Giáo trình dành cho kỹ sư cntt cơ bản bản 4

Phan nay bao gom cac chuong sau: \ \ Chuong 1: Giao thuc va dieu khien viec truyen Chuong 2: Ma hoa va truyen Chuong 3: Mang LAN va WAN Chuong 4: Thiet bi truyen thong va Phan mem mang.

T r-1 Li N(.-) i / \ fv! SA I I f A C

HAN i Y i- H 'i ( ( !iv(

V! i

CONG NGHE'- TH O N G TIN VA HO T R O ‘ DAG TA O

GIAO TRINH DANH CHO KY SIT CNTT COT BAN

o '

ft/IUC a luct*

M yc ly c 1

Phan 1 Cong nghf M $ng 9

1 Cac giao thuc va dieu khien truyen 10

Myc tieu cua chuong 10

Giai thi$u 11

1.1 Kien true mang 11

1.1.1 Boi canh ra dai cua Kien true m an g 11

1.1.2 Nguyen tSc chung va cac chuan cua Kien true m ang 12

1.1.3 Cac kieu kien true m ^ng 14

1.1.4 Cac chuan thyc te (De Facto) 14

1.1.5 To po mang va cac plurang phap ket n o i 14

1.2 OS! - chuan hoa cho giao thirc truyen thong 17

1.2.1 Tong quan ve O SI 17

1.2.2 Mo hinh tham chieu OSI co ban 18

1.2.3 Cac thu tyc truyen thong trong OSI 21

1.3 7 CP/IP - chuan thyc te cho giao thuc truyen thong 23

1.3.1 Tong quan ve TC P/IP 23

1.3.2 Cac thu tyc truyen thong trong TCP/IP 26

J 4 Dja chi duyc su dyng cho TC P/IP 27

1.4.1 Dia chi I P 27

1.4.2 Dja chi MAC 33

1 5 Gi«u>dj<£n thiet b| cuoi 32

1.5.3 D ong-I 3 3

1 5 4 RS-232C 34

i 6 Dieu khien tru yen 34

1.6.1 Tong quan va luong dieu khien truyen 34

1.6.2 Cac thu tye dieu khien truyen , 36

1.7 Bai t§p 42

2 Ma hoa va truyen tai 45

Myc tieu cua ch u o n g 45

Gidi thi^u 46

2.1 Ma h6a va dieu ch e 46

2.1.1 Ducmg truyen thon g 46

2.1.2 Ky thuat dieu c h e

2.1.3 Ky thu|t ma h o a 48

2.2 Cong ngh$ tru y e n 49

2.2.1 Kiem tra loi 49

2.2,2 Kiem tra dong b g 52

2.2.3 Phuong phap don kenh 54

2.2.4 Phuong phap nen va giai nen

2.3 Phuong phap truyen va d u 6ng truyen thong 59

2.3 j Cac lop cua kenh truyen 60

2.3.2 Cac kieu duong truyen 61

2.3.3 Cac phuong phap chuyen mach 62

2.4 Bai t$p 70

3 Cac mang (LAN va W AN ) 73

Muc tieu cua chut wig

Gidi th*£u .

73

'7 1 3 1 L A N 74

i 1 i :i th <:iM i A N 7 J

7S

1 1 3 k J.V,, I,/, J,% V| L A N rr )

3 1.4 Cac ca’u phan LA N 78

3.1.5 Phuang phap kiem soat truy nhap mang LA N - 83

3.] 6 TI>iei bi ke\ noi Jien-LAN 88

3.1.'/ Cong ngh£ tang toe dp mang LAN 91

3 2 Internet : 92

3.2.1 Boi dinh ljch su cua vi§c phat trien Internet 93

3.2.2 Cau true cua Internet 94

3.2.3 Cong ngh£ Internet 96

3.2.4 Loai hirih may chu (servers) 97

3.2.5 C’£c djch vy Internet 100

3.2.6 May tim kiem 103

3.2.7 Cac kien thuc lien quan toi Inem et 104

3 3 An ninh m ang 105

3.3.1 Bao ve tinh kin va ngan ch|n gid in ao 106

3.3.2 Xam nhap bat h<?p phap va bio ve chong virus m&y tinh 113

3.3.3 Cac bif n phap dam b io tinh sin sang 115

3.3.4 Bao vf tinh rieng t u 117

3.4 Bai t|p ’ 120

4 Thiet bj truyen thong va phan mem mang 124

M uc tieu cua chuong 124

4.1 Thiet bj truyen thong 125

4.1.1 Phuang tien truyen (Cap truyen thong) 125

4.1.2 Thiet bj truyen thong ngoai vi 128

4.2 Phan mem mang 130

4.2.1 Quan ly m ang 130

4.2.2 Me dieu hanh mang (:\!< )S) 132

4.3 Bai lap 135

5 C up niuil vt* Cong ngi it; mang 137

3

5.1 Tien ho Cong n g h e 138

5.1.1 Tien hoa trong vien thong - —* 138

5.1.2 LAN khong d a y - I4i 5.2 XML (Ngon ngu* danh dau mo rp n g) .146

5.2.1 XM L(Ng6n ngu* danh dau md rQng) 147

5.2.2 Unicode va van ban khong phai Latin (Non roman) 149

5.2.3 Khong gian ten (Namespace) 151

5.2.4 DTD (Djnh nghla kieu tai lieu) -152

5.2.5 Djnh nghia 1 ii<?c d o 154

5.2.6 XSL (Ngon ngir kieu cach trang mo rpng) 157

5.2.7 Mo hinh doi tugng tai lieu X M L 158

5.2.8 Su* dyng XML trong tai lieu HTML 161

5.2.9 Giao dien XML SQL Server O LE-D B 162

5.2.10 May dau trudc da phuong tien (Flash) 165

6 Tra ldi bai t|p 167

6.1 Tr& lai bai tap cho Quyen 4 Phan 1 Chuang 1 (Cac giao thuc va kiem soat truyen) 167

6.1.1 Danh sdch dap a n 167

6.1.2 Dap an va H uang d an ! 167

6.2 Tra loi cho Quyen 4 Phan 1 Chuong 2 (Ma hoa va truyen tai) 172

6.2.1 Danh sach dap a n 172

6.2.2 Dap £n va Hudng d a n 172

6.3 Tra ldi cau hoi cho Quyen 4 Phan 1 Chuong 3 (Cac mang (LAN va W A N )) 1 7 8 6.3.1 Danh sach dap a n 178

6.3.2 Dap an va Huong J a n 178

6.4 Tra loi bai tap cl to Quyen 4 Phan 1 Chuong 4 (Thiet bi truyen thong va phan mem m ang) 183

6 4 I i )anh sach dap a n 183

b 4.2 Dap an va I iuong d a n 184

Phan ? Cdng nghv co >*><id ItOu 186

on

i.I Muc dich cua CSDL 188

! 2 Mb hinh CSD L i 89 1.2 j Mo hinh hoa du li^ii 190

1 .22 Mo hinh dir h£u khai niern 190

1.2.3 Mo hinh du lieu logic • 191

1.2.4 Lu<?c do 3 -ta n g 192

13 Phan tich du lieu 193

1.3.1 ERD 193

1.32 Chuan hoa 194

14 Thao tac du it£u 197

1.4.1 Phep toan t£p hop 197

1.42 Phep quan h e 199

15 Bai tap ^ 201

2 Ngon ngu co s6 du li£u 205

Muc tieu cua chucrng 205

21 Ngon ngu co so du li$u la g i? 206

2.1.1 Ngon ngu djnh nghla du lie u 206

2.12 Ngon ngu* thao tac du li§ u 206

2 13 Ngon ngu ngudi dimg cuoi 206

22 SQL 207

2.21 SQL; Ngon ngu ca so du li§u 207

2.22 Cau true cua SQ L 207

1.3 Djnh nghia ca sa dir du li<?u, dieu khien truy nhap va nap du lieu 208

2.31 Djnh nghla ca so du* ti£u 208

2 31 Dinh nghia Suae d o 209

2 3 3 Djnh nghui baiig 210

2.3 4 D§c irung va djnh nghia gov nhin 212

2.3 5 DiOu kiucn liny nhap dii' !ivu 213

6 r

2.4.1 Xu ly truy v an 214

2.4.2 Xi> ly khdp — 228

2.4.3 Sir dung truy van c o n 230

2.4.4 Su dyng goc n h in 234

2.4.5 Xu* Jy thay d o i 235

2.4.6 Tong ket ve S Q L 237

2.5 Su dyng m o rong cua SQL 246

2.5.1 SQL dugc nhung 246

2.5.2 Thao tac dung con tro 247

2.5.3 Thao tac khong dung con tr6 251

2.6 Bai t|p r— 253

3 Quan trj co s6 du lieu 257

M uc tieu ciia ch u a n g 257

3.1 Chuc nang va d£c trung cua he quan trj co so du* lieu (DBMS) 258

3.1.1 Vai tr6 cua D BM S 258

3.1.2 C huc nang cua DBMS , 259

3.1.3 D§c trung cua DBM S 261

3.1.4 Cac kieu DBMS : 266

3.2 Co so dir lieu phan b o 268

3.2.1 D&c trung cua co so du lieu phan bo 268

3 2 2 Cau true cua co so du lieu phan b o 270

3.2.3 B q n h a dem cua may khach (client cach e) 270

3.2.4 Xac nhjjn (com m itm ent) 271

3.2.5 Ban sao 272

3.3 Cac bien phap duy tri tinh toan ven co so du lieu 273

3.4 Bai ta p 274

4 Cap nhat ve Cong right? Co so du litju 275

Myc tieu cua chuong 275

(.;I6 > thit?n 276

•Li Quan !y uit CSUL Io n .27b

5 ii d loi bai l§ p 284

5 i Tra lai cho Quyen 4 Phan 2 Chuong i (Tong quan ve co so du lieu ) 284

5.1.1 Danh sach d ip An 284

5.4.2 Ira loi va mo ta 284

5.2 Tra lai bai t|p cho Quyen 4 Phan 2 Chuang 2 (Ngon ngu* c a so du li§u ) u 292

5.2.1 Danh s£ch dap an 292

5.2.2 Tra loi va mo ta 292

5.3 Tr£ lai cho Quyen 4 Phan 2 Chuang 3 (Quan ly co so du lieu) 298

5.3.1 Danh sach dap an 298

5.3.2 Dap an va mo .299

T ra aru ihuQt n gu 301

7

P h a n 1

Cong nghe Mang

Phan nay giai thich mpt cach he thong de cho nguoi hpc cong ngh£ mang Ian dau tien co the de dang thu dupe tri thuc trong nhung linh v\rc nay Phan nay bao gom cac chuong sau:

\

\ Chuong 1: Giao thuc va dieu khien viec truyen

Chuong 2: Ma hoa va truyen

Chuong 3: Mang (LAN va WAN)

Chuong 4: Thiet bi truyen thong va Phan mem mang

1 Cac giao thu»c va dieu khien truyen

M uc tieu cua chuong

Trong cac He thong mang sir dyng may tinh, truyen thong dupe thyc hien dya tren cac giao thuc chung Kien true m ang la can de x i c djnh va hieu chinh cac giao thuc nay Khi viec truyen thong thyc te du*<?c thyc hien, viec dieu khien truyen bao gom c&c giao thuc truyen khac nhau dupe sir dyng.

Chuong nay cung cap cho nguoi dpc kh£i niem chung ve kien true mang va y nghia cua no trong viec hpc ve cac giao thuc dieu khien truyen.

1 Hieu dupe sy can thiet cua kien true mang, chuan hoa, cac kieu kien true va cac chuan thyc te v.v

2 Thu dupe tong quan va hieu dupe cac kien true mang dien hinh, yi dy nhu OS! va TCP/IP, giao thuc

phan cap cua ch u n g , vai tro cua moi tang phan cap v.v

3 H qc ve die co che dieu khien va hieu dupe c&c giao thuc dieu khien truyen dien hinh, nhu "Dieu khien lien ket phuong thuc co ban" va "thu tyc H P L C ".

Gioi thieu

Ket noi rnang mo da co nhieu lien bp ion cirng voi viec trai rong cua Internet va Intranet Xay dung cac he thong mang mo cho phep truyen thong voi cac co quan khac khong don gian la van de noi cac phan cung dirpc san xuat

tu ca?c nha may khac nhau qua phuong tien truyen.

Khi xay dyng cac h# thong mang, dieu khong the thieu dupe la phai thoa thuan tuan theo cac giao thuc truyen thong de viec truyen thong dupe thuc hi£n Cac giao thuc truyen thong thay doi cung voi cac he thong may tinh

va durdng truyen, va nhieu giao thirc khac nhau da dupe chap nh§n ca 6 Nhat ban va d nude ngoai, di tu cac kieu nha cung cap nhat djnh toi cac kieu dirpc chuan hoa bdi cac to chuc cong cong Cung vdi sy gia tang trong cac he thong dupe noi v6i cac he thong mang khac, nhu Internet, kien true mang dang tro thanh ngay cang quan trpng hon.

Cac giao thuc truyen thong

Giao thuc truyen thong 1^ mpt t§p cac quy tac tao kha nang cho truyen thong Khi ban truyen thong bang di$n thoai hoac thu tin, co mpt so cac quy tSc da dupe xac dinh trudc ban phai tuan theo de tao kha n&ng truyen thong Ngupc lai, ban c6 the noi rang neu ca hai ben ton trpng cac quy tac thi viec truyen thong tin cay moi tro nen co the du<?c.

Vi truy§n du* li£u cung bao gom truyen thong vdi cac ben khac (noi nhan du li£u dupe truyen) qua duong truyen, cac quy tac nhat djnh (giao thuc truyen) de truyen thong duoc yeu cau va khi cac quy tac nay dupe tuan thu, moi

co the truyen thong tin cay dupe.

K ie n tr u e m a n g

Kien true mang la cau true nen cua mang, va no x&c d|nh thiet ke he thong ve logic, khong chi ve cac giao thuc,

ma cdn la cac dang thuc thong di#p, c ic ma va phan cung Tuy nhien, kien true mang liic ban dau co tinh chat la

d6ng kin trong hau h§'t cac trudng hpp Bdi vi mpt so cac nha s&n xuat (nha che tao phan cung) xac djnh ra cac kien true mang (nhu SNA cua IBM, v.v ) co the tao nen cac mang sd huu ri£ng cua hp, co nhieu mang khong c6 kh& n£ng lien noi vdi cac mang dua tren cac kien true mang khac.

Tren nen tang nay To chuc tieu chuan quoc te ISO dS de nghj va chuan hoa cai gpi la kien true mang OSI (Lien noi He thong md) nhu mpt kien true mang dupe chuan hoa quoc te, no dpc lap vdi cac yeu to cua nha san xuat

Cho du khong la giao thuc chuan Quoc te, TCP/IP (Giao thuc dieu khien truyen/Giao thuc Internet), dupe sir dyng nhu giao thuc chuan cho Internet, dupe sir dung rpng rai v& trd thanh chuan cong nghiep thuc te cho truyen du lieu.

Theo tinh huong dupe neu dai arong d tren, trong chirang nay ban se hpc ve y nghia, chii djnh va dieu khong the thieu dupe cua kien true mang thong qua viec hpc cac giao thirc truyen thong (chu yeu la OSI va TCP/IP).

1.1 Kien true mang

Theo djnh nghTa cua ) IS (Chuan Cong nghiep Nhat ban), "kien true mang" la "cau true logic va nguyen ly van hanh cua h f thong mang" Tuy nhien, do la mpt djnh nghla rat triru tupng Vay chung ta hay xem sir ra ddi cua kien true mang de hieu dirpc y nghia ciia no Rdi chung ta se di tit tong quan den giai thich cac cau phan chi tiet cua kien true mang

C ac hv’ th o n g m a n g d a u lie n la " L a ’: lu; ‘ h u n t; ta p t r u n g v a o m a y c h u " { " lio s t - c c n t r u b y s te m s ’ ), co n g h ia la m ay

d m \in li jn h th ie i bj d a u ru n i ya n g o a i y i n a o d u u i s u d yn g 1 m b h u o n g lhonv> ih u o jig ia h a n u san x u a t m a v -c h ii

la d ie m cot y e u il'o n g vn;< \a y Ji.rn g he ilinitj.- i >» hr* l)t<>n)' K m ih ,m in'i i u iij; d in u; ' i y t h in g .ic t ii in th u \'< m <,ir yeu cau cua m o i u n g d u n g

• Bien gidi giua phan cung va dieu khien truyen thong va cac chuc nang ung dyng da tro nen ma nh$t.

Phong trao giam quy mo da lam tSng toe viec chuyen doi tu "cac he thong t£p trung vao may chu'' sang "c a t he thong phan bo'" va su can tiiiet de xay dyng mot moi trudng he thong nhieu nha cung cap su dyng he thong ma tra thanh nhan to quan trong cho sy ra doi cua kien true rn$ng.

N hu mot van de thyc te' khuynh hudng cac he thong md da duyc tang toe bdi sy gia tang cua Internet tren quy

mo toan the giai, va dieu nay yeu cau cac may tinh co the duyc ket noi bat ke tai nha s<kn xuat ho^c ung dung dupe six dyng Do dd, nguoi ta trong dpi rin g sy can thiet ve kien true mang,- mo ta cau true logic vh cac nguyen

ly v$n hanh cua cac he thong m$ng vk djnh nghia cac giao thuc truyen thong cho trao doi du lifu thyc se t&ng

han nua trong tuong lai.

1.1.2 N guyen tac chung vd cac chuan cua Kien true m ang

Tuy nhien, da nay sinh ra nhung van de sau

Y nghia cua kien true m^ng da dupe da dpng tdi trong cac thu£t ngu truu tupng tren, va bay gip chung ta se xem xet npi dung trong ckc thu£t ngu xac djnh han.

Kien true m^ng djnh nghia va phan loai toan bp cac chuc nSng (thiet bj noi va cac phirung phap dieu khien truy nh|p, v.v ) can cho viec truyen du lieu Them vao do, nd xkc djnh "cac giao thuc phan cap" tuong ung vdi moi

phan lo$i va xac djnh die giao thuc va giao dien giua cac tang cua giao thuc phan cap Bang cach thiet l^p cau true he thong qua sir dyng cac giao dien va giao thuc da xac djnh, nd t$o kha nang v§n h£nh cac he thong m?ng mpt cach hieu qua.

Trong kien true mang, toan bp cac yeu to vat ly cua ni?ng (thiet bi va chuong trinh, v.v ) dtrpc mo hinh hoa va cau true hoa va xir ly nhu mot mang logic D$c bi?t han, cac cau phan chinh cua m^ng logic la:

• "n u t/' co nghia la phan cung, nhu cac may tinh va cac thiet bj xu ly truyen thong,

• "lien ket, "co nghia la dudng truyen thong,

• "xir ly," cd nghia la cac chuong trinh ung dyng

ffivh J.7.1 Mutig logic

Myt'tg

Trong m^ng logic, cac mang con noi cac nut (cac may tinh, v.v ) lai dupe noi voi nhau boi cac thiet bj ket noi mang (cac cong - gateways, v.v ) nhu da chi ra tren Hinh 1.1.1.

Viec chuan hoa kien true mang co cac ly>i ich sau.

• Neu cau true la n\Qt, mpt h£ thong co the dupe xay dung b&ng cach thay doi giao di^ri, tham chi khi cac san pham tir cac nha san xuat khac nhau dupe to hpp lai Luc d£uy vi£e xay dung h? thong dupe dieu khien boi nha san xuat, nhung vi£c chuan h6a kieh true mang da tao nen kha n2ng lam cho nguoi dung su dyng eac san pham phu hop nhat v6i inyc dich cua hy (xay dyng h£ thong nhieu nha s&n xuat).

• Viec sir dyng h£ thong tuan theo cdc giao difn chuan lam cho vi§c phat trien, mo rpng va bao tri he thong de dang hon.

• Tham chi cac h£ thong dupe phat trien dQC lap co the de dang dupe tich hpp, tao ra hieu qua Ion, dac biet trong vi£c xay dyng c ic he thong phan bo".

• Toan mang co the dupe xir ly mpt each logic: Vi dy, kieu he thong mang la gi khong quan trpng, no se khong

£nh huong toi cau true, v.v

Hinh 1.1.1 so sanh viec sir dyng kien true m^ng chuan dien hinh (OS1) voi kieu khong chuan

Hirth 1.1.2 Su dung OSI /khong sir dung OSl

GW iiuicOf)# iy A — GWKhNi uitc m*n^ GW G• & * * / Ki£n true m*ng

C -ui i4>ii ihu>ln vl6s miiu c<k ciiKi liiuc Co ih* lru>cn ilMtag tik»

Nlur minh lu:u trong lnnh 1.1.2, vi(*c truyen (hong khong the thuc hien dupe neu khong co viec chuyen doi l«.il

&kh> ihuv, tru pm Mr Ji.mj; kscn true cluuwi nhu < ).->!

1.1,3 Cac kieu kien true m ang

Co mot so Strong 16n cac kien true mang, bao gom cac kien true rieng cua nha san xuat (SNA cua IBM, v.v.), cao kien true dtrg»c chuan hoa quoc te, cung nhu cac chuan thuc te, Trong so' do, cac kien true mang dien hinh la OSI

(Lien noi he thong m d) va TCP/IP (Giao thuc dieu khien truyen/CJiao thuc Internet).

Hinh 1.1.1 dua ra cac kien true mang khac nhau.

Hinh 1.13 Cac kieu kien true mang

1 4

Ki£n true m^ng (NA)

NA m a

NA phu hgp v6i nh& cung cap cm th&

p - <OS!>

<TCPyiP>

- SNA (IBM)

- DECnet (DEC)IPX/SPX (Nowell)' Apple Talk (Apple Computers)

1.1.4 Cac chuan thuc te(D e Facto )

Cac kien true mang bao gom mQt so kien true dien hinh nhu TCP/IP va OSI Tuy nhien, khong giong nhu OSI, TCP/iP khong phai la kien true dirge thiet lap boi ISO ho$e boi mQt to chuc chuan hoa tuong tu* TCP/IP duoc sir

d\mg cho mang lcm nhat the gidi, Internet, va no cung la mQt dac trung chuan ciia UNIX, he dieu hanh chinh cho c&c m£y tram v& cac m iy chu Ndi c^ch khac, no da tro thanh mQt chuan cong nghiep thy-c te.

Mol quan he giua TCP/IP va OSI duQe giAi thich trong myc 1.3 TCP/IP.

1.1.5 To po m qvg va cac phucmg phap ket noi

Viec ket noi cac may tinh va cac thiet b\ dau cuoi, v.v qua duong truyen tao nen kha nang xay dyng nhieu loai

cau hinh mang khac nhau, tuong ung voi quy mo va myc dich sir dyng.

Cac cau hinh mang dien hinh duoc chi ra tren hinh 1.1.4.

<D Kieu Vdng

K ie u v o n g la mQt cau h in h tr o n g d o cac n u t (cac m ay tin h , v.v ) d u p e n o i th e o mQt v o n g k h e p k in d u o n g tru y e n

D u o n g tr u y e n tr o n g lo<=ti cau h in h m a n g n a y n g a n va de d ie u k h ie n N huQ C d ie m la n e u c h i n ip t n u t h o n g , co the

g a y a n h h u d n g d e n toa n m ang

Trong kieu mat hrdi, hai hoac nhieu dtrimg dan toi moi mit sau cho cau true tong the ia m o t mang luoi Dieu nay

co nghia la th a m chi neu mot nut hong, nut nay 16 tin*' du«,» ho qua bang each tim duong (lua chQn duong

tr u y e n ), co n g h ia ra n g d o On cay cua man}> la ra t tao

i ’r o n ^ k ie u btiu, m o i n u t d u o c no t \ u l m g t n u t tr u u ^ ta in (bg la p kt-l d u o n g , v v ) tio n g m ot u iu h in h d a n g '.»ao

Cho du mpt isul hong, no se khong lam anh huong den toan bp he thong, nhung neu nut trung tam hong, toan filing se khortg lam viec niry.

With 1.1.i Td po (topology) mang

*5

Trang kieu Bus, tat ca cac nut dupe noi tai dudng truyen chung.

Cau h'rnh bus de dang them ho$c loai bo cac nut ma khong lam iinh hu6ng tai toan bp he thong va dong thoi cung tiet kiem Tuy nhien khi co nhieu nut va iupng truyen tin 16n (lupmg thong tin can truyen trong 1 khoang thoi gian xac djnh) t£ng len, sy dyng dp dCr lieu co the xay ra tren duong truyen chung va hieu qua truyen (thong lupeng) co the gism dpt ngpt.

De de hieu, chung ta se su dung mpt mong don gian vai mpt may tinh trung tain dtrpc noi bai mpt vai cac thiet bj dau cuoi qua duong truyen nhu mpt v» dy dun gian de giai thich cac phuong phap ket noi cac mang.

Co ba phuong phap ket noi dien hinh duyc bit dpng tuong ung tot nhat voi khoang each truyen va iupng du* lieu, v.v Chung la:

* Ket noi diem toi diem (l\»inl tn point)

* K e t n o i da d ie m ( M u ltip o in t <

» Ket !'iOi rhuyen nuu/h (’nvtLlicti)

0 i t i i ' i n o i i t i c i n i i n i i i d n i i n p o t u i i

Trong ket noi da diem, nhieu thiet bj phan nhanh duoc noi lien tiep toi cung mpt dudng truyen Sau d6, cac thiet

bj dau cuoi duoc noi t6i thiet bi phan nhanh

Cau hinh nay cho phep tao nen mpt mang re hon mang sir dyng cau hinh diem-tcri-diem khi ma khoang cach truyen dai va lupng truyen du lieu it Tuy nhien, vi dimg chung ducmg truyen chinh, cac thiet bj dau cuoi khac ph&i chd trong khi mQt thiet bi dau cuoi dang truyen du* lieu.

dilu cudi ddu cudi

Trong ket noi tap trung, duong truyen dupe noi toi mQt bQ tap trung (concentrator), bQ tap trung nay dupe noi toi

mQt may chu qua dudng truyen toe do cao (hinh 11-7)

Day co the la cung mQt phuong phap truyen thong nhu da dupe sir dyng trong cau hinh diem-toi-diem, trong do moi thiet bj dau cuoi dupe noi rieng le toi may chu Tuy nhien, gia thanh cua duong thue bao nho hon truong hpp cau hinh diem-tdi-diem, cho phep xay dung mpt mang rat kinh te ma chu y nhieu den dung lupng cua dudng truyen giua may chu va bp tap trung Noi each khac, tai dir lieu tu moi thiet bj dau cuoi toi bp tap trung can ph^i dupe tinh tdi khi thiet keinang.

Hinh 1.1.7Cau hinh ket not tap trung

Tokyo

1 I Oud7i<y73|t^P

i16 caoMay uJtu

FukuCjkd

ap

k6sp' Thi6t.b|.d£u cu6i f*3 ] HaKota

I 11 Miyazaki

1.2 OSI - chuan hoa cho giao fhu’c truyen thong

17

Muc nav neu mpt tone quan ve kien true mang da dupe chuan hoa quoc te OSI (I.ien noi cac he thong mo) duoc

thiet lap boi ISO (to chuc tieu chuan quoc te) va giai thich ve vai tro cua cac tang cua mo h'rnh nay va quan he voi lieu de' v.v

1.2.1 Tong quern ve G Sl

OSI la mpt chuan quoc te dirge thiet l£p dau tien boi iSO va ITU-TS (Hiep hoi vien thong quoc te - Tieu ban chuan hoa vien thong quoc te) Noi cach khac OSI la mot kien true m?ng chuan quoc te va dpc Up voi nha san xuat.

Vai tro cua OSI duoc neu d$i cuong tren hinh 1-2-1.

Chung ta hay gia thiet rang nguoi Nh§t chi co the noi tieng Nh|t va nguoi Due chi co the noi tieng Due Neu hai

Hinh 1.2.1 Truyen thdng giua ngudi N hat va ngudi Due

<OSl>

Tidng Anh, ngfin ngif qudc i6

diwc sis dung giua cdc ph&n dich vien

Viec phien djch phai duoc thuc hien nhu mot cau noi va cho phep truyen thong giua hai ben Tieng Anh hoac mot ngon ngu quoc te chung duoc sir dung de phien djch Vai tro cua ngon ngu* chung la vai tro ciia OSI trong kien true m$ng.

N6i mpt cach khac, )o?i phan mem nao dang ch?y tren m?ng khong phai la van de va bat ke lo?i du lipu nao dang dupe truyen, viec truyen thong du lieu khong co van de van c6 the dupe thuc hien mpt each binh thuong tren mang luan thu OSI

Khi mpt so mang khac nhau duyc noi lai, cac chuc nang truyen thong tru nen phuc tap, da dang va roi ram Vice nhom cac chuc nang thanh mpt giao thuc phan cap tao dien kien thuijin lai cho viec c6 dupe mpt tong quan OSI

ra doi voi y tuong nay, va mo hinh OS! gom co 7 tang Noi dung tlujc r>u cua 7 tang (phan cap giao thuc) dupe giai thich chi tiet trong phan 1.2.2

Khi tong ket cac cai loi > «>.* phan tang, > hung t,i nhan ituo«' dit-m - ai

ivj i h u c c u a rnut «»>ng hi lhd>’_ do», d i f i i ytv ; k l u m g a n h .hi/wiig n cnc wauu t h u c k h a c * iV

nv.hia-■vi t’l-i V 'Vi I

,'ijig ViCC triCii klt.lt i!«j«'C lii'tlC i'liCi'i i.i ch1 daii)'

• Cac tang d m ac thap hon co the dugc xir iy nhu hpp den, co nghia ta cac chuc nang truyen thong phuc t?p co

the dugc don gian hoa.

Viec phan tang la cut- ky quan trong trong kien true m^ng, bdi vi luon can can nhac xem xet de bao dam:

• Tinh in gang bang

Cac giao thue dugc xac dmh giua ding cac tang.

• T in h d $ c la p

Th|m chi neu mot tang bj thay doi, dieu nay khong lam anh hudng toi cac tang khac.

Trong mo hinh tham chieu c a b^n OSI va cac mo hinh mo khac, moi tang dugc trim tugng hoa la "tang thu N" va

18

De thuc hien truyen thong giua cac he thong md, can co cac module chuc nang, nhu cac chuong trinh truyen thong dugc ggi la cac "th yc the", va hai hoac nhieu thyc the ton tai trong moi tang N Moi quan he giua tang N

va cac tang d muc cao horn va thap hon dugc chi ra tren Hinh 1.2.2.

Hinh 1.2.2 Mfii quatt h? giua tang N va cac tang 6 muc cao han vd thap hon

Sir dyng hinh 1.2.2, moi quan h£ giua cac tang khac nhau dugc giai thich van tat nhu sau.

• Djch vu ma Lang (N) cung cap cho tang tren (N+l) dugc ggi ta djch vy (N) Binh thudng, tang (N) tich hgp cac djch vy ma no nhan dugc tu tang (N -l) vdi cac chuc nang rieng cua no va cung cap dieu nay dudi dang djch vy (N).

• Giao thuc dugc su dyng giua cac thuc the (N) dugc ggi la giao thuc (N).

• Hanh ddng (djch vy) thyc hien chuc nang trao doi thong tin giua tang (N) va cac tang cao hon va thap hon, cd nghia hanh dgng nhu giao dien giua cac tang, dugc ggi la djch vy nguyen thuy (N) Cd 4 djch vy nguyen thuy, nhu "veu cau" ("request").

• Diem truy nhap giua tang nhan djch vy (N) va tang (N) dirge ggi la Diem truy nhap djch vy (N) (SAP).

• Kenh truyen thong logic dirge sir dyng de trao doi du lieu giira cac thyc the (N) dirge ggi la ket noi (N).

1.2.2 Md hinh tham chieu OSI ca ban

( 1 ) Cau tru e

Hinh ! 2 3 mioh hoaihi ra cau intf nia md hinh th.im chieu OS! ct/bon

ffinh 1.2.3 MS hinh tham chieu OS! cur ban

r&ng i>ng dung I TSng Uiu- / Cuuy c ip cac djch vy truyfen thong cart cho c ic tVn-j dyng

T&no trinh b&v ■ T ing mu* 6 Bi^u dien cSO* lieu ujch v i anh dang '.hue

! T ing v$n chuyen ; T in a thu1 4 B io daiii truytn d iv li§u git>a d iu cu6s {wul-to-end), v.v.

T^ny m^ng i T in g u u r i Cac ch!>c n in # iir« d^ong v.v

T&nq Ii6n k£t dl> ii£u ' T in g thu 2 8 io d im v$n chuyen dt> li$u giua cac h$ th6ng iin can, k iim s o it I6i, v.v

U n g V it ly ; T in g thi> 1 (j ndi v i cac ch in n6i, phuong ti§n truy^ri v.v

Bay tang nay co the duoc phan chia thanh cac tang cao hon va thap hum nhu* dupe chi ra nhu sau.

C ac tang 6 muc cao hon tu tang ung dyng toi tang phien cung cap cac chuc nang cua djch vy truyen thong.

C ac tang 6 m uc thap hon tu* tang van chuyen toi tang vat ly: Cac chuc nang truyen du lieu.

Cac tang 6 muc thap hon chu yeu bao dam vi«?c van chuyen du li£u c6 chat luong cao, va cac tang 6 muc cao hon sir dyng cac chu*c ning cua tang thap hon de cung cap cac dich vy cho cac ung dung.

Tang ung dyng la tang thu 7 va la muc cao nhat va xu* ly chii yeu bing viec cung cap cac djch vu nhu:

FTAM (Truy nhgp va Quan ly truyen t£p - File Transfer Access and Management)

RDA (Truy nh|p co so du* lieu tu xa* Remote Database Access)

VT (Dau cuoi ao - Virtual Terminal)

Hinh 12.4 Cac chuc tt&ng cht'nh cua tang ihtg d\tH%

©Tang trinh bay (tang thu 6)

Tang trinh bay la mpt muc 6 duoi tang ung dyng va thuc hien chuyen doi cac d$ng thirc dir lieu, v.v de dam bao truyen hieu qua cac loai thong tin khac nhau Trong tang img dung 6 muc tren, viec mo ta thuong duyc thyc hi|n bing cach dung he thong bieu dien duoc g<?i la "cu phap triru tiring", nil ung de co the trao doi thong tin hieu qua gi ua cac mang, cii phap triru tuong duoc djch thanh dang thirc du li£u (duyc gyi la "cu phap truyen") trong tang trinh bay, trong do anh xa cu phap triru tugng va cu phap truyen, v.v duyc thyc hien Cac chuc nang ciia tang trinh bay cho ph£p tang ung dyng cung cap cac djch vy ma khong can biet den viec giai ma dtr lieu va bieu dien v£t ly cua may tinh doi tac khac.

Hinh 1 2 5 Dich gitfu cu phap trim tuyntg va a t phap truyen

i

(2) Tang phien {tang thu 5)

Tang phien \h mpt muc 6 dudi tang trinh bay va thuc hien chu yeu "quan ly doi tho$i" Viec quan ly doi tho3i

dieu khien va quan ly luong du lieu giua cac irng dung va cac hf thong bang cach sir dung kha nang truyen dir lieu dau cuoi-dau cuoi do tang vjn chuyen cung cap.

Phucmg thuc truyen thong co the dupe d£t mpt cach tuy y Trong trudng hop truyen thong binh thudng (truyen E-mail, v.v ),vi dy sii dyng truyen ban cong (mot chieu t$i mot thdi diem) Trong trudng hop truyen thong hai chieu dong thdi (nhu trong cac he thong hpi nghj video, v.v )/ truyen song cong (ca hai chieu dong thdi) duoc su dyng Bang cach thiet l£p diem dong bo, viec truyen co the dupe thuc hien l$i tir diem dong bp trong trudng hpp truyen hong do bat c& nguyen nhan nao trong khi truyen du lieu, Thdi gian mat di vi v§y co the dupe giam toi thieu.

Hinh 1-2-6 Diem dong bp

vi£c iruy£n vdi t\f fciiip 60

cia tic tfi&n bQ

Lk

DWfm <K5ng b$ piw

I jDi&n ding difoh

Chuong \

Chutmg 3

Chuong9

Tang v|n chuyen 1& mpt muc d dudi tang phien va chuc nang cua no la de bao dam chat lupng truyen du lieu giua dau cuoi cua he thong (end-to-end) Vi v$y, neu chat lupng cua cac djch vy dupe cung cap bdi tang dudi la khong day du, tang v£n chuyen se bu chat lupng xau b&ng cach phdt hien vh khoi phuc 16i phy.

Tang mang la mpt muc d dudi tang v§n chuyen va lien quan chu yeu tdi viec chpn dudng (routing) va chuyen m?ch Khuyen cao X.25 cua ITU-T (xem phan 1.5.2 ve lo$t X) ve giao thuc muc goi dupe biet den nhieu.

H inh 1-2-7Chuc n an g tint ducmg

: Ofc <3»&ii l6i dkli trung khi lim iSufrng

Trong khi tang v|n chuyen o tren bao dam truyen di> lieu giua dau cuoi cua he thong, tang nay lien quan den viec lya chgn duong di phu hpp nhat de bao dam viec truyen du lieu "trong suot".

Tang lien ket du lieu la mpt muc 6 dudi tang van chuyen va dam bao viec truyen du lieu trong suot va khong co loi.

Noi chung, cac vai tro cua tang lien ket du lieu bao gom dieu khien truyen, nhu HDLC (dieu khien lien ket du lieu 6 muc cao), thiet l§p ket lien ket noi du lieu, dieu khien loi (CRC (kiem tra vong du thua)), ma hoa, v.v (Chi tiet ve cac thu tyc di£u khien truyen, xem phan 1.6 Dieu khien truyen.)

Trong m$ng LAN (M$ng cue bp), tang nay cung lien quan den di£u khien truy nh§p, nhu CSMA/CD (da truy nhap sir dyng song mang/phat hien dyng dp) va chuyen th^ bai, va dieu khien lien ket logic, nhu LLC (dieu khien lien ket logic), v.v

Tang v^t ly la mpt muc 6 duoi tang lien ket du- lieu va truyen cac tin hieu dien ("0" va "1") sir dung phuong tien truyen (cap xo3n ho$c dong tri,ic, cap quang, v.v.)

Mpt so cac giao dien trong thyc te DCE (Thiet b\ dau cuoi mach dir Ji£u) v& DTE (T hiet bj dau cuoi dir lieu) la:

Loat chuan X cua ITU-T: X.21 va nhung cai khac; xac djnh hinh dang o noi va bdng chan,

Lo$t V: V.24 va nhung cai khac, xac djnh modem, v.v sir dung cho dirong tuong ty (Analog)

ISDN (Mang tich hyp dich vu so) giao dien dau cuoi loo 1 1 xai djnh TA (Bp thich ung dau cuoi), v.v

CKi tiet horn ve cac giao dien, xem phan \3 < Vu giao di(*n dau rnoi

1.2.3 Cac thu luc truxfcn thou# tro it# ( ) SI

.H in h 1 -? H so sanh.C IS!, v o i -c.vr h i H i i ' < - ! u :h-^ni ct m oi o tn i.' • { y N h a t bdn va m ot 't v‘ h ik k i i^ o a i

Iltfth t'/.-X < ‘i ' $ <‘ll> h I l/l llJMV; 111

f Cat; 4a i lit**

/ rat; 4ai /vi cAc ss

*+■ eOna ty A v& cOnk iy B

n t NhAn h&ng tur nguoi dua bang

a o a

□□□ cftuylii til eOfig ly Hang h fo <Ju^«c

A tdi btfu ditn

Hang h6* duoc van chuyen qua Amsterdam

"3TMum g ngt/oi phu:

S Iv y chuyen bay cfa in

I ju*kl» nhi^m cho

^ iOfi AiiftKiikm

Trong may ba)1

Bu6c *i£p theo chuy& i idti sftii bay Rome

i n n vM chuyen bay

j * ^ c h o d in khi tdi R Trong may bay

1

C 6ag ty ii iy)

f^t^Tcfiuin"bT”

rn&u roa coftg iy HHI B v& r.uuig m iii ldi cha tjch cOns

j \ Ngudi

\ jL Ngudi phk*> dich djch

j f i C r tȣng anh sang li&vg y

NhAn viAii buu di£n chuyen hang tdi ngufo nh^ii

□ DO

o o o H iog hfc* ilw^c mang tir buu dȣn

tdi tdng ly B Owii cung u)i sin bay Rome

Khi truyen thong dupe thyc hi£n su dyng OSI trong thyc te' cac thu tyc sau duyc thyc hien.

1 Khi yeu cau truyen thong phat ra, kenh truyen thong dupe du<?c thiet lap trudc tien (thiet lap ket noi).

2 Khi du lieu dupe chuyen qua m6i tang t$i ben giri, tieu de (cac thong tin dieu khien) dirge gan them

vao vai du- ii£u cua ngu6 i dung trudc khi du lieu dupe gui di

3 Khi du lieu duac chuyen qua moi tang 6 ben nhan , tieu de du<?c loai b6 lan lu*Qt.

4 Khi viec truyen du lieu diryc thyc hien xong, kenh truyen thong dug»c dong l$i (ket noi bj ngat).

5 Cac tai nguyen truyen thong dupe giai phong va qua trinh xir ly d uac hoan thanh.

Cac tieu de duac them vao bai tang (N) duac gpi la tang thong tin dieu khien giao thuc PCI tang (N), va dir lieu cua ngir6i dung tang (N) dugrc ggi la dan vj du lieu djch vy SDU tang (N) Dir lieu gQp ca hai phan duac gpi PDU tang (N) (dan vi du lieu giao thuc) C6 nghia PDU tang (N) d u g c ho try bdi SDU tang (N -l) (Hinh 1-2-9).

H in h 7-2-4 M o i ijmut h £ g iin t c a c tieu tie tui « n c tang

PDU : Dun vi dd lidu gian link' SDU : £kai vj dH li^u djch vy

P C I : TUAng tin li£m so4l giaoth&r

1.3 TCP/IP - chuan thuc te cho giao thuc truyen thong

TCP/IP da trd thanh mpt giao thuc chuan thvrc te cho m^ng rpng nhat tren the gi6 i, tire la Internet Myc nay clira

ra mpt tong quan va giai thich giao thuc phan cap va vai tro cua moi tang cua giao thuc nay trong khi so sanh no voi mo hinh OSI.

1.3.1 Tong quan ve TCP/IP

Giong nhir mo hinh OSI, TCP/IP ciing co giao thire phan cap Ve ea ban, no duue can true tir 4 tang sau voi moi tang chua mot so giao thuc (giao thirc phan cap)

fang irng dung

Pa nr, v.’tii i lutycn

So sanh giua OSI va TCP/IP dupe chi ra d hinh i 3.1.

* 4

llin h 1.3.1 So sank cac kien true phan ra p gum TCP/IP vu OSI

< m hinh tham cH6u OSI > <TCP/fP>

T i n g In tern et (IP )

T in ggiao dten m$ng

TELNETFTPNMTP

SMTP POP3

ONS

DHCPHTTPOSS

NFSNTPV2XDR

SNMPCMOTMiB 2

100 BASE«T

■i s e e a r e 5 TcfttfeCg

4 ,1 6 M b {*

IEEE 802.12 lOM&AnyLM

100 Mbp*

iTlkTS ATM Forum ATM

ANSI X 3T I2 FOCK

100 M ttt*

U xafT ak 23Q-4 kbps

Triln khai c6c 4Utog truyln th6ng nhtrcAp xoln ddi, cap d6ng true cap qua^g v.v

d i truvln chu& bit

TCP va IP deu la c i c giao thuc quan trpng, moi giao thuc deu c6 die chuc n^ng sau:

• T CP (Gao thuc v?n chuyen; phuong thuc hudng ket noi) * bao dam dp tin cay cao.

• IP (Giao thuc Internet; phuong thuc phi ket noi)« bao dam truyen du lieu toe do cao

Cac phuong thuc hudng ket noi va khong ket noi duoc giai thich ngan gpn nhu sau.

Phuong thuc hudng ket noi yeu cau ket noi true tiep (kenh Logic) dupe thiet lap giua ngudi gui va ngudi nhfin trudc khi du lieu dugc truyen Du* lieu duoc truyen qua kenh nay di den thiet bj dich cuoi Khi viec truyen dupe hoan thanh, ket noi bj n g lt Viec thiet lap ket noi lam phat sinh vi§c truyen thong co dp tin cay cao.

C£c hofct dpng dupe chi ra d Hinh 1.3.2, bang viec dung dien thoai lam vi dy.

Hinh 1.3.2 liin lt litth hifthtg k it ndi (di$n tliO Q i)

(1) Quay *5 * >K*i ri6i • >tdc 06i tev kfiic *uat hl$n \ j^-y

Ket noi doge Ket thuc

d ) Phuong thuc p h i ket noi (IP)

P h m xn g th u c p h i k d noi i>*> qu a su 11'ii«*f k ip kc-{ noi tru e n e p va v»ec d a n h ke n h iru y e ri thi»n^ *r«« « ‘ k h i d iv !>eu

d u o c tru y e n , cd n g h id t i n g k h o n g cd j u d a m ba o la d u liv u si* td i n o i n h a n M a t khac, no tau nen k h a iu \n g tr u y e n

d ir heu toe d p cao V i vay, d ie u k ie n tr u o c trm i de sir di.4ii}' ph u < m g th u c pha ket n o i ia v u v i r l ■ y •:»* th o n ^ p h a i

d u o c th u c h ie n tre n d u o n g tru y e n co d o tin cay * de la m tan g xac suat diV lie u td i d iro c n o t n ln n

Hoat dpng d u gc chi ra tren hinh 1.3.3, sir dung thu gtVi bun dien nhu mot v.( dy.

Hinh 1.3,3 Hinh £nh cm khSng k e t noi (Unrgih bint iti$n)

Ket noi khong duoc thiet l$p truoc

Nhu da chi ra a tren, vai tro cua TCP va IP trong mo hinh TCP/IP cho phep truyen tren internet mpt cach tin c$y

va toe dp cao Co nghia, TCP bao dam truyen dir lieu vai dp tin cay cao, sao cho chuc nang nay co the bi bo qua trong IP, ket qua dan den truyen dir lieu voi toe dp cao.

Tang ung dyng la tang cao nhat lien quan den cac djch vu gan lien voi cac irng dung ciia ngudi dung.

Cac djch vy tren Internet dupe thyc hi£n bdi cac giao thuc ciia tang nay.

Cac giao thuc chinh dupe chi ra d duoi (Chi tiet, xem phan 3.2, Internet)

* D N S (H £ thong danh ten m ien): Giao thuc anh cac ten mien vdi dja chi IP.

* H T T P (G iao thirc chuyen giao sieu van ban): Giao time truyen t£p trong ngon ngu HTML.

* FT P (File Transfer Protocol): Giao thuc truyen tep.

* SM T P (Sim ple M ail Transfer Protocol): Giao thuc truyen thu don gian.

* PO P3 (Post O ffice Protocol Version 3): Giao thuc nhan thu tu mail servers.

* N N TP (N etw ork New s Transfer Protocol): Giao thuc truyen tin tren m$ng.

* T EL N E T (TELecom m unication NETwork): Giao thuc cho phep truy nhflp vao thiet bj dau cuoi tu xa.

* SNMP (Simple Network Management Protocol): Giao thirc quan ly mang dan gian.

* D H CP (D ynam ic Host C onfiguration Protocol): Giao thuc thiet l$p dja chi IP dpng.

(?) T a n g van chuyen

Tang van chuyen la mpt muc d dudi tang ung dung va chuc nang cua no la cung cap djch vu de chuyen du lieu giua dau cuoi cua he thong (end-to endj

I lai giao thuc sau bao dam dp tin cay va UK do cao

* T C P : D a m bao d o tin * ay < ao

* U DP ( G i a o Uu.ii g u i l l i o i u ; l m i h m i o i d u n g } \ h a y 1 I 1 0 v i y e d a m K j o d o t s n i a y u u ) , g i a o t i m e n a y d a m b a t )

Uk do CcK>.

N h u da de ^ap tfc n , p lm u n g th in < uu t;.an U i 'j l it i* ia h u u n g ket m i!, n h u n g g ia o th u e I la k h o n g ket r> a

Giao thuc nao trong hai giao thuc duac so dung se dupe xac djnh bdi lang vmg dung muc cao hem, TCP la phu hyp khi lupng du »>?u ldn s e dupe truyen lien tyc, va UDP la phu hpp khi du li£u kich thudc nhd (goi) duoc truyen khong lien ty c

d ) Tang Internet

Tang Internet la mpt muc d dudi tang van chuyen va chuc n&ng cua no Ik de chpn dudng (lya chpn dudng truyen

thong) va tao kha nang chuyen tiep (relay) cho du li§u dupe truyen qua cac mang, nhu Internet.

Giao thuc IP cd vai trd eye ky quan trpng trong tang nay, vi no them cac tieu de IP (thong tin dieu khien) va gui cac buc du li§u IP (don vj thong tin du li£u dupe su dyng trong TCP/IP) tu noi gui den noi nh$n lai diem nay noi doi tac dupe nhan biet qua dja chi IP (dupe mo ta sau) chua trong tieu de IP, va vi£c tim dudng toi uu dupe thyc hif n de gui dur li§u den noi nhan.

Cac giao thuc sau dupe su dvmg de tim dudng

• RIP (Giao thuc thong tin tim dudng): Giao thuc chua thong tin de lya chpn dudng truyen thong.

• OSPF (Md dudng ngan nhat trudc tien - Open Shortest Path First): Giao thuc kh5c phuc nhupc diem cua RIP.

Tang giao di£n mang la mpt muc d dudi tang Internet va thuc hi£n truyen thdng trong suot khong loi cho bat ky mpt loai du li£u nho.

Tang giao di£n mang TCPAP mpt tang ket hpp cac chuc n&ng cua tang v$t ly va tang lien ket du li£u cua OSI

De thu an tien, tang lien ket dir ii§u cua mo hinh tham chieu OSI dupe chia thanh cac nhom giao thirc cua tang LLC (Dieu khien lien ket logic - Logical Link Control) va tang MAC (Dieu khien truy nh§p phuomg ti?n - Media Access Control).

Ba giao thuc dupe mo ta nhu sau.

« SLIP (Giao thuc Internet dudng noi tiep - Serial Line Internet Protocol): SLIP la mpt giao thuc ket noi diem-tdi-diem sir dyng dudng cong cpng (dudng di£n thoai, v.v ) va cac bifn phap chong hong va dieu khien loi la dupe xu ly bdi cac tang d muc cao hon.

• PPP (Giao thuc Diem tdi diem): PPP la giao thue co ban thyc hi£n cung chuc nang nhu SLIP, nhung dupe thiet ke de cung cap cac chuc nang cai tien hon ve m$t quan iy, v.v

» ARP (Giao thuc Phan gi^i dja chi): ARP la mpt giao thuc de anh x$ dja chi IP tdi dja chi MAC (dia chi tang MAC dupe mo ta sau).

2.3.2 Cac thu tuc truyen thong trong TCP/IP

Cac thu tuc truyen thong trong TCP/IP ia giong nhu cac thu tuc dupe thuc hi£n trong OSI.

J Khi yeu cau truyen thdng dupe phat ra, ket noi dupe thiet lap.

2 O ben gui, cac lieu de (thong tin dien khien) dupe gan them vao du lieu cua nguoi dung khi no di qua mdi tang trudc khi du lieu duoc gui di

.VO ben nhan, ca« tieu de duoc loai bo Ian luul khi dir hen di qua moi lang

•i Khi vice huycn du lieu hoan (hanh, ket inn hi ngot

C a c t.ii n g u y e n t r u y e n t h o n g d troi i-i.u p h o n ^ va p h i e n l a m v ice k t h u c

1.4 Dia chi duac sir dung cho TCP/IPo * * <,/

V)ia chi di/grcstr dung de xac djnh nui dich, v.v khi tien hanh truyen

TCP/IP sir dyng hai kieu dja chi sau de xac djnh dich can truyen den.

• Dja chi IP (dja chi logic)

• Dja chi MAC (dja chi v$t ly)

1.4.1 Dia chi IP

Cac may tinh duQc noi tren Internet duQc gan mQt dja chi IP 32-bit (giao thuc Internet), boi vi dja chi IP phai khong bj trung I£p trong bat ky tinh huong nao, nen trung tarn thong tin mang (NIC) phai chju trach nhi£m tren toan the gi<M, t§p trung hoa vifc quan ly va cap phat dja chi IP T^i Nhat ban, Trung tarn thong tin m$ng N hjt ban (JPN1C) chju trach nhi§m cap phat dja chi IP trong nuoc Dieu nay co nghia la dia chi IP phai duQc nhan tir JPNIC

khi b^n l$p ke ho?ch xay dy-ng mQt mang ma no co nhu cau djnh truoc la d u Q c noi t6i Internet.

Oja chi IP duQc cap phat sau khi can nh£c x e m x e t den quy mo cua m Qt m$ng, v.v

Hinh 1.4.1 minh hoa cau true cua dia chi IP.

Hinh 1.4.1 Cau true itfa chi If*

Bl&u cfr&o trong ph&n

Bi^u di&n Iroog th£p ph&n

Hai phan cua dia chi IP chi ra nhu sau:

• Phan dia chi mang: Mang nao m a dja chi IP ihuoi vao

• Phan dia chi may chu: Oja « hi cua may tin}*

D ja c h i IP duQ c n h u m t h a n h b o n la p U: A ten \ ) lim n y, m iy t voi cat noi d w n ^ v

m a n g va p h a n d ja c ia m ay r ! iu

a ki cl i lliu iH cua e rr- p h a n d ja chi

Hinh i.4.2 Din c h i IP ( l o p dia chi A ttri \6pD)

** ”

->h$m vt turwiy Ihiclt SG ntytitf c6 ttitfdung jJiJc/C 36 eAc ch? itt&y chu

xac dinh tr&n mao^

Lop 8 LdpC

i

nI ^u

1iiLcfcD (Chi sir dyog cho c ic ptx»ny thi/c truyen xAc djnft)

Dja chi trong do 32 bit toan la 0 ho$c 1, va phan mang la "127" d u g c sir dyng trong cac tnrong hpp dac bietva

kjiong thuong d u g c sir dyng.

Lop dja chi A la de su dyng trong cac mang quy mo rat Ion Hinh 1-4-3 chi ra cau true cua lop dja chi A.

Hinh 1.43 Cau true cua lop d ja ch i A

<C&u true dja ch! jP su* dyng trong mang di$ri r$ng <3u*0'c t6 chi>c bdi s6 li/p ’ng Ion m£y tlnh>

• L i— - ■ V l_Sj

* 7 b it - ► Ull

0 P h & n 5|a c h i m a n g

Bit dan dau: "0"

Phan dja chi mang: 7 bit

Phan dja chi may chii: 24 bit

So lu<mg cac mang ma dja chi cap phat dug>c co san la: 126

So lirgng dia chi may chii co san de cap phat cho mpt mang: 16,777,214

Ldp dja chi B duvc sir dyng cho cac mang co kich thiroc Ion va trung binh, trong do vi£c thieu dia chi co sar> tro th&nh van de nghiem trong Kinh 1-4-4 chi ra cau true ciia lop dia chi B

Hinh 1.4.4 Cau true cua lop dja ch i B

C au true d ja ch i IP su d y n g tro n g cac m ang co k ich th ira c l&n v a trung binh

I 0 P han d ia c h i m ang Phan d ia ch i m a y chu

Bit ciSn dau *10"

Ph&ri dja chi m«tny 14 bit

Ph&n dia chi may chu: 16 bit

S6 ii/Q'i'.y cac in$ny nia dia chi ciip phai du-Q-c la co san 16,382

$6 lu'Ony dia chi may chu c6 sSn cho viec c&p phai cho mpt many Id 6b,534

^ i - , f - > : / “>

2 9

lop dja chi A va U.

Hinh 1.4.b minh hoa cau true cua lop dja chi C

<Cku true dia cni IP aw oyng trong Uooy cac many quy mo nho>

c Phlin dja chi’ mang Ph&n dja chi m £y chu

Bit dSn dc»u "110“

PhAn dja chi mang: 21 bit

iPh£n dja chi «rt£y cnu: fi bit

SA Iuqtuj c£c mang ma dia chi c&p.ph3t duvc la c6 sSn 2,097,160

S6 lu'p'ng dja chi m£y chu c6 s3n d£ Ccip pi£t cho mQt mang te: 254

@ L a p D

Dja chi lop D khdng chua phan dja chi may chu va chi dupe su dung cho cac phuong thuc truyen thong dac bi£t.

Hinh 1.4.6 minh hoa cau true cua lop D.

Hinh 1.4.6 Cau true cua Ifrp D

<Ciu true dja chi IP sur dyng trog c&c phuong Ihurc truyen cy the (dja chi da quang ba nhom: s2 giai tliich sau>

1 0 So nhom (Dja chi da quang ba nhom)

Mftt na mang con ia ky thu|t dug>c ra doi vi can thiet de su dyng hi§u qua dja chi IP, khi so' luong dja chi co sin fcrd nen khan hiem.

Trong trudng hop dja chi lap dja chi B, ch&ng han, so luong cue dai dja chi cua may chu co the dupe'cap phat cho cnQt mang la 65,534 Tuy nhien, hi£n rat kho de hinh dung mpt mang bao gom mpt so luong Ion may tinh nhu vay-

Do do dja chi mang con d u gc six dyng 6 day de tang so lugng dja chi mang chi biing cach su dyng phan dja chi

cua may chu Phuong phap duoc dung cho dieu nay dupe goi ia "mat na mang con." Noi cach khac, m|it na mang con chi ra mien dja chi mang va dja chi mang con Cy the hon, m^t n$ mang con chi ra phan dja chi mang la "1"

va phan dja chi may chu la "0," nhu minh hoa tren hinh 1.4.7.

\y U rn n* m f ng con

ii

*— tya chi rr^ng - ♦ -D ja ch f m*t >« Oja chi i>viy chu — >

Theo cach nay, th$m chi neu cung mQt dja chi mang, dja chi mang con se khac nhau va tao nen mQt m a n g hoan

M$t so dja chi IP co nhung y nghia d$c biet Do la:

• D|a chi mang

• Dia chi Qu&ng ba

• Dia chi da quang ba nhom (Multicast)

Dia chi mang la dja chi ma trong do phan dja chi may chu cua dja chi IP bao gom toan 0, va cung la thich hop de coi chung nhu bien ten cua mang.

Dia chi Qu&ng ba la dja chi ma phan dja chi may chu cua dja chi IP bao gom toan 1 Nhurig dja chi nay dugc dung de quang ba du lieu toi tat ca cac nut thuQc vao mang, v.v Tuong phan voi dieu dja chi quang ba dirge dung, dja chi dugc su dung de gtri toi chi mot nut xac djnh, duQc gQi \h "dja chi quang ba duy nhat" ("unicast

address/')

Dja c h i da q u a n g ba duoc s ir dung de g u i d ir lie u loi ta t ca cac n u t thuQc vao m p t n h o m xac d jn h Dia chi IP lo p

d ja c h i D d u Q c s ir d u n g d e n h a n d i£ n m p t n h o m xac d jn h (n h o m da cju an g ba)

Trong I iinh 1.4.8, dja chi IP I6 p dia chi C duoc sir dung trong mang ! va 2.

Vt voy, cac p h a n d ja c h i m a y chn (8 b it th a p ) ba o g o m to a n 0, k ie u n h u " x y:/ 0" va "a b c 0 ," n h u n g d a y !a d ja chi

m a n g cua m a n g t u o n g im g

N g u y c la i Khi p h a n d ja chi m a y chu b a o g o m to a n i, n h u " v y /.2 S S " va "a b c >^ / ' ih i d a y la J ia c h i q u a n g ba

Khi d ii liy u d u o c d e d ja du to i d ja c h i na y (ciu d jn h "x y / 25*3/') th i d ir lie u d u o c U u y i-n to i lai t j cai n u t ( /v i to

A 4 ) th u o c van m a n g na y (M a n g i tr u n g vs d u na y)

Nigugrc lai, neu ban chi muon gui dll' lieu toi B2 thdi, thi dja chi mot quang ba nhu "a.b.c.2" dirge su dung.

Dsu t.hi da quang ba duyc su dyng de gui du U?u toi tat ca cac nut (A3, M , B3y 134) thupc vao nhorn da quang ba

Da qudiig W nh6m M

1.4.2 Dja chi M AC

Dja chi IP dupe sir dyng de phan biet cac nut ket noi toi mpt m$ng Tuy nhien, vifc nhan dang dja chi IP xay ra t^i tang giao thirc TCP/IP Vi v§y, dja chi co kha nSng thi^c hien nhan d$ng 6 tang giao dien m^tng (mpt muc 6 duoi

tang Internet) dupe yeu cau de thuc hien truyen thong v£t ly Do la dja chi MAC (Dieu khien truy nh$p phuong tien).

Dja chi MAC la mpt dja chi 48-bit dupe cap phat cho lung phan cung (Cong LAN: 'Phiet bj dupe dung de noi tdi m?ng).

Hinh 1.4.9 minh hoa vi du cua cau true dja chi MAC.

Hinh 1.4.9 VY du cua cau true ilia chi MAC

Nh ifi\ rtui ±tu\ xu«U —

(m3 nhA win *u£l)

• Nh*n dang nha sin xuat: So ID xac d jn h nha san xua't

• Nhan dang san pham; So'ID xac dinh cho phan cung va dugc them vao boi nha san xuat

Dja chi MAC duyc the hi§n 6 ky phap he 16, vdi moi byte duoc phan cach bai hoac Vi du, dja chi tren Hinh 1,4.9 co the duyc the hien nhu "54 39 - A6 - IB - 02 - C l" ho|c "r^4 39 : A6 : IB ; 02 : Cl

32

Trong mo hinh TCP/IP, dja chi IP dupe sir dyng nhu dja chi noi nh?n viec truyen Tuy nhien, tren thyc te de phat

du lieu tai noi nh£n trong mang, dia chi MAC cua noi nhan phai duyc xac djnh Do do can phai anh xa dja chi IP t6i dia chi MAC ARP d6ng vai tro cua inh xa nay.

ARP la mot giao thuc de chuyen doi dja chi IP thanh dja chi MAC, va sip xep thyc te d u ac chi ra tren hinh 1.4.10.

Hinh 1.4.10 Cache AliP

<3)j < 2 >

0 )

□

A1Dja cnJ IP x y i, 1

OjacftiMAC: 12-34-5^78-90-AB

A2OjacfcilP: x,y,*,2

A3

Dja cHi MAC: 6^-78-90-AB CD-EF

CDC6i ARP bao gom dja chi IP cua nguoi nh§n (x.y.z.2) duoc gui toi tat ca c&c nut bSng cach quang ba.

CDNut (A2) co dja chi IP cua nguai nhan dupe bao trong go; ARP tra 'ai dja chi MAC duy nhat cua no (34-56-78-90-AB-CD) cho nguoi gui.

<DDya tren dja chi MAC nhan duyc, du lieu se duyc truyen.

Se mat thoi gian vk hieu qua thap han neu thu tyc nay luon duyc sir dung de doi dia chi IP thanh dja chi MAC

Bai vay, anh xa cua dja chi IP da duyc dieu tra va dja chi MAC diroc giu trong danh sach, va vi v§y viec anh xa co the dupe thyc hien blng cach su dyng cac danh sach nay nhu cac chi muc.

1.5 Giao di£n thiet bi cuoi

Giao dien thiet bi cuoi noi tai dieu kien duac thu xep va cac phuang phap dieu khien truyen de dam bao viec truyen dupe thyc hien giua cac thiet bj cuoi Dac biet han, dieu nay lien quan den cac kieu dau cam va cac chuan

ve cac muc tin hieu, va cac chuan ve dieu kien van hanh Ba kieu sau la cac giao dien thiet bj cuoi dien hinh, va moi kieu duac djnh nghia theo khuyen cau cua ITU-T.

• Dong-V: Giao dien giua DTR va DC F voi dudng luong tu

• Dong-X: Chao dien giua D Tb va DC Li voi duang so

• Ddng-f: Giao dien cho ke* noi loi duong IS! )l>!

Sau day se mo ta chung va giai thich dac trung dac biet cua moi loai Mo ta « bi net va giai thich them nira ve thiet

hj va duong iruyen duyc de cap trung * uc hang door ch»» hung v inr« mg 7

3 3

2.5.1 D dng-V

Deng V lam tai lipu v6* cac giao difei giira DTE-DCE (MODEM) duoc sir dyng de truyen dCr lieu voi dudng tirong tv

Hinh 1.5,1 Cac giac dien V

Ten giao di£n 0 |nh nghia

V 10 (X 26) D$c trung di£n cua cic mach trao dAi ddng kdp khdng cdn bing van ning duvc sir dyng trong c&cthiAt b| IC trong ITnn vyc

truyen du» li$u

V.11 (X 27) D$c trung <Jidn cua c ic mach trao dAi ddng kdp edit bAng van ning du-pc si> dgng trong c ic thi£t bj IC trong ITnh vyc tnjyAn

dO lidu

V.21 C ic modem 300-bps sir dyng trdn cac mang di£n thoai chuyen mach cdng cdng; truyen song c6ng

V 22 C ic modem 1,200-bps sir dyng trdn cac mang difcn tho$i chuyAn mach cdng cdng vi dirtmq thud bao; truyen sonq cdngV.23 C ic modem dAng bd vi khdng dAng bd 600/1.200-bps su* dyng trdn c ic mang didn thoai chuyen mach cdng cdng

V.24 Djnh nghia cic mach trao dAi giua thiAt bj dAu cuAi dir li$u vi thiAt bj dAu cuAi m^ch di> li$u

V.26 GAc modem 2,400-bps sir dyng tren dudng thud bao bAn diy

V.26l>»s C ic modem 1,200/2,400-bps sir dyng trfin c ic mang didn thoai chuyen mach cdng cdng; truyen bin cdng

V.26ter Cdc modem 2,400-bps sir dyng tr£n during hai day; truyAn song cdng

V.27 C6c modem 4,500-bps cd bQ cd bo can bAng cd thA diAu chinh bAng tay sir dyng bAn diy (song cdng) hoAc tren during diy

thud bao (bin cdng)

V.27bis C ic modem 2,400/4,800-bps cd bd cin bAng cd thA diAu chinh bang tay sir dyng bAn diy (song cdng) hoic trdn dird’ng day

thud bao (bin song cdng)

V.27ter Cdc modem 2,400/4,800-bps sir dyng trdn cac mach di$n thoai chuyen mach cdng cdng; truyen bin cdng

V.2B D$c trung didn cua cdc mach trao dAi ddng kdp khdng can being

V.2Q Cac modem 9,600-bps sir dyng trdn cac mach thud bao bAn diy diAm-td-i-diAm; song cdng (4-diy) vi bin cdng (2-diy)V.32 Cdc modem 9,600-bps sir dyng trdn during tiai day; truyAn song cdng

V.33 Cdc modem 14.4-kbps sir dyng trdn during thud bao bAn day

V.35 Giao didn trung kA tAc dd du* Jidu 48-kbps sir dyng dirdrig dii thdng 6 0 -1 0 8 kHz

1.5.2 D d n g -X

Dong-X lam tai li<?u ve cac giao di£n gii>a DTE-DCE (Dorn vj djch vy so; DSU) duoc su* dyng de truyen voi duong so" X.20, X.21 va X.25 (chuyen m$ch goi) duoc su* dyng rong rai.

Hinh 1.5.2 Cac giao dien ddnx~X

T4n giao di^n Djnh nghTa

X.20 Giao didn DTE-DCE (truyAn thdng khdng ddng bd) giira thiAt bi d£u cuAi dir li^u (DTE) vi thiAt bi dAu cuAi mach dir li$u (DCE)

dA truyAn start-stop trdn cic mang di$n thoai chuyAn mac.h cdng cdng.

X 20bis £)$c ti thiAt bj <5Au cuAi di> li^u (DTE) duvc thiAt kA cho vi^c giao tiApvdi cic modem toat-V hai day khdng dAng bd su dyng

trdn cic mang truy nhip cdng cdng.

X.21 C6c giao di^n glOa thiAt b| dAu cuAi mach du liAu (DCE) vi ihiAl bj diu cuAi du1 li$u (DTE) sir dyng cho vin hinh dAng bd trdn

cic m$ng di$n tho<ii chuyAn mach cdng cdng.

X.21bis D§c t i DTE du'Q'c thiAt kA dA giao liAp vdi phuang thirc ddng-V dAng bd trong c ic mang dt$n tliogi chuyAn mach cdng cdng.

X.24 Lie< kfi cic djnh nghia cho cac mach trao dAi giOa thiAt bj diu cuAi mach dir iidu (DCE) vi ihiAt b| dAu cuAi du li^u su dyng

tren cic mang tfi£n Iho^i chuyen m^ch cdng cdng

X.26 C ic g«ao didn giua thiAl bi d iu cuAi mach dir lidu (DCE) v i thiAt b| d iu cuAi du lieu (DTC) ctio cuc UuAt bi cd k^t ndi tn/c tiAp

id'i cac m^ng cdng cdng chuyAn m^»ch got

1.5.3 Dong-1

Dong-1 d in h n^hia cac gu to dn,m tiiu it su d u n ^ de kol no t ihiet b» ludi voi d u o n g IS D N N o mnv; d u y c th a m cl m m

n h ir m ot g ia o d ie n n g u o i N o c iin g d jn h n g h id d ie m ket n o i lo g ic g iira DTE-DC \i cho vie c d u n j* vo i

iS D N

Hinh 15.3 Cdc giao di?n dong-1 va ISDN

1 430 Giao di£n nga&i dunq/manq t&na vat ly t6c Jg cor b in ISDN □2c t£ t&ng 1

I 431 Giaodi£n nh6m ngudi dung/m^ng t4ng v$t ly t6c dd chinh D#c & t&ng 1

Q 921 D$ng thi>c khung ISDN 6t tang tien k&t dt> lieu

s D$c t£ t£ng 2

Q 922 Djch vy mang phuong thuc khung ISDN {Chuyen khung -

Frame Relay)

D$c t3 tin g ti&n k£t du* li$u

a 931 Giao dien ngi/fri dung/m^ng ISDN cho ki&u thdng diep v£ nOi

T E1: Thi&t bj d&u cu6i chu&n ISDN

TE2: Thi&t bj kh6ng d£u cu6i ISDN (non-terminal equipment)

TA: B$ thich i>ng t h ilt bj <J&u cu6i (Terminal adapter)

NT-1: D an vj djch vy s6 (DSU)

NT2: PBX, v.v

Di&m R, S, T: TCrng di&m giao di$n (dirge xac djnh b6i dong-l 400)

ISDN bao gom diem tham chieu giao di§n logic nhu R, S va T trong Hinh 1-5-3 Diem phan tach dupe tim giua R

RS-232C (Chuan khuyen cao 232C) la mQt chuan duQc chap nhan b6 i EIA (Hiep hQi Cong nghi^p dien tir, USA)

da tro thanh khuyen cao V.24 ciia ITU-T RS-232C djnh nghia cac dac trung khac nhau duQc sir dyng cho truyen khong dong b Q giua DTE-DCE ( B q dieu che/'giai dieu che MQdd; MODEM) de truyen du lieu voi duong tuong t\r Boi vi MODEM chi quan ly dur li(?u noi tiep, RS-232C cung duQc xac djnh cho du li?u noi tiep.

Dieu khien truyen la kha nang dieu khien duQc sir dung de dam bao vi(sc truyen d u lieu chat lu (,m g cao, hieu q u a

va tin cay Cac buoc lUryc thirc i>lt^n 6 day da d ir o c he thong hoa thanh mQt I oat cac quy tac dupe gQi la "cac thu tuc dieu khien truyen."

1.6.1 Tong quttn va Itwng diiht khien truyen

( ! ) Tong qu an v6 dieu khien truyen

M o t bo d ie u k h ie n va cac t l i i i tin duyt yeu cau tic J a m !>a<# v i a U u y e u tin iit;u lu v u qua \ t tin -.ay :\‘Oi liu:-,*;

35dieu khien va cac thu tyc nay duoc gSn nhan "dieu khien truyen", bao gom hon dieu khien sau.

Bieu khien duoc su dyng trong tnrdng hyp vi<?c chuyen mach dieu khien chuyen doi giua noi va ngat cua duong truyen dir lieu Trong trudng hop dudng thue bao, bdi vi quan he giua ngirci gin va ngudi nhan la co dinh dieu khien duemg ia khdng can thiei.

Dieu khien dong bo dieu phoi d?t thdi gian trao doi du lieu cung nhu luong du lieu "dieu khien luong".

Dieu khien dong bp bao gom cac phuong thuc nhu dong bo start-stop, dong bQ SYN, va dong bo khung, v.v Dieu khien luong hieu chinh toe dp truyen du li§u.

(Chi tiet ve dong bd, xem inyc 2.2.2 Dieu khien dong bd)

Dieu khien loi, phat hien, sua chua va truyen l£i du li£u bi loi.

(Chi tiet ve cac phuong phap phat hi|n loi, xem myc 2.2.1 Dieu khien loi.)

Lien ket du* lieu la dudng tao kha nang truyen thdng v$t ly giua nguoi gui va ngudi nh£n Dieu khien lien ket du li£u thiet l$p lien ket du li<?u va thyc hien truyen dir lieu tuong ung vdi thu tyc xac djnh va sau do ket thuc lien ket du lieu.

Luong dieu khien truyen noi chung trong cac mang di<?n thoai chuyen m^ch va dudng thue bao duyc chi ra tren Hinh 1.6.1.

Hinh 1.6.2 Thiet lap vd duong lien ket dir ti$u

£ KAt thuc HAn k£t riO* lidu Sau khi truyen d u li$u xong, k4t thuc lidn k£t d u !i$u

c

NgSt kfet n6i d u o n g truyen thdng

1 Pha 1 (not dudng) (khong can cho dudng thue bao): Dong thdi vdi quay so ben doi tac va ket noi duong, thief

bi truyen thong can thiet (MODPM, v v ) duyc ^0* d trang thai hoat dyng

2 Pha 2 (‘I hiet lap lien ket du ii<*u): Hen doi tac duo*-' gy«, va hoi xem co kha nang truyen thong vdi doi tar khong

va Ira loi dime \ac nhan Nei; tra loi la "Co the truyen thdng", lien ket dfr lieu ban dan duyc thiet lap (,.»» thdi diem nay

3 Pha 3 {Truyen dir lieu): Rang rarh thiet lop lien ket du hen viec truyen du lien dihu thuc hien, (rone khi dim khien khac nhiiu (dieu klucn dong ho va dieu khien lt.it, duoc thiu hiyn

4 Pha 4 (Ket thuc lien ket du ti$uh Sau khi hoan thanh truyen dir lieu, viec kiem tra'truyen thong giua hai doi tac dtrpc ket thuc, va sau do lien ket du lieu dupe ket thuc.

5 Pha 5 (Ngat lien ket) (Khdng can thiet cho dudng thuc bao): Lien ket bj ngit.

1.6.2 Cac thu tuc dieu khien truyen

Hinh 1.6.2 minh hoa cac thu tyc dieu khien truyen dien hinh dupe sir dyng de dam bao truyen d u lieu hieu qua,

tin c|y.

Hinh 1.6.2 Cac thu tuc dieu khien truyen

Trong che dp TTY (Go di|n tin), thao tac vien thyc hien dieu khien doi vai viec truyen du lieu Bai vi cac thu tyc dieu khien truyen bj bd qua, no dugfc gpi & thu tyc bj bd qua Dieu nay dupe sir dyng rpng rai cho truyen thong

m iy tinh c i nhSn sir dyng duang tdc dp thap (Idp 300-bps).

TTY la mpt phuong thuc, trong d6 mpt luong ky ty ch?y theo dudng truyen t$i thai diem phim dupe go Bai vi chi mtrc dieu khi^h thap nhat dupe yeu cau de truyen du lieu, nen thao t&c vien dupe yeu cau thyc hien hanh dpng sira chua neu c6 tryc trjc xay ra (cac loi truyen, v.v )

Trong che dp TTY, ngudi gui truyen du lieu dya tren viec phat ra mpt yeu cau truyen du lieu Khong dieu khien

nho dupe thyc hien, nhu xac nh?n tr?ng thai cua doi tac khac, v.v.

Ve ca ban, chi co ba dieu khien sau dupe sir dyng trong che dp TTY, va vi v^y dp tin cay la thap.

Ngudi nhan x ic nhan danh gidi ciia du lieu bSng dau phan each, nhu CR (Phim xuong ddng).

C£c ma dieu khien luong dupe sir dyng de bat dau va ket thuc truyen du* lieu dtrpc sir dyng khac nhau phu hpp vdi toe dp xu ly ben ngudi giri va ngudi nhan tuong ung.

Ve phuong dien ljch sir, thu tuc co ban co nhat da dupe thiet l§p nhu chuan JIS X 5tX)2 vao nam 1975.

-Don yf\ truy&n €> o t i v j k h 6 i

Chi&i d& dir 8$ s6 nguyen cua ky V (£-bit)

7 6c <30 dudrng tuang thich Thich hgp cho du&ng c6 t6c d$ ldn toi 9,600 bps

Hifcu q u i truyen Binh tht/frng (t6t han phuung thUc thu tyc bj k>?i b d i

Phutyna thirc truy&n thong B in cong (Phuong thuc md1 r$ng $t> dyng song c6ng to in p h in )

Trong thu tyc co ban, 10 ky ti^r dieu khien truyen duoc chi ra tren H'rnh l-6-4.dug>c su dyng de dieu khien truyen.

Hinh 1.6.4 Cac ky tptiieu khien truyen

SCH B it d iu d$t tldu d£ Ky ly blit d iu phuang thuc ca b in

STX Blit d iu vSn b in Ky ty di&u khi&n tru yin ch! ra bit d iu vSn bin Khi co ti6u dfe, n6 du g c su dyng di k it thuc fcTX K it thuc v ia b in K it thuc ingt v3n b in

EOT K & thuc truyen Ghi ra k it thuc cua mOt ho$c n h iiu vSn b in

ETB K it thuc khdi truyen C|il ra k it thuc vi$c tic h khdi do tinh d in vi$c truyen

SYN Rfii d&ng D irr b io d&ng bO trong trang thai c6c ky t y k h ic I i khong d u vc gui v i duy tri d6ng b<».

ENQ Y iu ciu Owe sir dyng d6 y6u cAu vi^c x ic n h in ttr phia d6i tic

ACK X ic nhin Ky ty d i ^ u kh»6n d u g ’C gCri tt> phia ngi/d'i n h in nhu> mpt x ic n h in cho b6n gui.

NAK xac nhin tir chdi Ky tu* di^u khi£n d u g c gu i tir nguai n h in nhu mOt x ic n h in t«> chAi cho b in gui.

OLE T ho it lldn k6t dfr-ltyj Ky ty d iiu khi^n d ugc su dyng khi th im di^u khiAn truyen d ^ tttay ddi y.nghTa cua m§t s^ huu

h^n c ic ky ty theo sau.

Thong diep trong thu tyc co b&n bao gom phan tieu de va phan du* li£u.

Hinh 1.6.5 D$ng thifc thong bao cua mpt thu tyc ca ban

P han tieu de: C h o u th o n ^ tin d ie u k h ie n de Ir u y e n (c<> th e b j ho tjim )

Phan d tr lie u : U ir li<?u diu.n ih ia th a n h m ot so cac k h o i de im y e n , va BBC (K y t y k ie m tra k h o i) d u y c th e m vao

cuoi a i i m o i k h o i ( th u o n g d»ro» j ’ an r.h ir h il k ie m Ir.t rh a n is th«*o c h if'u do c, va k ie u ia le)

3 8

Hai phuong phap dac trang cua thu tyc co ban de thiet lien ket noi dir li£u: Tranh chap va tham do/lira chon

Tranh chap la phirong phap dupe su* dyng trong truong hyp ket noi diem-toi-diem Nguoi gui (tram chu) gui ma ENQ, va sau kl\i nhan ma ACK tu ngudi nhan, vifc truyen du li£u dupe bSt dau, tuc la de nhan duoc quyen

truyen, ma ENQ phai dupe gui truoc tien, va vi vay phuong phap nay doi khi con dupe coi nhu phuong phap

"den truoc, duoc phyc vy truoc".

Hinh 2.6.6 Tranh chap

Phuong phap nay bao gom hai thao tac sau.

Thu tyc HDLC (Dieu khien lien ket du li£u muc cao - High-level Data Link Control) la mQt thu tyc dieu khien truyen de truyen thong du li£u hi£n dai, toe dQ cao.

Hinh 1-6.9 f>gc truiig ciia HDLC

Md l»6n k£t

Di&u khi&n lidn k6t SSnu l$nh/d£p i>ng

Don vj truy&n TO’i 8 khung c6 th6 du-grc gu*i lidn ti&p

E)i&u khi£n l6i CRC {Ki6m tra du1 thtra v6ng - Cyclic Redundancy Check)

TAc dO di/d-ng tiw n g thich Qu*&ng 2,400-bps ho$c cao han trung binh - ho$c t6c d<» cao

Phuong thuc truyen thong Song c6ng

<D Cau true khung

Trong thu tuc HDLC, thong tin dupe truyen trong cac khung

Hinh 1-6-JO Cau true khung

b Trudng dja chi (A; 8-bits)

Trudng dja chi chira dja chi cua ngudi gui va ngudi nh^n cua khung.

c Trudng dieu khien (C; 8-bits)

Trudng dieu khien chira thong tin ve kieu khung so thu tu cua khung v.v

Co ba kiou kliung:

k h u n g th o n g tin (1) I )u liu y e n th o n g tin

K i l l i n g g i a m s a i (S)- { hi, n h a n v i c e n h a n klmng va yeu ran can tniyr-n lai