n)/lg e) mal 1I((li.

I, R2=LR 4, Nhu v~y mQt cau can bang la cau co:

d) n)/lg e) mal 1I((li.

2. M(;mg hlllh sao (star) Iii. m<.tng dicu khitn liung Wm, cach sftp xep v~t 1y

giong ngoi sao- hinh 2.76 (b). T<.tl Uim la may

Xlr Iy

trung (j.m cua m~ng ho~c la mQt thiet bi t~p trung cac moi truyen thong; cac nut dUQ'c bo' Iff chung quanh

va

noi tiep voi may trung tam (vi dl,l, m<.tng di9n Ihm.li). Neu trung tam hong se hong d. m';lng.

3. M(;mg phJn nip IIOi}C liinl! cd ... · (hierarchy/tree) gam mQt 10<;1t cac nhanh hQi tl,l gian tiep t<;11 diem dinh cay (hlnh 2.76 c). Trong h~ lhong nay. giiIa hai tr<;1m bat ky chi co m¢t duang truyen. D<;1ng m~ng nay c6 the hinh thanh tiI m¢t

so cae hi; thong m<;lng buyt. M<!-ng hlnh cay thLIemg

SlI

dJ,lng eho khoiing each cae nut IOn hem 100m.

4. M(lIIg w)ng (rin;?) ia m~ng _{tapa khong co trung tam, tat}d d.e nut dLIqe noi vong khcp kin (hlnh 2.76 d), khoang caeh gifra cae nut thlIl'mg nho hem i OOm. Dfrii~u trang h~ thong lien tJ,le hru thong quanh eho den khi co h~ thong nao do nh~n no. Dfrli¢u co the dung dLIqe eho tat cii cae nut.

5. Mt;mg mat llltfi (mesh), khong co mQl hlnh mau nhat djnh - hlnh 2.76e. Truyen thong gifra de nut thong qua cae duemg dil li¢u phue.

Thu~t ngu m<;lng eJ,le be) (LAN) duqe Slr dl,lng khi mq.ng thiet l~p trong khu vl!e dja Ii h~p ho~e chi 2, 3 may vai nhau ho:)c nhu tat cii. thiet bj trong eung toa nhit ho~e giua d.e toa nha trcn eung mQt dia dicm xay dtpIg. LAN thuang dung m<;lng buyt, vong ho~e sao.

M~ng di¢n rQog (WAN) ia m~ng noi lien cae may tfnh, thie't bj dau euoi va cae m<;lng el,le bQ tren to~m quoe ho:)e

a

cap quae gia thong qua oLICmg oay oi¢n tho~i ho~e de eong ey truyen thong khac.

M~ng toim cau (IN1ERNET) la h¢ thong gam cae m'.lng may tinh duqe lien ket voi nhau trcn ph<;lm vi toan the giai, t<;\o dieu ki¢n thu~n Iqi eho cae dieh VlJ twyen thong dilli¢u, nhLI dang nh~p tir xa, truyen d.c t¢p tin, thLI tin di¢n tlr va cae nh6m thong tin khae.

2.5.3. Giao thuc (protocol)

Dil li¢u truy6n ehua hai lo~i thong tin, mQt ia iO<;li du ii¢u may muon truyen sang may khae, io~i kia thu~t ngu gQi 1.1 dil lir;u giao "lIfC (data protocol) duqe

Slr

dyng bai giao di¢n gifra may tinh va m'.lng d~ dieu khicn vi¢e ehuyen giao dfr Ji¢u VaG trong m<;lng ho~e tir mOt m<;lng VaG trong m')t may vi tfnh. Giao thue 1.1

t~p cae lieu ehurin chi phoi vi¢e ehuy~n tM thong tin, oieu khi~n thai gian,tuan tl! truy e~p va ki~m soat I6i trong trao dbi thong tin. M9t giao thue c6 3 thanh phan IiI:

1. ell pJuip (syntax) xue dinh dC).ng thue dfr li¢u,

cae

mue tin hi¢u va

rna

hoa.

2. Ngttnghfa (semantics) giai quyct dong bQ hoa, diell khien va xLc Ii loi. 3. Djnh thiJi gian (timing) giai quyet van oe tuan tt! eho dfr li¢u va ehQn toe

oQ eua dfr li¢u.

(ISO) ua d~nh ra m9t h¢ thong giao thuc chulln 7 tOp g9i la mo hlnh lien ket

cae h¢ thong md OSI (Open System lntercanection). Cae 16p nay ta:

1. Lap v¢11i (physical layer) mieu

ta phan c(rug

d.e m<;lch chuyen cha thong tin giua hai thiet b~ nhlI lo~i ca.p dung. cong xuat/nh~p, mue ui~n ap va

cae

chan d.m.

2. LOp kef no,' dtt lif}u (data link layer) HI. ldp xac d~nh giao thlrc gui va nh~n thong baa, phat hi~n va slra 16i. sap xep hqp If dl"r 1i~u duqc truycn.

L&p

nay lien quan den vi¢c goi du li~u thanh cae g6i va d~t chung vao trang d.p. roi Hiy chung khoi cap t\li di~m nh~n cuoi.

3. LOp mqng (network layer) giai quyet ul1ang truyen thong, glli va giu thea

dlIong nhAt u~nh, dicu khitn cac thong haa HCn m\lng va dam b~l.O thong baa dung ndi.

LOp

truyin tdi (transport layer) cung cap phlIoog phap

rna

thea d6 du

li~u duqc truyen di. No thiet l~p va gill m6i quan h¢ gilra may truyen va may

nh~n.

5. Up thea phiell (session layer) lien quan t6i vi~c thiet l~p d6i tho<;li gilr3 d.c qua trinh lrng dlfng dU"qc noi v6i nhau bai m~ng. No co trach nhi¢m ljuyct djnh thai gian b~t/tat truyen th6ng giua hai tr::tm .

6. LiJp trinh bay (Presenration lager) lien quan v6i vi¢c cho phcp

tM hien

di.i li~u da giai

rna

dllqc truyen thea hinh thlrC phu. hqp v6i che' Hie cua ngU"m

sit

d\,lng.

7. LOp lIng d~ng (application layer) dam bao r~ng dl1 li~u truyen giiia hai (mg dl,lng bat ky dU"qc hieu va cung cap cho nguoi siJ dl,lng cac chuc nang

Xlr

Ii thong tin va ca.c d~ch vl:\ (mg dQ.ng Cl:\ the nhu giao thuc truyen t¢p FfP ha~c thu

di~n ttl.

2.5.3.1. Cae chuilD

ve

m~Dg

Thu~t ngu truyen thong deli rQIIR dUQ"c dung cho m<;lng. trang do thong tin

duqc dieu bien tren tan s6 mang tan s6 va tuyeD. moi trlICmg truy€n 1ft cap dong tI1.).c. D~c trlffig cua ca.c m<;lng tapo Cl:\C bq dai rQng la mQt m~ng buyt voi cac nMnh. Truyen dai r(mg cha phep mQt tUQ'ng s:6ng m<;lng uin so radio da dicu bien truy~n dbng thai (co the truyen tach ha~c truyen don (multiplex)). t'!-o Cd h9i cho cac dl1Cmg truyen thong da kenh.

Truy/n hallg

sci

chlqc su dl,lllg khi thong tin soluu thong tfl!c tiep trang m6i truem.g truycn. Truy~n bang co sa bi h(;ln chc ve clf Iy truyen dan va chi cho phcp thlfc hi~n m¢t kcnh lruycn thong trong mot hie.

Vi~n

Ky

thUi}t Di¢n tu va Di~n (Institute of Electrical and Electronic Engineers - IEEE)

My

dii phiit trien mot s6 lieu chuan cho m(;lng cl,lc b(l. Cae tieu chufln nay dllqc su dl,lng

de

xac dinh cac m~ng b~c thap hC1I1

duqc

phat trieD cho nhfrng ml,lc dich Cl,l the sau:

IEEES02.1 (A) Tieu chufln m~ng cl,lc b¢ va m;:tng trung lam. Mieu ta chung

va

cau true.

IEEES02.1 (B) Quan Ii dia chi. m(;lng may tfnh & m;;mg internet. IEEES02.2 IEEES02.3 IEEE802.4 IEEE802.5 IEEES02.6 IEEES02.7 IEEES02.S

Tieu chujn m;:tng cl,lc bO d~mh cho cac dieu khien lien kct logic. thl!c hi¢n chUc nang lap ket n6i dCr li~u clla OSL

PhllC1I1g phap t6 chuc tham nMp nhicu moi bang cam nMn song m~ng c6 do xung d¢t (CSMA/CD) va d~c tinh lap V?t If.

PhUC1I1g phap truy c~p m~ng buyt truyen

rna

thong bao

va

cac d?c tinh cua lap v~t If.

PhllC1I1g phap truy c~p yang truy~n

rna

thong baa

va

cac d~c

tinh clla lap v~t.

Ticu chuan m~ng trung tam. Tieu chuan m;:tng CI,1C bo diii f(lng. Tieu chuan cap quang.

2.5.3.2 Ml)t

so

giao thuc dlJ(1c sit dl,lug trong cong nghi~p

Co mot s6 tieu chu&n dl.!a tren m6 hlnh lap OSI thllo-ng ullqc su dl,1ng. Hang

General Motor phit trien giao th/fc (if J<Jng che't(lo (ManuJacturing Automation Protocol-MAP) cho cac ang dl,1ng tl.! dong trang cong xuemg. Tieu chuan nay

dllqc chap nh~n n)ng rai trong cong nghi¢p san xuat. Slf il.!D chQn cac giao thac l<,ti cac 16'p khac nhau phan anh yeu d.u doi vai h~ thong M hqp v6i. moi trllCm.g san xuat. Lap I

va

2 dllqc thlfc hi~n trong philn cLing di~n tU. lap 3 va 7 dung cho phan memo Truycn bang dili r(mg duqc

Slr

dl,1ng cha lap v~t Ii thea tieu chutln IEEE S02.4. Phuang phap truyen bang diii rong cho phep h~ thong dllqc

Slt dl,\.ng cho nhl1n.g dich vI,\. ngaai nhl1n.g

lap

yeu cau truyen thong MAP.

H~

thong

rna

thong baa

vaj

m<;lng buyr duqc sii dl,lllg cho lap ket noi dCr li~u thea lieu chu<ln IEEES02.4 v&i bo dieu khien n6i logic (logical link cantrol-LCL)

M

IEEE 802.2 cap 1. Doi vai cac lap khac

co

the su d~ng tieu churin ISO. T<:ti lap 7, MAP gam cd. djch V1J. thong bao san xuat (manufacturing message service- MMS). m9t Cmg d~ng dang k~ ve truyen th6ng tren m~t bang san xuat (factory floor communication), no xac d~nh cac ho~t d9ng giao ket giua cac b9 dieu khi8n J~p trlnh (PLC) va may dicu khi~n so ho~e nguoi may. Hlnh 2.77 minh h9a mQt m~ng MAP.

Ciao tMlc Wlll phong va

ky

thuat (technical and office

protocol-TOP) la tieu ehuftn do Hang Boing Computer Service phat trien, kM giong MAP nhung gia re

VI

si'r dl,lng h~ thong bang co sd. IDnh 2.78 the hi~n mQt m~ng TOP. Khac v6i MAP trang lap 1 va 2 si'r dl,lng ho~c truyen thong bao v6i m9t vong IEE802.5 ho~c t6 chuc tham nh~p nhicu moi bang

cam

nMn song m~ng _{c6 do xung d¢t}

(CSMA/CD) viii m<), mang buy'- Cung nhu v~y d lOp 7 cae giao thue

Tr~m

! May I ,I Tram

~ £ong SI .:

T~ bao '

: di~u khien

Hinh 2.77: Giao fMe MAP

Tram 1 ~

Ilinh 2.78: Giao ,h/re TOP ling d~ng c~ the lien quan nhieu den yeu cau cua m9t van phong hem Ia uoi hoi cua m9t m~t bang san xuat. Theo phuemg phap tham nh~p CSMA/CD. m6i nut

deu co quyen blnh d~ng trong vi~c tMm nMp vao kenh truyen nhung pMi nghe ngong truoc khi truyen xem c6 sl! truyen nao khae kh6ng.

Cae kiln Ink hif th{/flg mqng (systems network architecture- SNA) do IBM

phat tri~n lil tieu chufin thi€t k€ cho san phfim cua IBM. SNA duqc ehia thanh 7 lOp. Cac lap nay kMc voi cac lOp eua OSI khong nhicu, ehu yeu la khac d lOp 4 va 5.

Mqng c()ng nghi¢p Profifhus duqe phat tritn va to chue bdi PNO (Profilbus

User Organization) la m~ng truong thong tin

rna,

chufin hoa theo tieu chu&n chau Au. tuy theo ling d~ng c~ the c6 the' lil.: PROFILBUS-t"'MS (Thong tin dicn fa giiia cac thiet bj dieu khien PLC, PC); PROFILBUS-DP (thi€t ke d~c bi~t cho ca.e m<).ng ghep n6i tl! d9ng giiia cae h~ thong tl! d¢ng hoa v6i cae thiet b! philn tan). Kien truc giao thti'c ella m<).ng cOng nghi~p PROFILBUS tuan thil cau truc 7 lap nhu OSI nhung kh6ng si'r u~ng cac lOp J~6. Ngoai ra con m(it so tieu chuan ve m~ng khac dang duqc phat tri~n tren cd sa h~ md.

2.5.3.3. Cae ehu~n giao di~n

Ciic chuan giao di~n

Hl

thuQc lap giao di~n v~t If trang mo hlnh tham khao

osr

(Open Service Interconection), lien quan den d~c tfnh ki thu~t v~ co clla d.p va colC b¢ noi, d~c tinh di~n moi noi, cac mieu ta chuc nang cua giao di¢n g6m rnicu ta d~c tfnh chan dm - tin hi~u va d.c dinh nghia tin hi~u, d~c tinh dc thu n1C

eM

di~u khien va truyen tai dfr li~u.

Churin giao di~n pho thong nhat la cang RS232, do American Electronic Industrie Association (EIA) dinh r6 tinh chat van nam 1962. Chuin giao di~n lien quan den thiet hi dau cuoi dfr li¢u ( data terminal equipment -DTE) va thiet bj m<;1ch driu cu6i dfr li¢u (data circuit- terminating equipment -DCE): Thiet bj d,l.u cuoi dfr li¢u c6 the nMn hoijc gi'ti dfr li¢u thong qua giao di¢n den m¢t b¢ di~u khien. DCE cung cAp ket noi cho DTE va~ m;:tng truy~n thong va nguqc l<;1i. Ngoai ra, DCE con ket thuc va khoa m;:tch. Khi duang truy~n di¢n tho;:ti tUo'ng tt! (analog) la moi tfl1O'ng truy~n thong thl DEC 1.1 m¢t modem. Khi uuang truyen la so thI DCE la

M

djch vl,l kenh ho~c

M

dich vl,l dfr li~u.

Ngoai chu.1n RS-232C va RS-232-C clla EIA con co d.c chukin V.24

ella

CCIlT (Comite Consultarif International Telegraphique

et

Telephonique). cac chudn DTE/DCE kbac g6m RS-366A cua EIA, X.20, X.21

va

X.35 cua

ccrrr.

2.6. MODUN Xl! Li

Modun xU If, xiIlf thong tin do modun giao di¢n va mbdun do luang cung cap. Thanh phan chfnh clla mbdun nay Ia bQ dieu khien. Ngay nay cac bQ vi xu 15' (j.lP) dong vai tro quan trQng trong cac bQ di~u khi~n. Do c6 rAt nhi~u lo;:ti )J.P, tir dem gian den phuc t;:tp hi¢n dang co tren thi twang, nen tren co sij cau truc bQ

Xlr

Ii clla may vi tinh co the dua fa m¢t tbng quan ve diu truc clla)J.P nhu sau;

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