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Gio trnh Mng My Tnh

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TrangGII THIU.................................................................................................................................3 CHNG 1 - GII THIU V MNG MY TNH..............................................................4 1.1 Lch s mng my tnh.......................................................................................................4 1.2 Mt s khi nim c bn...............................................................................................5 1.3 Mng ngang hng (Peer to Peer) v mng c my ch (Server based)...........................8 1.4 Cc h iu hnh mng.....................................................................................................9 1.5 Cc dch v mng............................................................................................................10 1.6 Lm th no tr thnh mt chuyn nghip vin v mng my tnh?........................12 CHNG 2 - M HNH OSI..................................................................................................14 2.1 Kin trc phn tng v m hnh OSI (Open System Interconnect).................................14 2.2 ngha v chc nng ca cc tng trong m hnh OSI..................................................16 2.3 p dng m hnh OSI......................................................................................................20 2.4 M t cc thnh phn ca khun d liu (Frame)........................................................22

CHNG 3 - NG TRUYN VT L............................................................................27 3.1 Truyn d liu: tn hiu tng t (analogue) v tn hiu s ho (digital)...................27 3.2 Cc c tnh ca ng truyn mng............................................................................28 3.3 Cc mng LAN: Baseband v Broadband.......................................................................30 3.4 Cc loi cp mng...........................................................................................................30 CHNG 4 - CC GIAO THC MNG (PROTOCOLS)..................................................38 4.1 Giao thc (protocol) mng l g?....................................................................................38 4.2 B giao thc TCP/IP (Transmission Control Protocol / Internet Protocol) ..................39 4.3 B giao thc IPX/SPX (Internetwork Packet Exchange / Sequenced Packet Exchange ) ..................................................................................................................................................42 4.4 B giao thc Microsoft Network ( NETBIOS, NETBEUI, SMB).....................................43 4.5 Mt s Protocols khc.....................................................................................................46 CHNG 5 - CC HNH TRNG (TOPOLOGIES) CA MNG CC B (LAN)......48 5.1 Cc c trng c bn ca mng cc b (LAN).............................................................48 5.2 Cc hnh trng LAN n gin........................................................................................50 5.3 Cc hnh trng LAN hn hp..........................................................................................53 5.4 Cc h thng giao vn mng..........................................................................................55 5.5 5.6 Kin trc Ethernet...........................................................................................................58 Mng Token Ring............................................................................................................63

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Gio trnh Mng My Tnh Trang 2 CHNG 6 GII THIU WINDOWS 2000.......................................................................70 6.1 Cc phin bn ca Windows 2000....................................................................................70 6.2 Mt s c im mi ca Windows 2000.......................................................................71 6.3 M hnh workgroup v m hnh domain trong Windows 2000.........................................76 CHNG 7 CI T WINDOWS 2000 SEVER...............................................................80 7.1 Ci t Windows 2000 Server..........................................................................................80 7.2 ng nhp ti mt Domain ............................................................................................88 7.3 Cc cng c qun tr.........................................................................................................90 7.4 Hp thoi bo mt Windows 2000 .................................................................................90 CHNG 8 - QUN TR TI KHON NGI DNG.....................................................93 8.1 Cc loi ti khon ngi dng (user)..............................................................................93 8.2 Lp k hoch ti khon ngi dng................................................................................94 8.3 To ti khon ngi dng cc b v ti khon ngi dng min................................97 8.4 Thit lp h s ngi dng (User Profile)...................................................................108 CHNG 9 - QUN TR TI KHON NHM................................................................116 9.1.Cc loi nhm trong Windows 2000................................................................................116 9.2.Lp k hoch nhm Local Domain v nhm Global.......................................................117 9.3.To v xo cc nhm........................................................................................................117 9.4.Thm cc thnh vin vo nhm........................................................................................119 TI LIU THAM KHO........................................................................................................125

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GII THIUYu cu c cc ti liu tham kho cho sinh vin ca khoa Cng ngh Thng tin - Trng Cao ng Cng nghip 4 ngy cng tr nn cp thit. Vic bin son ti liu ny nm trong k hoch xy dng h thng gio trnh cc mn hc ca Khoa. cng ca gio trnh c thng qua Hi ng Khoa hc ca Khoa v Trng. Mc tiu ca gio trnh nhm cung cp cho sinh vin mt ti liu tham kho chnh v mn hc Mng my tnh, trong gii thiu nhng khi nim cn bn nht v h thng mng my tnh, ng thi trang b nhng kin thc v mt s k nng ch yu cho vic bo tr v qun tr mt h thng mng. y c th coi l nhng kin thc ban u v nn tng cho cc k thut vin, qun tr vin v h thng mng. Ti liu ny c th tm chia lm 2 phn: Phn 1: t chng 1 n chng 5 Phn 2: t chng 6 n chng 9

Phn 1, bao gm nhng khi nim c bn v h thng mng (chng 1), ni dung chnh ca m hnh tham chiu cc h thng m - OSI (chng 2), nhng kin thc v ng truyn vt l (chng 3), khi nim v ni dung c bn ca mt s giao thc mng thng dng (chng 4) v cui cng l gii thiu v cc hnh trng mng cc b (chng 5) Phn 2, trnh by mt trong nhng h iu hnh mng thng thng nht hin ang dng trong thc t: h iu hnh mng Windows 2000 Server. Ngoi phn gii thiu chung, ti liu cn hng dn cch thc ci t v mt s kin thc lin quan n vic qun tr ti qun ngi dng. Tham gia bin son gio trnh c: Ging vin Nguyn Vn Bnh bin son chnh cc chng 1, 2, 5 Ging vin T Duy Cng Chin bin son chnh cc chng 3, 4, 9 Ging vin Nguyn Ch Hiu bin son cc chng 6, 7, 8.

Mc d c nhng c gng hon thnh gio trnh theo k hoch, nhng do hn ch v thi gian v kinh nghim son tho gio trnh, nn ti liu chc chn cn nhng khim khuyt. Rt mong nhn c s ng gp kin ca cc thy c trong Khoa cng nh cc bn sinh vin v nhng ai s dng ti liu ny. Cc gp xin gi v T H thng my tnh Khoa Cng ngh thng tin - Trng Cao ng Cng nghip 4. Xin chn thnh cm n trc.

Nhm bin sonThng 08/2004

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CHNG 1 - GII THIU V MNG MY TNHMC TIU CA CHNG Kt thc chng ny, sinh vin s c th: Nm s lc v lch s pht trin ca mng my tnh Hiu c khi nim mng my tnh cng nh hai yu t c bn ca n l kin trc v mi trng truyn. Nm c ba tiu ch c bn phn loi mng my tnh v hnh trng tng quan ca mng LAN. Nm c hai m hnh mng: ngang hng (peer-to-peer) v client/server. Bit c mt s h iu hnh mng thng dng. Nm c mt s dch v c bn c trn mng. Nhng yu cu cn c tr thnh mt chuyn nghip vin v mng my tnh.

1.1 Lch s mng my tnhT u nhng nm 60 xut hin cc mng x l trong cc trm cui (terminal) th ng c ni vo mt my x l trung tm. V my x l trung tm lm tt c mi vic: qun l cc th tc truyn d liu, qun l s ng b ca cc trm cui v.v, trong khi cc trm cui ch thc hin chc nng nhp xut d liu m khng thc hin bt k chc nng x l no nn h thng ny vn cha c coi l mng my tnh. Gia nm 1968, Cc cc d n nghin cu tin tin (ARPA Advanced Research Projects Agency) ca B Quc phng M xy dng d n ni kt cc my tnh ca cc trung tm nghin cu ln trong ton lin bang, m u l Vin nghin cu Standford v 3 trng i hc (i hc California Los Angeless, i hc California Santa Barbara v i hc Utah). Ma thu nm 1969, 4 trm u tin c kt ni thnh cng, nh du s ra i ca ARPANET. Giao thc truyn thng dng trong ARPANET lc t tn l NCP (Network Control Protocol). Gia nhng nm 1970, h giao thc TCP/IP c Vint Cerf v Robert Kahn pht trin cng tn ti vi NCP, n nm 1983 th hon ton thay th NCP trong ARPANET. Trong nhng nm 70, s lng cc mng my tnh thuc cc quc gia khc nhau tng ln, vi cc kin trc mng khc nhau (bao gm c phn cng ln giao thc truyn thng), t dn n tnh trng khng tng thch gia cc mng, gy kh khn cho ngi s dng. Trc tnh hnh , vo nm 1984 T chc tiu chun ho quc t ISO cho ra i M hnh tham chiu cho vic kt ni cc h thng m (Reference Model for Open Systems Interconnection - gi tt l m hnh OSI). Vi s ra i ca OSI v s xut hin ca my tnh c nhn, s lng mng my tnh tnh trn ton th gii tng ln nhanh chng. xut hin nhng khi nim v cc loi mng LAN, MAN.

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Ti thng 11/1986 c ti 5089 my tnh c ni vo ARPANET, v xut hin thut ng Internet. Nm 1987, mng xng sng (backborne) NSFnet (National Science Foundation network) ra i vi tc ng truyn nhanh hn (1,5 Mb/s thay v 56Kb/s trong ARPANET) thc y s tng trng ca Internet. Mng Internet da trn NSFnet vt qua bin gii ca M. n nm 1990, qu trnh chuyn i sang Internet - da trn NSFnet kt thc. NSFnet gi y cng ch cn l mt mng xng sng thnh vin ca mng Internet ton cu. Nh vy c th ni lch s pht trin ca Internet cng chnh l lch s pht trin ca mng my tnh.

1.2 Mt s khi nim c bn1.2.1. Mng my tnh l g?Ta c th nh ngha: mng my tnh l mt tp hp cc my tnh c ni kt vi nhau bi cc ng truyn vt l theo mt kin trc no . Mt cch c th hn ta c th hiu mng my tnh bao gm s kt ni t hai my tnh tr nn. Cc my tnh ny c th giao tip vi nhau, chia x ti nguyn (cc a cng, cc my in v cc a CD-ROM v.v), mi my c th truy xut cc my xa hoc cc mng khc trao i cc file, d liu v thng tin hoc cho php cc giao tip in t.

1.2.2. Cc yu t ca mng my tnh.Nh nh ngha trn, hai yu t cn bn ca mng my tnh l: ng truyn vt l v kin trc mng. Kin trc mng bao gm: hnh trng (topology) ca mng v giao thc (protocol) truyn thng. ng truyn mng (medium) bao gm: loi c dy (wire): cc loi cp kim loi, cp si quang, v loi khng dy (wireless): tia hng ngoi, sng in t tn s radio v.v. Chi tit v cc ni dung ny s c trnh by cc chng sau.

1.2.3. Cc tiu ch phn loi mng my tnh.Da vo cc tiu ch khc nhau, ngi ta phn chia mng my tnh thnh cc loi khc nhau. Sau y l ba tiu ch c bn. a) Phn loi mng da trn khong cch a l, c ba loi mng:

Mng cc b (Local Area Network LAN): l mng c ci t trong mt phm vi tng i nh (trong mt phng, mt to nh, hoc phm vi ca mt trng hc v.v) vi khong cch ln nht gia hai my tnh nt mng ch trong khong vi chc km tr li. Tng qut c hai loi mng LAN: mng ngang hng (peer to peer) v mng c my ch (server based). Mng server based cn c gi l mng Client / Server (Khch / Ch). Mng th (Metropolitan Area Network MAN): l mng c ci t trong phm vi mt th hoc mt trung tm kinh t - x hi c bn knh khong 100 km tr li.

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Mng din rng (Wide Area network WAN): phm vi ca mng c th vt qua bin gii quc gia v thm ch c lc a. Cp truyn qua i dng v v tinh c dng cho vic truyn d liu trong mng WAN. Mng ton cu (Global Area Network GAN): phm vi ca mng tri rng ton Tri t. Mng chuyn mch knh (circuit switched networks): khi c hai thc th cn trao i thng tin vi nhau th gia chng s c thit lp mt knh c nh v c duy tr cho n khi mt trong hai bn ngt kt ni. Cc d liu ch c truyn theo con ng c nh ny. K thut chuyn mch knh c s dng trong cc kt ni ATM (Asynchronous Transfer Mode) v dial-up ISDN (Integrated Services Digital Networks). V d v mng chuyn mch knh l mng in thoi. Phng php chuyn mch knh c hai nhc im chnh: Phi tn thi gian thit lp ng truyn c nh gia hai thc th. Hiu sut s dng ng truyn khng cao, v c lc trn knh khng c d liu truyn ca hai thc th kt ni, nhng cc thc th khc khng c s dng knh truyn ny. Mng chuyn mch thng bo (message switched networks): Thng bo (message) l mt n v thng tin ca ngi s dng c khun dng c qui nh trc. Mi thng bo c cha vng thng tin iu khin trong c phn a ch ch ca thng bo. Trong mng chuyn mch thng bo, gia hai thc th truyn thng tn ti nhiu ng truyn khc nhau. Cn c vo a ch ch, cc thng bo khc nhau c th n ch theo nhng con ng khc nhau. Phng php chuyn mch thng bo c mt s u im: Hiu sut s dng ng truyn cao, v c th phn chia gia nhiu thc th. Mi nt mng c th lu tr thng bo cho n khi knh truyn rnh mi gi thng bo i, do gim c trnh trng tc nghn mng. v.v

b) Phn loi mng da trn k thut chuyn mch, cng c ba loi mng:

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Nhc im chnh ca phng php chuyn mch thng bo l khng hn ch kch thc ca cc thng bo, do c th dn n ph tn lu tr tm thi cao. K thut chuyn mch thng bo thch hp vi cc dch v thng tin kiu th in t (Electronic Mail)

Mng chuyn mch gi (packet - switched networks): mi thng bo c chia thnh nhiu phn nh hn gi l cc gi tin (packet) c khun dng qui nh trc. Mi gi tin cng c phn thng tin iu khin cha a ch ngun (sender) v a ch ch (receiver) ca gi tin. Cc gi tin thuc v mt thng bo c th truyn ti ch theo nhng con ng khc nhau.

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K thut chuyn mch gi v c bn ging k thut chuyn mch thng bo, nhng c hiu qu hn l ph tn lu tr tm thi ti mi nt gim i v kch thc ti a ca cc gi tin c gii hn. Nhng kh khn ca k thut chuyn mch gi cn gii quyt l: tp hp cc gi tin ti ni nhn to li thng bo ban u cng nh x l vic mt gi. Do c nhiu u im nn hin nay mng chuyn mch gi c dng ph bin hn cc mng chuyn mch thng bo. Vic tch hp c hai k thut chuyn mch knh v thng bo trong mt mng thng nht gi l mng dch v tch hp s ho (Integrated Services Digital Networks ISDN) ang l mt trong nhng xu hng pht trin ca mng ngy nay. c) Phn loi mng da trn kin trc mng (topology v protocol). V d nh mng System Network Architecture (SNA) ca IBM, mng ISO (theo kin trc chun quc t), mng TCP/IP v.v.

1.2.4. Tng quan v hnh trng mng (topology) LANHnh trng mng ch yu th hin trong cc mng LAN. Mi chun v LAN c cc quy tc ring cho vic ni dy. Cc quy tc ny nh ngha vic kt ni ng truyn, nhng yu cu v phn cng v cch thc sp xp cc thnh phn khc nhau. C ba yu t xc nh bn cht ca mt mng LAN: Hnh trng mng. ng truyn. K thut truy xut ng truyn.

a) Hnh trng mng (Topology)Cch sp t hnh hc (hoc vt l) s ni dy mng my tnh gi l hnh trng mng (topology). C hai loi hnh trng: Hnh trng vt l ca mt mng m t con ng cc cp mng c nh tuyn. N khng xc nh kiu ca cc thit b, phng php kt ni hoc cc a ch trn mng. Hnh trng lun l ca mt mng m t con ng m mng hot ng trong khi truyn thng tin gia cc thit b khc nhau. Cu trc vt l y ca ng truyn mng c gi l hnh trng vt l. Hnh trng vt l ca mt mng c phn thnh ba loi hnh dng hnh hc c bn: bus, ring hoc star. Ba hnh trng ny c th kt hp to thnh cc hnh trng hn hp (hybrid) nh: star-wired ring, star-wired bus v daisy chains (Chi tit v cc hnh trng ny s c kho st chng 3 - Topology). Khi chn mt topology mng vt l, ta nn tp trung vo cc c tnh sau: o Tnh d dng sp t.T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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b) Hnh trng vt l (Physical topology).

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o Tnh thun tin cho vic cu hnh li. o Vic chn on v sa cha cc s c tng i d dng. o Chi ph, hiu sut, tin cy, kh nng m rng mng trong tng lai, kiu v chiu di ca cp mng.

c) Hnh trng lun l (Logical topology)Hnh trng lun l ca mng xc nh cc c tnh truyn d liu ca n, chng hn nh m hnh giao vn mng. i vi cc mng LAN, hai hnh trng lun l thng thng nht l Ethernet v Token Ring.

1.3 Mng ngang hng (Peer to Peer) v mng c my ch (Server based)1.3.1 Mng ngang hng (peer-to-peer network)Cc mng peer-to-peer l mt v d rt n gin ca cc mng LAN. Chng cho php mi nt mng va ng vai tr l thc th yu cu cc dch v mng, va l cc thc th cung cp cc dch v mng. Phn mm mng peer-to-peer c thit k sao cho cc thc th ngang hng thc hin cng cc chc nng tng t nhau. Cc c im ca mng peer-to-peer: Cc mng peer-to-peer cn c bit n nh cc mng workgroup (nhm lm vic) v c s dng cho cc mng c 10 ngi s dng (user) lm vic trn mng . Mng peer-to-peer khng i hi phi c ngi qun tr mng (administrtor). Trong mng peer-to-peer mi user lm vic nh ngi qun tr cho trm lm vic ring ca h v chn ti nguyn hoc d liu no m h s cho php chia x trn mng cng nh quyt nh ai c th truy xut n ti nguyn v d liu . Cc u im ca mng peer-to-peer: o n gin cho vic ci t. o Chi ph tng i r. Nhng nhc im ca mng peer-to-peer: o Khng qun tr tp trung, c bit trong trng hp c nhiu ti khon cho mt ngi s dng (user) truy xut vo cc trm lm vic khc nhau. o Vic bo mt mng c th b vi phm vi cc user c chung username, password truy xut ti cng ti nguyn. o Khng th sao chp d phng (backup) d liu tp trung. D liu c lu tr ri rc trn tng trm.

1.3.2 Mng c my ch (Server based network / Client-Server network)T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Mng server based lin quan n vic xc nh vai tr ca cc thc th truyn thng trong mng. Mng ny xc nh thc th no c th to ra cc yu cu dch v v thc th no c th phc v cc yu cu (cn gi l cc thc th p ng yu cu dch v). Cc my tnh c gi l cc file server thc hin vic x l d liu v giao tip gia cc my tnh khc trong mng. Cc my tnh khc c gi l cc workstation (my tnh trm). Cc mng server based thng c s dng cho cc mng c 10 ngi s dng v thc hin cc cng vic chuyn bit sau: File v Print Servers - qun l truy xut ca user ti cc file v cc my in. Application Servers my ch c nhim v cung cp cc ng dng, cc phn mm cho cc my trm trong mi trng client/server. Database Server - my ch c ci t cc h thng C s d liu (DBMS) nh SQL SERVER, Oracle, DB2 phc v cho cc nhu cu ng dng truy xut d liu trn mng. Communication Server - my ch phc v cho cng tc truyn thng, giao tip trn mng nh Web (Web Server), mail (mail Server), truyn nhn file (FTP server)

Mail Servers - hot ng nh mt server ng dng, trong c cc ng dng server v ng dng client, vi d liu c ti xung t server ti client. c im ca mng server based: o Kh khn trong vic ci t, cu hnh v qun tr hn so vi mng peer-topeer o Cung cp s bo mt tt hn cho cc ti nguyn mng. o D dng hn trong vic qun tr sao chp d phng d liu (backup). Thm ch c th lp lch cho cng vic ny thc hin t ng.

1.4 Cc h iu hnh mngCng vi vic ghp ni cc my tnh thnh mng, cn thit phi c cc h iu hnh c ci t trn tng my tnh c trong mng. Trong c cc h iu hnh trn phm vi ton mng c chc nng qun l d liu v tnh ton, x l mt cch thng nht. Nhng h iu hnh dng cho mng my tnh c nhn peer-to-peer bao gm: o Microsoft Windows for Workgroups 3.11 o Microsoft Windows 9X, ME o Microsoft Windows NT Workstation o Microsoft Windows 2000 Professional o Microsoft Windows XP Professional o Novell Netware LiteT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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o Linux for Workstation Nhng h iu hnh mng my tnh c nhn ph bin nht cho mng server based bao gm: o Windows NT Server o Windows 2000 Server v Advanced Server o Unix (bao gm c Linux) o Novell Netware

1.5 Cc dch v mngCc mng kt ni hai hoc nhiu hn cc my tnh vi nhau cung cp mt s phng php cho vic chia x v truyn d liu. Nhiu c im m mt mng cung cp c xem nh cc dch v (services). Cc dch v thng thng nht trn mt mng l: th in t (email), in n, chia x file, truy xut Internet, quay s t xa (remote dial-in), giao tip(communication) v dch v qun tr (management service). Cc mng ln c th c nhng my ch (server) ring, mi my ny thc hin mt trong cc dch v mng. Vi cc mng nh hn, tt c cc dch v mng c cung cp bi mt hoc vi my ch. (Mt my ch c th cung cp nhiu dch v mng).

1.5.1 Cc dch v file v in nCc dch v file ca mt mng c th c s dng chia x cc phn mm ng dng nh cc chng trnh x l vn bn, cc c s d liu, cc bng tnh hoc cc chng trnh email. Cc chng trnh ny c chy trn mt my ch trung tm, c ngha l chng khng phi ci t cc b trn mi my tnh. Chnh iu ny gim bt thi gian v chi ph ci t, cp nht cc file trn tng my tnh, v mi th c lu tr trong mt v tr trung tm. Cc dch v file cho php cc user chia x d liu v cc ti nguyn khc nhanh v tit kim. Email c gi trong vi giy. Cc file a truyn thng (multimedia file) vi kch thc ln d dng truyn qua mng. Cc web site c th gip chng ta cp nht thng tin mi nht. Cc ti nguyn qu him nh CD-ROM, fax modem, scanner v.v c th chia x dng chung trn mng. Cc my in c th dng chung trn mng nh cc dch v in mng. Ngi qun tr mng c th ci t, qun tr, chn on v sa cc li xy ra trn cc my in mng d dng hn do s lng cc my in trong mng gim i v cng vic qun tr my in mng c th c thc hin trn chnh my tnh m ngi qun tr ang ng nhp m khng cn trc tip n tng my in.

1.5.2 S bo mt v qun tr c tp trungCc file v chng trnh trn mt my tnh c th c bo v vi cc quyn ch cho cc user no c php truy xut v truy xut mc no. Cc user ch cn ngT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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nhp vi mt ti khon user hp l s cho php h truy xut d liu v ti nguyn mng trong gii hn quyn (permission) c cp. Nhng ti nguyn m mt user c th thy trn mng c th b n i i vi cc user khc. Cc mng cho php cc user truy xut d liu ca h t bt k my tnh no trong mng. V d liu ca h c lu tr trn mt my tnh ch. Vic sao chp d phng d liu (backup) cng tr nn d dng hn v ngi qun tr ch cn backup mt my tnh (my ch server). Chnh vic lu tr cc d liu quan trng trn mt v tr tp trung cho php iu khin v qun tr d liu cht ch hn, tit kim thi gian hn so vi vic lu tr d liu trn mi my tnh ring l.

1.5.3 Cc dch v th in t (e-mail)Vic chuyn e-mail gia cc user trn mt mng LAN hoc gia cc user trn mt mng LAN v Internet c qun l bi cc dch v th tn (mail service) mng. iu kin mi ngi c th giao tip trn mng bng e-mail l mi ngi phi c mt a ch e-mail.

1.5.4 Cc dch v giao tip (Communication services)Cc dch v giao tip mng cho php cc user bn ngoi kt ni ti mng t xa thng qua mt ng dy in thoi v mt modem. Cc dch v ny cng cho php cc user trn mng kt ni ti cc my hoc mng khc bn ngoi mng LAN. a s cc h iu hnh mng (Network Operating System NOS) c cc dch v ny bn trong, chng hn: o Windows NT 4.0 c Remote Access Server (RAS) o Windows 2000 Server c Routing and Remote Access Server (RRAS) o Netware c Network Access Server (NAS) Cc my tnh ang chy cc dch v giao tip c gi l cc my ch giao tip (communication server) v chu trch nhim qun l cc giao tip. Mt khi user ng nhp vo mng t xa v c xc nhn l hp l thng qua my ch giao tip h s c cc quyn truy xut m h mong mun ging nh ang ngi mt my tnh trm c kt ni vt l trc tip vi mng (tr trng hp ngi qun tr hn ch vic truy xut khi ng nhp t xa).

1.5.5 Cc dch v InternetCc dch v Internet bao gm cc my ch World Wide Web (WWW) v cc trnh duyt (browser), kh nng truyn file, s nh a ch Internet, cc b lc bo v. Cc dch v ny l cn thit i vi cc mng hin nay cho php giao tip v chuyn i d liu ton cu.

1.5.6 Cc dch v qun tr (Management services)T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Cc cng vic qun tr mng tr thnh phc tp hn i vi cc mng c kch thc ln, c bit khi n m rng qua cc chu lc khc nhau (Cc mng WAN). Cc dch v qun tr cho php nhng ngi qun tr mng qun tr tp trung cc mng ln v phc tp. Cc cng vic qun tr ny bao gm: theo di v iu khin lu thng, cn bng ti, chn on v cnh bo cc li, qun tr ti nguyn, iu khin v theo di s cho php, kim tra tnh bo mt, phn b phn mm, qun tr a ch, backup v phc hi d liu.

1.6 Lm th no tr thnh mt chuyn nghip vin v mng my tnh?C nhiu cch tr thnh mt ngi chuyn nghip v mng my tnh. Hoc c hc tp cc trng i hc, cao ng hoc ly cc bng cp thng qua vic hc cc kho ca cc cng ty v tham d cc k thi. Mt s vn bng ca cc cng ty bao gm: Microsoft Certified Systems Engineer, Novell Network Engineer hoc cc vn bng ca Cisco v Intel. Mt s lnh vc chuyn nghnh v mng my tnh l: o Bo mt mng. o Thit k Internet v Intranet. o Qun tr mng. o Tch hp d liu v ting ni. o Tnh ton di dng v t xa. o Tch hp d liu v c ch chng li. o Kin thc su v cc sn phm mng ca Microsoft cng nh ca Netware. o Kin thc su v vic cu hnh v qun tr cc thit b tm ng (router) Ngoi nhng kin thc k thut su sc (k nng cng), mt ngi chuyn nghip v mng my tnh cng cn phi c cc k nng mm tt. Cc k nng ny bao gm: o K nng quan h vi khch hng. o K nng giao tip bng li v bng vn bn. o Va c kh nng lm vic c lp va c kh nng lm vic tp th. o C kh nng qun l v lnh o. o Tnh tin cy cao.

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Cu hi n tp chng 11. Mt s cc my tnh phn b trn mt vng a l rng v c kt ni vi nhau bng cc cp v cc thit b khng dy l mt a. LAN b. MAN c. WAN d. Virtual network. 2. Cc thnh phn c bn ca kin trc mng l (chn 2) a. Topology c. Protocols 3. Hai m hnh mng l . a. Wire c. Wireless 4. C hai loi hnh trng : a. Physical topology b. Simple topology c. Complex topology d. Logical topology 5. Mt trong nhng c im ca mng LAN: a. Khong cch xa nht gia hai trm ln hn 100 km b. Khong cch xa nht gia hai trm vo khong vi chc km c. C hai cu trn u ng. 6. Lch s mng my tnh cng chnh l lch s ca Internet a. ng b. Sai 7. Nhng nhc im ca mng server-based l: (chn 2) a. Ci t phc tp b. Bo mt km c. Khng c c ch sao chp d liu tp trung d. Chi ph t hn so vi mng peer-to-peer 8. Nhng nhc im ca mng peer to peer l: (chn 2) a. Ci t phc tp b. Bo mt km c. Qun tr phc tp d. Khng c c ch sao chp d liu tp trung 9. Trong mng peer-to-peer khng tn ti bt k my server no. a. ng b. Sai 10. Nhng dch v thng thng nht trn mng l: (chn 3 ) a. Dch v File b. Dch v Email c. Dch v th mc d. Dch v in e. Dch v chia x b. Peer to peer d. Server Based Network b. Form of the network d. Physical Media

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CHNG 2 - M HNH OSIMC TIU CA CHNG Kt thc chng ny, sinh vin s c th: Hiu mt cch khi qut v kin trc phn tng mng my tnh. Nm c tng quan v m hnh OSI Hiu v nm c ngha cng nh chc nng ca cc tng trong m hnh OSI p dng m hnh OSI trong vic phn tch mt qu trnh trong mng my tnh. Hiu c cc thnh phn ca mt khun dng (frame) d liu.

2.1 Kin trc phn tng v m hnh OSI (Open System Interconnect)2.1.1 Kin trc phn tng gim phc tp ca vic thit k v ci t mng, hu ht cc mng my tnh hin c u c phn tch thit k theo quan im phn tng (layering). Mi h thng thnh phn ca mng c xem nh mt cu trc a tng, trong mi tng c xy trn tng trc n. S lng cc tng cng nh tn v chc nng ca mi tng l tu thuc vo cc nh thit k. Tuy nhin, trong hu ht cc mng, mc ch ca mi tng l cung cp mt s dch v nht nh cho tng cao hn. Hnh 2.1 l mt kin trc phn tng tng qut, vi gi thit A v B l hai h thng my tnh thnh phn ca mng c ni vi nhau.H thng A Tng N : : Tng i + 1 Tng i Tng i - 1 : : Tng 1 Giao thc tng N H thng B Tng N : : Tng i + 1 Tng i Tng i - 1 : : Tng 1

Giao thc tng i + 1 Giao thc tng i Giao thc tng i - 1 Giao thc tng 1

Giao din i+1 / i Giao din i-1 / i

ng truyn vt l Hnh 2.1 Minh ho kin trc phn tng tng qut

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Nguyn tc ca kin trc phn tng l: Mi h thng trong mt mng u c cng cu trc tng (s lng tng, chc nng ca mi tng l nh nhau). Sau khi xc nh cu trc tng, cng vic k tip l nh ngha mi quan h (giao din) gia hai tng k nhau v mi quan h gia hai tng ng mc hai h thng ni kt vi nhau. Nu mt h thng mng c N tng th tng s cc quan h (giao din) cn phi xy dng l 2*N 1. Trong thc t, d liu khng c truyn trc tip t tng th i ca h thng ny sang tng th i ca h thng khc (tr trng hp tng thp nht trc tip s dng ng truyn vt l truyn cc chui bt (0,1) t h thng ny sang h thng khc). Qui c d liu bn h thng gi (sender) c truyn t tng trn xung tng di v truyn sang h thng nhn (receiver) bng ng truyn vt l v c th i ngc ln cc tng trn.

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2.1.2 Tng quan v m hnh OSIKhi thit k mng my tnh, cc nh thit k t do la chn kin trc ring ca mnh. T dn n tnh trng khng tng thch gia cc mng: phng php truy nhp ng truyn khc nhau, s dng h giao thc khc nhau v.v S khng tng thch lm tr ngi cho s tng tc ca ngi s dng cc mng khc nhau. Nhu cu trao i thng tin cng cao th tr ngi cng ln, n mc khng th chp nhn c i vi ngi s dng. Tnh hnh lm cho cc nh sn xut v cc nh nghin cu, thng qua cc t chc chun ho quc gia v quc t cn phi xy dng c mt khung chun v kin trc mng lm cn c cho cc nh thit k v ch to cc sn phm v mng. V l do , T chc tiu chun ho quc t (International Organization for Standardization ISO) lp ra mt tiu ban nhm pht trin mt khung chun v kin trc mng. Kt qu l vo nm 1984, m hnh tham chiu OSI (Open System Interconnection Reference Model) ra i. M hnh OSI l mt tp cc m t chun cho php cc my tnh khc nhau giao tip vi nhau theo cch m. T m y ni ln kh nng 2 h thng khc nhau c th kt ni trao i thng tin vi nhau nu chng tun th m hnh tham chiu v cc chun lin quan. M hnh OSI phn chia kin trc mng my tnh thnh 7 tng tng Vt l (Physical), tng Lin kt D liu (Data Link), tng Mng (Network), tng Giao vn (Transport), tng Phin (Session), tng Trnh din (Presentation) v tng ng dng (Application). Mi tng khc nhau c tp cc chc nng ring v ch giao tip vi cc tng k cn trn v di v giao tip vi tng i din (ng mc) trn cc my tnh khc. (Hnh 2.2) T khi c m hnh OSI, nhiu nh sn xut my tnh thay i kin trc mng phn tng ca h tun th cc tng ca m hnh OSI. V d, cc chc nng giao tip c phn chia thnh mt tp cc tng. Mi tng thc hin cc chc nng cn thit giao tip vi cc h thng khc. Mi tng da trn tng k tip bn di thc hin nhiu hn cc chc nng nguyn thu (primitive function). Bn thn mi tng cng cung cp cc dch v cho tng k tip pha trn n. Ni mtT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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cch khc tng N s dng cc dch v ca tng N-1 v cung cp cc dch v cho tng N+1. Mt cch l tng, cc tng nn c nh ngha sao cho nhng thay i trong mt tng khng i hi nhng thay i trong cc tng khc. Ni mt cch khc, tng ca vic phn tng l chia mt vn ln thnh mt s cc vn nh c th qun l c. H thng m A7 6 5 4 3 2 1 APPLICATION PRESENTATION SESSION TRANSPORT NETWORK DATA LINK PHYSICAL

H thng m 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 1NG DNG TRNH DIN PHIN GIAO VN MNG LIN KT D LIU VT L 7 6 5 4 3 2 1

ng truyn vt l Hnh 2.2 M hnh OSI 7 tng

2.2 ngha v chc nng ca cc tng trong m hnh OSI2.2.1 Tng vt l (Physical Layer)Tng vt l l tng thp nht trong m hnh OSI. Tng ny lin quan n cc qui tc truyn dng bit khng c cu trc qua ng truyn vt l. Tng ny nh ngha: Cu trc mng vt l. Nhng m t v mt c v in cho vic s dng ng truyn. Cc qui tc m ho vic truyn cc bit v cc qui tc nh thi. Tng vt l khng bao gm vic m t ng truyn v khng cung cp bt k c ch kim sot li no. Phn cng kt ni mng c coi l thuc v tng vt l bao gm: Cc b giao tip mng (Network Interface Card NIC, Adapter, v.v) Cc b tp trung (Concentrator, Hub), cc b chuyn tip (Repeater) dng ti sinh cc tn hiu in. Cc u ni (connector) cung cp giao tip c kt ni cc thit b vi ng truyn (cc cp, cc u ni BNC BayoNette Connector)

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Cc b iu ch v gii iu ch (MODEM MOdulation-DEModulation) thc hin vic chuyn i gia tn hiu s ho (digital) v tn hiu tng t (analog).

2.2.2 Tng lin kt d liu (Data Link Layer)Tng lin kt d liu chu trch nhim iu khin tt c cc giao tip gia tng mng bn trn n v tng vt l bn di n. D liu nhn c t tng mng c phn chia thnh cc khi ring bit (khun dng - frame), sau chng c a ti tng vt l v cui cng truyn ra mng. Mc ch chnh ca vic thc thi giao thc tng lin kt d liu l: T chc cc bit thuc tng vt l thnh cc nhm thng tin c gi l cc khun dng (frame - ging nh mt byte, mt frame l mt dy lin tc cc bit c nhm li vi nhau nh mt n v d liu) Pht hin v sa sai li. Kim sot lung d liu. nh danh cc my tnh trn mng .

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Tng lin kt d liu b sung thng tin iu khin ring ca n vo pha trc gi d liu. Thng tin ny bao gm: a ch (vt l) ca my ngun v my ch (Source address, Destination address) . Thng tin v chiu di ca frame.

Mt khi d liu c truyn trn mng, tng lin kt d liu ch thng tin phn hi (Acknowledge ACK) t my tnh nhn, bo cho bit l n nhn c tt c cc gi. Tri li, cc gi cn thiu s c truyn li. Tng lin kt d liu khng lin quan n vic ti sao mt gi khng n c ch, tng ny ch quan tm n s kin l, nu mt gi no khng n ch th n phi c truyn li. Nh vy tng lin kt d liu cung cp cc phng tin m bo s tin cy cho vic truyn thng tin.Destinatio n Address Source Address Control Informatio n Error Checking Informatio n

Data

Hnh 2.3 Mt frame d liu c n gin ho

gm:

Cc thit b kt ni mng c xem nh thuc v tng lin kt d liu bao Bridges (Cc cu ni) Intelligent hubs (cc hub thng minh)

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Tng con MAC l lp con pha di ca tng lin kt d liu. N chu trch nhim b sung a ch vt l ca my tnh ch vo frame d liu.2. iu khin lin kt lgc (Logical Link Control LLC)

Tng con LLC l lp con pha trn ca tng lin kt d liu v chu trch nhim cung cp mt giao tip chung cng nh cung cp tnh tin cy v cc dch v kim sot lung d liu. N thit lp v duy tr lin kt cho vic truyn cc frame d liu t thit b ny ti thit b khc.

2.2.3 Tng mng (Network Layer)Tng mng l tng th ba ca m hnh OSI. Mc tiu chnh ca n l di chuyn d liu ti cc v tr mng xc nh. lm iu ny, n dch cc a ch lgc thnh a ch vt l tng ng v sau quyt nh con ng tt nht cho vic truyn d liu t my gi ti my nhn. iu ny tng t nh cng vic m tng lin kt d liu thc hin thng qua vic nh a ch thit b vt l. Tuy nhin, vic nh a ch ca tng lin kt d liu ch hot ng trn mt mng n. Tng mng m t cc phng php di chuyn thng tin gia nhiu mng c lp (v thng l khng ging nhau) c gi l lin mng (internetwork) V d, cc mng cc b (LAN) Token Ring hoc Ethernet c cc kiu a ch khc nhau. kt ni hai mng ny, ta cn mt c ch nh a ch ging nhau m c th c hiu bi c hai loi mng . Kh nng ny c cung cp bi giao thc chuyn i gi Internet (Internet Packet Exchange IPX) mt giao thc tng mng trong h iu hnh Novell Netware. Vic nh a ch ca tng lin kt d liu chuyn d liu ti tt c cc thit b c gn ti mt mng n v nh vo cc thit b nhn xc nh xem d liu c c truyn ti n hay khng. Tri li, tng mng chn mt con ng xc nh qua mt lin mng v trnh gi d liu ti cc mng khng lin quan. Mng thc hin iu ny bng vic chuyn mch (switching), nh a ch v cc gii thut tm ng. Tng mng cng chu trch nhim m bo nh tuyn (routing) d liu ng qua mt lin mng bao gm cc mng khng ging nhau. Mt vn c th ny sinh khi vic nh tuyn d liu qua mt lin mng khng ng dng l s khc nhau ca kch thc gi d liu m mi mng c th chp nhn. Mt mng khng th gi d liu trong cc gi c kch thc ln hn kch thc ca gi d liu m mt mng khc c th nhn c. gii quyt vn ny, tng mng thc hin mt cng vic c gi l s phn on (segmentation). Vi s phn on, mt gi d liu c phn tch thnh cc gi nh hn m mng khc c th hiu c - gi l cc packet. Khi cc gi nh ny n mng khc, chng c hp nht (reassemble) thnh gi c kch thc v dng ban u. Ton b s phn on v hp nht ny xy ra tng mng ca m hnh OSI.

2.2.4 Tng giao vn (Transport Layer)Tng giao vn nng cp cc dch v ca tng mng. Cng vic chnh ca tng ny l m bo d liu c gi t my ngun phi tin cy, ng trnh t vT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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khng c li khi ti my ch. m bo truyn d liu tin cy, tng giao vn da trn c ch kim sot li c cung cp bi cc tng bn di. Tng ny l c hi cui cng sa li. D liu cng vi thng tin iu khin m tng giao vn qun l gi l cc phn on (segment) Tng giao vn cng chu trch nhim kim sot lung d liu. Tc truyn d liu c xc nh da trn kh nng m my ch c th nhn cc gi d liu c gi n n nh th no. D liu my gi c phn chia thnh cc gi c kch thc ti a m loi mng c th qun l. Chng hn, mt mng Ethernet khng th iu khin cc gi c kch thc ln hn 1500 byte, v th tng giao vn nhn d liu v chia n thnh cc gi 1500 byte. Mi gi con ny c gn mt s trnh t, dng hp nht n v tr ng bi tng giao vn ca my nhn. Cng vic ny c gi l sp xp theo trnh t (sequencing). Khi gi d liu n my nhn, n c hp nht theo ng trnh t nh lc gi. Sau mt thng tin bo nhn (acknowledgement - ACK) c gi quay tr li my gi bo cho n bit rng gi d liu n chnh xc. Nu c li trong gi d liu th mt yu cu truyn li gi c gi quay tr li thay th cho ACK. Nu my gi ban u khng nhn c thng tin ACK (hoc yu cu truyn li) trong mt khong thi gian nh trc, gi d liu gi c xem nh b tht lc hoc b h, khi n s c gi li. Trong mng TCP/IP, cc chc nng TCP (Transmission Control Protocol) thuc v tng giao vn. Trong mng Novell Netware s dng IPX/SPX th giao thc SPX (Sequence Packet Exchange) hot ng tng giao vn.

2.2.5 Tng phin (hay Tng giao dch - Session Layer)Tng phin qun l cc lin kt ca user trn mng cung cp cc dch v cho user . V d mt ngi s dng ng nhp vo mt my tnh mng ly file th mt phin (hay mt giao dch / mt lin kt) c thit lp cho mc ch truyn file. Tng phin to iu kin thun li cho vic giao tip gia cc h thng yu cu dch v v cc h thng cung cp dch v. cc phin giao tip c kim sot thng qua c ch thit lp, duy tr, ng b ho v qun l cc phin (hay cn gi l cuc hi thoi dialogue) gia cc thc th truyn thng. Tng ny cng tr gip cc tng trn nh danh v kt ni ti cc dch v c th s dng trn mng. Nu mt phin giao tip b ngt, tng phin xc nh v tr khi to li vic truyn pht mt khi phin giao tip c ti kt ni. Tng phin cng chu trch nhim xc nh thi hn ca phin giao tip. N xc nh my tnh hoc nt no c th truyn u tin v truyn trong bao lu. Tng phin s dng thng tin a ch lgc c cung cp bi cc tng bn di nh danh tn v a ch ca cc my ch m cc tng trn i hi.

2.2.6 Tng trnh din (Presentation Layer)Tng trnh din qun l cch thc d liu c biu din. N l trnh dch gia ng dng v mng. C nhiu cch biu din d liu, chng hn nh cc bng m ASCII v EDBCDIC cho cc file vn bn. Tng trnh din bin i d liuT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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sang mt nh dng m mng c th hiu c. N cng chu trch nhim m ho (encrypt) v gii m (decrypt) d liu - chng hn nh d liu c m ho d liu n c gi ti ngn hng, nu ta giao dch trc tuyn vi ngn hng qua Internet.

2.2.7 Tng ng dng (Application Layer)Tng ng dng cha cc giao thc v chc nng i hi bi ng dng ca ngi s dng thc hin cc cng vic truyn thng. N khng lin quan n cc ng dng thc s ang hot ng nh Microsoft Word hoc Adobe Photoshop. Cc chc nng chung bao gm: Cc giao thc cung cp cc dch v file t xa, nh cc dch v m file, ng file, c file, ghi file v chia x truy xut ti file. Cc dch v truyn file v truy xut c s d liu t xa. Cc dch v qun l thng bo cho cc ng dng th in t. Cc dch v th mc ton cc nh v ti nguyn trn mng. Mt cch qun l ng nht cc chng trnh gim st h thng v cc thit b. v.v. Nhiu dch v ny c gi l cc giao tip lp trnh ng dng (Application Programming Interface API). Cc API l nhng th vin lp trnh m ngi pht trin ng dng c th s dng vit cc ng dng mng.

2.3 p dng m hnh OSIBng sau y tng kt cc chc nng ca m hnh OSI: Tng ng dng Trnh din Phin Giao vn Mng Lin liu Vt l kt Chc nng Chuyn thng tin t chng trnh ny ti chng trnh khc. iu khin nh dng vn bn v hin th chuyn i m. Thit lp, duy tr v kt hp cc phin truyn thng. m bo phn pht chnh xc d liu. Tm ng v qun l vic truyn thng bo. D M ho, nh a ch v truyn thng tin. Qun l kt ni phn cng

Cch d nht xem xt m hnh OSI v p dng n trong hot ng mng l tm hiu mt qu trnh c th din ra trong mng. Mt trong nhng cng vic c

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thc hin nhiu ln trong mt ngy trn hu ht cc mng l c mt th in t (E-mail). Sau khi ngi s dng ng nhp vo trong mng v khi to chng trnh email, qu trnh kim tra th mi bt u. u tin tng ng dng xc nhn yu cu (request) v th thng qua mt API chun c xy dng trong ng dng. Tng ng dng nhn yu cu ny v chuyn n thnh mt yu cu d liu c c t my ch e-mail. Yu cu c chuyn ti tng trnh din. Tng trnh din nhn yu cu v xc nh xem n nn c nh dng nh th no theo kiu mng ring m yu cu ang hot ng trn . Tng ny cng xc nh xem c bt k i hi no v m ho hay khng. D liu sau khi c nh dng (v c th c m ho) c truyn ti tng phin. Tng phin nhn yu cu v gn mt th (token) d liu ti n. Th ny l mt n v d liu iu khin c bit m n bo cho phn cn li ca mng l ngi s dng c quyn truyn d liu. D liu v th c truyn ti tng giao vn. Khi ti tng giao vn, d liu v cc thng tin iu khin c chia thnh cc khi c kch thc c th qun l c. Nu d liu qu ln thch hp trong mt frame tng lin kt d liu, tng giao vn s phn chia d liu thnh cc khi nh hn v gn mt s trnh t (sequence number) hay nh danh (identifier) cho mi khi. Sau tng khi c truyn ti tng mng. Tng mng b sung thng tin a ch lgc ti d liu m n nhn c t tng giao vn sao cho cc tng k tip s bit c a ch ngun v ch ca d liu . Cc khi d liu tip theo c truyn cng vi thng tin nh a ch ti tng lin kt d liu. Mt khi d liu n c tng lin kt d liu, chng c ng gi thnh cc frame ring r. Mi frame ny km theo gii thut kim tra li c bit nh l Frame Check Sequence (FCS) - vng ghi m kim sot li c chn cui mi frame. Tng lin kt d liu sau b sung thm mt header ti frame trc khi truyn n ti tng vt l. Phn header ny bao gm a ch vt l ca c hai nt gi v nt nhn. Khi d liu bt u ti card giao tip mng (NIC) tng vt l, n c gi ra mng. Tng vt l khng b sung bt k th g ti frame v tng ny cng khng quan tm xem ci g c trong frame. N n gin ch ly d liu (cc bit) v truyn n trn mng. Mt khi cc gi d liu n c nt nhn, chng c ly li nh NIC ca tng vt l bn h thng nhn v c truyn tip ln qua cc tng h thng . Mi mt tng dch thng tin c b sung bi cc tng tng ng bn h thng gi v sau truyn gi ln tng bn trn cho ti khi cui cng gi c hp nht v yu cu c thc thi. Nt nhn sau to ra mt p ng (response) v gi n quay tr li nt gi ban u i theo trnh t chnh xc nh m t trn. Mi tng k tip ca m hnhT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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OSI b sung thng tin iu khin, thng tin nh dng hay thng tin nh a ch ti d liu m n iu khin. H thng nhn phin dch v sau s dng thng tin b sung khi n o ngc tin trnh, truyn d liu t tng vt l ln ti tng ng dng.Flow Control, Sequencing and Error Checking Logical Addressing Information Data Framing, Error Checking and Physical Addressing Information

Data Data Data Data Data Data Data

Tng ng dng Tng trnh din Tng phin Tng giao vn Tng mng Tng lin kt d liu Tng vt l

Hnh 2.4 D liu c truyn qua m hnh OSI

Bng sau y tng kt n v d liu do cc tng qun l: Tng Tng ng dng, trnh din, phin Tng giao vn Tng mng Tng lin kt d liu Tng vt l n v d liu Data Segment Packet Frame Bit

2.4 M t cc thnh phn ca khun d liu (Frame)Nh ta thy phn trn, d liu khi truyn ngang qua mng c phn tch thnh nhng khi nh, c kch thc ph thuc vo hnh trng lgc ca mng . Nh i vi mng Ethernet khng th s dng cc khi d liu ln hn 1500 byte. Cc khi d liu nh ny c gi l cc frame (khung hoc khun dng). C hai loi frame: Ethernet v Token Ring tng ng vi tn hai loi mng c s dng thng thng nht.

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Cng ty Xerox Corporation bt u pht trin Ethernet vo nm 1970. Sau do lin kt gia Xerox Corp. vi DEC v Intel, Ethernet c ci tin v hin gi c 4 cng ngh Ethernet ch yu ang c s dng 10Base2, 10Base5, 10BaseT v 100BaseT. Token Ring c pht trin bi IBM vo nm 1980 v da trn lin kt gia cc nt vi cng ngh vng (ring): mt th bi (token) c truyn quanh cc nt. Mt nt ch c th truyn d liu trn mng sau khi n nhn c th bi. Cp ni mng hnh thnh mt vng (ring hoc circle) v cc tn hiu d liu c truyn ch theo mt hng quanh vng. Mc d v l thuyt c th truyn c hai frame Ethernet v Token Ring trn cng mt mng, nhng iu ny khng thc hin trong thc t. Giao tip Ethernet khng th phin dch cc frame Token Ring v tri li. Mt mng lun ch l Ethernet hoc Token Ring ch khng th ng thi c hai. Tuy nhin c th kt hp cc giao thc trn cng trn mt mng. Chng hn, c th s dng c hai b giao thc TCP/IP v IPX/SPX trn mng mng Ethernet, v c hai giao thc ny cng s dng mt kiu frame d liu.

2.4.1 Mt khun d liu Ethernet in hnhHeader TrailerFrame Check Sequence (Error Checking Informatio

Preamble

SFD Start of Frame Delimite r

Destinatio n Address

Source Addres s

Length

Data

Pad

Control information

Hnh 2.5 Mt khun d liu Ethernet in hnh

Cc thnh phn ca frame Ethernet 802.3 bao gm:

Preamble (Phn m u) nh du bt u ca ton b frame, l tn hiu thng bo ti mng rng d liu ang truyn. (V trng ny l mt phn ca qu trnh giao tip, nn n khng c tnh vo kch thc ca frame) Start of Frame Delimiter (SFD) Cha thnng tin khi u ca vic nh a ch frame. Destination Address Cha a ch ca nt ch. Source Address Cha a ch ca nt ngun.

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Length (LEN) Cha chiu di ca gi. Data Cha d liu c truyn t nt ngun. Pad c s dng tng kch thc ca frame ti kch thc yu cu nh nht l 46 byte. Frame Check Sequence (FCS) Cung cp mt gii thut xc nh xem d liu nhn c c chnh xc hay khng. Gii thut c s dng thng thng nht l Cyclic Redundancy Check (CRC).

2.4.2 Mt khun d liu Token Ring in hnhControl informationFrame Check Sequence (Error Checking Informatio

Start Delimit er

Access Contro l

Frame Contro l

Destinati on Address

Source Addres s

Data

End Delimite r

Frame Status

Start Delimit er

Access Contro l

End Delimit er

Token Frame

Cc thnh phn ca frame Token ring 802.5 bao gm:

Hnh 2.6 Mt khun d liu Token Ring in hnh

Start Delimiter (SD) Bo hiu bt u gi. N l mt trong ba trng to thnh khun dng Token Ring. Access Control (AC) Cha thng tin v u tin ca frame. N l trng th hai to thnh khun dng Token Ring. Frame Control (FC) nh ngha kiu ca frame, c dng trong Frame Check Sequence. Destination Address Cha a ch ca nt ch. Source Address Cha a ch ca nt ngun. Data Cha d liu c truyn t nt ngun, cng c th cha thng tin qun l v tm ng.

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Frame Check Sequence (FCS) c s dng kim tra tnh ton vn ca frame. End Delimiter (ED) Bo hiu kt thc frame. N l trng th ba ca khun dng Token Ring. Frame Status (FS) Bo hiu nt ch nhn dng v sao chp ng frame hay khng.

2.4.3 Gii thiu cc chun c t mng IEEE 802.xT chc tiu chun ho Quc t (ISO) chu trch nhim xy dng m hnh OSI. Chnh ISO cng thng qua mt tp cc chun c gi l n Project 802, c dng chun ho cc thnh phn vt l ca mt mng. Cc chun ny do Vin K thut in v in t (Institute of Electrical and Electronic Engineers IEEE) xy dng, bao gm cc vn lin quan n kh nng kt ni, mi trng truyn mng, cc gii thut kim tra li, s m ho v cc cng ngh khc. Bng sau y tng qut ho cc chun trong n Project 802 :Chu n 802.1 802.2 802.3 802.4 802.5 802.6 802.7 802.8 802.9 802.10 802.11 802.12 Tn Internetworking Logical Link Control Ethernet LAN Token Bus LAN Token Ring LAN Metropolitan Area Network (MAN) Broadband Technical Advisory Group Fibre-Optic Technical Advisory Group Integrated Voice / Data Networks Network Security Wireless Networks High-Speed Networking Gii thch Bao gm vic nh tuyn, to cu ni, v cc giao tip lin mng. Lin quan ti vic kim sot li v kim sot lung d liu qua cc frame. Bao gm tt c cc dng ng truyn v giao tip Ethernet Bao gm tt c cc dng ng truyn v giao tip Token Bus Bao gm tt c cc dng ng truyn v giao tip Token Ring Bao gm cc cng ngh, nh a ch v cc dch v MAN Bao gm mi trng truyn, giao tip v cc thit b khc cho mng bng tn di rng. Bao gm ng truyn cp quang v cc cng ngh cho cc loi mng khc nhau. Bao gm s tch hp ting ni v d liu qua mt ng truyn mng. Bao gm cc vn v kim sot truy xut mng, s m ho, xc nhn v cc vn bo mt khc. Cc chun cho mng khng dy. Bao gm cc cng ngh 100Mbs-plus, k c 100BaseVG-AnyLAN

Cu hi n tp chng 2

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1. Mc tiu ca vic phn tch thit k cc mng my tnh theo quan im phn tng l: (chn 1) a. d dng cho vic qun tr mng b. gim phc tp ca vic thit k v ci t mng c. nng cp h thng mng d dng hn d. Khng phi cc l do trn 2. Nu mt h thng mng c 8 tng th tng s cc quan h (giao din) cn phi xy dng l . a. 16 b. 24 c. 15 d. 22 3. Tng ca m hnh OSI c th giao tip trc tip vi tng i din ca h thng my tnh khc. a. Application b. Data link c. Network d. Physical. e. Transport 4. Nhng tng no ca m hnh OSI cung cp vic kim sot lung d liu?(chn 3) a. Data-Link b. Transport c. Application d. Presentation e. Network 5. Mt gi (packet) mng bao gm: (chn 1) a. Mt header, mt body v mt trailer b. Mt a ch ca my gi v mt thng bo c. Mt chui vn bn vi thng tin nh dng d. Mt URL tng ng vi mt a ch www. 6. n v d liu do tng Lin kt D liu qun l l . a. Bit b. Packet c. Frame d. Segment 7. Mt Router lm vic tng no trong m hnh OSI? a. Data-Link b. Transport c. Application d. Presentation e. Network 8. Nhng vn lin quan n kim sot truy xut mng, m ho, xc nhn v bo mt mng thuc chun no trong cc chun do IEEE 802.X xy dng? a. 802.2 b. 802.3 c. 802.4 d. 802.5 e. 802.10 f. 802.11 9. Tng no ca m hnh OSI lin quan n cc dch v h tr trc tip phn mm truyn file, truy xut c s d liu v e-mail. a. Application b. Data link c. Network d. Physical. e. Transport 10. Mt cch tng qut, d liu c th truyn trc tip t mt tng ca h thng gi sang thng tng i din (ng mc) ca h thng nhn trong m hnh OSI . a. ng b. Sai

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CHNG 3 - NG TRUYN VT LMC TIU CA CHNG Kt thc chng ny, sinh vin s c th: Nm c l thuyt chung v cc loi tn hiu cng nh cc c tnh c bn ca ng truyn mng. C nhng kin thc v nhng thng s c bn v cc loi cp mng.

3.1 Truyn d liu: tn hiu tng t (analogue) v tn hiu s ho (digital)Tn hiu truyn i trn mng hoc l tng t (analog), hoc l s (digital)

3.1.1 Tn hiu tng tTn hiu tng t l tn hiu bao gm hng lot cc sng lin tc do s bin i ca in p. N cng tng t nh qu trnh truyn tn hiu trn in thoi. Tn hiu tng t khng c kh nng loi b nhiu trn ng truyn trong qu trnh truyn d liu, v do nhiu s lm cho qua trnh truyn d liu khng c tnh chnh xc cao. Cc i lng c trng cho tn hiu tng t l: Bin v tn s. i lng o tn s l Hz. Mt trong nhng vn ca tn hiu tng t l chng b suy gim. Bin ca tn hiu s t l nghch vi khong cch m tn hiu truyn i. Khi tn hiu tng t i qua cc thit b nh HUB, hay Repeater th bin ca tn hiu c khuych i, nhng nhiu cng v vy m c khuych i theo (Hnh 3.1).

Hnh 3.1 Tn hiu tng t

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3.1.2 Tn hiu sTn hiu s c to thnh t gi tr ca cc xung in p. Nhng khi chng i qua cc thit b nh HUB hay Repeater th chng ch truyn hay lp li cc tn hiu nguyn mu 1 hay 0 , qu trnh ny gi l ti to li. Tn hiu s t b nh hng ca nhiu do c tin cy cao hn so vi tn hiu tng t (Hnh 3.2).

Hnh 3.2 Tn hiu s

3.2 Cc c tnh ca ng truyn mngMt s vn cn quan tm khi quyt nh mi trng truyn thng trn mng, bao gm: dung lng (throughput), bng thng (bandwidth), chi ph, kch thc, linh ng, cc thit b lin kt, v nhiu. Dung lng (throughput hay capacity) l lng d liu i qua ng truyn trong mt n v thi gian. n v l MegaBits/giy (Mbps). Dung lng ca mng my tnh ph thuc vo khong cch a l v mi trng ang s dng. Bng thng (bandwidth) l i lng dng o s sai bit gia tn s ln nht v tn s nh nht ca mi trng truyn. N lin quan trc tip n dung lng ca ng truyn, nu mt mng my tnh ang hot ng tn s 870MHz v 880Hz th bng thng ca n l 10MHz. Thng thng bng thng l lng d liu tht s i qua ng truyn. n v o l Hz.

So snh tn hiu s tn s cao v tn s thp

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Chi ph l mt trong cc yu t quan trng n ph thuc vo mt s cc yu t nh: chi ph ci t, chi ph c s h tng, chi ph bo tr v h tr v.v... Kch thc v quy m ca mi trng truyn thng mng my tnh ph thuc vo s nt trn mi phn on, s phn on v chiu di ca mi phn on. Vic chn la cp no s nh hng n cc yu t trn. S nt trn mi phn on cng nhiu s lm suy gim tn hiu trn ng truyn. Tn hiu sau khi i qua mi nt s b suy gim v do d liu nhn c nt sau c th khc nt trc. S nt trn mi phn on v chiu di tng cng ca c phn on u ph thuc vo dng cp ang dng. Mt yu t khc cng ng quan tm l tr tn hiu. tr l thi gian t lc tn hiu c truyn i cho n khi nhn c tn hiu. V d khi dng MS Word x l mt vn bn c ly trn server, khi ngui dng nhn Save trn thanh toolbar, th tr l thi gian c tnh t khi MS Word hin ra thng bo i qua m hnh OSI ra card mng ti cp, i qua trng truyn dn , qua HUB/SWITCH/ROUTER ti card mng trn server i qua m hnh OSI v c chp nhn bi server. Li trn ng truyn c th xy ra khi thi gian tr l ln. Do mi dng cp thng hay qui nh s phn on v chiu di ti a cho mt phn on trnh li xy ra. Thit b lin kt (Connectors) l cc thit b dng lin kt dy mng vi cc nt trn mng. Cc nt ny c th l cc trm lm vic, cc my ch, cc my in, HUB, Switchs, Routers. C mt s thit b nh: BNC, TConnector, RJ45. (Hnh 3.3)

Hnh3.3 Mt s thit b mng Nhiu in t: bt k h thng cp no cng c nhiu. Nhiu cng nhiu th cng nh hng n cht lng ng truyn. C 2 nguyn nhn chnh gy ra nhiu l do in v do tn s sng m thanh.T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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3.3 Cc mng LAN: Baseband v BroadbandCc mng cc b chia lm hai loi: Mng cc b bng thng c s v mng cc b bng thng rng (Baseband v Broadband LAN). a. Mng cc b bng thng c s: (Baseband LAN) l dng mng LAN ch cho php truyn mt dng tn hiu trn ng truyn hay ni khc i ch c mt knh truyn ( tn s ) duy nht h tr truyn s do nhanh hn rt nhiu so vi k thut truyn tn hiu tng t.

b. Mng cc b bng thng rng: (Broadband LAN) thng thng

mng cc b khng thuc loi ny. Mng cc b bng thng rng thng s dng cp xon hay cp cp quang to ra nhiu knh truyn d liu.

ng vi mi knh truyn s c mt tn s sng khc nhau, n s dng sng m thanh, tn hiu truyn i l tng t do c th x l cc tn hiu vi cc tn s khc nhau. Vi bng thng rng ng truyn c chia thnh dy tn s, mi tn s ng vi mt loi d liu , theo cch ny th cc tnh hiu nh m thanh, hnh nh. c th truyn cng mt lc. Mng bng thng rng thch hp cho cc bnhvin v cc vin i hc.

3.4 Cc loi cp mngCc phng tin ni mng c chia lm hai nhm: c quy nh gii hn v khng quy nh gii hn . Phng tin c quy nh gii hn thng l cp, v cc phng tin khng qui nh l: sng v tuyn, laser, viba v tia hng ngoi. H thng cp chia ra lm ba loi : cp ng trc (Coaxial), cp xon i (twisted-pair) v cp si quang (optical fiber)

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3.4.1 Cp ng trc (Coaxial cable)L loi cp xut hin u tin, gm hai dy dn: mt li bn trong v mt lp bc ngoi. (Hnh 3.4)

Hnh3.4 Cp ng trc Cp ng trc chia ra lm hai loi

Cp ng trc dy (Thick cable) - 10BASE-5 Cp ng trc mnh (Thin Cable) - 10BASE-2

Mt s thng s k thut v 2 loi cp ny:

Cp ng trc mnh (10BASE2)Tc truyn d liu ( Max) S repeaters (Max) Chiu di ti a cho 1 phn on S trm ti a trn 1 phn on

Gi tr10 Mbps 4 185 meters 30

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Cp ng trc mnh (10BASE2)S trm ti a Khng cch ti thiu gia hai trm 90 0.5m

Gi tr

Cp ng trc dy ( 10BASE-5)Tc truyn d liu ( Max) S repeaters (Max) Chiu di ti a cho 1 phn on S trm ti a trn 1 phn on S trm ti a Khng cch ti thiu gia hai trm

Gi tr10 Mbps 4 500 meters 50 300 Multiples of 2.5m

Cp ng trc dy (RG-62) thng c dng trong mt mng my tnh n to thnh cc ng xng sng (backbone) trong h thng mng (Hnh 3.5)

Hnh 3.5 S mng dng cp ng trc dy Cp ng trc mnh (RG-58A/U) thng dng ni cc trm lm vic trn mt mng cc b (Hnh 3.6).

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Hnh 3.6 S mng dng cp ng trc mnh Cp ng trc c cc tnh cht sau:

B nh hng ca nhiu bn ngoi v phi c bc lm gim nhiu nh hng . Khi khong cch mng ln, n c th thu ly cc nhiu tp m v nhiu t xe c v cc ngun in khc. Pht ra cc tn hiu khc.

3.4.2 Cp xon i (Twisted Pair cable)C hai loi cp xon i:

C bc ngoi (Shielded Twisted Pair cable - STP)

Khng bc ngoi (Unshielded Twisted Pair cable - STP). Ring loi cp dng cho mng Ethernet l loi cp xon i khng bc ngoi hay cn gi l cp UTP (Hnh 3.7).

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Hnh 3.7 Cp xon i Ngoi ra cp UTP loi 5 cn gi l cp 10BASE-T Cp xon i c cc tnh cht sau L h thng cp kinh t nht C th dng nhng ng cp in thoi c sn trong mt s trng hp C chiu di hn ch C th b nh hng bi nhiu bn ngoi

3.4.3 Cp quang (Fibre-Optic cable)

Mt s c im c bn ca cp si quang:

C nhiu kch c khc nhau v chng chuyn ti nh sng ch khng phi in. Thng c dng kt hp vi nhng loi cp khc nh l mt ng ni kiu xng sng gia cc server v cc LAN C u th ln v chiu di cp v tc truyn nhanh hn hn cc loi cp khc Khng pht ra tn hiu Khng b nh hng ca nhiu bn ngoi

Cc thng s k thut ca h thng cp rt quan trng, c th kim tra theo 5 tnh cht sau: Chiu di - H s suy gim - Nhiu chen ngang u cp - Tp nhiu - tht thot

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Vic ni cp Vic chn loi cp l mt iu quan trng khi lp t mt mng. Trong cc loi cp th cp quang l loi cp an ton nht nhng gi thnh rt cao. Bng so snh cc tnh nng ca cp Yu t so snh Cp UTP Cp ng trc Gi c Thp Trung bnh Bng Thng Trung bnh Cao Chiu di Hng trm feet Hng ngn feet Nhiu Kh nhiu Thp tin cy Cao Cao Cp quang Cao Cc k cao Hng dm Khng c Rt cao

Cc thnh phn ca mt mng s dng cp ng trc 10BASE-2 -Card giao tip 10BASE-2 : hu ht tt c u h tr h thng cp ny. Card cho loi ny phi c mt u ni loi BNC ni vo dng cp chnh . Trn ng cp chnh c gn mt u ni T-Connector gn vo mt u ni BNC pha sau card . Nu my khng c a cng th phi gn thm mt Boot ROM. - B tip sc (Repeater): l mt thit b chn thm, dng ni 2 on cp chnh v lm tng tn hiu truyn qua li gia chng. - Cp: l loi cp ng trc c in tr l 50 Ohm ng knh 0.2 inch - Cc u ni cp kiu BNC: c gn vo hai u ca khc cp - Cc u ni T-Connector kiu BNC dng a tnh hiu vo v ra - Cc u ni thanh ngang kiu BNC c dng ni hai khc cp li vi nhau - Cc Terminal gn hai u cui ca on mng, c in tr l 50 Ohm Khi ni mng bng loi cp ny, phi tun theo cc quy tc v hn ch sau: - Chiu di ca mi on cp chnh ti a l khong 185 mt - Dng cc T-Connector ni cp vi card mng - Ch dng ti a 4 repeater ni kt 5 on cp mng chnh, trong ch c 3 on l c dng ni vi trm lm vic, 2 on cn li ch dng ni n nhng khong cch xa. - Chiu di ti a ca ton mng l 910 mt - Ti a c 30 nt trn mi on mng, cc nt y bo gm: my tnh, server, repeater, router. Cc thnh phn ca mt mng khi dng cp xon i (10BASE-T hay l UTP) Cc trm lm vic c ni vo mt HUB, c tc dng lm khuych i tn hiu t server ti v pht i tip ti cc my khc trn mng * Cc thnh phn ca mt mng dng cp UTP - Card giao tip mng 10BASE-T - HubT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Cu hi n tp chng 31. Cng ngh cp ng trc ................ h tr nhiu knh, mi knh chim khong 6 MHz. a. Thick b. Baseband c. Broadband d. Thin 2. iu no l khng ng khi ni v cp si quang trong cc iu sau? a. It has a lower noise level b. Light signals do not attenuate as quickly as electric signals c. Light propagates more quickly through glass than electric signals d. It is easy to wiretap 3. Vic tng tc truyn c th tng nh hng ca nhiu v v vy gi tr ca tn hiu. a. ng b. Sai 3. Loi mi trng truyn no trong cc loi sau khng phi l mi trng trng nh hng? a. Twisted pair wire b. Coaxial cable c. Fiber optic cable d. Microwave 4. K thut chuyn t d liu s ho sang tn hiu tng t gi l ....... a. Manchester encoding b. Modulation c. Multiplying d. Negotiation 5. Bn chu trch nhim bo tr my tnh Microsoft Windows 2000 Server trn mng cng ty ca mnh. Card mng trong server hin thi c kt ni ti mng. Bn thy c mt u ni 15 chn pha sau ca card giao tip mng (NIC) ang ni ti mt transceiver bn ngoi. Loi cp no c s dng cho kt ni mng? a. ThinNet coaxial (10Base2) b. ThickNet coaxial (10Base5) c. Twisted-pair (10BaseT) cable d. Fiber-optic cable 6. Nhng loi cp no thuc v cng ngh Ethernet 10 Mbps? (Chn tt c cc cu tr li ng) a. 10Base2 b. 10Base10 c. 10BaseTLd. 10BaseUT e. 10BaseFL f. 10Base5

7. Hai loi cp no c s dng vi u ni BNC connector v cc thnh phn terminator? a. 10Base2 b. 10Base10 c. Thinnet d. 10BaseUT

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CHNG 4 - CC GIAO THC MNG (PROTOCOLS)MC TIU CA CHNG Kt thc chng ny, sinh vin s c th: Hiu c khi qut khi nim giao thc mng my tnh. c im v ni dung cc giao thc con ca cc b giao thc thng thng ang s dng: TCP/IP, IPX/SPX, MicroSoft Network. C so snh chng vi m hnh OSI.

4.1 Giao thc (protocol) mng l g?Tp hp tt c cc quy tc, quy c m bo cho cc my tnh trn mng c th giao tip vi nhau gi l giao thc. Nh vy cc my trn mng mun giao tip vi nhau th phi c chung mt giao thc. Vai tr ca giao thc l quan trng, khng th thiu. V d mt s giao thc nh: TCP/IP, SPX/IPX, v.v... Cc dng lin kt: Giao thc hng kt ni v giao thc khng kt ni (Connectionless & Connection- Oriented protocols) Giao thc c kh nng nh tuyn v giao thc khng c kh nng nh tuyn (Routable & non - Routable protocols)

4.1.1 Giao thc hng kt ni v giao thc khng kt ni

c im ca giao thc khng kt ni:

a. Khng kim sot ng truyn b. D liu khng bo m n c ni nhn c. D liu thng di dng datagrams V d: giao thc UDP ca TCP/IP

c im ca giao thc hng kt ni:

a. Ngc li vi giao thc khng kt ni , kim sot c ng truyn b. D liu truyn i tun t, nu nhn thnh cng th ni nhn phi gi tn hiu ACK (ACKnowledge) V d: cc giao thc TCP, SPX

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4.1.2 Giao thc c kh nng nh tuyn v giao thc khng c kh nng nh tuyn

Giao thc c kh nng nh tuyn

L cc giao thc cho php i qua cc thit b lin mng nh Router xy dng cc mng ln c qui m ln hn V d, cc giao thc c kh nng nh tuyn l: TCP/IP, SPX/IPX

Giao thc khng c kh nng nh tuyn

Ngc vi giao thc c kh nng nh tuyn, cc giao thc ny khng cho php i qua cc thit b lin mng nh Router xy dng cc mng ln. V d v giao thc khng c kh nng nh tuyn l : NETBEUI Hin c 3 loi giao thc thng hay s dng: TCP/IP SPX/IPX (Novell Netware) Microsoft Network

4.2 B giao thc TCP/IP (Transmission Control Protocol / Internet Protocol)TCP/IP c thit k hon ton c lp vi cc phng php truy cp mng, cu trc gi d liu (data frame), mi trng truyn, do m TCP/IP c th dng lin kt cc dng mng khc nhau nh mng LAN Ethernet, LAN Token Ring hay cc dng WAN nh: Frame Relay, X.25 Hnh 4.1 so snh b giao thc TCP/IP vi m hnh OSI. TCP/IP l mt lp cc giao thc ( protocol stack) bao gm cc giao thc sau:

4.2.1 FTP (File Transfer Protocol).FTP cung cp phng php truyn nhn file gia cc my vi nhau, n cho php ngi s dng c th gi mt hay nhiu file t my mnh ln h thng bt k (upload) v nhn mt hay nhiu file t mt h thng bt k v my mnh (download)

4.2.2 TelnetVi Telnet, ngi s dng c th kt ni vo cc h thng xa thng qua mng Internet.

4.2.3 SMTP (Simple Mail Transfer protocol)L giao thc cho php thc hin dch v truyn nhn mail trn mng Internet.T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Hnh 4.1 So snh giao thc TCP/IP vi m hnh OSI

4.2.4 TCP v UDPHai giao thc ny ng vai tr ca tng transport, c trch nhim to lin kt v dch v kt ni d liu (datagram communication service) TCP (Transmission Control Protocol) l giao thc chuyn giao chnh trong TCP/IP. TCP cung cp mt ng truyn c tin cy cao, l lin kt c nh hng (connection oriented protocol), khi phc cc gi d liu b mt trong qa trnh truyn. Qu trnh truyn d liu theo TCP l cc byte, gi d liu TCP bao gm cc thng tin sau

Thng tinSource Port Destination port Ch s th t ACK Window TCP Checksum

Chc nngThng tin v a ch cng (port) ca my gi Thng tin v port ca my nhn Ch s th t tnh t byte u tin trong d liu TCP Ch s byte m ngi gi nhn c t ngi nhn B m d liu cho TCP Xc nh tnh ton vn d liu trong TCP header v TCP data

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S port20 21 23 80 139

Dch vFTP ( Data) FTP (Control) Telnet HTTP NETBIOS

UDP (User Datagram protocol) l loi lin kt mt mt hay mt nhiu, khng nh hng (Connectionless), khng c tin cy cao, thng hay dng khi dung lng d liu truyn ti trn mng l nh. Cc thng tin trong UDP header bao gm:

Thng tinSource Port Destination port TCP Checksum

Chc nngThng tin v port ca my gi Thng tin v port ca my nhn Xc nh tnh ton vn d liu trong TCP header v TCP data

Mt s port UDP thng dng:

S port53 137 138 161

Dch vDomain name system NETBIOS NAME NETBIOS Datagram SNMP

4.2.5 Cc giao thc IP, ARP, ICMP, RIP.ng vai tr ca tng Internet c chc nng tm ng (routing), nhn dng a ch (addressing), ng gi (package) IP (Internet protocol) l dng giao thc cho php tm ng (routable protocol), nhn dng a ch (addressing), phn tch v ng gi. Mt gi IP bao gm IP header v IP payload, trong IP header bao gm cc thng tin sau:

IP Headera ch IP gi a ch IP nhn Identification Checksum

Chc nngThng tin v a ch IP ca my gi Thng tin v a ch IP ca my nhn Nhn dng cc mng con nu c trong a ch IP Xc nh tnh ton vn d liu trong phn IP header

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ARP (Address Resolution Protocol) c chc nng phn gii mt a ch IP thnh mt a ch giao tip trn mng. ICMP (Internet Control Message Protocol) c chc nng thng bo li cc li xy ra trong qua trnh truyn d liu.

4.2.6 NDIS (Network Driver Interface Specification) v ODI (Open Data Interface)Hai giao thc ny ng vai tr ca tng DataLink, cho php mt card giao tip (interface card) c th giao tip vi nhiu giao thc khc nhau trn mng. ODI c pht trin bi Novell v Apple, ban u ODI driver c vit cho Novell v Macintosh

NDIS c pht trin bi Microsoft v 3 COM c cc phin bn nh NDIS, NDIS2 v NDIS3. Cc phin bn c dng cho Windows for workgroup, NT 3.5, cn cc phin bn mi dng cho WinNT 4.0 hay Windows 2000.

4.3 B giao thc IPX/SPX (Internetwork Packet Exchange / Sequenced Packet Exchange )So snh IPX/SPX vi m hnh OSI (Hnh 4.2)

Hnh 4.2 So snh giao thc IPX/SPX vi m hnh OSI

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Cng ging nh TCP/IP, IPX/SPX l mt lp giao thc bao gm cc giao thc sau:

4.3.1 SAP (Service Advertising Protocol)L giao thc dng qung co a ch ca server v cc dch v khc trn mng nh File servers v Print server dng SAP.

4.3.2 NCP (Netware Core Protocol)X l qu trnh tng tc gia client v server, v d nh vic chia x cc ti nguyn trn mng.

4.3.3 SPX (Sequenced Packet Exchange )Cung cp lin kt nh hng (connection oriented protocol) trn IPX.

4.3.4 RIP (Routing information Protocol)L giao thc tm ra ng i tt nht cho cc gi d liu.

4.3.5 IPX (Internetwork Packet Exchange)L giao thc khng nh hng, dng xc nh a ch mng v tm ng trn mng IPX/SPX, IPX cung cp dch v v datagram.

4.3.6 ODI (Open Data Interface)Giao thc ny ng vai tr ca tng DataLink, cho php mt card giao tip c th giao tip vi nhiu giao thc khc nhau trn mng. ODI c pht trin bi Novell v Apple, do ban u ODI driver c vit cho Novell v Macintosh

4.4 B giao thc Microsoft Network (NETBIOS,NETBEUI,SMB) Microsoft Networking l s kt hp ca IBM & Microsoft, n l lp cc giao thc, so snh vi m hnh OSI ( Hnh 4.3 )

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Hnh 4.3 So snh giao thc Microsoft Networking vi m hnh OSI NetBIOS : Network Basic Input Output System NetBEUI : Network Extended User Interface Microsoft Network bao gm cc giao thc sau:

4.4.1 RedirectorGiao thc ny c tc dng: Lm cho ti nguyn trn mng tr thnh cc b. Trc tip truy xut ti ti nguyn trn cc server tng ng

4.4.2 SMBC chc nng tng t nh tng biu din, cung cp lin kt ngang hng gia client v server, cho php thnh lp cc mng ngang hng.

4.4.3 NetBIOSGiao thc ny dng thnh lp phin lm vic gia cc my tnh. N c cc c im sau:

Hot ng ti tng Session. Dng tn c 15 k t t nhn dng. Thnh lp lin kt gia 2 my truyn d liu Cho php lin kt khng nh hng Dng broadcast nh dng cc my tnh trn mng.

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C ch hot ng ca NetBIOS bao gm 4 phn : NetBIOS Interface NetBIOS Management NetBIOS Datagram NetBIOS Session

NetBIOS Interface Bao gm cc hm API chun cho php cc ng dng c th gi hay nhn thng tin t server. NetBIOS Interface cn thc hin chc nng NetBIOS trn TCP/IP. NetBIOS Management Bao gm nhng chc nng sau . ng k v hy tn: cho php cc my c th ng k mt tn nhn dng trn mng v sau xa i khi thot khi mng . Phn gii tn (Name Resolution): khi c mt chng trnh NetBIOS mun giao tip vi mt chng trnh NetBIOS khc, th a ch IP ca chng trnh ny phi c phn gii thnh NETBIOS name, NETBIOS trn TCP/IP s thc hin chc nng ny. NetBIOS Datagram Qun l cch truyn cc datagram theo lin kt khng nh hng. Cc datagram c th truyn cho mt ngi hay mt nhm ngi no s dng c ch NetBIOS Name. NetBIOS Session Qun l cch truyn cc datagram theo lin kt c nh hng v theo th t c tin cy cao. N s dng giao thc TCP thnh lp mt lin kt v kt thc khi cn thit. Xem hnh v (Hnh 4.4)

Hnh 4.4 C ch NETBIOS

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4.4.5 NetBEUI

L giao thc thch hp cho cc mng LAN nh t 10 - 200 my Nhanh, hiu qa, t tn vng nh.

4.4.6

NDIS

c pht trin bi Microsoft v 3 COM c cc phin bn nh NDIS, NDIS2 v NDIS3. Cc phin bn c dng cho Windows for workgroup, NT 3.5, cn cc phin bn mi dng cho WinNT 4.0 hay Windows 2000.

4.5 Mt s Protocols khc

DLC (Data Link Control): dng lin kt IBM mainframes v my in ca HP NFS ( Network File System) : l giao thc dng trn UNIX SNA ( System Network Architecture) dng trn my IBM X-windows: tp cc giao thc (MIT) di dng Graphic giao tip vi ngi s dng trn Unix.

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Cu hi n tp chng 41. Mc no trong cc mc sau khng phi l mt thuc tnh TCP/IP trong mt mi trng nh tuyn? a. TCP/IP address b. Subnet mask c. Default gateway d. DNS server 2. Mt mng LAN, trong cc my tnh c kt ni ti mt HUB vi cp xon i, tt nht c th c m t nh: a. Mt hnh trng star lgc b. Mt hnh trng bus lgc v mt hnh trng star vt l. c. Mt hnh trng ring hoc loop. d. Mt hnh trng bus vt l. 3. Giao thc no trong cc giao thc sau khng phi l mt giao thc c th nh tuyn? a. FTP b. IP c. NetBEUI d. SMTP 4. Giao thc no chuyn i datagrams m khng c thng tin ACK hoc truyn m bo? a. TCP b. ASP c. TCP/IP d. UDP 5. Mt trong nhng khc nhau chnh gia NetBEUI v TCP/IP l: a. NetBEUI l nh tuyn v TCP/IP l khng nh tuyn. b. NetBEUI l khng nh tuyn v TCP/IP l nh tuyn. c. NetBEUI th kh qun l. d. TCP/IP cu hnh d dng hn so vi NetBEUI. 6. Cc yu cu ti thiu cho vic nh a ch trong mt mng da trn giao thc TCP/IP? a. IP address, Subnet Mask, v default gateway. b. MAC address v subnet mask. c. IP address. d. IP address v subnet mask. 7. Nhng li ch m TCP c so vi UDP? a. TCP cho php cc gi ln hn c gi qua mng nh ci tin hiu sut ng dng. b. TCP c mt c ch "gi li" ngn chn vic mt gi d liu. c. TCP s dng mt header nh hn UDP. d. Khng phi nhng iu trn. 8. Giao thc no trong cc giao thc giao vn sau c s dng cho vic chi cc tr chi trn Internet? a. TCP b. IPX/SPX. b. NetBEUI d. UDP 9. Giao thc no c s dng gn cc a ch IP tnh? a. ARP b. Proxy ARP c. DHCP d. TCP/IP 10. Ci g c s dng trong giao thc tch host ID khi network ID? a. Network address b. Node address. c. Default gateway d. Subnet mask.T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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CHNG 5 - CC HNH TRNG (TOPOLOGIES) CA MNG CC B (LAN)MC TIU CA CHNG Kt thc chng ny, sinh vin s c th: Nm c cc c trng c bn ca mng cc b. Hiu c cc c im cng nh cc u v nhc im ca cc hnh trng LAN n gin: bus, star v ring, cng nh c im ca cc hnh trng LAN hn hp. Hiu c ba k thut chuyn mch: knh, thng bo v gi; So snh ba k thut chuyn mch ny. Nm c ni dung c bn hai phng php truy xut ng truyn: CSMA/CD v Token Passing. Nm c cc yu t (c v l thuyt v k thut c bn) to nn kin trc mng Ethernet v mng Token Ring

5.1 Cc c trng c bn ca mng cc b (LAN)Trong mc 1.2.3 phn u ti liu ny, khi phn loi cc mng my tnh da trn yu t chnh l khong cch a l, ta c cc loi mng nh mng cc b (LAN), mng th (MAN), mng din rng (WAN) v mng ton cu (GAN). Tuy nhin khong cch a l gia cc trm ca mng cng ch l mt trong cc c trng ca mng cc b. Cn c cc c trng khc (nh tc truyn, t sut li, ) cng ng vai tr quan trng quyt nh hiu sut v s pht trin ca LAN. Sau y l mt s c trng c bn ca LAN cho php phn bit LAN v cc loi mng khc, c bit l vi WAN.

5.1.1 c trng a lCng nh c trnh by trong mc 1.2.3, mng LAN l mng c ci t trong mt phm vi tng i nh (trong mt phng, mt to nh, hoc phm vi ca mt trng hc v.v) vi khong cch ln nht gia hai my tnh trm ch trong khong vi chc ki-l-met tr li. Tuy nhin gii hn v khong cch ny cng ch c tnh cht tng i. V vy, khng th ch ly c trng v a l phn bit LAN vi cc loi mng khc.

5.1.2 c trng tc truynMng cc b c tc truyn thng cao hn so vi mng din rng (WAN). Hin nay, tc truyn ca LAN c th t ti 100 Mb/s.

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5.1.3 c trng tin cyT sut li (error rate) trn mng LAN thp hn nhiu so vi WAN: c th t t 10-8 n 10-11.

5.1.4 c trng qun lMng cc b thng l s hu ring ca mt c nhn hoc t chc no (trng hc, doanh nghip, v.v) do vic qun l khai thc mng hon ton tp trung, thng nht. Tuy nhin, vi s pht trin nhanh chng ca cng ngh mng, cc c trng ni trn cng ch c tnh cht tng i. S phn nh gia mng cc b v mng din rng s ngy cng m hn. Hnh 5.1 cho ta mt s tm tt cc vn cn xem xt khi tm hiu v mng cc b.Headend Token bus Token ring CSMA/CD Slotted Ring Register insertion Office Camp us Industr y Applicatio n Rando m Baseban d Coaxial Medium Access Control Cable Thick cable Collision avoidance Rfmodem s CATV networks Thin cable

Fiber optic Twisted pair

LA NStandard Bodies

BusRin g EIA ISO Star

Private System s

ECMA

IEEE

Hnh 5.1 S tm tt nhng vn lin quan n mng LAN T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Nhng vn lin quan n ng truyn vt l (Transmission media) c tm hiu chng 3. Chng ny tp trung xem xt v hnh trng (topology) v k thut truy xut ng truyn (Medium Access Control) LAN.

5.2 Cc hnh trng LAN n ginNh trnh by trong phn 1.2.4, mng cc b c ba hnh trng n gin l bus (ng trc), star (hnh sao), v ring (vng). Sau y ta s ln lt tm hiu cc hnh trng ny.

5.2.1 Hnh trng BUSMt hnh trng bus vt l (cn gi l hnh trng bus tuyn tnh) cn bn s dng mt ng cp chung di gi l ng xng sng (backborne hay bus). ng cp ny cn c gi l ng truyn chnh (trunk line) hoc phn on mng (network segment). C nhng on cp ngn c gn vi ng xng sng bng cc u ni (tap) kt ni vi cc thit b mng (Cc tap l nhng thit b c kh dng phn tch tn hiu in hoc in t). Tuy nhin cc hnh trng bus hin nay ch yu gn cc my tnh trc tip vi ng truyn chnh bng u ni ch T (T-connector). ng truyn chnh c kt thc (terminate) hai u bng cc terminator loi b cc tn hiu trn dy sau khi n truyn qua mi thit b gn vi bus. Tt c cc nt (bao gm my ch file, cc my trm, v cc thit b ngoi vi) c kt ni ti ng truyn chnh (Hnh 5.2).

Terminator

T-connector Hnh 5.2 Hnh trng BUS vt l

Bus

Terminator

a s cc hnh trng bus cho php cc tn hiu in hoc in t lan truyn theo c hai hng u im ca hnh trng BUS: S dng cc chun c thit lp, ci t tng i d dng. i hi ng truyn cp t hn cc hnh trng khc. Cch b tr dy rt n gin, d m rng v tin cy.T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Nhc im ca hnh trng BUS: Kh khn trong vic cu hnh li, c bit khi khong cch v s cc u ni vt qu mc ti a cho php. Vic chn on v c lp cc li kh khn. Mng s khng ho t ng (down) khi c li hoc t cp.

5.2.2 Hnh trng STARMng dng hnh sao c mt b x l trung tm (HUB) cn gi l b chuyn tip nhiu cng (multiport repeater) hay b tp trung (concentrator) m tt c cc nt (my ch file, cc my trm, v cc thit b ngoi vi) gn vi n qua ng cp (Hnh 5.3). Cc mng hnh sao c th c lng trong cc mng hnh sao khc to thnh mng hnh cy hoc mng phn cp

HUB

Hnh 5.3 Hnh trng STAR vi HUB trung tm

D liu trn mng STAR truyn qua HUB trc khi tip tc ti ch. HUB qun l v iu khin tt c cc chc nng ca mng. HUB cng hot ng nh mt b chuyn tip lung d liu. N c s dng trong cc mng ARCnet, Token Ring, FDDI (Fiber Distributed Data Interface) v cc mng cc b 10BaseT vi cp xon i, cp ng trc hoc cp si quang. Nhng v d in hnh ca hnh trng STAR l cc kin trc mainframe v minicomputer, trong my ch (host) l mt b chuyn mch (switch) tp trung. Trong mng hnh sao, nu mt cp b t, n ch nh hng ti nt (my trm) ni ti HUB bng cp . Tuy nhin nu HUB b h th ton b phn on mng kt ni ti HUB s ngng hot ng. a s cc mng cc b Ethernet hin nay u s dng hnh trng STAR v kh nng m rng v d dng kt ni vi cc mng khc. Chng cng d dng c lp cc li xy ra vi cp mng. Nhiu mng bus v ring c cng c nng cp chuyn sang mng hnh sao. u im ca hnh trng STAR:T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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D ci t v cu hnh li. D gii quyt cc s c. Li ng truyn t ng c lp phn on mng b li. Khng cn phi ngt mng khi cn kt ni thm hoc tho b bt cc thit b mng. Nhc im ca hnh trng STAR: i hi nhiu cp hn cc hnh trng khc. Vic tn ti mt HUB tp trung (hoc concentrator) ng ngha vi vic tn ti kh nng ngng hot ng ca ton phn on mng khi HUB c s c.

5.2.3 Hnh trng RINGMt hnh trng RING vt l l mt hnh trng vng (vng kn lin kt im-im). Mi thit b kt ni trc tip ti vng hoc gin tip qua mt thit b giao tip v cp. Mi thit b hot ng nh mt b chuyn tip (repeater), khuch i tn hiu gia cc my trm.

data repeater

Cc tn hiu in hoc in t c truyn t thit b ny ti thit b khc ch theo mt hng. Mi thit b kt hp mt thit b nhn cp n (receiver) v mt thit b pht (transmitter) cp i. Cc tn hiu c lp li v ti sinh mi thit b sao cho s suy hao l nh nht. Mt v d s dng hnh trng vng l mng cc b Token Ring. Loi mng vng ny s dng vic truyn th bi (token passing) cho php tng my tnh gi d liu trn mng. Mt th bi (token) l mt gi d liu nh (3 byte) cho php cc nt truy xut mng. Nt (my tnh) gi phi ly th bi v b sung thng tin aT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

Hnh 5.4 Hnh trng RING

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ch, thng tin iu khin ring cng vi d liu hnh thnh mt frame d liu. Sau frame ny c truyn trn mng ti nt k tip trong vng. Nu frame d liu khng phi dnh cho nt k tip th nt ny ti sinh li tn hiu v truyn tip n trn mng. Qu trnh ny tip tc cho n khi nt nhn ly c frame d liu. Sau khi nhn c frame d liu, nt nhn p li nt gi ban u bng cch pht ra mt p ng truyn trn mng cng dng mt frame d liu. Frame ny di chuyn quanh mng theo cng hng trc y cho n khi n chm ti nt gi ban u. Khi frame ny s b loi b khi mng, v mt th bi mi li c sinh ra v truyn trn dy cho mt nt khc nhn n, to frame d liu v truyn tip v.v. Qu trnh ny m bo l bt k thi im no ch c th c mt nt truyn d liu trn mng . u im ca hnh trng RING:

Cc li v cp xc nh d dng Vng i (Dual loop ring) c th chng li tt. Vic ci t, thay i v cu hnh li kh khn hn hnh trng bus. Li v ng truyn trn cc vng n lm ngng hon ton hot ng ca mng. Cc u ni kh t, c bit l cc u ni IBM (IBM connectors).

Nhc im ca hnh trng RING:

5.3 Cc hnh trng LAN hn hp5.3.1 Star-Wired RingMt mng hnh trng star-wired ring s dng cch sp xp vt l ca mng hnh sao, nhng tch hp phng php truyn th bi (token passing). D liu c gi quanh star theo mt vng khp kn. iu ny cho php c ch chng li tt hn mng star v b sung thm tnh tin cy ca vic truyn th bi. Nhng mng vng hin nay thng s dng hnh trng hn hp ny. Trong hnh 5.5 di y, cc ng ni lin nt m biu din cp vt l kt ni hub v cc trm theo hnh trng STAR, trong khi cc ng khng lin nt biu din vng lun l ca hnh trng RING.

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Hnh 5.5 Hnh trng mng cc b Star-wired Ring

5.3.2 Star-Wired BusMt hnh trng star-wired bus l mt dng khc ca hnh trng hn hp. Cc nhm my tnh trm c kt ni ti hub theo dng hnh sao, sau cc hub c kt ni vi nhau qua ng trc n (single bus). iu ny cho php lin kt d dng cc phn an mng khc nhau v thng c s dng trong cc mng Ethernet v Fast Ethernet.

Hnh 5.6 Hnh trng mng cc b Star-wired Bus

5.3.3 Daisy-ChainedMt mng hnh dng vng hoa cc (daisy chain) th tng t nh hnh trng star-wired bus. Cc mng s dng hnh trng star-wired bus hoc star-wired ring c th kt ni vi nhau hnh thnh mt chui vng hoa phc tp hn. y l mt k thut n gin m rng mng LAN vi chi ph b sung t. Cc qun tr mng nn nh rng, nhng hnh trng mng n gin nh Ethernet b hn ch v s phn on c th kt ni m khng b

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mt tnh ton vn d liu. Mc d v mt vt l rt d dng m rng mng, nhng nu chng ta vt qu s phn on xc nh, mng ca ta s c li.

Hnh 5.7 Mt Daisy-chain c hai mng cc b Star-wired Bus

5.4 Cc h thng giao vn mngModem Hub

Repeater

Bridge

Router

Hnh 5.8 Minh ho vic kt ni cc thit b ca mng LAN (Hub, Repeater, Bridge, Router, Modem v.v.).

Hai h thng giao vn mng ph bin nht l Ethernet v Token Ring. Nhng khi nim c bn m c hai hnh trng lgc ny s dng c trnh by phn di y.

5.4.1 K thut chuyn mch (Switching)K thut chuyn mch l mt thnh phn ca hnh trng lgc mng m n xc nh cch thc cc kt ni c to ra gia cc nt (hoc trm) trn mng. C ba kiu chuyn mch: chuyn mch knh (circuit switching); chuyn mch thng bo (message switching); v chuyn mch gi (packet switching). Mi h thng giao vn mng u da trn mt trong ba kiuT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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phng php chuyn mch ny. Ni dung v cc k thut chuyn mch ny c th xem li mc 1.2.3. Phn tip theo ch trnh by nhng nt khi qut v cc k thut ny. 1) K thut chuyn mch knh (Circuit Switching) Trong k thut chuyn mch knh, mt kt ni c thit lp gia hai nt mng trc khi chng khi to vic truyn d liu. Mt tng bng thng c dnh ring cho kt ni ny v vn tip tc duy tr cho ti khi mt trong hai thc th kt thc giao tip. Mt khi knh giao tip c thit lp, ton b d liu s tip tc i theo cng mt con ng t nt gi ti nt nhn. Kiu chuyn mch ny khng hiu qu v n chim dng bng thng cho trong sut khong thi gian cc nt kt ni. 2) K thut chuyn mch thng bo (Message Switching) K thut chuyn mch thng bo v k thut chuyn mch knh c chung mt c im l d liu (ton b thng bo) lun lun i theo cng mt ng. Tuy nhin chuyn mch thng bo khng duy tr mt kt ni lin tc. Khi mt kt ni c to ra gia hai thit b, d liu c truyn ti thit b th hai, sau kt ni b hu b. Tip theo mt kt ni c thit lp gia thit b th hai v thit b th ba. Mt khi d liu c truyn ti thit b th ba, kt ni c gii phng. Qu trnh c th tip din cho n khi d liu ti ch cui cng. Kiu chuyn mch ny s dng chng trnh lu tr v y ti (store and forward). D liu c y i t mt thit b ny ti thit b k tip, lu tr ti trc khi c y ti thit b th ba. K thut chuyn mch thng bo i hi b nh lu tr tm thi cao v nhng ph tn x l ti cc nt trung gian. 3) K thut chuyn mch gi (Packet Switching) Nh trnh by trong mc 1.2.3, k thut chuyn mch gi ngt d liu thnh nhng khi d liu nh, kch thc ca n c th qun l c nhng khi ny c gi l cc gi (packet) - trc khi chng c truyn ngang qua mng. Mi mt gi c th c con ng ring qua mng ti ch cui cng ca n v mi gi c c hai a ch ngun v a ch ch. Ni mt cch khc, mi gi c th tm c knh nhanh nht ti ch bt k thi im no. Nt ch trn mng chuyn mch gi nhn cc gi v hp nht chng li theo ng trnh t ban u da trn thng tin iu khin bn trong gi. K thut ny to ra nhng ph tn, m n khng thch hp cho vic truyn hnh nh v m thanh. u im ln nht ca k thut chuyn mch gi l khng tn ti mt con ng c nh trong khi d liu c gi t mt nt ny ti nt kia v khng i hi vic x l bi cc thit b trn ng truyn. K thut chuyn mch gi c s dng trong cc mng Ethernet, FDDI v Frame Relay.

5.4.2 a truy nhp c cm nhn sng mang / Pht hin xung t (Carrier Sense Multiple Access / Collision Detection - CSMA/CD)T B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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Cc h thng tranh chp hot ng da trn nguyn tc: vic truy xut ng truyn c thc hin trn c s thc th no chim dng ng truyn u tin s c quyn truyn d liu. Trc khi mt trm Ethernet truyn d liu, n lng nghe knh truyn c trng thi tch cc hay khng. Giao thc Ethernet thng c m t nh giao thc lng nghe trc khi truyn (listen before talking). Mt knh truyn c gi l tch cc (activity), nu nh c bt k tn hiu ang c truyn bi mt trm Ethernet no . S xut hin ca mt tn hiu truyn c gi l sng mang (carrier). Mi trm c th cm nhn s c mt ca mt sng mang. Nu mt trm pht hin knh truyn ang trng thi bn (trng thi tch cc), trm khng thc hin vic truyn d liu. Sau khi bit cui cng ca frame truyn qua, tng Ethernet Data Link tip tc ch ti thiu 9,6 mili giy to ra khong cch gia cc frame. cui thi im ny, nu mt frame d liu ang ch c truyn v nu knh truyn rnh, qu trnh truyn c khi to. Nu trm khng c d liu truyn, n li tip tc qu trnh cm nhn sng mang (Listen Before Talk - LBT). Khong cch gia cc frame cung cp thi gian hi phc (recovery time) cho cc trm Ethernet khc. Nu mt trm vn c truyn d liu khi knh truyn ang trng thi bn, s ng (collision) xy ra v kt qu l d liu khng n c trm ch hoc nu c n th cng b sai lch. Nu knh truyn trng thi rnh (khng mt sng mang no c pht hin), trm ang lng nghe c quyn truyn d liu. V c nhiu trm c kt ni ti knh Ethernet s dng c ch cm nhn sng mang nn h thng ny c gi l a truy nhp c cm nhn sng mang (Carrier Sense with Multiple Access - CSMA). Mt s ng cng s s xy ra nu hai trm quyt nh truyn d liu cng mt thi im m knh truyn khng trng thi tch cc. Nhng ng xy ra trong sut qu trnh hot ng bnh thng ca mng cc b Ethernet v cc trm truyn d liu ch da vo mt s kin duy nht: c tn ti mt sng mang trn knh truyn hay khng. Cc trm Ethernet gim thiu s ng bng cch pht hin nhng ng khi chng xy ra. V th thut ng CSMA/CD m t c ch truy xut ng truyn Ethernet, trong CD l vit tt ca Collision Detect (pht hiCc trm t). C ch pht hin xung t ny ngctruyi l gnghe trong n xung lng nghe Ng g n, i tn hiu khi ni (Listen truyn Talk LWT). Khi xy ra xung t cc ptrmch While cnh bo, ti tc (ang ng truyn d liu ) ngng vic truyn d liu. Trm u tin pht hin ra xung t s gi mt tn hiu sng mang c bit ti tt c cc trm kYesni ti t mng cnh bo s kin xung t ny. Sau khi mt xung t xy ra, tt c cc trm ch i trong mt thi on ngu nhin no . Vic truyn ch xy Yes ra sau khi kt thc thi on ny. Vic x l tr truynPhtn trc khi d hin hp cho ng Truy d li truyn c th gim i nhng xung t.n V thu Ethernet khng thch xung truy thc. cc ng dng thi gian Gin sau y minh ha qu trnh CSMA/CD.No No

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5.5 Kin trc EthernetS m t v mng Ethernet c xc nh trong chun IEEE 802.3. V giao thc, mng ny s dng phng php CSMA/CD truy xut ng truyn. Hnh trng chnh ca Ethernet l ng trc bus tuyn tnh, tuy nhin mi thnh phn ca n c th l hnh trng star. (Star-wired bus)

5.5.1 Cc loi cp mng EthernetEthernet c th hot ng trn ba loi cp khc nhau, mi loi c nhng hn ch, yu cu v cc thnh phn ring. Mng Ethernet ch yu s dng cp Ethernet chun (Thicknet) v cp Ethernet mnh (Thinnet). Chi tit v cc loi cp ny xem li phn Coaxial cable ca chng 3. Ngoi hai loi chnh trn, hin nay trong cc mng cc b Ethernet cn s dng loi cp xon i khng bc kim loi (unshielded twisted-pair UTP). Chi tit v loi cp ny xem li phn Twisted Pair Cable ca chng 3. Chun Ethernet IEEE 802.3 m t ba loi cp s dng trong mng Ethernet l 10Base2, 10Base5 v 10Base-T (xem li chng 3). Mng Ethernet l mt la chn tt cho cc mng c lu lng i khi thay i mnh. Mng Ethernet khng thch hp cho cc kin trc mng cc b c yu cu ti n nh. Mt u im ca mng Ethernet l kh nng s dng cc giao thc khc, c bit l giao thc TCP/IP (Transmission Control Protocol/Internet Protocol). Chnh iu ny lm cho mng Ethernet d dng cho vic truy xut cc minicomputer v cc trm cng sut cao. Mng Ethernet cng l mtT B mn HTMT Khoa CNTT - Trng Cao ng Cng Nghip 4

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chn la tt cho cc mng trong mi trng k thut, v cc nt trong mi trng ny thng l cc trm ci t h iu hnh UNIX s dng giao thc TCP/IP.

5.5.2 Phn on mng EthernetMt mng Ethernet bao gm cc nt gn ti ng trc bus ca n nhng c ly khc nhau. ng trc bus ny thc s l cp chnh di ca mng Ethernet. Phn cp chnh ny v cc nt gn ti n c gi l phn on mng Ethernet (Ethernet trunk segment). a s cc mng Ethernet khng thc thi mt cp di. Thng thng cp phn on mng c chia thnh mt dy cc cp c kt ni qua cc b chuyn tip(repater), cu (bridge) v cc b tm ng (router). Bng phn 5.5.3 v 5.5.4 di y l nhng m t chun IEEE 802.3, trong cp phn on c gii hn trong khong cch c th truyn mt tn hiu. Cp phn on c chiu di cc i v b hn ch s nt c th gn ti n. Phn on mng c th c chia thnh cc n v nh hn bng vic s dng cc u ni (connector). Phn on mng cp ng trc dy c chiu di ti a 500 mt (1640 feet) v c th c ti a 100 nt. Phn on mng cp ng trc mnh c chiu di ti a 185 mt (607 feet) v c th gn ti a 30 nt. Mt b chuyn tip (repeater) l mt thit b dng m rng chiu di ca cp phn on mng Ethernet. Cc phn on mng b sung c th m rng phn on mng Ethernet, tuy nhin mt phn on mng khng th c m rng vt qu gii hn xc nh. Ch rng mi nt cui ca mt phn on phi c gn u ni terminator v mt trong cc nut phi c ni t. Mng Ethernet khng c mt hub hoc concentrator ring nh i vi hnh trng ring hoc star. Mi cp phn on ring r ng vai tr nh mt hub hoc concentrator. Mt mng Ethernet cng c th kt hp cc cp Thinnet v Thicknet trong cng mt mng. Tuy nhin mi loi cp c c tnh k thut ring v vic ci t mng phi tun theo cc c tnh ca c hai loi cp ny.

5.5.3 Cc quy tc ni cp Ethernet mnh (10Base2)Cc tham s cho cp Ethernet mnh (10Base2) c trnh by trong bng di y: Cc tham s cho cp Ethernet mnh (10Base2) Tc cc i ca d liu S repeater cc i Chiu di cc i cho phn on cp ng trc S trm cc i / 1 phn on 4 185 mt 30 Gi tr 10 Mbps

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Tng s trm cc i Khong cch nh nht gia cc trm

90 0,5 mt

5.5.4 Cc quy tc ni cp Ethernet dy (10Base5)Cc tham s cho cp Ethernet dy c trnh by trong bng sau: Cc tham s cho cp Ethernet dy (10base5) Tc cc i ca d liu S repeater cc i 10 Mbps 4 Gi tr

Chiu di cc i cho phn on cp ng 500 mt trc Chiu di cp cc i ca transceiver 50 mt Chiu di cc i ca phn on mng ni 1500 mt kt S trm cc i / 1 phn on Tng s trm cc i Khong cch gia cc trm 100 300 n*2,5 mt (n=1,2,3, )

5.5.5 Mng Ethernet dng chung (Shared Ethernet)Cc mng