> ping 193.105.210.76

sau n Enter

Nu kt qu c Reply (tr li ) ngha l mng hot ng tt

Xem hnh di

Hnh 3: S dng lnh Ping

Chng 1:Gii thiu tng quan v mng11.1Gii thiu v mng my tnh11.1.1nh ngha1Mng my tnh l s kt ni gia cc my tnh vi nhau nhm mc ch trao i d liu. Cc d liu trao i l tt c nhng g ngi s dng yu cu nh:11.1.2Phn loi1C nhiu cch phn loi mng c th l phn loi theo phm vi, theo cu trc hay theo phng thc x l thng tin bn trong mng11.2Cc phng php kt ni my tnh31.2.1Phng tin kt ni.31.2.2Kt ni my tnh qua cng thng tin31.2.3Kt ni my tnh bng MODEM31.2.4Ni mng my tnh Mng LAN31.2.5Ni mng my tnh- Kt ni mng rng41.3H iu hnh v qun l mng41.4Cc loi mng v cc th tc thng tin41.4.1Mng in thoi c nh4Chng 2:M hnh phn lp mng52.1Khi nim52.2M hnh OSI6Chng 3:Mng Lan v cc chun93.1Mng LAN93.2Cc Chun LAN103.2.1LLC - iu khin kt ni Logic.103.2.2Chc nng lp MAC15Chng 4:Gii thiu v cc Protocol v cc loi mng224.1TCP/IP224.1.1TCP Transport control Protocol224.1.2UDP (user Datagram protocol)294.1.3Internet Protocol : IP294.1.4Th tc phn gii a ch ARP (Address Resolution Protocol)33Chng 5:Cc thit b kt ni mng405.1Repeater405.2Cu ni - Bridge415.2.1Cu hc trong sut TLB425.2.2STB425.2.3SRB425.3Thit b chn ng Router425.4Gateway44Chng 6:Chn ng trong mng456.1L thuyt v GRAPH456.1.1Cc khi nim v l thuyt Graph456.1.2Quyt nh ng i ngn nht476.2Th tc chn ng Routing Protocol49Chng 7:Thc hnh vi mng my tnh507.1Xy dng mng LAN.507.1.1Cc thit b cn thit517.1.2Ci t phn mm517.1.3Ci t cu hnh cho cc my527.2Kim tra hot ng v S dng mng537.2.1Kim tra thng mng Lnh Ping53

TCP Header

IP Header

SN=1001

SN=1201

SN=1401

SN=1601

A=1601

W=1000

SN=1801

SN=2001

SN=2201

SN=2401

A=2601 W=1400

Header

150