KỸ THUẬT CHUYỂN MẠCH-NGUYỄN THỊ KIM CÔNG-VTO2B

7/29/2019 K THUT CHUYN MCH-NGUYN TH KIM CNG-VTO2B

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B THNG TIN V TRUYN THNG

TRNG C CNTT HU NGH VIT HNKHOA TIN HC NG DNG

N : K THUT CHUYN MCH TI: TM HIU V CNG NGH ATM

GVHD: Trn Th Tr Vinh

LP : CCVT02B

SVTH : Nguyn Th Kim Cng

Nng 12/ 2011


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C CNTT Hu Ngh Vit Hn Chuyn Mch ATM

LI NI U

Trong nhng nm gn y, h tng vin thng v ang pht trin nhanh chngc v cng ngh v chat lng dch v. Trong , cc h thng chuyn mch l thnhphn ct li vi phc tp bc nht, cc chc nng c thc hin bi h thngchuyn mch hay mt b phn cung cp cho khch hng, cng ngh hin i. K thutchuyn mch l mt trong nhng k thut nn tng trong cc mng truyn thng. S

pht trin ca chuyn mch lun gn lin vi s pht trin ca h tng mng. VitNam cng nh cc nc trn th gii , hin nay c nhiu nha khai thc vin thngkhac nhau vi s a dng ca cng ngh v cu hnh mng cng nh dch v cung cp.Qua nhiu nm, vic thit k h thng chuyn mch ngy cng tr nn phc tp hn cung cp cc phng tin b sung cho php cc mng c kh nng cung cp nhiu

dch v hn na ti khch hng v gip cho vic vn hnh cng nh bo dng trnn d dng hn.

H thng chuyn mch tr thnh mt phn phc tp nht , tp trung cao nhthm lng cng ngh hin i, hm lng cht xm v hm lng cc chc nng xl thng tin. c c cch nhn tng quan v vai tr v v tr v s pht trin ca hthng chuyn mch trong mng vin thng ni chung .

Hc tp v nghin cu mn hc k thut chuyn mch mang li cho sinh vinngnh in t vin thng c kin thc c s ca mt lnh vc k thut chuyn mchcng nh tip cn cc gii php k thut v cng ngh chuyn mch mi. l l do

em chn ti Cng ngh chuyn mch ATM.Ni dung gm c:

Chng I: Gii thiu c bn v h thng chuyn mch

Chng II: Trnh by mt s loi chuyn mch c bn trong h thngchuyn mch

Chng III:Trnh by v k thut ATM

Trong qu trnh lm em kh trnh khi mt s sai st v chun b kin thc cha cthc t nn mong gio vin v cc bn quan tm v gp cho bi lm c th honchnh hn.

Xin chn thnh cm n!

SVTH: Nguyn Th Kim Cng Trang ii


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MC LC

LI NI U ..................................................................................................... ii

MC LC ..........................................................................................................iii

DANH MC CC T VIT TT .................................................................viiiAAA ...................................................................................................................viii

Authentificaton ,Authorization and Accounting ...........................................viii

Nhn thc,cp php, tnh cc .......................................................................viii

ATM ..................................................................................................................viii

Asynchronous Transfer Mode .......................................................................viii

Phng thc truyn ti khng ng b .........................................................viii

ATDM ............................................................................................................... viiiAsynchronous Time Divission Multiplexing ..................................................viii

Ghp knh phn chia theo thi gian ng b ................................................viii

B-ISDN ..............................................................................................................viii

Integratited Service Digital network ..............................................................viii

Mch s tch hp a dch v bng rng .........................................................viii

CLP ....................................................................................................................viii

Cell Loss Priory ................................................................................................viii

u tin tn tht t bo .....................................................................................viii

CoS .....................................................................................................................viii

Class Of Service ................................................................................................viii

Lp dch v ......................................................................................................viii

CS .......................................................................................................................viii

Call Server ........................................................................................................viii

My ch cuc gi ..............................................................................................viii

DSLAM .............................................................................................................viii

Digital Subcriber Line Access Multiplexer ....................................................viii

B ghp knh truy cp DSL ...........................................................................viii

FCS ....................................................................................................................viii

Fast Circuit Switching .....................................................................................viii

Chuyn mch tc cao ..................................................................................viiiGFC ..................................................................................................................viii

SVTH: Nguyn Th Kim Cng Trang iii


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General Flow Control ......................................................................................viii

iu khin lung chung ...................................................................................viii

GMPLS ............................................................................................................. viii

Generalized Multi Protocol Label Switch ......................................................viii

Chuyn mch nhn a giao thc tng qut ..................................................viii

HEC ...................................................................................................................viii

Heacler Error Check ....................................................................................... viii

Trng kim tra li phn tiu ................................................................... viii

IP ........................................................................................................................viii

Internet Protocol ..............................................................................................viii

Giao thc internet ...........................................................................................viiiISO .....................................................................................................................viii

International Organization For Standardization ..........................................viii

T chc tiu chun quc t ..............................................................................viii

LAN ...................................................................................................................viii

Local Area network ......................................................................................... viii

Mng ni ht .....................................................................................................viii

NGN ...................................................................................................................viiiNext Generation ...............................................................................................viii

Mng th h sau ................................................................................................viii

OSI .....................................................................................................................viii

Open System Interconnection .........................................................................viii

M hnh kt ni m ..........................................................................................viii

PCI .....................................................................................................................viii

Protocol Control Information .........................................................................viii

Giao thc iu khin thng tin ...................................................................... viii

PSTN ....................................................................................................................ix

Public Switched Telephone network ................................................................ix

Mng chuyn mch in thoi cng cng ........................................................ix

PT .........................................................................................................................ix

Payload Type ......................................................................................................ixKnh ti tin .........................................................................................................ix

SVTH: Nguyn Th Kim Cng Trang iv


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PVC ......................................................................................................................ix

Permannent virtual circuit ................................................................................ix

Knh o cc nh ................................................................................................ix

QoS .......................................................................................................................ix

Quality Of Service ..............................................................................................ix

Cht lng dch v .............................................................................................ix

RIT .......................................................................................................................ix

Routing Information table ................................................................................ix

Bng nh tuyn .................................................................................................ix

STDM ..................................................................................................................ix

Synchronous Time Division Multiplexing ........................................................ixGhp knh theo thi gian ng b ....................................................................ix

SVC ......................................................................................................................ix

Switched Virtual Circuit ....................................................................................ix

Chuyn mch knh o ........................................................................................ix

TE .........................................................................................................................ix

K thut lu lng ............................................................................................ix

VC ........................................................................................................................ixVirtual Channel ..................................................................................................ix

Knh o ................................................................................................................ix

VCI .......................................................................................................................ix

Virtual Channel Identifier .................................................................................ix

Nhn dng knh o .............................................................................................ix

VPI .......................................................................................................................ix

Virtual Path Identifier .......................................................................................ix

Lung o ..............................................................................................................ix

VoiP .....................................................................................................................ix

Voice Over IP ......................................................................................................ix

Thoi trn nn giao thc internet .....................................................................ix

WDM ...................................................................................................................ix

Wavelength Division Multiplexing ...................................................................ixGhp knh theo bc sng ................................................................................ix

SVTH: Nguyn Th Kim Cng Trang v


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DANH MC HNH V BNG ..........................................................................x

........................................................................................................................xiv

CHNG I: GII THIU V K THUT CHUYN MCH .................. 1

1.1. Mt s khi nim c bn ...................................................................................1

1.1.1 nh ngha chuyn mch ........................................................................11.1.2 H thng chuyn mch ..............................................................................11.1.3 Phn loi chuyn mch ..............................................................................1

Hnh 1.1 Cc kiu chuyn mch c bn ..................................................................2

1.1.4 Cc thnh phn trong mng vin thng ......................................................3

Hnh 1.2. Cc thnh phn ca mng vin thng ....................................................3

1.2 Qu trnh pht trin ca k thut chuyn mch ............................................3

CHNG II: CC K THUT CHUYN MCH C BN ..................... 62.1 Chuyn mch knh .............................................................................................6

2.1.1 Gii thiu v chuyn mch knh ................................................................6

Hnh 2.1 Chuyn mch knh ........................................................6

2.1.2 nh ngha trng chuyn mch ..............................................................72.1.3 Phn loi chuyn mch knh .......................................................................72.1.4 Nu nguyn tc trng chuyn mch khng gian v thi gian ................8

Hnh 2.2 Chuyn mch khng gian ....................................8

Hnh 2.3 Cu to chuyn mch thi gian ...................................9

Hnh 2.4 Nguyn l chuyn mch thi gian T ...................................10

2.2 Chuyn mch gi ............................................................................................11

2.1.1 Gii thiu v chuyn mch knh ..........................................................11

Hnh 2.5: Nguyn l phn on v to gi ......................11

Hnh 2.6: Mng chuyn mch gi .........................................................................12

2.1.2 nh ngha chuyn mch gi ....................................................................12

2.2.3 C s k thut chuyn mch gi ................................................................132.2.4 Nguyn tc c bn ca chuyn mch gi ..................................................142.2.5 ng dng ....................................................................................................14

Chuyn mch gi c ng dng trong truyn d liu .....................................14

2.3 M hnh h thng m OSI ..........................................................................14

Hnh 2.7 M hnh phn lp OSI RM ......................................15

Hnh 2.8 Cc phng php chuyn mch c bn .................16

Hnh 2.9 ng gi d liu theo m hnh OSI .......................................................17

Hnh 2.10 Chuyn mch datagram v chuyn mch knh o ............................17

.......................................................................................................18

SVTH: Nguyn Th Kim Cng Trang vi


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CHNG III: CNG NGH CHUYN MCH ATM .....................18

3.1 Tng quan v cng ngh ATM ........................................................................18

3.1.1 S ra i ca ATM ...................................................................................18

3.2 Cc c im chnh ca ATM .......................................................................18

3.1.3 Khi nim ATM ........................................................................................18

Hnh 3.1 M t s bin i tr ca t bo ....................................20

3.1.5 Cu trc t bo ATM ................................................................................20

Hnh 3.2 Cu trc mt t bo ATM ...................................................................20

Hnh 3.3 Cu trc phn lp ATM .........................................................................21

Hnh 3.4 Cu trc tiu t bo ............................................21

....................................................................................................22

3.1.7 Cu trc phn lp ca ATM ...................................................................22

Hnh 3.5 M hnh phn lp OSI ...........................................................................23

3.1.8 K thut ghp knh trong ATM ................................................................23

3.3 c im k thut chuyn mch ATM ........................................................24

3.3.1 Nguyn tc nh tuyn trong chuyn mch ATM ..................................24

Hnh 3.7 Nguyn tc t nh tuyn ...............................24

Hnh 3.8 Nguyn tc bng iu khin ...................................................................25

3.3.2 Qa trnh chuyn mch v x l gi trong ATM ....................................253.3.3 Nguyn l hot ng ca chuyn mch ATM .........................................26

Hnh 3.9 Chuyn mch VP v VC .........................................................................27

3.4 ng dng v xu hng pht trin ...................................................................28

3.4.1 ng dng .................................................................................................28

Bng 3.1 S phn loi ca cc dch v ng dng truyn thng . .28

Bng 3.2 S phn loi ca cc dch v ng dng phn phi ............31

3.4.2 Xu hng pht trin ATM .........................................................................32KT KUN .......................................................... 34

SVTH: Nguyn Th Kim Cng Trangvii


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DANH MC CC T VIT TT

AAA Authentificaton ,Authorizationand Accounting

Nhn thc,cp php, tnh cc

ATM Asynchronous Transfer Mode Phng thc truyn ti khngng b

ATDM Asynchronous Time DivissionMultiplexing

Ghp knh phn chia theo thigian ng b

B-ISDN Integratited Service Digitalnetwork

Mch s tch hp a dch vbng rng

CLP Cell Loss Priory u tin tn tht t bo

CoS Class Of Service Lp dch v

CS Call Server My ch cuc gi

DSLAM Digital Subcriber Line AccessMultiplexer

B ghp knh truy cp DSL

FCS Fast Circuit Switching Chuyn mch tc cao

GFC General Flow Control iu khin lung chung

GMPLS Generalized Multi Protocol LabelSwitch

Chuyn mch nhn a giaothc tng qut

HEC Heacler Error Check Trng kim tra li phn tiu

IP Internet Protocol Giao thc internetISO International Organization For

StandardizationT chc tiu chun quc t

LAN Local Area network Mng ni ht

NGN Next Generation Mng th h sau

OSI Open System Interconnection M hnh kt ni m

PCI Protocol Control Information Giao thc iu khin thng tin

SVTH: Nguyn Th Kim Cng Trangviii


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PSTN Public Switched Telephonenetwork

Mng chuyn mch in thoicng cng

PT Payload Type Knh ti tin

PVC Permannent virtual circuit Knh o cc nh

QoS Quality Of Service Cht lng dch v

RIT Routing Information table Bng nh tuyn

STDM Synchronous Time DivisionMultiplexing

Ghp knh theo thi gianng b

SVC Switched Virtual Circuit Chuyn mch knh o

TE K thut lu lng

VC Virtual Channel Knh o

VCI Virtual Channel Identifier Nhn dng knh o

VPI Virtual Path Identifier Lung o

VoiP Voice Over IP Thoi trn nn giao thcinternet

WDM Wavelength DivisionMultiplexing

Ghp knh theo bc sng

SVTH: Nguyn Th Kim Cng Trang ix


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DANH MC HNH V BNG

LI NI U ..................................................................................................... ii

MC LC ..........................................................................................................iii

DANH MC CC T VIT TT .................................................................viii

AAA ...................................................................................................................viii

Authentificaton ,Authorization and Accounting ...........................................viii

Nhn thc,cp php, tnh cc .......................................................................viii

ATM ..................................................................................................................viii

Asynchronous Transfer Mode .......................................................................viii

Phng thc truyn ti khng ng b .........................................................viii

ATDM ............................................................................................................... viii

Asynchronous Time Divission Multiplexing ..................................................viii

Ghp knh phn chia theo thi gian ng b ................................................viii

B-ISDN ..............................................................................................................viii

Integratited Service Digital network ..............................................................viii

Mch s tch hp a dch v bng rng .........................................................viii

CLP ....................................................................................................................viiiCell Loss Priory ................................................................................................viii

u tin tn tht t bo .....................................................................................viii

CoS .....................................................................................................................viii

Class Of Service ................................................................................................viii

Lp dch v ......................................................................................................viii

CS .......................................................................................................................viii

Call Server ........................................................................................................viiiMy ch cuc gi ..............................................................................................viii

DSLAM .............................................................................................................viii

Digital Subcriber Line Access Multiplexer ....................................................viii

B ghp knh truy cp DSL ...........................................................................viii

FCS ....................................................................................................................viii

Fast Circuit Switching .....................................................................................viii

Chuyn mch tc cao ..................................................................................viii

GFC ..................................................................................................................viii

SVTH: Nguyn Th Kim Cng Trang x


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General Flow Control ......................................................................................viii

iu khin lung chung ...................................................................................viii

GMPLS ............................................................................................................. viii

Generalized Multi Protocol Label Switch ......................................................viii

Chuyn mch nhn a giao thc tng qut ..................................................viii

HEC ...................................................................................................................viii

Heacler Error Check ....................................................................................... viii

Trng kim tra li phn tiu ................................................................... viii

IP ........................................................................................................................viii

Internet Protocol ..............................................................................................viii

Giao thc internet ...........................................................................................viiiISO .....................................................................................................................viii

International Organization For Standardization ..........................................viii

T chc tiu chun quc t ..............................................................................viii

LAN ...................................................................................................................viii

Local Area network ......................................................................................... viii

Mng ni ht .....................................................................................................viii

NGN ...................................................................................................................viiiNext Generation ...............................................................................................viii

Mng th h sau ................................................................................................viii

OSI .....................................................................................................................viii

Open System Interconnection .........................................................................viii

M hnh kt ni m ..........................................................................................viii

PCI .....................................................................................................................viii

Protocol Control Information .........................................................................viii

Giao thc iu khin thng tin ...................................................................... viii

PSTN ....................................................................................................................ix

Public Switched Telephone network ................................................................ix

Mng chuyn mch in thoi cng cng ........................................................ix

PT .........................................................................................................................ix

Payload Type ......................................................................................................ixKnh ti tin .........................................................................................................ix

SVTH: Nguyn Th Kim Cng Trang xi


12/49


PVC ......................................................................................................................ix

Permannent virtual circuit ................................................................................ix

Knh o cc nh ................................................................................................ix

QoS .......................................................................................................................ix

Quality Of Service ..............................................................................................ix

Cht lng dch v .............................................................................................ix

RIT .......................................................................................................................ix

Routing Information table ................................................................................ix

Bng nh tuyn .................................................................................................ix

STDM ..................................................................................................................ix

Synchronous Time Division Multiplexing ........................................................ixGhp knh theo thi gian ng b ....................................................................ix

SVC ......................................................................................................................ix

Switched Virtual Circuit ....................................................................................ix

Chuyn mch knh o ........................................................................................ix

TE .........................................................................................................................ix

K thut lu lng ............................................................................................ix

VC ........................................................................................................................ixVirtual Channel ..................................................................................................ix

Knh o ................................................................................................................ix

VCI .......................................................................................................................ix

Virtual Channel Identifier .................................................................................ix

Nhn dng knh o .............................................................................................ix

VPI .......................................................................................................................ix

Virtual Path Identifier .......................................................................................ix

Lung o ..............................................................................................................ix

VoiP .....................................................................................................................ix

Voice Over IP ......................................................................................................ix

Thoi trn nn giao thc internet .....................................................................ix

WDM ...................................................................................................................ix

Wavelength Division Multiplexing ...................................................................ixGhp knh theo bc sng ................................................................................ix

SVTH: Nguyn Th Kim Cng Trangxii


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DANH MC HNH V BNG ..........................................................................x

........................................................................................................................xiv

CHNG I: GII THIU V K THUT CHUYN MCH .................. 1

1.1. Mt s khi nim c bn ...................................................................................1

1.1.1 nh ngha chuyn mch ........................................................................11.1.2 H thng chuyn mch ..............................................................................11.1.3 Phn loi chuyn mch ..............................................................................1

Hnh 1.1 Cc kiu chuyn mch c bn ..................................................................2

1.1.4 Cc thnh phn trong mng vin thng ......................................................3

Hnh 1.2. Cc thnh phn ca mng vin thng ....................................................3

1.2 Qu trnh pht trin ca k thut chuyn mch ............................................3

CHNG II: CC K THUT CHUYN MCH C BN ..................... 62.1 Chuyn mch knh .............................................................................................6

2.1.1 Gii thiu v chuyn mch knh ................................................................6

Hnh 2.1 Chuyn mch knh ........................................................6

2.1.2 nh ngha trng chuyn mch ..............................................................72.1.3 Phn loi chuyn mch knh .......................................................................72.1.4 Nu nguyn tc trng chuyn mch khng gian v thi gian ................8

Hnh 2.2 Chuyn mch khng gian ....................................8

Hnh 2.3 Cu to chuyn mch thi gian ...................................9

Hnh 2.4 Nguyn l chuyn mch thi gian T ...................................10

2.2 Chuyn mch gi ............................................................................................11

2.1.1 Gii thiu v chuyn mch knh ..........................................................11

Hnh 2.5: Nguyn l phn on v to gi ......................11

Hnh 2.6: Mng chuyn mch gi .........................................................................12

2.1.2 nh ngha chuyn mch gi ....................................................................12

2.2.3 C s k thut chuyn mch gi ................................................................132.2.4 Nguyn tc c bn ca chuyn mch gi ..................................................142.2.5 ng dng ....................................................................................................14

Chuyn mch gi c ng dng trong truyn d liu .....................................14

2.3 M hnh h thng m OSI ..........................................................................14

Hnh 2.7 M hnh phn lp OSI RM ......................................15

Hnh 2.8 Cc phng php chuyn mch c bn .................16

Hnh 2.9 ng gi d liu theo m hnh OSI .......................................................17

Hnh 2.10 Chuyn mch datagram v chuyn mch knh o ............................17

.......................................................................................................18SVTH: Nguyn Th Kim Cng Trangxiii


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CHNG III: CNG NGH CHUYN MCH ATM .....................18

3.1 Tng quan v cng ngh ATM ........................................................................18

3.1.1 S ra i ca ATM ...................................................................................18

3.2 Cc c im chnh ca ATM .......................................................................18

3.1.3 Khi nim ATM ........................................................................................18

Hnh 3.1 M t s bin i tr ca t bo ....................................20

3.1.5 Cu trc t bo ATM ................................................................................20

Hnh 3.2 Cu trc mt t bo ATM ...................................................................20

Hnh 3.3 Cu trc phn lp ATM .........................................................................21

Hnh 3.4 Cu trc tiu t bo ............................................21

....................................................................................................22

3.1.7 Cu trc phn lp ca ATM ...................................................................22

Hnh 3.5 M hnh phn lp OSI ...........................................................................23

3.1.8 K thut ghp knh trong ATM ................................................................23

3.3 c im k thut chuyn mch ATM ........................................................24

3.3.1 Nguyn tc nh tuyn trong chuyn mch ATM ..................................24

Hnh 3.7 Nguyn tc t nh tuyn ...............................24

Hnh 3.8 Nguyn tc bng iu khin ...................................................................25

3.3.2 Qa trnh chuyn mch v x l gi trong ATM ....................................253.3.3 Nguyn l hot ng ca chuyn mch ATM .........................................26

Hnh 3.9 Chuyn mch VP v VC .........................................................................27

3.4 ng dng v xu hng pht trin ...................................................................28

3.4.1 ng dng .................................................................................................28

Bng 3.1 S phn loi ca cc dch v ng dng truyn thng . .28

Bng 3.2 S phn loi ca cc dch v ng dng phn phi ............31

3.4.2 Xu hng pht trin ATM .........................................................................32KT KUN .......................................................... 34

SVTH: Nguyn Th Kim Cng Trangxiv


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CHNG I: GII THIU V K THUT CHUYN MCH

1.1. Mt s khi nim c bn1.1.1 nh ngha chuyn mch

Chuyn mch l mt qu trnh thc hin u ni v chuyn thng tin cho ngi sdng thng qua h tng mng vin thng. Chuyn mch trong mng vin thng baogm chc nng nh tuyn cho thng tin v chc nng chuyn tip thng tin. Nh vytheo kha cnh thng thng khi nim chuyn mch gn lin vi lp mng v lp lienkt d liu trong m hnh OSI ca t chc tiu chun quc t ISO.

1.1.2 H thng chuyn mch

Qu trnh chuyn mch c thc hin ti cc nt chuyn mch, trong mng chuynmch knh thng gi l h thng chuyn mch ( tng i) trong mng chuyn mchgi thng c gi l thit b nh tuyn ( b nh tuyn).

1.1.3 Phn loi chuyn mch

Xt v mt cng ngh, chuyn mch chia thnh hai loi c bn: chuyn mch knhv chuyn mch gi. Mt khc, chuyn mch cn c chia thnh bn kiu: chuynmch knh, chuyn mch gi v chuyn mch t bo

Cc khi nim c s v cng ngh chuyn mch c thc hin trong hnh 1.1(a,b,c0di y.

a) Chuyn mch knh: hai dng thng tin trn hai mch khc nhau

SVTH: Nguyn Th Kim Cng Trang 1


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b) Chuyn mch gi: cc tuyn ng c lp trn mng chia s ti nguyn

c) Chun mch gi knh o: cc gi tin i trn knh oHnh 1.1 Cc kiu chuyn mch c bn

Mng chuyn mch knh thit lp cc mch (knh)ch nh ring cho kt ni trckhi qu trnh truyn thng thc hin. Nh v, qu trnh chuyn mch c chia thnh3 giai on phn bit: thit lp, truyn v gii phng. thit lp, gii phng v iukhin kt ni (cuc gi) mng chuyn mch knh s dng cc k thut bo hiu thc hin. i ngc vi mng chuyn mch knh l mng chuyn mch gi, chia cclu lng d liu thnh cc gi v truyn i trn mng chia s. Cc giai on thit lp ,truyn v gii phng s c thc hin ng thi trong mt khong thi gian v

thng c quyt nh bi tiu gi tin.



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1.1.4 Cc thnh phn trong mng vin thng

L mt tp hp bao gm cc nt mng v cc ng truyn dn kt ni gia haihay nhiu im xc nh thc hin cc cuc trao i thng tin gia chng. Mngvin thng cung cp a dng cc loi hnh dch v vin thng cho khch hng, t dchv truyn thng nh in thoi, Fax, truyn s liu cho n cc dch v mi nhInternet, VOD, thng mi in t

Hnh 1.2. Cc thnh phn ca mng vin thng

Thit b u cui l cc trang b ca ngi s dng giao tip vi mng cungcp dch v. Hin nay c nhiu chng loi thit b u cui ca nhiu hng khcnhau ty thuc tng dch v (v d nh my in thoi, my fax.). Thit bu cui thc hin chc nng chuyn i thng tin cn trao i thnh cc tnhiu in v ngc li.

H thng chuyn mch l thnh phn ct li ca mng vin thng c chc nngthit lp ng truyn gia cc thu bao. Ty theo v tr ca h thng chuynmch trn mng ngi ta chia thnh tng i chuyn tip quc t, tng ichuyn tip lin tnh, tng i ni ht

Thit b truyn dn c s dng ni cc thit b u cui hay gia cc tng i vinhau v truyn cc tn hiu mt cch nhanh chng v chnh xc. Thit b truyn dnc phn loi thnh thit b truyn dn thu bao v thit b truyn dn chuyn tip ,ni gia cc tng i

1.2 Qu trnh pht trin ca k thut chuyn mch

Chuyn mch l qu trnh thc hin u ni tuyn lin lc gia hai thu bao (inthoi, my tnh, fax.) thng qua mt hay nhiu h thng. H thng c gi lchuyn mch. Khi nim chuyn mch thoi c ngay t khi pht minh ra my inthoi vo nm 1786, vo thi gian qu trnh thit lp tuyn ni c thc hin nhin thoi vin v ban u ni; hnh thc chuyn mch ny cn c gi l chuyn

mch nhn cng. Cng vi s pht trin cc ngnh cng nghip, tng i cng tngbc c ci tin v hon thin, t tng i nhn cng ln tng i t ng s dngc in, tng i in t v tng i in t SPC, tng i bng rng vv



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Tng i nhn cng u tin c a vo khai thc ti thnh ph NewHeivenebang Conneckticut (USA) vo nm 1878 ch sau 2 nm sng ch ra my in thoi caA.G Bell. T n nay, mng in thoi pht trin ht sc mnh theo nhu cuthng tin lien lc in thoi. Do vy rt nhanh chng tng i nhn cng t ti giihn kh nng ca n v tng t ng ha c anh em A.B.Strowger thc y

Tng i t ng do A.B.Strowger sang ch c tn gi l tng i c in h tng nc(th h 1) c a vo s dng nm 1892 trn c s b tm chn tng nc c anhem A.B.Strowger sang ch nm 1889. Tip nhm nng cao cht lng v kinh t,tng i R le (my th h 2), tng i ngang dc iu khin trc tip c sang chnm 1926 v vo nm 1938 tng i Crossbar-No1 vi phng php iu khin ghi

pht l tng i th h 3. Nhng tin b v thnh tu trong cng ngh in t v mytnh thc y tng ng dng vo lnh vc tng i in thoi. Qa trnh chuyni t chuyn mch in c sang chuyn mch in t (th h 4), c bit l tng is c c trng bi vic to ra h thng thng nht chuyn mch v truyn dnthng tin. Vo khong thp nin 60 ca th k 20, xut hin sn phm tng i in t

s l s kt hp gia cng ngh in t vi k thut my tnh. Tng i in t scng cng u tin ra i c iu khin theo chng trnh ghi sn SPC(StoredProgram Control), c gii thiu ti bang Succasunna, Newjersey, USA vo thng 5nm 1965. Trong nhng nm 70 hng lot cc tng i thng mi in t s ra i.

Mt trong nhng tng i l tng i E10 ca CIT-Alcatel c s dng tiLannion ( France). V thng 1 nm 1976 Bell gii thiu tng i in t s cngcng 4ESS. Hu ht cho n giai on ny cc tng i in t s u s dng hthng chuyn mch l s v cc mch giao tip thu bao thng l analog, cc ngtrung k l s. Mt trng hp ngoi l l tng i DMS100 ca Northern Telecoma vo nm 1980 dng ton b k thut s u tin trn th gii. H thng 5ESS cahang AT &T c a vo nm 1982 ci tin rt nhiu t h thng chuyn mch4ESS v c cc chc nng tng thch vi cc dch v ISDN. Sau hu ht cc hthng chuyn mch s u a ra cu hnh h tr cho cc dch v mi nh ISDN, dchv cho mng thng minh, v cc tnh nng mi tng thch vi s pht trin ca mngli. Vo nhng nm 1996 khi mng Internet tr thnh bng n trong th gii cngngh thng tin, n tc ng mnh m n cng nghip vin thng v xu hng hit cc mng my tnh, truyn thng, iu khin, vin thng tr thnh mt bi ton cngii quyt. Cng ngh vin thng ang bin i theo hng tt c cc loi hnh dch vhnh nh m thanh, thoi s c tch hp v chuyn mch qua cc h thng chuynmch. Mt mng c th truyn bng rng vi cc loi hnh dch v thoi v phi thoi,tc cao v m bo c cht lng phc v(QoS) thnh cp thit trn nn tngca mt k thut mi: K thut truyn ti khng ng b ATM v trn l cc ngdng cho thoi v phi thoi. Cc h thng chuyn mch in t s cng phi dn thayi theo hng ny cc tng i chuyn mch bng rng ra i. Hin nay rt nhiu cccu kin v thit b chuyn mch quang c nghin cu, pht trin v ctrin khai mt s nc trong tng lai khng xa cc h thng chuyn mch quang

bng rng s thay th cho h thng chuyn mch hin ti cung cp cc chuynmch tc cao v rng bng ln.

S khc bit ny bt u t nhng nm 1980, PSTN chuyn hng tip cn phng

thc truyn ti bt ng b ATM h tr a phng tin v QoS, sau chuynhng sang cng ngh kt hp vi IP chuyn mch nhn a giao thc hin nay.Trong khi Internet a ra mt tip cn hi khc so vi PSTN qua gii php trin



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khai kin trc phn lp dch v CoS (class of service) v hng ti m bo chtlng dch v QoS thng qua m hnh tch hp dch v IntServ v phn bit dch vDiffServ, cc chin lc ca Internet theo hng tng thch vi IP, mng quang vhng ti mng chuyn mch nhn a giao thc tng qut GMPLS (generalizedmultiprotocol label switch). Cng ngh chuyn mch nhn a giao thc MPLS ra i

vo nm 2001 l s n lc kt hp hai phng thc chuyn mch hng kt ni(ATM,ER) vi cng ngh chuyn mch phi kt ni (IP), cng ngh chuyn mch nhna giao thc MPLS nh ngha khi nim nhn (Label ) nm trn mt lp gia lp 2 v3 trong m hnh OSI, vi mc tiu tn dng ti a cc u im ca chuyn mch phncng (ATM, ER) l s mm do, linh hot ca cc phng php nh tuyn trong IP.Mt s quc gia c h tng truyn ti cp quang pht trin tt c xu hng s dngcc k thut chuyn mch quang v s dng cc cng ngh trn nn quang nhGMPLS, IP qua cng ngh ghp bc song quang WDM (wavelength divisionmultiplexing) , kin trc chuyn mch trong mng th h k tip NGN.



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CHNG II: CC K THUT CHUYN MCH C BN

2.1 Chuyn mch knh

2.1.1 Gii thiu v chuyn mch knh

y l phng php c s dng t lu trong mng in thoi PSTN. Ngy nayphng php ny vn c s dng trong mng ISDN. N s dng phng php ghpknh theo thi gian TDM. Trong thng tin trn 1 knh c truyn theo 1 chu ku n 125 Us 1 khe thi gian c nh, tp hp cc khe thi gian trong khong125Us to thnh 1 khung thi gian. Knh truyn trong mng chuyn mch knh lknh thc c thit lp trc khi yu cu thit lp cuc gi trong mng. Do

phng php ny thiu tnh mm do do thng tin phi truyn theo 1 tn s c nhdn ti gii hn v mt tc v khng thch hp cho vic truyn cc dch v bng

rng c c im khc nhau.

Hnh 2.1 Chuyn mch knh

khc phc s thiu mm do ca ch truyn n tc trong chuynmch knh ngi ta a ra h thng chuyn mch knh a tc MRCS (maltiratecircuit swiching). Cc ng ni trong MRCS c chia thnh n knh c bn gmkhung thi gian c di khc nhau, mi cuc lin lc c th xy dng t n knh ny.Thng thng cc knh c bn cho 1 cuc ni l:

+ Mt knh c tc l 1024Kbit/s

+ 8 knh H1 c tc l 2048Kbit/s

+ Mt knh H4 c tc l 139Kbit/s.

MRCS rt phc tp do mi knh c s ca 1 ng ni phi gi ng b vi ccknh khc nhau m bo tnh trong sut v mt thi gian. Ngoi vic s dng tinguyn chung ca MRCS khng t hiu qu: khi mi knh H1 bn th khng th


iu khin

Chuyn mch

i tng sdng

i tng sdng


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thip lp them 1 knh no khc trong khi c th H4 vn ri. Do vy y cha phi lgii php cho mng bng rng.

Cc ti nguyn trong h thng chuyn mch knh tc cao FCS (fast circuitswiching) ch c cung cp khi thng tin c gi i. Sau khi gi xong thng tin tinguyn c gii phng tr li. S cung cp ny c thit lp mi ln gi nh trongtrng hp chuyn mch gi nhng di s iu khin ca tn hiu bo hiu lin ktnhanh (fast associated signaling) ch khng nm trong chuyn mch gi.

Khi thit lp cuc gi ngi s dng yu cu rng ca bng tn bng snguyn ln rng bng ca knh c bn. H thng dlc ny cha cung cp tinguyn ngay m n ghi li cc thng tin v chuyn mch, thng tin v rng bngtheo yu cu, thng tin v a ch ca ch c chn. Khi bn pht bt u gi thngtin lc ny h thng bo hiu rng bn pht c thng tin c gi i yu cu chuynmch phn phi ti nguyn ngay lp tc. Qua y c th thy FCS kh phc tp vkhng thch hp cho B-ISDN v kh nng thit lp, hy b cuc ni v iu khin c

h thng rt phc tp , khng p ng c yu cu v mt thi gian.2.1.2 nh ngha trng chuyn mch

Chuyn mch knh c hiu l k thut chuyn mch m bo vic thit lpcc ng truyn dn dnh ring cho vic truyn tin ca mt qu trnh thng tingia hai hay nhiu thu bao khc nhau

.Chuyn mch knh c ng dng cho vic lin lc mt cch tc thi m qu trnh chuyn mch c thc hin mt cch khng to cm gic v s chmtr (tnh thi gian thc).

Chuyn mch knh tn hiu s l qu trnh kt ni, trao i thng tin cc khethi gian gia mt s on ca tuyn truyn dn TDM s.

2.1.3 Phn loi chuyn mch knh

Da vo dng tn hiu i qua trng chuyn :

+ Chuyn mch tong t

+ Chuyn mch s.

*Nhc im ca chuyn mch tng t

Trng chuyn mch c cu trc phn tng, nhiu tng nn qu trnh khai thc

s c tn tht ln,ng thi vic khc phc nh hng ln nhau gia cc phnt chuyn mch rt kh khn.

Tn hiu i qua trng chuyn mch b suy hao nhiu v suy hao ny rt khcnhau i vi cc tip im chuyn mch khc nhau.

Khng xc nh c tr thi gian cho tn hiu trong knh thoi khi quatrng chuyn mch.

Gy tp m ln

Trng chuyn mch cng knh v c gi thnh cao.

Cc nhc im ny s c khc phc khi s dng trng chuyn mch s.



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2.1.4 Nu nguyn tc trng chuyn mch khng gian v thi gian

a) Nguyn tc trng chuyn mch khng gian

.Cu to

+ Ma trn cc tip im sp xp thnh cc hng v cc ct.

Hnh 2.2 Chuyn mch khng gian

+Trng chuyn mch khng gian cho php chuyn mch t TSj ca PCM u voti TSj (cc TS cng ch s) ca mt PCM khc u ra.

+ lm c iu , cc ct nh iu khin ngi ta chia ra cc nh. Mi nh gn lin vi mt khe thi gian u vo. S th t ca n c nh s t 00 n31 nu cc tuyn PCM u vo l loi 32 khe thi gian.

+ tin hnh iu khin u ni cho mt tuyn u vo vi mt tuyn u ra no th cn phi thao tc tip im s tng ng l giao im ca hng v ct .

+ Mi tip im chuyn mch hng ct c a ch ha bi mt a ch nh phn.a ch ny c ghi b nh iu khin.

b) Nguyn tc trng chuyn mch thi gian

Cu to

+ B nh ting ni dng ghi tt c cc bt tin ca 1 khe thi gian no ca PCMv c cc tin vo 1 khe thi gian cn thit cho PCM.

+ B nh iu khin l iu khin qu trnh ghi c cc thng tin nh.



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+ hon thnh c cc nhim v trn th mi b nh pha c s khe thi gian cami tuyn PCM.

Hnh 2.3 Cu to chuyn mch thi gian

Nguyn l:

Trng chuyn mch thi gian tn hiu s thc hin qa trnh chuyn i ni dungthng tin t 1 khe thi gian khc, vi mc ch gy tr cho tn hiu. Qu trnh gy trtn hiu c thc hin theo nguyn tc trao i khe thi gian ni TSI. Trng chuyn

mch thi gian T c hai iu khin: iu khin u vo thc hin qu trnh ghi thngtin c iu khin v c ra tun t. iu khin u ra thc hin ghi thng tin tun t vc ra iu khin

Chuyn mch thi gian iu khin u vo

+ Khi b nh thoi SMEM l thit b ghi nh truy xut ngu nhin RAM (s lngngn nh: n; dung lng ngn nh: 8 bt). Nh vy b nh SMEM lu ton b thngtin trong mt khung tn hiu PCM. m bo tc lung thng tin qua trngchuyn mch, tc ghi c ca CMEM phi gp 2 ln tc lung trn tuyn PCMu vo hoc u ra.

+ Khi iu khin khu vc gm mt s khi nh: B nh iu khin CMEM lu trcc thng tin iu khin SMEM, s th t ca ngn nh v ni dung d liu trongCMEM th hin cc ch s khe thi gian TS cn trao i ni dung tin. TS.C nhn tnhiu t ng h h thng iu khin cc b chn SEL1,SEL2 nhm ng b haqu trnh ghi c thng tin d liu cho CMEM, SMEM.


Ting ni

iu khin

TSj

TSi TSiPCM vo

TSj

PCM ra


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Hnh 2.4 Nguyn l chuyn mch thi gian T

+ Theo nguyn tc ghi vo tun t, ni dung thng tin trong TS3 s c a vongn nh s 3. Vi yu cu chuyn i trn, h thng x l trung tm s chuyn thngtin ti CMEM thng qua ng d liu iu khin, b nh CMEM s lu ch s khe

thi gian TS3 ti ngn nh s 8. Con tr a ch ca CMEM s qut ln lt, ng bvi cc khe thi gian trn tuyn PCM, nh vy khi con tr a ch tr n ngn nh s8 trng vi thi im xut hin khe thi gian s 8 trong khung PCM. B chn SEL1 schuyn tn hiu c ti CMEM CMEM chuyn d liu iu khin ti SMEM,thngtin cn chuyn t CMEM ti SMEM trong trng hp ny l 3(0011) SEL2 acon tr a ch ti nh s 3, ng thi cp tn hiu iu khin c ra ni dung thngtin ti nh s 3 ca SMEM.

+ Nh vy ti thi im xut hin khe thi gian TS8, ton b ni dung thng tin caTS3 c chuyn qua trng chuyn mch. Qa trnh chuyn mch c lp li theo

chu k 125microgiay hnh thnh nn knh thng tin qua trng chuyn mch. Nucng vi yu cu chuyn mch t TS3 sang TS8 v trng chuyn mch hot ngtheo kiu ghi vo c iu khin v c ra tun t RWSR(random write sequence read)th ti ngn nh s 3 ca CMEM s lu thng tin a ch TS8.

+ Trng chuyn mch thi gian T mang tnh khng gian nu xt trn kha cnh v trkhng tin d liu trong cc ngn nh ca CMEM. Chuyn mch T lun gy tr tnhiu v tr ln khng vt qu mt khung PCM.

Chuyn mch thi gian iu khin u ra

+ iu khin u ra thc hin ghi thng tin tun t v c ra theo diu khin

+ Khi d liu c a vo TSj th dc ghi ti SMEMj v c c ti TSi no .

+ CMEM vn c ghi vo nh da vo nh ghi d liu voSVTH: Nguyn Th Kim Cng Trang10


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2.1.5 ng dng

Chuyn mch knh c ng dng trong thng tin thoi

2.2 Chuyn mch gi2.1.1 Gii thiu v chuyn mch knh

K thut chuyn mch gi ngy nay tr thnh mt k thut rt c tim nngv quan trng trong lnh vc Vin thng bi v n cho php cc ngun ti nguyn vinthng s dng mt cch hiu qu nht. Chuyn mch gi c th thch ng vi rt nhiukiu loi dch v v yu cu ca ngi s dng. Trn th gii ngy nay, mng chuynmch gi cng ang c pht trin rt mnh m v s dng ch yu cho cc dch vtruyn thng s liu gia cc my tnh. Tuy vy chuyn mch gi cng ang th hinhiu qu v tnh hp dn ca n cho cc dch v vin thng khc nh in thoi, Videov cc dch v bng rng khc.

Hnh 2.5: Nguyn l phn on v to gi

Nguyn l ca chuyn mch gi l da trn kh nng ca cc my tnh tc cao v cc cch thc tc ng vo bn tin cn truyn sao cho c th phn on cccuc gi, cc bn tin hoc cc giao dch (Transaction) thnh cc thnh phn nh gi lGi tin. Tu thuc vo vic thc hin v hnh thc ca thng tin m c th c nhiumc phn chia. V d mt cch thc hin ph bin c p dng ca chuyn mch gihin nay l bn tin ca Ngi s dng c chia thnh cc Segment (on) v sau cc Segment li c chia tip thnh cc gi (Packet) c kch thc chun ho. CcSegment sau khi c chia t Bn tin ca ngi s dng s c x l chun ho tip

bng cch dn u (Leader) v ui (Trailer), nh vy chng cha ba trng sliu l: u cha a ch ch cng cc thng tin iu khin m mng yu cu v dnh s th t ca Segment #, m knh Logic tch cc thng tin ngi s dng ghp knh, nh du Segment u tin v Segment cui cng ca bn tin v nhiuthng tin khc lin quan ti chc nng qun l v iu khin t u cui-ti-ucui.

i vi cc gi tin truyn qua mng chuyn mch gi cn phi cha cc muto khung nh du im u v im cui ca mi gi. Tiu (Header) ca gitng t nh u ca Segment, ngoi ra n cn c thm cc thng tin m mng yu

cu iu khin s truyn ti cu cc gi qua mng, v d nh thng tin cn b sungvo tiu ca gi l a ch ngun, a ch ch, s th t ca gi v cc khi s liuiu khin chng vng lp, qun l QoS, suy hao, lp gi v.v.SVTH: Nguyn Th Kim Cng Trang11

Transaction / Message c di L

u Trng tin CRC Trng tin c di ti M bit(M>=N)

Tiu Ti tin (Ti Nbit) CRC

To khung bt u To khung kt thc

Segment#1 Segment#2 .. Segment#n

Bn tin

Segment

Gi


26/49


Trng kim sot li CRC cho php h thng chuyn mch gi pht hin saili xy ra trong gi nu c, nh m bo yu cu rt cao v chnh xc truyn tin.

Tng s tin cha trong cc trng s liu u ca Segment v Tiu caGi l rt quan trng. Thng thng cc trng s liu ny c khong t 64 n 256

bit trong tng s N khong 1000 bit.

Hnh 2.6: Mng chuyn mch gi

Cc gi tin s c chuyn qua mng chuyn mch gi t nt chuyn mchny ti nt chuyn mch khc trn c s Lu m v pht chuyn tip, ngha l mint chuyn mch sau khi thu mt gi s tm thi lu gi mt bn sao ca gi vo bnh m cho ti khi c hi pht chuyn tip gi ti nt tip theo hay thit b u cuica ngi s dng c m bo chc chn. Bi v mi qu trnh thng tin c ct

nh thnh cc gi ging nhau nn cc bn tin d di hay ngn u c th chuyn quamng vi s nh hng ln nhau t nht v nh s chuyn ti cc gi qua mng cthc hin trong thi gian thc nn chuyn mch c th p ng c yu cu hotng mt cch nhanh chng k c khi c s thay i mu lu lng hoc khi c s c mt thnh phn khc ca mng.

Hnh 2.6 minh ho nguyn tc hot ng ca mng chuyn mch gi. Cc bntin ca ngi s dng t thit b u cui pht A s khng c gi i mt cch tc thv trn vn qua mng ti thit b u cui thu B nh trong mng chuyn mch bn tin,m s c ct v to thnh cc gi chun nt chuyn mch gi ngun PSW S. Mi

gi s c pht vo mng mt cch ring r c lp v chng s dch chuyn v ntchuyn mch gi ch PSW theo mt ng dn kh dng tt nht ti bt k thiim no, ng thi mi gi s c kim tra gim st li trn dc ng i.

2.1.2 nh ngha chuyn mch gi

L mt loi k thut gi d liu t my tnh ngun n my tnh ch qua mngdng mt loi giao thc tha mn 3 iu kin sau:

+ D liu cn vn chuyn chia nh ra thnh cc gi ( hay khung) c kch thc (size)v nh dng (format) xc nh.

+ Mi gi s c chuyn ring r v c th n ni nhn bng cc ng truyn(router) khc nhau. Nh vy chng c th dch chuyn trong vng thi gian.

SVTH: Nguyn Th Kim Cng Trang12

User A PSW

PSWS

User A


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+ Khi ton b cc gi d liu n ni nhn th chng s c hp li thnh d liuban u.

+ c im chnh ca chuyn mch gi l s dng phng php kt hp tuyn truyndn theo yu cu. Mi gi c truyn thng tin i ngay sau khi ng thng tintng ng ri. Nhu vy cc ng truyn dn c th phi hp s dng mt s ln ccngun tng i t hot ng.

2.2.3 C s k thut chuyn mch gi

K thut chuyn mch gi da trn nguyn tc chuyn i thng tin qua mng didng gi. Gi tin l thc th truyn thng hon chnh gm 2 phn: tiu mang ccthng tin iu khin ca mng hoc ngi s dng v ti tin l d liu thc cn chuynqua mng. Qa trnh chuyn thng tin qua mng chuyn mch gi c coi l mngchiua s ti nguyn. Cc gi tin s chuyn giao t cc nt mng ny ti cc nt mngkhc trong mng chuyn mch gi theo nguyn tc lu m v chuyn tip, nn mngchuyn mch gi cn c coi l mng giao trong khi mng chuyn mch knh c

coi l mng trong sut i vi d liu ngi s dng.Trn hng tip cn tng i n gin t kha cnh dch v cung cp , cc dch v

c cung cp trn mng vin thng chia thnh dch v thoi v dch v phi thoi,trong i din cho dch v phi thoi l dch v s liu. Chng ta hiu rng , s hav gi ha thoi l hai vn hon ton khc nhau. Trong mng chuyn mch inthoi cng cng PSTN hin nay tn hiu thoi c s ha , v k thut chuynmch truyn thng c p dng l k thut chuyn mch knh. D liu thoi chc gi l gi ha nu nhng gi ny c chuyn ti trn mng chuyn mchgi. Trong mc ny chng ta s xt nhng vn k thut chuyn mch c bn c

ng dng trong h thng chuyn mch: K thut chuyn mch knh v k thutchuyn mch gi. Mng in thoi cng cng c pht trin trn mng chuyn mchknh cung cp cc dch v thoi truyn thng. Cc mng d liu nh cc mng cc

b LAN, mng Internet l mng chuyn mch gi rt thch hp trao i d liu.

Bng 2.1 So snh mt s c im ca dch v thoi v d liu

c im Dch v thoi Dch v d liu

Bng thng

Bng pht bng thng

Nhy cm vi li

Pht li thng tin

tr

Kiu kt ni

C nh v thp(di 4kb)

Khng

Thoi li nu c li

Khng th thc hin c

Thp v n nh

Hng kt ni

Thay i

Ln(100/1000:1)

Khng cho php li

Thc hin d dng

Ln v c th thay i

C th l phi kt ni



28/49


Cc dch v thoi trong mng PSTN hin nay s dng k thut iu ch PCM vchim bng thng ln hn cho mi cuc gi th cht lng cuc gi thoi cng khngv th m tt hn. Tri li i vi cc dch v d liu bng thng rt quan trng. Mts ng dng i hi bng thng ti 1Gb/s hoc cao hn.

2.2.4 Nguyn tc c bn ca chuyn mch gi

Unicast v multicast: cc kt ni trong mng vin thng thng l cc kt ni imti im. V vy lu lng a vo mt u vo ca ma trn chuyn mch ch yu cuduy nht mt u ra. Tuy nhin cc ng dng nhue video/audio hi ngh hay qung bd liu li yu cu nhiu u ra ng thi. h tr chuyn mch a hng h thngchyn mch c b sung them c ch sao cho php d liu gia cc u vo v ura.

thng qua v tc ( speedup): thng qua ca trng chuyn mch c

nh ngha nh l t s ca tc u rat rung bnh trn tc u vo trung bnh khitt c cc u c lu lng chim 100% ti tc ng dy. thng qua catrng chuyn mch l dng v h hn bng 1.

Nghn v tranh chp u ra: vn tc nghn v tranh chp u ra thng xy ra ticc trng chuyn mch khng gian, i vi trng chuyn mch thi gian vn tcnghn c x l ti b ghp knh. Hin tng tc nghn c ng cc xung t khngt gii quyt ti cc v tr khc nhau ca trng chuyn mch. Tranh chp u ra xyra khi c nhiu hn mt yu cu u vo cng mun kt ni ti u ra cng mt thiim .

c tnh kt ni: mt quy trnh kt ni gm 3 giai on tch bit: thit lp kt ni,truyn thng tin v gii phng kt ni

2.2.5 ng dng

Chuyn mch gi c ng dng trong truyn d liu

2.3 M hnh h thng m OSI

Trong khong nhng nm 70, cng nghip my tnh bt u pht trin rt mnh vnhu cu kt ni thng tin qua mng tng ln rt nhanh. Cc h thng my tnh cn traoi thng tin qua rt nhiu hnh thi khc nhau ca mng. H thng m ra nhm tiu

chun ha cho tt c cc u ni gi l m hnh kt ni h thng m OSI.Mc tiu m hnh OSI l m bo rng bt k mt x l ng dng no u khng

nh hng ti trng thi nguyn thy ca dch v hoc cc x l ng dng giao tiptrc tip vi cc h thng my tnh khc trn cng lp (nu cc h thng cng c htr theo tiu chun OSI). M hnh OSI cung cp mt khung lm vic tiu chun chocc h thng. Cu trc phn lp c s dng trong m hnh l c 7 lp, c th phnloi thnh 2 vng chnh.



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Hnh 2.7 M hnh phn lp OSI RM

+ Lp thp cung cp cc dch v cu cui ti u cui p ng phng tin truyns liu, cc chc nng hng v pha mng t lp 3 ti lp 1.

+ Lp cao cp cc dch v ng dng p ng truyn thng tin, cc chc nng hngv ngi s dng t lp 4 n lp 7.

M hnh OSI c th chia thnh 3 mi trng truyn dn

+ Mi trng mng: lin quan ti cc giao thc , trao i cc bn tin v cc tiu chun

lin quan ti cc kiu mng truyn thng s liu khc nhau.+ Mi trng OSI: cho php them vo cc giao thc hng ng dng v cc tiuchun cho php cc h thng kt cui trao i thng tin ti h thng khc theo hngm.

+ Mi trng h thng thc: xy dng trn m hnh OSI v lin quan ti c tnh dchv v phn mm ca ngi sn xut, n c pht trin thc hin nhim v x lthng tin phn tan strong thc t.

Nhng mi trng ny cung cp nhng c tnh sau:

+ Giao tip gia cc lp .


Lp ng dng

Lp mng

Lp trnh din

Lp phin

Lp truyn ti

Lp mng

Lp lin kt d liu

Lp vt l Lp vt l

Lp lin kt d liu

Lp mng

Lp truyn ti

Lp phin

Lp trnh din

Lp lin kt dliu

Lp vt l

Lp ng dng

NODE

H thng A H thng B

Giao thc


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+ Chc nng ca cc lp, giao thc nh ngha tp hp ca nhng quy tc v nhngquy c s dng bi lp giao tip vi mt lp tng ng tng t trong h thngt xa khc.

+ Mi lp cung cp mt tp nh ngha ca dch v ti lp k cn.

+ Mt thc th chuyn thng tin phi i qua tng lp.Cc chc nng chi tit ca cc lp c nh ngha trong tiu chun OSI 7498 v

chun X.200 ca ITU-T. Cc c tnh c bn c tm tt nh sau:

+ c tnh hng kt ni yu cu cc giai on kt ni phn bit gm: thit lp ktni, truyn thng tin v gii phng kt ni. Mt kiu kt ni khc i ngc vi kiuhng kt ni l kiu phi kt ni. Phi kt ni cho php cc thc th hin trong cc tiu thc th thng tin.Cc giai on kt ni nh trong chuyn mch knh khng cn tnti m thay vo l phng php chuyn theo mt giai on duy nht gm c 3 giaion.

S khc bit gia chuyn mch bn tin v chuyn mch gi nm ti qu trnh x l bntin, chuyn mch gi thc hin vic phn on bn tin thnh cc thc th ph hp ving truyn v cu hnh mng, cc gi c th c kch thc thay i hoc c nh,

phng php chuyn mch vi cc gi c kch thc c nh c gi l chuyn mcht bo. Nh vy mt bn tin ngi dng c th phn thnh nhiu gi. Sau qu trnhchuyn mch cc gi s c ti hp hon nguyn li thng tin ca ngi s dng.

Hnh 2.8 Cc phng php chuyn mch c bn

K thut chuyn mch gi cho php kt ni thng tin t u cui qua qu trnh chias ti nguyn, s dng cc tp th tc v cc kt ni c tc khc nhau truyn ccgi tin v c th chuyn gi trn nhiu ng dn khc nhau. C hai kiu chuynmch gi c bn: chuyn mch data gram DG v chuyn mch knh o VC (virtualcircuit).


Thi gian

Thit lp

Truyn

Thi gian

Gii phngThit lp+truyn+gii phng

Tr hng i

Tr truyn lan

Thi gian gi

Thit lp+truyn+gii phng

a) chuyn mch knh b) chuyn mch bn tinc) chuyn mch gi


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Hnh 2.9 ng gi d liu theo m hnh OSI

Chuyn mch datagram: chuyn mch datagram cung cp cho cc dch v khngyu cu thi gian thc. Vic chuyn gi tin ph thuc vo cc giao thc lp cao hocng lin kt d liu. Chuyn mch kiu datagram khng cn giai on thit lp ktni v rt thch hp i vi dng d liu c lu lng thp v thi gian tn ti ngn.

Chuyn mch knh o: yu cu giai on thit lp tuyn gia thit b gi v thit bnhn thng tin, mt knh o c hnh thnh gia thit b trong ng dn chuyn

mch; knh o l knh ch c xc nh khi c d liu truyn qua v khng ph thucvo logic thi gian.

Hnh 2.10 Chuyn mch datagram v chuyn mch knh o



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CHNG III: CNG NGH CHUYN MCH ATM

3.1 Tng quan v cng ngh ATM3.1.1 S ra i ca ATM

ATM phng thc truyn ti khng ng b, cung cp cc dch v bng rng tnglai.

ATM ln u tin dc nghin cu ti trung tm nghin cu CNET (ca francetelecom) v Bell Lads vo nm 1983, sau tip tc pht trin ti trung tm nghincu Allatebell t nm 1984. Cc trung tm ny tch cc nghin cu nhng nguyn lc bn v gp tch cc trong cng vic thit lp cc tiu chun u tin v ATM.

Hin nay cng ngh ATM pht trin ti kh hon ho v n nh. Cng ngh

ny c nghin cu v trin khai ti nhiu nc trn th gii. Nhiu mng ATM c trin khai, bc u cung cp dch v bng rng vi khch hng. Vic ngdng cng ngh ATM vo mng vin thng c bt u vo nm 1990.

ATM l s kt hp ca cng ngh truyn dn v cng ngh chuyn mch qua mnggiao tip chun, da vo cng ngh ATM phn chia v ghp ting ni, s liu, hnhnh. Vo trong mt khi c chiu di c nh gi l t bo.

3.2 Cc c im chnh ca ATM3.1.3 Khi nim ATM

ATM l phng thc truyn khng ng b k thut chuyn mch gi cht lngcao. C phng thc truyn ti nh hng, chuyn gi nhanh da trn ghp khngng b phn chia thi gian.

ATM kt hp tt c nhng li th ca k thut chuyn mch trc y vo mtk thut truyn thng duy nht. S dng cc gi c nh gi l cc t bo, n c thtruyn ti mt hn hp cc dch v bao gm thoi, hnh nh, s liu, c th cung cpcc bng thng theo yu cu. ATM c th loi tr c cc nt c chai thng xyra cc mng LAN v WAN hin nay.

3.1.4 Cc c im ca ATM

ATN truyn theo phng thc khng ng b, tc l cc thng tin c truyn tu pht n u thu mt cch khng ng b v c th hin nh sau: thng tin xuthin ti u vo ca h thng c np vo cc b m, sau chng c chia nhthnh cc t bo v truyn ti qua mng. ATM c hai c im quan trng l:

+ Th nht: ATM s dng cc gi c kch thc nh v c nh gi l t bo ATM(ATM cell), cc t bo nh cng vi tc truyn ln s lm tr truyn v bin ngtr gim nh i vi cc dch v thi gian thc. Ngoi ra kch thc nh cng sto iu kin cho vic hp knh tc cao c d dng hn.

+ Th 2: ATM cn c mt c im rt quan trng l nhm mt vi knh o thnh

mt ng o nhm gip cho vic nh tuyn c d dng.



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Phng thc truyn ti trong ATM gn ging vi phng thc chuyn mch gi. Vn c mt s c im khc so vi chuyn mch gi nh sau:

+ ph hp vi vic truyn tn hiu thi gian thc thi th ATM phi t tr nh, tc l cc t bo phi c di ngn hn cc gi thng tin trong chuyn mchgi.

+ Cc t bo c on mo u nh nht nhm tng hiu qu s dng v cc ngtruyn c tc rt cao.

+ m bo tr nh th cc t bo c truyn nhng khong thi gianxc nh, khng c khong trng gia cc t bo.

+ Trong ATM th t cc t bo bn pht v bn thu phi ging nhau ( m bonht qun v th t ).

Nhng c im ny gip mng ATM c s mm do v linh hot v n c th to ras tng thch v mt tc truyn ca cc t bo (tc ca thng tin) v tc ca

thng tin c to ra (tc thay i ngun tn hiu).ATM c th iu khin tt c cc kiu lu lng: voice, audio, video, text, data.,

c ghp knh v chuyn mch trong mt mng chung. Trong mng ATM rngbng c th gn li trong thi gian thc cho bt k kiu lu lng khc nhau no theoyu cu, c th thy y l mt cng ngh cho mi mi trng LAN, GAN,PSTN.y l nguyn nhn ni bt lm cho ATM c la chn lm cng nghchuyn mch v truyn dn chung cho cc dch v trong mng B-ISDN.

Cc tnh nng u Vit ca ATM v mi trng ATM l:

+ Ghp knh khng ng b (ATDM) v thng k cho mi kiu lu lng.

+ Gn rng knh rt linh hot v mm do.

+ Gim cc mng ring

+ Chp nhn mng hin c nh kt ni chng vi mng ATM mi.

+ Tc truy cp cao( 155Mbt/s-16g]Gbt/s)

Tit kim gi thnh OA&M ( operation administrantion and maintenance) nh cngngh cao v ng nht.

Bn cht ca ATM l lin kt truyn cc t bo vi cc thng tin c to ra v

ATM cung cp kh nng ghp knh thng k vi ng truyn. Do trong ATM tn dng c dung lng truyn dn trong cc thi im c hot ng thp cangun thng tin vi thay v truyn i cc t bo khng c ch , l cc t bo truyni trong khong thi gian ny, s c cc ngun thng tin khc nhau c thay th.Trong trng hp ny, s c nhiu ngun thng tin khc nhau c thay i (VBR)truyn i trn cng mt ng truyn th kh nng ghp knh thng k l rt cao.

T bo ATM c kch thc c nh v kt hp vi ghp knh, gip cho vic t hpnhiu ngun tn hiu khc nhau trn mt ng truyn c d dng, t cc nhkhai thc c th cung cp nhiu dch v cho khch hng trn cng mt ng truyn.

Tuy nhin ATM khng phi khng c nhc im:+ Thi gian t hp t bo v tr bin ng t bo.



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+ Tr bin ng t bo sinh ra bi cc gi tr tr khc nhau ti nhng im chuyn mch vcc thit b tch/ghp knh, n n khong cch cc t bo b thay i. Trong tn hiu thoi

b nh hng rt nhiu nu xy ra tr ny.

Hnh 3.1 M t s bin i tr ca t bo

3.1.5 Cu trc t bo ATMCu trc t bo ca mt ATM

Phn tiu Header Section

Phn mang thng tin dch v Information Section

52

53

Hnh 3.2 Cu trc mt t bo ATM

c im ca ATM l hng lin kt nn khc nhau vi chuyn mch gi l ach ngun, ch v s th t cc gi tin l cn thit. ATM cng khng cung cp c chiu khin lung gia cc nt mng nhng c kh nng nhm mt vi knh o thnhmt ng o nhm gip cho vic nh tuyn c d dng hn. V vy chc nng c

bn ca phn tiu trong t bo ATM l nhn dng c cc ni o.

Da vo cu trc phn cp ca ATM theo s :


Tr ca mng Gi tr tr tng Gi tr tr gim

1

2345

6

8 7 6 5 4 3 2 1


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Hnh 3.3 Cu trc phn lp ATM

Tng ng vi hai cp giao din trn, ngi ta a hai dng cu trc phn tiu tng ng:

+ Cu trc phn tiu giao din gia ngi s dng v mng UNI

+ Cu trc phn tiu giao din gia nt mng NNI

Hnh 3.4 Cu trc tiu t bo


GFC VPI

VPI VCI

VCI

VCI PT CLP

HEC

Phn mang thng tin ca ngi sdng

VPI

VPI VCI

VCI

VCI PT CLP

HEC

Phn mang thng tin ca ngi sdng

Bt 8 7 6 5 4 3 2 1

Bt 8 7 6 5 4 3 2 1

1

2

3

4

5..53

byte

1

2

3

4

5..53

byte

u trc t bo ATM ti UNICu trc t bo ATM ti NNI

Mng cng

cng

Mng ring Mng ring

Mng cng

cng

Cc trm ktcui s dng

Cc trm ktcui s dng

Cc trm ktcui s dng

Cc trm ktcui s dng

NNI

UNI

Giao din gia cc nt mng

Giao din mng- khchhng


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ngha cc trng trong phn tiu .

+ GFC (general flow control) l trng iu khin lung chung. Trng ny chdng cho giao din UNI trong cu hnh im im, c di gm 4 bt, trong 2

bt dng iu khin v 2 bt dng lm tham s. C cu ny c tiu chun ha.+ VPI (virtual path identifier) v VCI (virtual channel identifier) l hai trng nh

tuyn cho t bo trong qu trnh chuyn mch.

- Vi UNI th c 8 bt VPI v 16 bt VCI.

- Vi NNI th c 12bt VPI v 16 bt VCI.

Hai trng ny ghi nhn dng lung o v knh o. c tnh c bn ca ATM lchuyn mch xy ra trn c s gi tr trng nh tuyn:

+ Mch xy ra trn VPI th gi l kt ni ng o

+ Nu chuyn mch xy ra trn VPI v VCI th gi l kt ni knh o.- PT (payload type ) l trng ti thng tin xc nh xem t bo ny mang thng tinkhch hng hay thng tin iu khin. N cng xc nh qu ti ca t bo thng tinkhch hng. Trng ny c c hai giao din v di 3 bt.

- CLP (cell loss prioryti ) l trng u tin b t bo dng ch ra kh nng cho phphoc khng cho php b cc t bo khi c hin tng qu ti xy ra.

+ Nu cc t bo c CLP =0 th mc u tin cao.

+ Nu cc t bo c CLP = 1 th c mc u tin thp.

Trng ny ch nhn hai gi tr 0 v 1 nn c di 1 bt v tn ti c hai giaodin.

- HEC ( heacler error check) l trng kim tra li phn tiu . Trng ny c di8 bt. N dng pht hin li ghp bt v sa li cho ng cc li ghp bt n .Cng vic ny c thc hin lp vt l.

3.1.7 Cu trc phn lp ca ATM

Theo m hnh tham chiu lin kt h thng m OSI (open system interconnection)ca t chc tiu chun ha quc t ISO (international standard organization). Mi h

thng m u c cc h thng con c sp xp theo th t.Mt PDU lp N bao gm thng tin iu khin giao thc PCI (protocol controlinformation) lp N v s liu t lp N+1 thng tin iu khin trao i gia cc thcth lp N.



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Lp cao nht

Lp N+1

Lp N

Lp N-1

Lp thp nht

Hnh 3.5 M hnh phn lp OSI3.1.8 K thut ghp knh trong ATM

Nhc im c bn ca STM l lng ph kh nng truyn ti ca h thng v kh xl ng thi tt c cc dch v yu cu (thm ch khng th x l c) c tc dng

bt rt khc nhau.

Kho st s b k thut dng trong ch truyn ti ng b STM l k thut ghpknh theo thi gian ng b STDM (synchronous time division multiplexing). STDMthc hin ghp knh ng b vi ng b h thng v cc khung tn hiu phi b trsp xp theo mt th t c nh lp li theo mt chu k hon ton xc nh bi ngh h thng.

Mi khe thi gian Tsi ca khung c gn cho knh lin lc c nh trong sut thigian ca qu trnh thng tin, do vy thng xy ra lng ph ngun ti nguyn v knh gn dnh ring cho mt qu trnh thng tin th cho d n khng c s dng (khikhng c thng tin truyn ) cng khng th dng cho cc qu trnh thng tin khc.

Khc vi ch ghp knh ng b, trong k thut ghp knh khng ng b ATDM(asynchronous time division multiplexing) khng cn nhim v gn khe thi gian choqu trnh thng tin c th na m c c bt k khe thi gian no ri th ATDM ghpgi cn truyn vo. Ni cch khc ATDM thc hin k thut ghp knh thng k,ngha l cc gi tin chun ca ngun tin c th ghp vo ng thi nhiu khe thi gianc ch s khe khc nhau v do vy ATDM t c mc mm do, linh hot, hiuqu cao so vi nhiu kiu dch v , mi tc bt v kiu lu lng khc nhau.

Gii php kt hp cc u im, khc phc cc nhc im ca k thut chuynmch knh v chuyn mch gi, s dng ATDM s c kh nng p ng tt cc yucu trong B-ISDN l vn ch yu ca cng ngh truyn ti khng ng b ATM.

Thut ng truyn bao gm c truyn dn v chuyn mch trong mng , mng ATMc kh nng ch gi s liu lin quan ti mt cuc ni khi n c thc s c s liu cn


.. ..

ng truyn vt l

H thng A H thng B


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truyn v khng c khe thi gian gn ring cho cuc ni . iu ny hon ton khcso vi c ch ng b khi ng vi cuc ni cn phi c khe thi gian dnh ringxc nh, v my thu STM khng th khi phc c thng tin cha trong cc khe thigian khc.

3.3 c im k thut chuyn mch ATM3.3.1 Nguyn tc nh tuyn trong chuyn mch ATM

C hai phng thc nh tuyn c s dng trong chuyn mch ATM lnguyn tc nh tuyn dng bng nh tuyn v t nh tuyn.

Theo nguyn tc ny: vic bin dch VPI/VCI cn phi thc hin ti u vo caccas phn t chuyn mch sau khi bin dch xong t bo s c thm phn m rng

bng mt nh danh ni b th hin rng x l tiu ca t bo. Tiu mi cat bo c t trc nh ni dung ca bng bin dch, vic tng thm tiu t bo y yu cu tng thm tc n b ca ma trn chuyn mch. Ngay sau khi t bo

c nh danh ni b, n c nh hng theo nguyn tc t nh hng. Mi cucni t u vo ti u ra c mt tn ni b nm trong ma trn chuyn mch xc nh.Trong cuc ni a im VPI/VCI c gn tn ni b nhiu chuyn mch do ckh nng cc t bo c nhn bn v nh hng ti cc ch khc nhau ph thucvo tn c gn.

Hnh 3.7 Nguyn tc t nh tuynQuy tc gn tiu cho t bo:

VPI/VCI = VPI/VCI mi + nh danh ni b.

- Nguyn tc bng nh tuyn

Theo nguyn tc ny, VPI/VCI trong tiu t bo c bin dch ti mi phn tchuyn mch thnh mt tiu mi v m s cng u ra thch hp nh mt bngnh tuyn gn vi phn t chuyn mch ny. Trong giai on thit lp cuc ni, nidung ca bng c cp nhp.


B nh tuynPhn tchuynmch tnhtuyn

Phn tchuynmch tnhtuyn

Bng

A B,n,m

B n B m


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Hnh 3.8 Nguyn tc bng iu khin3.3.2 Qa trnh chuyn mch v x l gi trong ATM

Giao thc ATM tng ng vi lp 2 nh nh ngha trong m hnh tham chiu (OSI)cc h thng m. ATM l kt ni c hng, mt kt ni cui- cui cn c thit lptrc khi nh tuyn cc t bo ATM. Cc t bo c nh tuyn da trn hai gi trquan trng cha trong 5 byte mo u t bo : nhn dng lung o(VPI) v nhn dngknh o (VCI) , trong mt lung o bao gm mt s cc knh o. S cc bt dnhcho VPI ph thuc vo kiu giao din. nu l ngi s dng (UNI), gia ngi sdng v chuyn mch ATM u tin, 8 bt dnh cho VPI. iu ny c ngha l c ti28= 256 lung o sn c trong im truy cp ngi s dng. Mt khc nu n l giaodin node mng (NNI), gia cc chuyn mch trung gian ATM, 12 bt s dnh cho

VPI. iu ny cho thy c 2+^= 4096 lung o c th c gia cc chuyn mch ATM.Trong c UNI v NNI, c 16 bt dnh cho VCI. V th c 216= 65536 knh o cho milung

S kt hp c VPI v VCI to nn mt lin kt o gia hai u cui. thay v c cngVPI/VCI cho ton b lung nh tuyn, VPI/VCI c xc nh trn mi lin kt cs thay i vi mi chuyn mch ATM. Mt cch c th, ti mi lin kt vo nmt node chuyn mch, mt VPI/VCI c th c thay th bng mt VPI/VCI khcti u ra bng s tham chiu ti bng gi l bng nh tuyn trong hcuyeenr mchATM. Vi bng nh tuyn mng ATM c th tng s lng cc ng nh tuyn.

Mi chuyn mch ATM c mt bng nh tuyn cha t nht cc trng sau :VPI/VCI c v VPI/VCI mi, a ch cng u ra v u tin. Khi mt t bo ATMn ng u vo ca chuyn mch n b chia thnh 5 byte mo u v 48 byte titrng.

Bng cch s dng VPI/VCI cha trong phn mo u nh gi tr VPI/VCI c ,chuyn mch tm trong bng nh tuyn VPI/VCI mi ca cc t bo ang i n.Khi tm thy gi tr VPI/VCI c s c thay th bng VPI/VCI mi. Hn na ach cng u ra tng ng v trng u tin c nh km trong 48byte ti trngtrc khi n c gi i n kt cu chuyn mch. a ch cng u ra ch ti cngu ra no m t bo c nh tuyn. C 3 kiu nh tuyn trong kt cu chuyn

mch: ch unicast l ch m mt t bo c nh tuyn ti mt s cc cng ura xc nh, multicast l ch mt t bo c nh tuyn ti mt s cng u ra v


Bng nh tuyn Phntchuynmch

Bng nhtuyn

Phntchuynmch

BngA Bm B Cn

B m B n


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broadcast l ch mt t bo c nh tuyn ti tt c cc cng u ra. Trng utin cho php chuyn mch truyn cc t bo mt cch c la chn ti cc cng u rahay loi chng khi b m y, ty theo yu cu dch v.

Cc kt ni ATM c thit lp trc hoc thit lp mt cch linh ng theo bo hiuc s dng, ging nh bo hiu UNI v bo hiu nh tuyn gioa din mng-mngring(PNNI). Thit lp trc c tham chiu ti cc kt ni o c nh (PVCs), thitlp linh ng c tham chiu ti cc kt ni o chuyn mch(SVCs). Vi cc SVCs

bng nh tuyn c cp nhp bi b x l cuc gi trong sut qu trnh thit lpcuc gi. Qu trnh thit lp cuc gi s tm c mt ng nh tuyn ph hp giangun v ch. VPI/VCI ca mi ng dn dc theo tuyn , cc a ch cng u raca b chuyn mch v trng u tin c xc nh v c b x l cuc gi invo bng. B x l cuc gi phi m bo rng ti mi chuyn mch VPI/VCI ca t

bo ang dn t cng u vo khc nhau c cng mt cng u ra l khc nhau. Michuyn mch ATM c mt b x l cuc gi.

3.3.3 Nguyn l hot ng ca chuyn mch ATMTa xt mt v d ng ng ca ATM cung cp dch v cho ngi dng. Thu bao

ATM c th nhn c dch v bng hai cch sau:

+ Qua knh o c nh PVC (permanent virtual circuit)

+ Qua knh o chuyn mch SVC(switched virtual circuit)

a) PVC: knh o c nh

Cc thnh phn c bn bao gm PABX l tng i ATM dng ring h tr chocc dch v in thoi. Router l b nh hng dng kt ni cc mng LAN qua

mng chuyn mch. MUX thc hin chc nng ghp knh cc t bo ATM. Ngiiu hnh mng ( network operator) c chc nng h tr cho vic thit lp/gii phngcc knh o c nh.

Vic thit lp knh PVC theo th tc sau tng t nh knh cho thu:

+ Thu bao gi nh cung cp yu cu knh PVC

+ Thu bao a a ch ch, tc bt yu cu v thi gian s dng.

+ in thoi vin a cc thng tin ny qua thit b kt thit lp knh tng tnh in thoi vin bnh thng.

+ Knh ni c thit lp+ Thu bao tr tin theo quy nh thu knh hay theo chi tit cuc gi

Nh vy i vi hnh thc PVC tng t nh th tc thu knh truyn thng nh n

- C u im sau:

+ Gn nh thi gian thc

+ rng bng theo u cu

+ Khng c th tc thit lp cuc gi

+ Nailed-up connection ngha l lun lun c mch ni gia cc im yu cu+ D m rng hay gii phng ng ni cui



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b)SVC: knh o chuyn mch

i vi phng thc ny khi cuc gi thit lp gi tr mc nh hoc theo nnglc hay gn tc l 64kb/s v ngay khi cuc gi thit lp mch s c gn chongi dng v dnh ring cho ngi dng (in thoi thng thng) ti ATM hub(trung tm ATM), n thch ng vi cc thng tin cha trong phn ti

Thu bao ch gi nhc my v quay s cuc gi hng ti ATM hub ( trung tmATM), n thch ng vi cc thng tin bo hiu t bo ATM. ATM hub kim tra tc bt yu cu, dng cc thng tin cha trong phn ti tin ca t bo ATM. Cc t boATM bo hiu qua mng ti ch thit lp ni. Khi t bo ti ch, ATM hub phach s gi t bo ngc li vi cc thng tin v knh o thit lp knh ni. Khi cct bo ny ti ch gi, ATM hub gn cho cc t bo gi tr VCI thch hp v mng

by gi bit nh tuyn c th th no. Khi thit lp ni xong tin ca ngi dng trongt bo cha VPI/VCI. Khi pht t bo ATM bo hiu t ch gi c cha a ch ch.Ti cc tng i ATM pht cc t bo ny theo kiu qung b. Ti cc ddicha chng

c kim tra, nu chng ch thc s th ch s pht ngc li. Trn ng i s gncc gi tr VPIi/VCIj v a vo phn ti tin ca t bo ATM. T bo no tr v thubao ch gi u tin chnh l ng i ngn nht.

c) chuyn mch VP v VC

Ti mt s nt chuyn mch vic bin dch VPI c thc hin cng vi vic bindch to nn s thay i ca VPC v VCI.

Hnh 3.9 Chuyn mch VP v VC

Dy cc t bo ATM c m bo cho mi VCC trong phm vi cng mt VPC.Cc tham s QoS nh: tc tn tht t bo, bin thin tr t bo. S c m

bo cho mi VCC. Ti thi im thit lp VCC cc tham s lu lng khch hng sc xc nh qua s tha hip giuqax mng v khch hng v sau mng s gimst cc tham s .

Tng t nh i vi cc kt ni o VCC, cc kt ni o VPC c th c dng chovic truyn thng tin gia khch hng vi khch hng, gia khch hng vi mng,



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gia mng vi khch hng. Vic thit lp v gii phng VPC c thc hin bng ccth tc qun l mng, ph thuc vo vic cc VPC s c gn hoc c cung cpkhi c nhu cu. Khi vic thit lp v gii phng cc VPC theo nhu cu c cmng hoc khch hng thc hin.

3.4 ng dng v xu hng pht trin3.4.1 ng dng

Da trn ITU-T I.211 cc dch v ng dng ATM c phn loi mt cch rng rithnh dch v truyn thng v dch v phn phi. Cc dch v truyn thng li cchia nh thnh dch v tng tc qua li, dch v kiu thng bo v dch v phc hitrong khi cc dch v phn phi c chia nh thnh nhng dch v m ngi sdng c th iu khin v nhng dch v m ngi s dng khng th iu khin.

Bng 3.1 S phn loi ca cc dch v ng dng truyn thng

Dch v Kiu thngtin Cc dch v mu Cc mu ng dng

Dch vtng tcqua li

Hnh nh vchuyn ngm thanh

in thoi truynhnh bng rng

Gio dc, mua bn, qun l t xa

Hi ngh truynhnh bng rng

Gio dc, mua bn, qun l t xa

Gim st hnhnh

Bo v cc ta nh, canh phnggiao thng

Dch v truynthng tin bnghnh nh, tingni

Truyn dn tn hiu TV, mthoi bng m thanh v truynhnh

m thanh

d liu

Chng trnh am thanh

Truyn dn a ngn ng, achng trnh

Truyn dn thng

tin s tc caokhng b gii hn

Truyn dn tc cao gia cc

LAN/MAN, truyn dn tranhtnh,CAD/CAM

Truyn dn file Truyn dn file d liu

X l t xa tc cao

iu khin thi gian thc,chung, kim tra t xa.

Sao chp t xa Truyn dn vn bn, hnh nh,



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tc cao hnh v

Ti liu Dch v lin lcbng hnh nhprecession

Cc hnh nh c bit, cc nh yhc

Dch v lin lcbng ti liu

Thng tin c s dng didng hn hp

Dch vkiu thng

bo

Hnh nhchuyn ngv m thanh

Dch v th tnbng truyn hnh

Video/audio P.O.I in t

Ti liu Dch v th tnbng ti liu

P.O.I in t i vi thng tindi dng hn hp

Cc dchv phchi

Vn bn, dliu, hnh v,nh tnh, nhchuyn i

Vn bn truynhnh bng rng

Vn bn truyn hnh bao gm nhchuyn ng,gio dc, mua bn,qun co, khi phc tin tc t xa

Dch v khiphc hnh nh

Gii tr, hc tp, gio dc, t xa,

Dch v khiphc hnh nhcht lng cao

Gii tr, hc tp, gio dc, t xa,lin lc bng hnh nh c bit,nh y hc

Dch v khiphc ti liu

Khi phc ti liu c bit ttrung tm thng tin

Dch v khiphc ti liu txa

Phn mm t xa

VDT

Ngi ta p dng dch v VDT, dch v c gi tr then cht c bsung v man truyn thng bng rng cho cc thu bao ti nh.

Dch v ny cho php lu gi cc chng trnh truyn hnh nh phim truyn,phim ti liu, cc chng trnh th thao v trm thu truyn hnh di dng s nnv cung cp mt lot dch v m khch hng yu cu thng qua mng ATM/B-ISDN, do ngi s dng c th la chn, thc hin, iu khin, khi phc vt cu hi cho chng trnh.

Dch v CATV v truyn hnh cho thue bao s c thay th bi dch v mngt nhn ny, dch v m ngi ta ch i rng n s nhanh chng tr thnh dch vmng cng cng.



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Dch v bo tang /th vin in t

Dch v ny cho php bn c s dng d liu ca cc th vin hoc bo tangdi hnh thc a phng t nhng trm thng tin a phng tin, ni m d liuc lu tr. Dch v ny c thit lp u tin bi cc trng i hc, cc th

vin cng cng v cc vin nghin cu mt cch ring bit, sau c a raphc v rng ri tng bc mt bi qu trnh tp trung cng vi mng.

Dch v mua hng t xa

Dch v ny cho php ngi s dng c th mua sn phm trn u cui aphng tin thng qua nhng danh mc hoc nhng ca hng o c lu gi dihnh thc a phng tin ti nh hoc vn phng. u tin dch v ny c trinkhai rt chm chp xung quanh mt s ca hng

KỸ THUẬT CHUYỂN MẠCH-NGUYỄN THỊ KIM CÔNG-VTO2B

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