1

CHNG 1: GII THIU TNG QUAN V TNG I IN

T S

Trong mng mng vin thng cc h thng chuyn mch c gi l tng i, c tng

i ni ht, tng i chuyn tip ni hat, tng i chuyn tip vng, tng i cng quc t,

trn nn mng Internet h thng chuyn mch c gi l b nh tuyn( router). H thng

chuyn mch PSTN, NGN cung cp n ngi dng cc nhu cu v dch v trong mng vin

thng theo xu hng pht trin n nn tng bng rng.

1.1. GII THIU H THNG CHUYN MCH TRONG MNG VIN THNG

1.1.1 Cu trc c bn ca mng vin thng

Mc tiu pht trin mng vin thng l cung cp cc loi hnh dch v in thoi,

Fax, truyn s liu, truyn hnh, dch v Internet, thng mi in t cho khch hng. Mng

vin thng l tp hp cc nt mng, nt mng l tp im kt ni thu bao u cui, gia

cc nt mng c kt ni bng truyn dn, chc nng chnh ca cc thnh phn c gii

thiu nh sau:

Hnh 1.1 Cc thnh phn ca mng vin thng

Thit b u cui: Thit b u cui ca ngi s dng giao tip vi nhau thng qua mng

cung cp dch v, nh my in thoi, my fax, my tnh c nhn, tng i thu bao, my ghi

pht hnh, pht thanh, knh s liu.

H thng chuyn mch: H thng chuyn mch l tp hp cc nt kt ni mng thu bao

ngi dng, c chc nng thit lp ng truyn gia cc thu bao. H thng tng i c

phn cp thnh tng i chuyn tip quc t, tng i chuyn tip lin tnh v tng i ni ht,

trong mng internet c gi l cc b nh tuyn (router) ngoi vi, b nh tuyn li.

H thng truyn dn: H thng truyn dn bao gm thit b v ng truyn dn ni cc

thit b u cui, hoc kt ni gia cc tng i vi nhau, bao gm h thng truyn dn cp

kim loi, cp ng trc, cp si quang, truyn dn v tuyn sng ngn, vi ba, truyn dn v

tinh.

My Fax

Thit b

chuyn mch

u cui d liu

in thoi

V tinh

truyn thng

Thit b u cui

in thoi

ng truyn dn Thit b chuyn

mch Thit b

u cui

My Fax

My tnh

2

1.1.2 Phn cp mng vin thng

Hip hi vin thng quc t ITU chun ha mng chuyn mch knh PSTN thnh

cc loi:

- Tng i cng quc t : l cc tng i cng (gateway) ca cc nc thc hin cc

kt ni quc t.

- Tng i chuyn tip ng di: l cc tng i toll, chuyn tip cc kt ni lin

lc gia cc khu vc trong mi quc gia.

- Tng i chuyn tip ni ht: l cc tng i Tandem, chuyn tip cc kt ni

lin lc gia cc tng i ni ht trong mt khu vc.

- Tng i ni ht: l cc tng i Local ni trc tip mng thu bao u cui.

hnh 1.6: V tr ca tng i trong mng PSTN

Hip hi vin thng quc t ITU pht trin h thng mng NGN trn nn chuyn

mch gi, trong cc thit b nh tuyn Router c phn chia thnh cc lp mng ring v

lin kt vi nhau theo cc chun giao din. Mng NGN s dng cng ngh chuyn mch mm

bao gm cc b iu khin cng phng tin MGC (Media Gateway Controller), b iu

khin kt ni lin lc (Call Agent), v cc thit b nh tuyn Router.

3

hnh 1.8: Cu trc mng NGN

1.2. QU TRNH PHT TRIN CA H THNG CHUYN MCH

Nm 1786, pht trin my in thoi ca A.G Bell, nm 1878, pht trin tng i nhn

cng u tin s dng ti thnh ph NewHeivene bang Conneckticut (USA), qu trnh thit

lp cuc gi c thc hin nh in thoi vin v bn u ni.

Nm 1889, hai anh em A.B Strowger sng ch b tm chn tng nc, nm 1892 pht trin tng i c in t ng tng nc (th h 1) c a vo s dng trn mng in thoi, tip l pht trin tng i Rle (th h 2), tng i ngang dc iu khin trc tip c sng ch nm 1926 v vo nm 1938 pht trin tng i Crossbar-No1, vi phng php iu khin ghi pht v c gi l tng i th h 3. Nm 1960, pht trin tng i in t s l s kt hp gia cng ngh in t vi k thut my tnh, c gi l tng i th h 4, tng i in t s c iu khin theo chng trnh ghi sn SPC (Stored Program Control), c s dng ti M (USA) vo nm 1965

T n nay, mng in thoi pht trin ht sc nhanh chng da theo nn tng s,

nm 1970, pht trin tng i E10 ca CIT Alcatel c s dng ti Php (France), nm

1976, hng in thoi Bell gii thiu tng i in t s cng cng 4ESS, c tnh chung

ca cc tng i in t s giai on ny u s dng h thng chuyn mch in t s v cc

mch giao tip thu bao Analog, cc ng trung k l s.

Nm 1980, pht trin tng i s vi cc giao din s DMS100 ca Northern Telecom

v hng AT&T a vo nm 1982, cung cp cc dch v, dch v ISDN cht lng cao

Nm 1990, mng Internet pht trin theo din rng, to ra hiu ng trin bng n pht

trin mng vin thng trn ton th gii theo xu hng hi t tch hp cc mng my tnh,

truyn thng, iu khin, trong tt c cc loi hnh dch v hnh nh, m thanh, thoi s

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c tch hp v chuyn mch qua cc h thng chuyn mch bng rng v m bo c

cht lng phc v(QoS).

Nm 1995, pht trin k thut truyn ti khng ng b ATM, truyn ti cc ng

dng cho thoi v phi thoi trn nn h thng chuyn mch mm, chuyn mch gi bng rng

ra i.

Sau nm 2000, trn th gii nghin cu v trin khai th nghim h thng chuyn

mch quang, v trong tng lai khng xa cc h thng chuyn mch quang bng rng s thay

th cho cc h thng chuyn mch hin ti cung cp cc chuyn mch tc cao v

rng bng ln.

TM TT CHNG 1

H thng chuyn mch c gi l tng i, v phn thnh cc cp : tng i ni ht,

tng i chuyn tip ni hat, tng i chuyn tip vng, tng i cng quc t, trn nn mng

Internet h thng chuyn mch gi c gi l b nh tuyn( router).

Mng vin thng l tp hp cc nt mng, nt mng l tp im kt ni thu bao u

cui, gia cc nt mng c kt ni bng truyn dn.

Mng NGN pht trin trn nn chuyn mch gi, trong cc thit b nh tuyn

Router c phn chia thnh cc lp mng ring v lin kt vi nhau theo cc chun giao din

Nm 1786, pht trin my in thoi, nm 1878, pht trin tng i nhn cng, nm

1892 pht trin tng i c in t ng, nm 1970, pht trin tng i in t s, nm 1990,

pht trin mng Internet, mng vin thng trn ton th gii pht trin theo xu hng hi t

tch hp tt c cc loi hnh dch v hnh nh, m thanh, thoi trn nn chuyn mch gi.

5

CHNG II: TNG I IN T S (DSS)

Trong mng chuyn mch in thoi cng cng, h thng chuyn mch c gi l tng

i, tng i c phn chia theo cc cp: tng i chuyn tip quc t, tng i chuyn tip

lin tnh, tng i chuyn tip ni ht v tng i ni ht. Sau nm 1980, tng i in t s

c a vo s dng rng ri trn mng vin thng ca cc nc. Ni dung ca chng s

gii thiu v cu trc tng i in t s; ting trnh thit lp kt ni cuc gi qua cc h

thng tng i DSS.

2.1 GII THIU TNG I IN T S (DSS)

Tng i in t s u tin thc hin cc kt ni theo chng trnh ghi sn SPC, m

ng cho vic pht trin cc tng i in t s, s dng h thng chuyn mch s v cc

mch giao tip thu bao thng l Analog, cc ng trung k l s v sau pht trin thnh

tng i in t s DSS, tng thch vi cc dch v thoi, dch v ISDN.

c im chung ca tng i in t s l s dng c trong mng chuyn mch ni ht, ng di, v quc t; c dung lng thu bao ln, nhiu ng trung k, c thng lng Erlangs cao, p ng c gn 100% cc cuc gi.

H thng iu khin s dng ngn ng lp trnh l Assembler, C hay CHILL, cu trc

phn h chuyn mch bao gm chuyn mch thi gian T, chuyn mch khng gian S, hay

chuyn mch ghp khng gian thi gian TST. Thch ng c vi cc loi giao tip thu

bao s v cc ng trung k s theo chun Bc M (1.544, 6,312, 44,736, 274,176 Mbps)

hay CEPT (2,048, 8,448, 34,364, 139,764Mbps).

H thng bo hiu tng i bao gm bo hiu thu bao, bo hiu lin i

Cht lng dich v m tng i cung cp phi phi tt th hin r, chnh xc, lun

nhn c tn hiu mi quay s, khng b ngt cuc gi khi ang m thoi, an ton v tin

cy cao, t h hng. Theo khuyn ngh ITU, mt tng i ch c php ngng hot ng

nhiu nht 2 gi trong sut thi gian lm vic, thi gian lm vic ca tng i t 20 n 30

nm.

Ngoi ra yu cu cc tng i phi c cc chng trnh h tr thch ng vi vic vn

hnh bo dng, qun l lu lng v tnh cc, d dng s dng cc dch v, gi thnh h v

d dng pht trin m rng trong tng lai.

2.2. S KHI TNG I IN T S

2.2.1. TNG I IN T SPC

Tng i in t s iu khin theo chng trnh ghi sn SPC (Stored Program Control) c cu trc nh hnh v 2.1. bao gm cc khi chc nng nh sau:

6

Tr-ng

chuyn mch

B x l

trung tm

Cc b /k

Module

-ng dy

Module

trung k

Module

-ng dy

Module

trung k

Li vo Li ra

I

C

I

C

Cc b /k

SC SC

Hnh 2.1 M hnh h thng chuyn mch in hnh

B chuyn mch: Gm cc b chuyn mch khng gian v thi gian, c chc nng

chuyn thng tin ca cc knh ng vo n ng ra khi c ue6u cu kt ni lin lc.

B iu khin: Gm c cc b vi x l trung tm v vi x l ngoi vi, ci t sn

chng trnh iu hnh, iu khin vic u ni s liu qua trng chuyn mch, v vn

hnh v bo dng h thng tng i in t s. i vi cc b vi x l th cp thc hin

chc nng h tr cc khi thit b ngoi vi theo lnh iu khin t b x l trung tm.

B giao tip IC: B giao tip IC th chin vic ghp v phn chia cc knh d liu gia

tc thp v tc cao theo chun ho cc lung s liu trc khi a vo trng chuyn

mch.

B giao tip ng dy thu bao v trung k: B giao tip ng dy thu bao v

trung k thc hin chc nng lin kt vi mng thoi ngoi vi v thc hin qu trnh bin i

cc tn hiu khc nhau thnh dng tn hiu chun truyn n trng chuyn mch.

B cung cp m hiu SC: B cung cp m hiu SC c chc nng cp m hiu bo hiu

cho ton h thng thu bao v tng i, bao gm cc bo hiu cho ng dy thu bao v bo

hiu cho ng dy trung k v bo hiu cho khi iu khin tng i.

2.4. TNG I IN T DSS

Tng i in t s DSS l s ci tin tng i SPC thch ng cho cc h thng

chuyn mch dung lng cao v cung cp dch v theo hng bng rng, cu trc tng i

in t s c th chia thnh 6 khi chnh nh sau: Khi chuyn mch SWNS; Khi kt ni

ng dng APS; Khi x l trung tm CPS; Khi iu khin ngoi vi PCS; Khi bo hiu

SIGS; Khi bo dng O&MS.

7

M

D

FSLC

SLC

TSAC

DL

CD

DGT

MF

SW-CRG

AT

AT

TM

DDF

TDNW

DTI

DTI

PCM

Distributor Scanner Marker

BT

CSS CAS

CC MM

IOC MMI

OMC External Mem

VDUOA&MS

CPS

PCS

SWNSAPS

SiGS

Sign Link

Subcribers

Trunks

System BUS

AUX equips

Hnh 2.2 S ca mt tng i in t s ni ht

2.4.1. Khi chuyn mch SWNS

Khi chuyn mch s c xy dng trn nn tng cu trc cc b chuyn mch khng

gian, chuyn mch thi gian v kt hp chuyn mch ghp TST. Chc nng ca khi chuyn

mch l thc hin vic kt ni vi cc cng ng vo v ng ra khi x l cuc gi v h tr

cho cc cuc gi a ng. Tn hiu truyn dn trn cc knh ngi dng c th l tn hiu

thoi hoc s liu xuyn qua h thng chuyn mch, u c x l vi chnh xc cao, i

vi cc knh s liu c th iu chnh tc truyn ton tc hoc bn tc nhm cn bng

lu thoi. ng thi, khi chuyn mch cn phn phi tn hiu ng h, tn hiu ng b v

h tr o lng v bo dng

2.4.2. Khi giao tip kt ni mng ng dng APS

Khi kt ni ng dng APS l cc kt ni vt l giao tip kt ni h thng chuyn mch

s vi cc khi giao tip ng dy thu bao analog, ng dy thu bao s, ng trung k

s v cc khi giao tip vi cc mng chuyn mch khc. ng thi APS cn h tr trao i

thng tin bo hiu gia tng i vi mng vin thng v h tr cc chc nng vn hnh v

bo dng OA&M, chc nng ca APS c m t theo tng b phn giao tip nh sau:

1. Khi giao tip ng dy thu bao analog.

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PABX

MDF

Thu bao th-ng

-ng dy CO line

Thu baocng cng

SLC

SLC

SLC

TS

AC

DTG

MF

Ti chuyn mch

SW-CD

LC

D

Hnh 2.3 Giao din ng dy thu bao Analog

Gi nhp i hay cn gi l gi phi dy chnh MDF.

L trang thit b thc hin kt ni vt l cc ng dy ngoi vi ti cc mch trong h

thng tng i in t s. MDF cha cc module gn kt pha ng dy thu bao l cc

phin dc trn c cha cc cu ch bo an, pha mch ng dy c u ni ti phin

ngang v gia phin dc v phin ngang c h thng dy nhy. H thng MDF cho php to

iu kin d dng, thun tin cho vic u ni v bo dng mng cp ngoi vi v mng cp

ni i, ng thi ti y thc hin cc bin php bo an cn thit cho con ngi vn hnh

khai thc h thng nh chng st, chng in p cao v dng in mnh nh cc b phng

in v cu ch, cun nng.

Vi mch gn khe thi gian TSAC

C nhim v to ra mt khong thi gian trn trc thi gian thc s dng cho mi mt

thu bao. Cc khe thi gian c ch s ny s c s dng trong sut qu trnh xy ra mt

cuc gi, v s dng cho cc cuc gi khc trong cc khong thi gian khc nng cao hiu

sut thit b. Thng thng cc knh 64Kb/s t mi thu bao c ghp knh thnh lung tc

cao hn gm 24 knh hoc 32 knh hng ti b tp trung thu bao DLCD

Thit b b tp trung ng dy s DLCD

Kt hp chc nng tp trung cc knh thng tin to thnh lung d liu tc cao hn

vi chc nng chuyn mch phn lu lng lung d liu nng cao hiu sut thit b. Trong

mt s tng i in t s DLCD c th thc hin nhim v chuyn mch cho cc thu bao

trn cng mt nhm, nhm gim ti cho trng chuyn mch chnh ca h thng tng i. B

tp trung ng dy s c iu khin bi b iu khin chuyn mch cc b SW-C. i

khi trn cc b tp trung thu bao cn c cc thit b ph tr s dng cho cc qu trnh thit

lp tuyn ni v giao tip vi thu bao. Nh qu trnh gi v tch cc tn hiu iu khin , to

m bo, nhn xung a tn vv.vv.

Thit b thu pht xung a tn MF.

Thc hin trao i thng tin bo hiu vi thu bao, l cc bo hiu trong bng nn cc

tn hiu ny c m ho di dng s v c gi trn tuyn thoi.

B to tone s DGT

9

Cc m bo, bn tin thng bo c s ho v thc hin u ni mt chiu ti cc thu

bao yu cu, mi bn tin s nm trn mt khe thi gian v tuyn thoi ny cng l tuyn thoi

mt chiu ti thu bao.

Mch ng dy thu bao SLC

L ni kt cui cho mt thu bao hay mt nhm thu bao, thc hin chc nng giao tip

gia tng i v cc thit b ngoi vi v cc phng din tn hiu gm c bo hiu gia thu

bao v tng i. Cc chc nng ch yu ca mch ng dy thu bao c th hin qua

nhm t vit tt cc ch ci u BORSCHT.

T R O B S H

LF

LF

COD

DEC

T

S

A

C

B iu khin

T SLC khc

Ti SLC khc

Ti SLC khc

Ti SLC khc

BUS kim tra

BUS chung

BUS ngunn cc SLC

SLC

Hnh 2.4 S khi chc nng ca BORSCHT

- Chc nng cp ngun

Cc thu bao s dng cc thit b u cui th ng cn c ngun nui do tn hiu thoi

to ra t micro rt nh v s b suy hao trn ng truyn t thu bao ti tng i. Ngi ta

thc hin bin php khuych i tn hiu m tn bin iu bng ngun mt chiu, v i ph

vi s tht thot khc nhau xut hin do chiu di ng dy. Dng in chy xuyn qua thit

b u cui s dng ph thuc vo in p ca tng i cung cp v tr khng mch vng

ng dy thu bao. Tr khng mch vng ng dy thu bao bng tng tr ri trn dy

thu bao v chnh thit b u cui. Di cng tc ca in tr vng thu bao c thit lp bi

yu cu cp ngun ca my u cui, nhy ca thit b, v tht thot truyn dn cho php.

Cc gi tr mch vng thng thng l t 1250 Ohm 1800 Ohm v suy gim cho php ti

tn s trung tm thoi 1KHz l 8dB ( chun USA).

m bo ti u vo tn hiu c mt gi tr danh nh i vi tt c cc thu bao

xa v gn u nh nhau . ( 1000Hz , 0dBm). Ngun in p cung cp n nh i vi tng i

ni ht l 48V, hay dng cung cp n nh trong khong 20mA-100mA. Cc h thng cp

ngun cho ng dy thu bao c chiu dng in p cp u t nhm trnh s n mn

in ho v xuyn m.

- Chc nng bo v qu p

Bt k loi tng i in t s no u yu cu s bo v trnh in p v cc in p

cao nguy him tc ng ti h thng chuyn mch v ngi qun l h thng. Mi thit b

bn dn u hot ng vi mt in p gi l in p danh nh. Nu hin tng tng p xy

ra ng thi vi qu trnh lm vic ca thit b, s xy ra hng hc. Chc nng bo v qu p

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(O) bo v mch in thu bao khi cc in p nguy him nh st n t ng dy thu bao

hay nh hng ca s phn phi in nng .

Bin php bo v

- Cu ch ti gi phi dy.

- Cc mch ngt in t nhy cao 0.03micro giy cho in p > in p danh nh

100% - 200%.

- Cc by in p nhm ngn mch xung t.

- Bo v thnh nhiu lp.

- Cp chung RING

Mt ngun in xoay chiu hot ng theo ch ngn hn lp li cn c p dng

vo mt ng dy thu bao rung chung bo hiu cho thit b u cui thng thng tun

theo cc thng s tiu chun c bn sau:

in p : 70 Vms - 110 Vms

Dng in: 50 mA - 100mA

Tn s : 25 Hz , 20 Hz , 50 Hz ..

Thi gian : dng 4giy v ngt 2 giy .

Mt s c im cp chung thit b u cui : c quy nh bi tng tr khng i

vi dng in xoay chiu : Z = Zc + Zr . Khi xut hin dng mt chiu do thu bao nhc

my, tn hiu chung lp tc c ngt lp tc bt k lc no trong khong c dng (ng) v

khng c dng chung(ngt).

- Gim st:

Gim st trng thi mch vng ng dy. i vi thu bao Analog vic gim st c

thc hin bng cch o dng in mt chiu DC trong mch vng ng dy thu bao. Khi

thu bao t my mch vng dng in mt chiu h mch. Khi thu bao nhc my , mch

vng DC ng kn do s c dng in DC cng khong 20-100mA.

- M ho v gii m: Nguyn l M ha/Gii m c trnh by k trong mn hc K thut

chuyn mch I

- Chuyn i 2 dy thnh 4 dy:

Tuyn thoi trong h thng chuyn mch s gm 4 dy, bin i 2 dy-4 dy c

thc hin u ni cho thu bao 2 dy. S chuyn i c thc hin qua bin p sai ng hay

h thng khuych i nhm m bo s n nh mch 4 dy v trit ting di Echo trn c

hng i v hng v. Bin php s dng cho cc b trit di l s dng tht thot thch hp

trn ng dn, tht thot ti thiu gia hai u dy theo yu cu m bo d n nh l

3dB, cung cp mt bin n nh 6dB trn vng. Tuy nhin i vi cc cuc gi quc t th cn

c n nh qua mng s ln hn. Mch in sai ng tch ring hng thu v hng pht

ca tn hiu ting ni tng t. ln ca tn hiu c th iu chnh c hng thu v

pht mt cch c lp.

- Kim tra

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Mt yu cu c bn cho bt k h thng tng i in t s ni ht no l kh nng

kim tra ca mi ng dy thu bao. S t chc o kim th ng dy thu bao l khc

nhau vi mi loi tng i nhng vn theo cc nguyn tc c bn sau:

- Qu trnh kim tra c th thc hin t ng hoc nhn cng.

- Thit b kim tra c th truy xut n bt k mt ng dy no trong khi o kim.

- Thit b kim tra c th nm trong h thng tng i hoc c lp vi h thng tng

i in t s.

Chc nng kim tra ny thc hin kim tra tuyn thoi trn ng dy hoc trong h

thng chuyn mch. Qua im truy nhp kim tra, ng dy c u ti thit b kim tra

ngoi v tuyn thoi trong c u ti thit b kim tra trong.

+ Kim tra ngoi

Kim tra ngoi bao gm trng thi ng/m mch vng, chp ng dy, in tr

ng dy, in p ngoi, trng thi u ni v trng thi bn. Kim tra cht lng ng dy

thu bao qua cc thng s : in tr , dng d ( T- R - Mass ) .

Mt s tiu chun ca thit b u cui Analog : R = ( 600 - 1999 ) ; C = (0.18 F -

0.38 F ) Dng d = 0.005 mA . Tn hiu chun ti u vo thit b: 1000Hz , 0 dBm .

+ Kim tra trong

Kim tra cht lng ng thoi , kim tra h thng chuyn thoi t trc phn m ho

xem h thng c di pha,di tn hay khng cng nh h thng c suy hao hay khng .

2. Khi giao tip ng dy thu bao s.

Cc h thng tng i in t s c h tr cc dch v ISDN cho cc dch v phi thoi

cng vi cc dch v thoi thng thng. ng dn s t tng i in t s ti thu bao

ISDN trn cc lung tc c s 2B+D, v 23B+D, hay 30B+D.

Codec

Hybrid

Truyndn vghpknh

s

Codec

Bn tin bo hiu c s

TX

RX

Ngun

TA

NTU

T O B Truyndn vghpknh

s MUX

D/SLTU

BUS kim tra BUS cp ngun

Bo hiu DSS1

16kbit/s

64 kbit/s

144 kbit/s2Mb/s

Hnh 2.5 Kt cui ng dy thu bao s

S khc bit ln nht ca mch ng dy thu bao s so vi ng dy thu bao

analog l cc chc nng BORSCHT khng ch nm trong khi SLC ca tng i m cn nm

mt phn ti pha thit b u cui thu bao. n v kt cui mng NTU cha cc chc nng

12

CODEC s dng kt ni ti cc n v truyn s liu. B tip hp u cui cha chc nng

CODEC v mch Hybird s dng cho cc thu bao s.

H thng bo hiu DSS1 trn c s bn tin bo hiu c thc hin qua phn chc nng

bo hiu nm ti NTU, thc hin gi v nhn bo hiu trn knh 16 kb/s thng qua b truyn

dn v ghp knh s. Mt s h thng tng i c th s dng knh bo hiu ny cho cc mc

ch khc nh truy nhp internet.

Ti b thch ng u cui TA cha lun chc nng cp m mi quay s, dng chung

cho thit b in thoi s. Cc ch th bo hiu c gi ti TA qua NTU di dng cc bn

tin.

NTU cho php cc cuc gi d liu ( data call), c h tr bi cc phn mm iu

khin tng i h tr cho cc cuc gi kiu phi thoi ny. NTU cung cp mt giao din

chun cho cc thit b u cui ( v d CCITT X21, X21 bis). Giao din ny cho php trc

tip truyn tn hiu s thng qua cc cng giao tip.

Cc chc nng nh cp ngun, bo v qu p v kim tra c thc hin qua cc khi

chc nng thuc Card D/SLTU c iu khin thng qua h thng bus.

3. Khi giao tip ng dy trung k s DTI.

Khi giao tip ng dy trung k s thc hin cc chc nng giao tip truyn dn tn

hiu s, tn hiu ng b ca khi chuyn mch s bn trong tng i vi mng vin thng,

bao gm cc nhim v chnh nh: Kt ni lin i gia ng trung k bn ngoi vi ng

trung k ni i, kt ni ni i trong h thng tng i gia cc phn h.

Tiu chun ch yu ca cc h thng tng i in t s dnh cho DTI l cc giao tip

tc tiu chun E1/T1 tng ng vi tc 2,048Mb/s v 1/544Mb/s. Tuy nhin, hin nay

khi s dng truyn dn quang tr nn ph bin cc h thng tng i in t s thng c

trang b cc b giao tip truyn dn s quang vi tc 8Mb/s, 34Mb/s, 140Mb/s vi cc

chun truyn dn 120 Ohm cp song hnh hoc 75 Ohm cp ng trc trn tc

2,048Mb/s.

thc hin nhim v truyn dn gia cc h thng tng i, h thng tng i in t

s c cc card giao tip truyn dn s hay cn gi l giao tip trung k s c 8 chc nng c

bn sau:

G Generation of Fram To khung truyn dn

A Alignment of Frame ng chnh khung

Z Zero String suppression Trit chui xung 0

P Polar conversion Bin i cc tnh ca tn hiu

A Alarm processing X l cnh bo t xa

C Clock recovery Khi phc tn hiu ng h

H Hunt during reFrame Tm t m a khung

O Office signalling Bo hiu lin i

Cc chc nng ny nm trong cc khi chc nng ca giao tip trung k s c th

hin trn hnh sau:

13

D

D

F

RX

TX

Bin iB/U

Bin iU/B

ngchnhkhung

Tch u khungTch TG

Tchbo hiu

CAS

Chnbo hiu

CAS

BiniS/P

BiniP/S

MUX/

DEMUX

ng h tng i

Thu pht bo hiu

T

TD

khc

Hnh 2.6 S d khi chc nng c bn ca giao din truyn dn s

Cc khi chc nng c bn

- Chuyn i m ng dy sang m nh phn H thng ng dy kt cui trn tuyn

truyn dn c mt vi loi m lng cc thng c s dng ( nh HDB3, 4B3T hay AMI).

H thng tng i in t s s dng kiu m nh phn truyn tn hiu. Thay v thit k

mt loi thit b kt cui tt c cc m ng dy khc nhau c th c s dng, DTI

thng cung cp mt giao tip chun n. Thng thng cc h thng tng i in t s kt

ni theo chun chu u th cc DTI da trn chun giao tip G.703 ca CCITT cho lung

2Mb/s s dng m HDB3. Sau khi nhn c tn hiu t ng truyn hay trc khi gi tn

hiu trn ng truyn th DTI thc hin bin i B/U v U/B.

- ng b khung : Mi h thng ng dy kt cui trung k s ti tng i s c thi

im bt u khung khc nhau, tu thuc vo chiu di ca ng dy v ngun nh thi ti

cc u xa. Tuy nhin, trong h thng tng i hot ng theo TDM cc khung phi c

ng b. iu ny c ngha l ti thi im bt u ca khe thi gian s 0 (TS0) trong khi

chuyn mch, tt c cc tuyn ng ca h thng s cng phi bt u khe s 0. S ng b

ny thc hin bng cch tr tn hiu s t mi ng dy ca h thng mt cch thch hp

trong hng nhn, tt c mi khung trng nhau trong tng i. DTI thc hin chc nng

ny nh mt b m, tc c ly ra bi b tch timing v tch u khung, sau c

ng b cng vi cc tn hiu ng h trong tng i cp ti, bt u ti thi im khung u

tin ca tng i. Cng vic c ra c thc hin mt cch ng b vi tt c cc DTI khc.

B m phi c kch thc ti thiu l mt khung ( 256 bit cho h thng 2.048 Mb/s).

- Chn vo v tch bo hiu CAS. Trong qu trnh truyn bo hiu gia cc h thng

tng i in t s vi nhau trn phng thc bo hiu CAS, cc thng tin bo hiu c

chn vo khe thi gian s 16 ca mi khung (TS16) v truyn lin tip theo cu trc a khung

( 16 khung). Chnh v c c ng b khung v a khung vi tng i khi thit b tch bo

hiu s tch cc thng tin bo hiu ra khi ng PCM v gi chng ti b x l bo hiu

x l cc thng tin bo hiu. Trong qu trnh chuyn thng tin bo hiu ti DTI c sn mt b

m nhn cc thng tin bo hiu v b m ny c dung lng ti thiu l 16 x 8bit = 128

14

bit. Hng pht tn hiu khng cn s dng cc b m cho bo hiu, cc thng tin bo hiu

c chn vo khe thi gian s 16 sau khi pht i tn hiu ng b ti TS0.

- Bin i ni tip- song song S chuyn i ni tip sang song song ca cc ng dy

truyn dn s PCM c thc hin bng cch ghi vo b m mi t m PCM tun t theo

tc ng b ti tng i (2.048 Mb/s) v c c ra ng thi ra BUS song song 8 bit.

Tc trn BUS song song s bng 1/8 ti u vo tc l bng 256Kb/s i vi lung PCM

2.048 Mb/s.

- Cc giao din truyn dn s h tr cc phng thc kim tra qua cc m chn l hoc

m kim tra CRC. Hoc bo v bng cch chia thnh 2 lung tn hiu ging ht nhau m

bo an ton. Ti DTI thng c cc ch u ni vng (loop) kim tra tuyn trc v sau

khi m ho .

- Cc giao din truyn dn s thc hin qu trnh nn cc dy bit 0 lin tip trnh

hin tng mt ng b xy ra trn khung.

2.4.3 Phn h Bo hiu SiGS

Trong mng vin thng bo hiu c coi l mt phng tin chuyn thng tin v

cc lnh t im ny n im khc, cc thng tin v cc lnh ny c lin quan n thit lp,

gim st v gii phng cuc gi. Bo hiu thc hin 3 chc nng chnh:

- Chc nng gim st: gim st ng thu bao, ng trung k...

- Chc nng tm chn: chc nng iu khin v chuyn thng tin a ch

- Chc nng khai thc v vn hnh mng: phc v cho vic khai thc mng mt cch ti

u nht.

Hnh 2.7 Phn loi bo hiu

Bo hiu c chia lm 2 loi: Bo hiu ng thu bao v bo hiu lin i.

Bo hiu ng thu bao: l bo hiu gia my u cui, thng l my in thoi

vi tng i ni ht

Bo hiu trung k lin i: l bo hiu gia cc tng i vi nhau.

BO HIU

Bo hiu knh

ring (CAS)

Bo hiu knh

chung (CCS)

Bo hiu thu bao Bo hiu lin

i

15

Bo hiu lin i gm 2 loi l bo hiu knh ring (CAS) v bo hiu knh chung

(CCS). Bo hiu knh ring hay cn gi l bo hiu knh lin kt l h thng bo hiu trong

bo hiu nm trong knh ting hoc trong mt knh c lin quan cht ch vi knh ting

Bo hiu knh chung l h thng bo hiu trong bo hiu nm trong mt knh tch bit vi

cc knh ting v knh bo hiu ny c s dng chung cho mt s lng ln cc knh

ting.

a/ Bo hiu knh ring CAS

Bo hiu knh ring l h thng bo hiu trong cc tn hiu bo hiu c truyn

trn knh ting hoc trn ng ring c lin quan rt cht ch vi knh ting, v nh TS#16

ca h thng PCM30, c ngha l i vi h thng bo hiu ny mi knh ting c mt ng

bo hiu ring c n nh, cc tn hiu bo hiu c th c truyn theo nhiu cch khc

nhau: trong bng, ngoi bng, hoc trong khe thi gian 16 trong t chc a khung ca h

thng PCM.

C nhiu h thng bo hiu knh ring khc nhau c s dng nh:

- H thng bo hiu xung thp phn n tn.

- H thng bo hiu 2 tn s.

- H thng bo hiu xung a tn.

H thng bo hiu a tn tn hiu c truyn di dng xung hoc m thanh, hoc t

hp ca cc m a tn s. Bo hiu a tn c s dng cho chc nng tm chn, bng cch

s dng 2 trong 5 hoc 6 tn s nm trong bng tn knh ting, tiu biu nht l h thng bo

hiu R2 ca CCITT.

Hnh 2.8 Bo hiu knh kt hp gia cc tng i

Tng i A

Tng i B

Chim

Cng nhn chim

a ch

B- tr li

m thoi

Xo hng v

Xo hng i

Cuc gi c gii phng

A t my

Thu bao B t my

Tng i B dnh mt knh v cc thit b thu a ch

Thu cc con s ca thu bao B

Thu bao B nhc my

Thu bao A Thu bao B

Cp chung cho thu bao B Cp HAC cho thu bao A

16

Tt c cc h thng bo hiu nu trn u c nhc im chung l tc tng i

thp, dung lng thng tin b hn ch do vy trong nhng nm 1960, khi cc tng i c

iu khin bng chng trnh lu tr (SPC) c a vo s dng trn mng thoi, th r rng

rng cn phi a vo mng mt phng thc bo hiu mi vi nhiu c tnh u vit hn so

vi cc h thng bo hiu truyn thng.

Trong phng thc bo hiu mi ny, cc ng s liu tc cao gia cc b x l

ca cc tng i SPC c s dng mang mi thng tin bo hiu. Bo hiu CAS th vn

c s dng trong cc mng in thoi nhng n ang c thay th bi h phng php

bo hiu chun v c nng lc hn gi l bo hiu knh chung CCS.

Cc ng s liu ny tch ri vi cc knh ting. Mi mt ng s liu ny c th

mang thng tin bo hiu cho vi trm n hng ngn knh ting. Kiu bo hiu mi ny c

gi l bo hiu knh chung v tiu biu l h thng bo hiu knh chung s 7.

b/ Bo hiu knh chung

H thng bo hiu lin i hin i c gi l CCS. N da trn nguyn tc truyn

thng tin gia cc my tnh ni m cc khung thng tin c trao i gia cc my tnh theo

yu cu. Cc khung ny bao gm thng tin v tuyn ni di dng cc bn tin bo hiu v a

ch ca tng i b gi, cc con s a ch v thng tin khi thu bao B nhc my tr li. Trong

hu ht cc trng hp trn ch cn mt knh s liu gia hai tng i. Knh s liu 64 kbt/s

trn mt khe thi gian ca mt khung PCM th c th dng cho tt c thng tin iu khin

gia cc tng i.

2.4.4 Phn h Ngoi vi iu khin PCS

. Phn h ngoi vi iu khin c nhim v phi hp gia cc giao din v phn h x l

trung tm tng cng nng lc x l cho ton b h thng tng i. Phn h PCS hot ng

nh mt b m tc x l cc mc thp ca iu khin ch yu gm cc chc nng sau:

Chc nng qut: C chc nng pht hin, xc nh v bo co cho b x l trung tm

CP v nhng s kin di dng tn hiu v trng thi, s thit b ca cc ng dy thu bao

v trung k. C th cc thit b qut ch xc nh cc thng s m khng cn x l m bo

thi gian thc. Cc thng s k thut tu thuc vo cu trc iu khin v nng lc ca tng

h thng, tuy nhin h thng phi p ng c cc yu cu c bn ca ngi s dng.( v d

sau khi nhc my 8 ms l h thng phi pht hin c s thay i trng thi t t my sang

nhc my). Chc nng ny c th thuc v phn h ng dng.

Chc nng phn b bo hiu ( Distribution) Thc hin vic chuyn i cc thng tin

bo hiu t dng ny sang dng khc. V d chuyn cc thng tin bo hiu di dng bn tin

sang cc dng s liu trn knh. Thit b phn b bo hiu c chc nng phn b cc bn tin

trao i qua BUS ti cc khi thit b cn nhn bo hiu cng nh cc lnh iu khin ti cc

khi thit b cp di.

iu khin chuyn mch cc b ( Marker) L khi thit b thc hin u ni chuyn

mch trong phm vi nh, gim lu lng cho trng chuyn mch chnh. Trong khi u ni

cc b c th c cc b u ni cho s s dng cho cc ng trung k ti v i cc tng i

c quan. Marker cng chnh l b iu khin u ni cc b cc tng chuyn mch di s

17

iu khin ca phn h x l trung tm, tc ng trc tip ti phn cng h thng bng cc tn

hiu iu khin.

BUS h thng (system bus) Cc thit b ngoi vi iu khin, cc thit b chuyn mch,

cc B x l trong h thng thng c kt ni ti BUS h thng. BUS h thng c nhiu

kiu cu trc hnh cy, mch vng, kiu HUB tu thuc vo cu trc h thng, Tuy nhin, tt

c u nhm t mc tiu an ton, tin cy cao v n gin v hiu qu.

2.4.5 Phn h x l trung tm CPS

Trong phn h x l trung tm c th c rt nhiu cc b x l thnh phn, mi mt b

x l c mt nhim v ring phn theo chc nng. Cc b x l c cu thnh t hai thnh

phn c bn l b iu khin trung tm CC (cc vi x l) v b nh chnh MM (main

memory).

CC

B nhch-ng trnh

B nhbin dch

B nhs liu

MM

PCS

OMS

H nh 2.9 M hnh n gin ca CPS

B nh chng trnh: Lu gi cc chng trnh hot ng ca h thng tng i di

dng cc tp chng trnh

B nh bin dch: Cha cc thng tin lin quan ti i tng cn qun l ca h thng.

Thng l s liu kiu bn c nh.

B nh s liu: Lu tr thng tin di dng cc s liu tm thi s dng cho qu trnh

x l cuc gi.

H thng x l thng c cu trc iu khin phn cp nh hnh v di y

H thng iu khin

H thng x l n H thng a x l

(Tp trung) ( Phn phi)

18

H thng 1 mc H thng phn cp

Phn chc nng Phn on 2 mc 3 mc

Hnh 2.10 Phn cp iu khin

Cu trc h thng iu khin

- H thng x l n: l dng iu khin c bn nht ca mt tng i SPC, trong

mt b x l n c s dng iu khin tt c cc chc nng.

- H thng a x l: trong mt h thng a x l, nhiu hn mt b x l c s dng

thc hin cc chc nng cn thit. Cc b x l ny c th c sp xp c th phn

chia tng th ti gi, hoc x l t hp phn h chc nng. Ph thuc vo s sp xp ny,

h thng a x l c th c phn chia thnh mt mc hoc hai mc, hoc cu trc phn

cp.

- H thng a x l mt mc: trong h thng a x l mt mc, cc b x l cng hot

ng v vic phn chia ti gia chng c thc hin theo nguyn tc c inh trc.

Cc b x l c th phn chia cng vic x l theo 2 nguyn tc chnh: phn chc nng v

phn chia theo dung lng.

- H thng a x l phn cp:

M - Marker

S - B qut

D - B phn phi

X l gi

Vn hnh v

bo dng

S M D

Ngoi vi iu khin

Mc 1

Mc 2

Mc 3

Mc phn cng

phc tp

phn mm

19

Hnh 2.11 H thng iu khin 3 mc

- Cc phng thc d phng cu trc iu khin

Mt tng i in thoi lun phi bo ton dch v cho thu bao cho d c s c. L

tng n c th trng thi khng hot ng khng qu 2 gi trong sut qu trnh sng ca

thit b l 40 nm. Mc d tin cy ca cc phn t in t rt cao nhng khng phi l

tuyt i. Do vy d phng lun cn thit ti mc x l p ng c yu cu v c tnh

ca tng i. Ni cch khc, phi d phng y , nht l i vi cc thit b iu khin

trung tm tng i c th hot ng lin tc ngay c khi thit b c s c bi bt k l do

g. Cc kiu d phng thng c s dng l:

+ D phng phn ti n, n+1

+ D phng nng

+ D phng song song

Tu theo cu hnh v yu cu cht lng v mc kinh t m ngi ta c th s chn

la cc kiu d phng thch hp.

2.4.6. Phn h vn hnh v bo dng OA&MS

Phn h vn hnh v bo dng di s iu khin ca b x l vn hnh v bo

dng OMP, thc hin cc cng vic nhm m bo cho h thng hot ng chc nng theo

ng yu cu t ra, cc chc nng chnh ca phn h vn hnh v bo dng bao gm: Qun

l, gim st, bo dng.

Qun l l chc nng thc hin qu trnh lu tr hiu r cc thuc tnh ca i

tng cn qun l v thay i mi trng hot ng ca h thng, v d nh cung cp cc s

liu v thu bao, to hoc xo mt ng dy thu bao hay trung k mi, thay i hay cp

nht dch v thu bao s dng, thay i thut ton nh hng v m bin dch, thay i t gi

cc, chuyn s liu tnh cc ti MTU v.v...

Gim st nhm xc minh s m bo mc chp nhn c ca dch v cung cp v

n c thc hin bng vic theo di thng k cc hot ng ca tng i, v s dng cc

php kim tra o th i tng, v d nh gim st trng thi Bn/Ri ca thu bao, trung k,

o lu lng v ti trn ng dy, cc trng thi thit b v gim st mc hot ng ca

cc b x l v.v...

Bo dng bao gm vic qun xuyn tt c cc chc nng m bo cho h thng lm

vic tt nht, qu trnh bo dng thc hin cc cng vic : pht hin li , cnh bo v nh

v khc phc cc s c do phn mm hoc phn cng trong tng i m bo sao cho h

thng lm vic n nh ngay c khi c mt vi s c thng thng xy ra trong h thng.

Trong mt tng i in t s thng ch c mt b x l chuyn trch x l cc cng

vic vn hnh v bo dng, tuy nhin OMS cha hu ht thng tin trong cc phn h khc v

20

nm trn ton b h thng. H thng tng i in t s c th thc hin cc chc nng vn

hnh v bo dng t ng hoc nhn cng tu theo yu cu, mc v tnh cht cng vic.

Trn thc t, cc cng vic qun l, gim st thng c gi chung l qu trnh vn

hnh khai thc h thng.

Vn hnh khai thc h thng

Mt cch tng qut cc cng vic lin quan ti qu trnh vn hnh khai thc bao gm:

Qun l ng dy thu bao;Qun l s liu bin dch v s liu tuyn; Qun l s liu

cc;Gim st , o ti v lu lng thoi

Qun l ng dy thu bao

Trong thc t ta c rt nhiu loi thu bao khc nhau v ng vi mi loi thu bao li c

th c cch qun l khc nhau. Tuy nhin, qun l thu bao cn phi thc hin cc cng

vic sau:

Hin th, phn tch cc tham s ca thu bao, nhm thu bao : Nh nhn vin khai

thc phi c kh nng nh v c thit b thu bao trn mt my, trn gi u dy MDF,

nm c cc dch v c kh nng cung cp cho thu bao...

Thay i cc c tnh ca thu bao, nhm thu bao khi c yu cu : Khi c yu cu

ng k mi dch v hay xo b dch v t pha thu bao, t nh qun l khch hng ...

To mi, xo b mt thu bao, hoc nhm thu bao khi c yu cu: Ch rng khi

trng thi ca thu bao phi c kim tra trc v sau khi thc hin lnh.

Qun l s liu bin dch v s liu tuyn:

Trong tng i c cc Files bin dch, xc nh s lin h gia cc thng tin a ch thu

c v cc s liu v cc ng trung k hoc cc mch in kt cui khc phc v cho

qu trnh thit lp cuc gi. Cc thng tin a ch thu c t thu bao a ti hoc t

ng trung k vo ( i vi cuc gi vo). Cc thng tin c to thnh cc bng bin

dch khc nhau tng ng vi cc ch s gi khc nhau ( Prefix) . Trong bng bin dch s

cha cc thng tin v cc tuyn ni ca cuc gi. V d khi tng i nhn c thng tin a

ch l s 0 u tin, tng i thc hin tin phn tch s xc nh l cuc gi ra, nu nhn

tip c con s 0 th khng nh l cuc gi quc t khi thu bao quay tip m quc gia tng

i s thc hin bin dch xc nh chim tuyn ni thch hp cho cuc gi ( nhm

trung k v ng trung k tng ng )...

Nhn vin khai thc tng i hon ton c th thay i cc s liu bin dch cho ph hp vi

s pht trin mng Vin thng trn thc t ang khai thc.

thc hin vic qun l Prefix, Route th chng ta cng c cc cng vic nh sau :

Hin th v phn tch chi tit cc tham s ca cc ch s gi khc nhau trong tng i (Prefix),

cc hng i m tng i qun l (Route). y l mt cng vic rt quan trng c t ra

khi thc hin cc cng vic lin quan ti Prefix v Route. N i hi nhn vin khai thc phi

c nhng kin thc nht nh v mng vin thng, cc k hoch trong mng nh: K hoch

nh s, tnh cc, to tuyn, bo hiu ...Qua vic hin th nhn vin iu khai thc bit c

cc tham s ca Prefix, Route nh : Ch s Prefix, hng i (gi vo hay gi ra), s con s

cn thu cho hng, biu cc ca hng , tn nhm trung k (nu l hng gi ra) ...

21

Ngi qun l h thng c th thay i, to mi, xo i cc ch s gi, hng i cuc

gi thng qua bn iu hnh h thng t ti tng i hoc cc trung tm bo dng t xa.

Qun l trung k nhm trung k : Cc cng vic cn thc hin khi qun l trung k,

nhm trung k nh hin th phn tch cc tham s ng trung k, nhm trung k,Thay i

mt s tham s ca ng trung k, nhm trung k theo yu cu ca nh qun l v to mi,

xa i trung k, nhm trung k.

Qun l s liu cc: Mi cuc gi hon thnh u phi c tnh cc theo mt biu

gi nht nh. Cuc gi xut hin ti nhng thi im khc nhau trong ngy, ngy trong nm

cng phi c tnh cc theo nhng biu gi khc nhau. thc hin c nhng cng vic

trong tng i phi c trang b cc chng trnh tnh cc thch hp. Hin nay tn ti

hai kiu tnh cc l :

+ Tnh cc theo bn tin cc chi tit ( tnh cc chi tit )

+ Tnh cc theo b m cc ( Meter )

Chc nng vn hnh v bo dng h thng tng i in t s cho php mm do thay

i cc thng s v cc ph hp vi yu cu ca khch hng.

Gim st , o ti v lu lng thoi

Qu trnh o, gim st ti, lu lng thoi c thc hin nh phn mm ca tng i.

Qa trnh ny c th c t ng thc hin bi h thng hoc do nhn vin khai thc yu

cu. Kt qu o, gim st c phn tch, x l v da vo cn b qun l mng c th

nh gi c kh nng lu thot lu lng thoi trn mt hng nht nh hoc i vi mt

ch s gi nht nh. t a ra cc gii php hu hiu nhm nng cao hiu xut s dng

mng vin thng.

Hin nay tn ti hai phng php gim st: Gim st thng xuyn v gim st tc thi.

Gim st thng xuyn: Gim st thng xuyn c thc hin lin tc bi h thng.

Sau mt khong thi gian nht nh h thng s t ng a ra cc bn tin quan trc v cc

thng tin nh: lu lng trn cc ng trung k, s chim dng cc thit bv s cc cuc

gi thnh cng , khng thnh cng...

Gim st tc thi: H thng s thc hin gim st mt i tng no khi c yu cu

ca nhn vin khai thc . Khi kt thc chu k quan trc h thng cng s a ra bn tin kt

qu v qu trnh quan trc . V d nh bn tin v lu lng trn mt hng ni xc nh

hoc lu lng i vi mt ch s gi xc nh...

Bo dng h thng

Pht hin li

Phi c thc hin nhanh chng,li va xy ra l phi c pht hin ngay. C cc

phng php pht hin li sau:

Gim st lin tc: Cc thit b c t ng kim tra trc khi c a vo phc v

lu lng. Nh kim tra cc ng trung k trc khi s dng ng trung k cho m

thoi... Nu n v b li lp tc n v s b kho li v b nh du l n v b li v

thng tin v li s c truyn n phn mm bo dng thc hin tip cc chc nng

khc .

22

Kim tra theo chng trnh con: Chng trnh ny c thc hin t ng theo mt chu

k nht nh hoc do yu cu ca nhn vin khai thc.

Gim st s phc v: Phng thc ny c thc hin theo hai cch khc nhau:

+Lin tc kim tra cc chc nng (nh kim tra chn-l, gim st thi gian).

+ nh gi hiu qu vic s dng thit b theo mt gi tr xc nh trc

Pht hin li

Thng bo li,cch ly li

Li nghim

trng?

Cnh bo

nh v li

Bn tin li

Kim tra, sa cha

Khng

C

H nh 2.12 Th tc chung bo dng tng i in t s

Thng bo li

Thng tin li c truyn ti phn mm bo dng, ti y thng tin li s c phn

tch v x l khng nh rng li c nghim trng hay khng, nu l li nghim trng h

thng s to bn tin cnh bo . C ba cp cnh bo:

- Cnh bo ti hn ( Critical Alarm )

- Cnh bo chnh ( Major Alarm )

- Cnh bo khng ph ( Minor Alarm )

Cch ly li

Khi pht hin li v khng nh l li nghim trng, h thng phi thc hin cch

ly ngay lp tc thit b li ra khi h thng ang hot ng. Thng thng vic cch ly li

ny c thc hin t ng.

nh v li

23

nh v li l qu trnh tm ra ngun gy ra li. c th xc nh c nguyn nhn

gy ra li, v tr li, h thng t ng chy chng trnh kim tra hoc do nhn vin khai thc

yu cu. Bn tin d on s c a ra khi kt thc chng trnh kim tra gip nhn vin

khai thc xc nh c v tr ca li .

Bn tin li

Trong nhiu trng hp , tng i c trang b cc phn mm cu hnh li mi khi

h thng c s c. Khi xy ra trng hp nh vy, thit b d phng s c thay th thit b

hng m bo h thng lm vic khng b gin on, lc ny cn c s can thip ca nhn

vin khai thc sa cha thit b hng v a h thng tr v ch lm vic bnh

thng.

ng thi vi vic pht hin li, h thng s chy chng trnh d on xc nh

kiu li, nh v li. Kt thc chng trnh d on, h thng s a ra mn hnh my in kt

qu v nguyn nhn v v tr li. Nhn vin khai thc da vo bn tin ny s c cc hnh ng

thch hp nhanh chng khc phc li.

Kim tra, sa cha li

Thng qua cc chng trnh kim tra v x l c ch dn trong ti liu ca tng i,

nhn vin vn hnh v bo dng thc hin ng cc bc sa cha li. Tuy nhin trong

mt s trng hp li nh h thng tng i in t s t khi phc, cn cc trng hp hng

hc s c sa cha theo phn cp chc nng ca nhn vin vn hnh v bo dng.

hnh dung mt cch tng qut cc cng vic vn hnh v bo dng chng ta xem xt mt

cch t chc ti liu cho qu trnh vn hnh v bo dng h thng tng i in t s.

Cc ti liu k thut i cng tng i ng vai tr rt quan trng trong qu trnh khai

thc bo dng h thng. Nh cc ti liu ny m nhn vin khai thc c th nhanh chng xc

nh cc nguyn nhn gy ra s c , tm c cc lnh thch hp yu cu tng i thc

hin mt cng vic c th no .

2.5. C IM V CU TRC PHN MM

Phn mm trong tng i s c phn chia theo chc nng lm 2 loi:

1/ Phn mm hot ng

2/ Phn mm tr gip

a. Phn mm hot ng: l t hp cc chng trnh cn thit vn hnh tng i. N

c th c phn tip lm 2 loi, l :

* Cc chng trnh h thng

* Cc chng trnh ng dng

Cc chng trnh h thng hu nh tng ng vi h thng iu hnh ca mt my

tnh thng thng. Phn mm h thng gm cc chng trnh ph hp vi cng vic vn hnh

v s dng ca b x l theo cc chng trnh ng dng.

Cc chng trnh ng dng : x l gi, qun l v bo dng tng ivv

24

b. Phn mm h tr: gm cc chng trnh hp ng, np, v m phng... chng c

ci t ti v tr trung tm, ta thng gi l trung tm phn mm, phc v mt nhm tng

i SPC.

2.5.1. Cc c tnh ch yu ca phn mm

Phn mm ca tng i s phi c h iu hnh thi gian thc. N phi c kh nng x

l ng thi mt s lng rt ln cc cuc gi, v n phi c cc c tnh ring bo m

cc dch v in thoi khng b ngt khi vn hnh hoc c khi ang m rng h thng.

Tnh thi gian thc: phn mm ca tng i phi p ng c kh nng x l lu

lng c nh trc v cc c tnh ca dch v. Cc kh nng x l lu lng ca cc

b iu khin ca tng i c biu th trong s lng cuc gi c x l trong 1 giy hoc

trong 1 gi.

Cht lng ca dch v: c nh gi thng qua 2 thng s

+Phn trm cc cuc ri gi so vi cc cuc gi hon thnh ti mc ti c nh

trc, v cc vn bn trong tng i nh sai li trong x l hoc tc nghn trong h thng.

+Phn trm cc cuc gi phi ch tn hiu mi quay s lu hn thi gian ch c

nh trc.

a chng trnh: Cc b x l iu khin trong tng i SPC hot ng theo kiu a

chng trnh c ngha l nhiu cng vic c hot ho ng thi ( hu ht lin quan n x

l gi). V d, trong mt tng i 30000 ng, c th c 3000 cuc gi ang c tin hnh

tin trnh m thoi, trong khi c 500 cuc gi ang c gii phng, c ngha l c

3500 cng vic ang c hc hin ng thi. Ngoi ra, h thng phi gim st, qun l mi

cuc gi trong b nh khi xut hin bt k mt s thay i no trong mi trng in thoi

bn ngoi, c lin quan n cuc gi th trng thi ca n cng c thay i theo.

2.5.2. T chc b nh trong tng i

Trong phn ln cc tng i SPC, kch c tng th ca mi chng trnh c kt hp

vi nhau ln hn rt nhiu so vi kch c ca b nh chnh. Do khng th to mi chng

trnh thng tr trong b nh chnh. Tuy nhin mt chng trnh ch c th thc hin c

khi n thng tr trong b nh chnh. a ra kh nng s dng tt nht b nh chnh, th

ch nhng phn sng ca cc chng trnh h thng v cc chng trnh p dng mi c

lu tr c nh trong b nh chnh. Cn tt c cc chng trnh khc khng hot ho c lu

ngoi b nh chnh trong cc kho lu ngoi cn gi l cc b nh ln. T ta thy rng,

trong bt k mt h thng chuyn mch no, nhiu chng trnh, gm c cc chng trnh

ln, nu khng c s dng thng xuyn th c lu trong cc b nh ln nh a, bng

t, Streamer v cc chng trnh i vi vic pht trin phn cng h thng hoc pht trin

phn mm c lu trong bng t

25

Phn mm tng i

Cc chng trnh Cc chng trnh

h thng ng dng

Cc chng trnh Cc chng trnh Cc chng trnh Cc chng trnh

thng tr trong thng tr trong thng tr trong thng tr trong

b nh chnh MM b nh ln b nh chnh MM b nh ln

* Lch trnh * Hp ng * Chng trnh nhn cc * Qun l

(Assembler) con s quay s

* iu khin thit b * Bin son * Chng trnh nhn bit * Bo dng

(Compiler) pha ch gi

* Cc chng trnh * In n vn bn * Chng trnh iu khin * Pht trin

b nh (Text Editer) chuyn mch dung lng

* Cc chng trnh * G ri (Debuger)

ng h thi gian * Chuyn File

thc * Th vin

* Kt ni (Link)

Hnh 2.13 Lu tr phn mm trong tng i

2.6. X L CUC GI TRONG TNG I

(1) Tn hiu nhc my:

Khi thu bao mun thc hin mt cuc gi th thu bao ch vic nhc my. Thao tc

ny s to ra tn hiu bo hiu khi u cuc gi (Off-hook Signal) nh qu trnh gii phng

mt tip im nm trn thit b in thoi ca ch gi, mch vng thu bao vi tng i kn

mch. Khi dng in mt chiu tng i cp cho my in thoi. Chc nng gim st S ca

mch ng dy thu bao s pht hin ti cc khi thit b lin quan.

(2) Xc nh thu bao ch gi

Cuc gi t thu bao ch gi s c pht hin bi mch in ng dy thu bao

tng i, sau b iu khin mch in mch in thu bao s xc nh s thit b EN

(Equipment Number) ca thu bao ch gi. EN l rt cn thit cho vic bin dch thnh s

danh b DN (Directory Number) ca thu bao thng qua bng bin dch. Cc ch s EN c

ngha nhiu hn v mt thit b vt l, cc ch s DN mang nhiu ngha v mt dch v ( v

d: Cc thu bao s dng h thng tng i in t s thc hin cc cuc gi nhng khng

cn thit quan tm ti EN m ch cn quan tm ti DN, cc dch v h tr cho thu bao s

c cung cp theo DN). Trn c s kt qu bin dch nu trn, tng i s c c nhng

thng tin quan trng phc v cho cuc gi hin hnh nh quyn lin lc, kiu my in thoi,

trng thi bn/ri, cc dch v ca thu bao ..v.v.

26

1

Tn hiu nhc myNhn dngthu bao gi

2

3

5

6

7

8

9

10

Cp pht b nh

Phn tch ch s

Chuyn mch to knh

4

Thu bao quay s

Cp chung vhi m chung

Tn hiu chungm hiu chung

Tn hiu tr li

Ct m hiu vdng chung

Gim st

Gii phng cuc ni

Thu bao ch gi Tng i Thu bao b gi

H nh 2.14 Tin trnh x l mt cuc gi ni i

(3) Cp pht b nh v kt ni vi cc thit b dng chung.

Mt trong cc chc nng ch yu ca tng i l iu khin. Mt s logic cn c din

gii cc s kin xy ra trong tin trnh cuc gi v trn c s a ra cc quyt nh cn

thit v hot ho cc tc ng tng ng. Khi tng i nhn c tn hiu yu cu khi to

cuc gi (Off-hook Signal), thit b iu khin s cp pht thit b chung v cung cp knh

thng cho thu bao ch gi. V d nh trong qu trnh x l cuc gi, tng i cp mt bn

ghi cuc gi (Call Record) - mt vng b nh cn cho sut tin trnh cuc gi, trong lu

tr mi chi tit lin quan. Mt v d khc v thit b dng chung trong tng i l cc my

thu /pht v b nh lu tr s danh b DN ca thu bao b gi, cc ch s ny khng ch

cn xc nh thu bao b gi m cn cung cp nhng thng tin cn thit khc lin quan

ti nhim v nh hng cho cuc gi qua mng. Qu trnh cp pht b nh thc hin trong

phn h x l trung tm ca tng i in t s, qu trnh cp pht cc thit b dng chung

c phi hp gia b x l trung tm v b x l ngoi vi.

(4) Thu v lu tr cc ch s DN

Sau khi nhn c tn hiu mi quay s thu bao ch gi s tin hnh pht cc ch s

DN ca thu bao b gi bng cch quay a s (My in thoi c) hay n s. Cc ch s ny

s c tng i SPC thu v lu tr vo mt vng nh trong b nh. Nu thu bao thc hin

quay s theo kiu DP, B qut ng dy thu bao s qut v xc nh cc con s b gi

gi v b x l trung tm. Nu thu bao thc hin quay s kiu m a tn th tn hiu trong

bng ny c gi thng ti b thu MF theo tuyn ng thoi. MF nhn cc con s v

chuyn i di dng s v trung tm x l.

27

(5) Phn tch s

Sau khi thu c cc ch s DN ca thu bao b gi, h thng iu khin cn phi phn

tch cc ch s ny xc nh hng ca cuc gi hin hnh. Nu cuc gi kt cui ti tng

i, ngha l kiu cuc gi ni i - khi c thu bao ch gi v thu bao b gi cng trong mt

tng i th ch c duy nht mt mch in cuc gi c nh hng ti - l mch in

ng dy thu bao b gi v khi nu dy thu bao b gi bn th cuc gi khng th tip

din thnh cng v tng i s pht tn hiu bo bn cho thu bao ch gi. Thu bao bn hay

ri c xc nh bi b qut ng dy Scanner. Tn hiu bo bn s c b pht Tone cp

pht trn tuyn ng thoi hng v ti thu bao ch gi.

(6) Chuyn mch to knh

n thi im ny, h thng iu khin tng i xc nh c r c hai mch in

thu bao ch gi v thu bao b gi. Nhim v tip theo l chn mt ng kt ni gia hai

thu bao qua trng chuyn mch ca tng i. Trong h thng iu khin ca tng i c cc

thut ton chn ng thch hp. Mi im chuyn mch trong ng kt ni chn cn

c kim tra m bo rng n cha b chim dng v sau chim v kho ng. Tng

i SPC c thc hin mt cch rt n gin l hi v lp c iu kin trong bng s liu

trng thi cha trong phn mm iu khin. Tuyn ng chuyn mch c iu khin bi

b x l gi trong phn h x l.

(7) Cp dng chung v tn hiu hi m chung

i vi cc cuc gi ni i, sau khi thc hin cc nhim v trong bc 6, tng i s

pht tn hiu chung cho thu bao b gi ng thi gi tn hiu hi m chung cho thu bao

ch gi. Bng cch tng i thng bo cho cc thu bao bit cuc gi c x l thnh

cng v cc thu bao c th tin hnh cuc ni chuyn in thoi. Tn hiu chung c cp

pht qua cc Rle chung ca mch ng dy thu bao. Hi m chung c cp t b to

tone qua tuyn thoi hng v ca thu bao ch gi.

(8) Thu bao b gi nhc my tr li

Khi thu bao nhc my tng i s thu c tn hiu tr li ca thu bao b gi. Knh

ni c la chn gia hai thu bao hnh thnh v cc thu bao bt u ni chuyn qua

tng i. Lc ny dng chung v tn hiu hi m chung phi b ct khi knh kt ni gia

hai thu bao, ng thi vic tnh cc c kch hot.

(9) Gim st cuc ni

Trong khi cuc ni din tin, chc nng gim st c thc hin nhm xc nh vic

tnh cc v pht hin tn hiu Gii phng cuc ni khi cuc gi kt thc.

(10) Gii phng cuc ni

Kt thc cuc ni cc thu bao t my, tng i nhn c tn hiu gii phng. Thit b

iu khin s gii phng tt c cc thit b v b nh tham gia phc v cho cuc gi hin

hnh, sau cng a cc thnh phn k trn v trng thi kh dng cho cc cuc gi tip theo.

Tin trnh x l cuc gi lin i dng bo hiu s 7

(1) Thu bao ch gi (TBCG): nhc my.

(2) Tng i ch gi (TCG): gi m mi quay s cho thu bao ch gi.

28

(3) TBCG: quay s.

(4) TCG: thu s, phn tch v nh tuyn chuyn cuc gi n ch. Bn tin SS7

c chuyn n tng i ch.

(5) Tng i b gi (TBG): thu bn tin SS7, xc nh trng thi ca thu bao b gi

(TBBG) (bn hay ri) v cp tn hiu chung nu TBBG ri. ng thi cng gi bn tin SS7

thng bo cho TCG trng thi ca TBBG.

(6) TBBG: nhc my.

(7) TBG thit lp kt ni, TCG bt u tnh cc.

(8) TBCG v TBBG: m thoi.

(9) TBCG hoc TBBG t my: cuc gi kt thc.

(10) TCG v TBG: ngng tnh cc, bn tin kt thc cuc gi c trao i.

* Lu x l gi (hnh 2.15)

Hnh 2.15: Lu x l cuc gi lin i trong chuyn mch knh

TM TT CHNG 2

Ni dung chng trnh by lch s, tnh nng dch v ca tng i in t s .Trong

chng i su vo phn tch cu trc chc nng , cu trc iu khin v phn mm qu trnh

x l cuc gi ca tng i in t s. Hin nay trong mng PSTN ca Vin thng Vit nam

ch yu l cc h thng DSS xut x t rt nhiu hng: NEAX, Siements, Alcatel. Do khun

kh ca ti liu nhm bin son ch trnh by h thng AlcateA1000E10 hin ang c s

dng rt nhiu trong mng ca vin thng Vit nam.

Rung chung

Telephone

m thoi

STP

Local SW Local SW

Telephoneee

Nhc my, nhn s IAM

m thoi

Ringback tone

Nhc my

STP

ACM

ANC

CBK

RLG

CLF Gc my

Gc my

29

CHNG 3: H THNG CHUYN MCH ATM

GII THIU CHNG

Pht trin h thng chuyn mch bng rng ATM gii quyt nhu cu cung cp dch

v bng rng cho ngi dng theo xu hng hi t cc dch v v in thoi, in thoi

truyn hnh nh, hi ngh truyn hnh, truyn s liu tc cao. ATM l h thng chuyn

mch gi x l tc cao, dung lng ln, cht lng truy nhp cao, v vic iu khin qu

trnh chuyn mch d dng, n gin, hiu sut cao theo cc giao thc TCP/IP .

Ni dung ca chng s trnh by cc vn v cu trc, nguyn l hot ng ca h

thng chuyn mch t bo ATM.

3.1. U IM CA CHUYN MCH ATM

Khi nim v mng thng tin s a dch v bng rng B-ISDN c da trn c s

cng ngh ATM- cng ngh c nh gi l phng thc truyn ti ca mng bng rng .

Nn tng ca cng ngh h tr cho B-ISDN l cng ngh quang SONET/SDH, mng thng

minh (IN) v cng ngh ATM.

Hnh 3.1:Nn tng cng ngh ATM

Mc d cc cng ngh c t c trnh cng ngh v thnh tu khoa hc k

thut cao nhng vn khng p ng c cc yu cu ca mng B-ISDN v nhu cu s dng

dch v ca khch hng. Tht vy vi k thut hin thi ta thy rng: i vi k thut chuyn

mch th c chuyn mch knh v chuyn mch gi v c chuyn mch knh/chuyn mch

gi nhanh u khng p ng c yu cu B-ISDN nhng nu kt hp c hai k thut ny

th hon ton c th p ng tt cho cc yu cu ca B-ISDN. Cn i vi k thut truyn dn

th ch truyn ti ng b (STM) rt lng ph ti nguyn v kh x l ng thi cho tt c

cc dch v yu cu c tc dng bit rt khc nhau, trong khi k thut ghp knh phn chia

thi gian khng ng b (ATDM) t c mm do, linh hot, hiu qu cao vi mi kiu

dch v vi tc bit v kiu lu lng khc nhau. Gii php mi l kt hp cc u im,

Mng thng minh

IN SONET ATM

Mng cp quang

ng b

BISDN

Truyn dn khng

ng b

30

khc phc cc nhc im ca c 2 k thut chuyn mch knh chuyn mch gi v s dng

ATDM s c kh nng p ng tt mi nhu cu ca B-ISDN l vn then cht thc hin

B-ISDN chnh l tng khoa hc v l bn cht ca cng ngh ATM.

Tm li ATM c th iu khin tt c cc kiu lu lng: thoi, vi deo, d liu, c

ghp thng k v chuyn mch trong mt mng chung. Trong mng ATM, rng bng c

th c gn li trong mt thi gian thc cho bt k kiu lu lng no theo yu cu. ATM l

cng ngh cho mi mi trng LAN, WAN, PSTN Cng ngh ATM c la chn l

cng ngh chuyn mch v truyn dn chung cho cc dch v B-ISDN vi cc tnh nng u

vit ca mi trng ATM l:

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

+ Gn rng bng tn linh ng v mm do.

+ Tc truy nhp cao.

+ Bo v u t cc mng hin ti nh c kt ni chng vi mng ATM mi.

+ Tit kim gi thnh OA & M nh cng ngh cao v ng nht

3.2. CC C TNH C BN CA TNG I B-ISDN

a/ Giao din ca nt mng B-ISDN

Giao din c bn ca nt mng B-ISDN vi cc nt khc trong mng c ch ra trn

hnh sau, h thng tng i B-ISDN giao tip trc tip vi cc truyn dn s tc cao hoc

cc thit b ghp knh SDH thng qua khi kt cui tng i ET. im giao tip trn hnh ch

ra l im tham kho AB..

Tng

chuyn

mch

ET

ET

ET

AB

Truyn dn s 155 520 kb/s

Truyn dn s 622 080 kb/s

Thit b

ghp knh

SDH

2 396 160 kb/s

Truyn dn s 2 396 160 kb/s

AB2

AB3

Chuyn mch Truyn dn

Hnh 3.2 Giao din ca tng i B-ISDN ti cc nt mng khc

Cc c tnh chc nng ca giao tip AB1 v AB2 c nh ngha nh sau:

Cu trc giao din v kh nng truyn ti

31

Cu trc giao din gm dng lin tc ca cc t bo

Ghp thng tin ngi s dng vi cc thng tin lin quan ti u ni , v d nh bo

hiu c mang trong t bo ATM trong c lin kt knh o v lin kt lung o.

Lc m ho cho cc giao din ny c m t trong khuyn ngh I.361 ca ITU-

T.

Kh nng truyn ti c nh ngha cho im giao tip tc AB1, AB2 v AB3.

AB1 Giao din i xng thc hin truyn cng mt tc trn c hai hng, kh nng

truyn ti l 149 760 kbit/s.

AB2 Giao din i xng thc hin truyn cng mt tc trn c hai hng, kh nng

truyn ti l 599 040 kbit/s.

AB3 Trong khi B-ISDN cn trong giai on bt u pht trin th cc chc nng kt

cui tng i cn c giao din vi cc thit b SDH ang hin c, kh nng truyn ti qua giao

din ny l 2 396 160 kbit/s.

Khun dng tiu t bo v m ho

Khun dng tiu ca t bo v m ho c nh ngha cho im tham kho giao

tip AB1 v AB2 theo tiu chun I.361 ca ITU-T .

nh thi

Chc nng nh thi cung cp cc thng tin cn thit cho truyn dn bit (phn t bo

hiu ) octet v ng bin t bo.

Vn hnh v bo dng

Cc chc nng vn hnh v bo dng h thng c h tr trn ton mng. Cc chc

nng ny c cung cp thng qua cc knh OAM.

c tnh vt l ca giao din

Cc giao din in v giao din quang

Ch nh knh o v lung o

Cc gi tr nhn dng lung o v knh o c th c thit lp theo 3 cch:

Qua cc chun n nh trc Qua chc nng mt bng qun l Qua cc th tc bo hiu theo yu cu

Bo hiu

Cc th tc bo hiu theo yu cu cho cc u ni VC c nh ngha bi khuyn

ngh ca ITU-T.

b/ Giao din truy nhp ca khch hng

B-ISDN c mt s giao din truy nhp ca khch hng ti cc nt mng, hnh di y

th hin mt s giao din c bn nht ca kt ni mng pha khch hng ti nt B-ISDN.

32

Vng

truy

nhp

khch

hng

B-ISDN

Cc

chc

nng

kt cui

tng i

B-ISDNVn hnh bo d-ng

nh thi

Lin kt knh v lung o

Hnh 3.3 Cc chc nng ca giao din khch hng

Lin kt knh o v lung o

T pha mng ring khch hng truy nhp ti h thng tng i B-ISDN c rt nhiu tc

khc nhau, v c h tr theo nhiu phng thc khc nhau mt s giao din c bn nh

sau:

VB11 Tc 155 520 kbit/s, hai hng, tc bit i xng

VB12 Tc 155 520 kbit/s hng ln, 622 080 kbit/s hng v, tc bit bt i xng

VB13 Tc 622 080 kbit/s, hai hng, tc bit i xng

VB14 Tc 622 080 kbit/s hng ln, 155 520 kbit/s hng v, tc bit bt i xng

VB2 u ni ti CON ca mng ring khch hng

VB4 u ni ti MUX ca mng ring khch hng, ghp bi VB11, VB12.

VB6 u ni ti AXC ca mng ring khch hng

nh thi

Cc giao din ny h tr cc thng tin nh thi cho truyn dn bit, octet v ng bin

t bo.

Vn hnh v bo dng

Tu thuc vo cu trc chung ton mng m tng i B-ISDN vi mng ring khch

hng c cc kiu thng tin vn hnh bo dng cho nhau, theo cc knh OAM.

3.3. CC CHC NNG C BN CA TNG I B-ISDN

a/ Cc chc nng u ni

Cc chc nng ny quan h trc tip ti cc u ni VC v VP qua nt mng chuyn

mch B-ISDN, v d chuyn mch v k thut truyn ti.

Cc chc nng ny lin quan ch yu ti cc lp thp ca m hnh tham kho giao thc

B-ISDN vi OSI, v d lp vt l, cc lp ATM v tng thch ATM (AAL).

Cc chc nng ny c th chia ra thnh 2 nhm chc nng nh hn l : chc nng kt

cui v chc nng chuyn mch.

33

Chc nng chuyn mch

cc t bo ATM

Cc chcnng kt

cui tng i

Cc chcnng kt

cui tng i

Cuc gi KHv bo hiu iu

khin u ni

Cuc gi mngv bo hiu iu

khin u ni

Cc chc nng x l

ti nguyn v u ni

Cc chc nng iu khin u ni

Cc chc nng iu khin cuc gi

Cc chc nng u ni

Cc chc nng iu khin

Cc chc nng vn hnh v bo d-ng

Hnh 3.4 M hnh chc nng c bn ca tng i B-ISDN

b/ Cc chc nng iu khin

Cc chc nng ny ch yu lin quan ti lp cao ca m hnh tham chiu B-ISDN, t

gc phn cng chc nng c th chia thnh cc chc nng bo hiu , x l dch v v ti

nguyn h thng.

X l qu ti trong mng chuyn mch knh lin quan ch yu vi gim st v gii hn

ca s lng cc cuc gi x l ng thi trong mt h thng. Tuy nhin, bng thng c

cp cho thi gian tin hnh cuc gi l c nh (v d 64kbit/s). Trong tng i B-ISDN th

cc t bo (bng thng) c p dng tu thuc vo yu cu s dng, iu ny s lm tng

kh nng qu ti ti mc t bo trong h thng tng i B-ISDN. Qu trnh x l qu ti trong

h thng c thc hin ch yu trn 2 mc : Mc u ni v mc t bo nhm chp nhn

hoc hu b cuc gi.

Ti mc u ni, h thng thc hin gim st cc cuc gi kim tra gii hn cc

cuc gi ng thi. Chc nng ny lm vic ch yu trn cc thng tin c ng

thp ( low dynamic) t trong h thng. V d cho cc chc nng ny nh sau:

iu khin qu ti cc b vi x l v cc ti nguyn khc trong h thng. (S

lng cc ngun ti nguyn kh dng).

Qu ti ca ghp knh. ( rng bng ti a cho php, s lng ti a cc VPI v

VCI cho php).

Qu ti x l cuc gi . ( S lng cc cuc gi trong pha thit lp, s lng cuc

gi trong pha u ni)

34

Ti mc t bo, tng ng vi qu trnh thc hin gim st cht lng phc v ca h

thng. Cc chc nng ny lm vic ch yu da trn cc thng tin ng ca h thng.

v d cho cc chc nng ny nh sau:

Qu ti ca mng chuyn mch .( Ch th qu ti t b m, lu lng hin thi

trong h thng).

Qu ti ca b ghp knh. ( Lu lng hin thi ca b ghp knh).

Qu ti trong h thng c th xy ra v mt s l do nh:

D n khng chnh xc ca h thng (v d, ti ti a ca b ghp knh khng

c nh ngha).

S bin ng trong trng thi ngun lu lng

Trc trc trong chc nng iu khin s dng.

c/ Cc chc nng vn hnh qun l v bo dng

Cc chc nng ny s dng cho qu trnh vn hnh, qun l v bo dng h thng,

khng bao gm cc chc nng thit lp cuc gi. V d, cc chc nng kim tra. Cc chc

nng ny s da trn cc nguyn tc TMN, theo khuyn ngh ca ITU-T chun M.3010 v

phin bn( serial) I.610.

d/ Cc chc nng kt cui

Cung cp cc chc nng lp vt l v cc chc nng lp ATM cng nh cc chc nng

tng thch ATM thc hin cc nhim v sau:

Chc nng lp vt l

Giao tip vi cc cng ngoi theo cc tiu chun. Phn lp phng tin vt l cung cp

kh nng truyn dn bit gm truyn bit v sp xp bit. Cc chc nng c th gm c m

ho ng dy v bin i in /quang.

nh thi bit. Chc nng nh thi bit cung cp phn t bo hiu m kt cui lin kt

khi phc li thng tin t dng bit tng th.

nh dng t bo. Chc nng nh dng t bo cung cp thi gian t bo cho mc nh h

tr cu trc t bo. nh dng t bo chun b cho dng t bo m mt nhn cho php

khi phc li ng bin t bo ph hp vi thut ton t tch dng.( ITU-T serial 1.432).

Cc dng t bo c tch trc khi truyn, ng bin t bo c xc minh v xc nhn

( s dng HEC) v dng bit c hp li sau khi truyn.

To v xc minh iu khin li tiu (HEC). Trong mt nhn vic kim tra xc minh

hoc thay i HEC ca mi t bo nhn c. Trong ch pht hin li, tt c cc t bo

c li ti tiu c loi b. Trong ch sa li, cc tiu li c sa li, chnh xc

i vi li bit n. Trong mt pht, n c tnh ton HEC v chn vo tiu t bo.

Tch tc t bo. Ghp tch tc t bo gm c chn v nn cc t bo ri, tng

thch tc t bo ATM vi kh nng ti ca h thng truyn dn.

35

Bo dng. Chc nng ny cung cp thng tin lin quan ti iu hnh hoc iu kin

hng ca giao din.

Cc chc nng lp ATM

To v tch cc tiu t bo. Ghp v tch cc tiu ca t bo ATM, kim tra

gi tr hiu lc ca cc phn t ring bit cha trong tiu , cc t bo c li trong

tiu s b o thi.

Bin dch tiu t bo. S dng trong qu trnh nh tuyn v kim tra.

iu khin chim dng ( iu khin tham s s dng, iu khin tham s mng).

c m t chi tit trong UPC v NPC trong serial I.371 ca ITU-T.

Ghp v tch cc t bo. Trong hng pht cc t bo c ghp thnh cc lung

tng thch vi tc chung t cc VP v VC ring. Cc gi tr VPI,VCI c th

nhn cc gi tr mi ph hp vi cu trc thc t.

Bo dng. Xem xt trong mt phn khc

Cc chc nng lp tng thch ATM (AAL)

Bo hiu AAL. Gm c cc chc nng bo hiu t pha ngi dng v chc nng

bo hiu mng.

AAL cho tng tc vi knh 64kb/s da trn ISDN. Cc h thng tng i B-ISDN

c th h tr chc nng knh 64kbit/s nh mt chc nng ring bit, chc nng ny

m t trong khuyn ngh serial I.580 nh thit b tng thch mng.

3.4. KIN TRC CHUNG CA H THNG CHUYN MCH BNG RNG ATM

ATM l mng kt ni nh hng, tt c cc t bo ATM trong mt kt ni thc t c

truyn theo mt tuyn ng nh sn. Nhng t bo thuc v mt u ni c xc nh bi

trng nhn dng ng o v knh o VPC/VCI. Cc chuyn mch gi thng thng hot

ng trong di 1 4000 gi tin/giy, trong khi , chuyn mch ATM cn phi x l s

lng gi tin rt ln t 100 000 n hng triu gi tin trong mt giy. V c bn, mt nt

chuyn mch ATM phi thc hin ba hot ng: nh tuyn, xp hng v bin dch tiu

ca cc t bo. Qu trnh nh tuyn l xc nh r t bo c chn ng no t mt

u vo n mt u ra yu cu. Vic xp hng c s dng gii quyt vn xung t

khi ti mt thi im c hn mt u vo c cng mt u ra yu cu. Trn thc t c nhiu

thit k khc nhau cho cu trc chuyn mch ATM. Tuy nhin, m hnh chc nng chung ca

mt h thng chuyn mch ATM thng bao gm ba phn chnh l:

* Giao din chuyn mch: Gm mt module iu khin u vo (IC) v mt module

iu khin u ra(OC).

* Trng chuyn mch t bo

* B x l iu khin: Bao gm hai phn chnh l iu khin chp nhn kt ni (CAC)

36

v qun l chuyn mch (SM).

H thng chuyn mch ATM c chc nng: Chuyn tip cc t bo d liu ngi dng

t cc cng u vo n cc cng u ra thch hp. H tr cc chc nng tng ng trong mt

phng iu khin v mt phng qun l ca m hnh tham chiu giao thc B-ISDN.

Cc h thng chuyn mch ATM c th gi vai tr nh cc cng giao tip vi nhng

mng khc nh N-ISDN, LAN Ngoi ra, n cn cha cc giao din khc trao i thng

tin iu khin v qun l vi cc mng c mc ch c bit nh mng thng minh (IN) v

mng qun l vin thng (TMN).

H nh 3.6 S khi chc nng ca mt h thng chuyn mch ATM

Cc

cng ra

IC OC Trng chuyn mch

H nh 3.5 Kin trc chung ca chuyn mch ATM

Cc

cng vo IC OC

B x l iu

khin

37

H thng chuyn mch ATM gm 5 khi chc nng c bn: M un u vo (IM), m

un u ra (OM), iu khin chp nhn kt ni (CAC), qun l h thng (SM) v khi chuyn

mch t bo (CSF).

Hot ng ca IM v OM c th c m t tng quan nh hnh v

H nh 3.7 S khi m un u vo (a) v m un u ra (b)

a/ M un iu khin u vo (IM)

Thc hin chc nng tch lung ATM khi khung truyn dn v x l cc chc nng

sau i vi mi t bo ATM:

- Kim tra li tiu t bo s dng trng HEC

- Bin dch cc gi tr VPI/VCI.

- Xc nh cng u ra

- Chuyn t bo bo hiu n CAC

- Thc hin iu khin tham s ngi dng/mng (UPC/NPC) cho mi kt ni knh

o/ng o (VCC/VPC)

- Thm vo t bo d liu ngi dng cc bt a ch b sung (c gi l th nh

tuyn) trn c s trng VPI/VCI trong tiu t bo. Th ny sau c CSF s

dng thc hin chc nng nh tuyn v b loi khi ra khi CSF.

b/ M un iu khin u ra (OM)

Thc hin vic phn phi t bo n ch hoc ti mt cng u vo ca mt nt

chuyn mch khc sau khi bin dch t bo. N thc hin cc chc nng sau:

- Loi b th nh tuyn c gn IM.

- C th bin dch cc gi tr VPI/VCI.

c

38

- To trng HEC mi.

- Chn cc t bo qun l v iu khin (nhn c t CAC v SM) vo lung t bo

u ra.

- Thch ng lung t bo vo khung truyn dn.

c/ Khi iu khin chp nhn kt ni (CAC)

CAC c chc nng thit lp, gim st v gii phng cc kt ni o. CAC nhn t bo

bo hiu t IM, tch ly thng tin bo hiu, bin dch v cp nht. Cui cng CAC to ra t bo

bo hiu mi v gi chng n OM.

d/ Khi qun l h thng (SM)

Cc chc nng qun l gm qun l li, qun l hiu nng, qun l cu hnh, qun l

tnh cc, qun l bo mt v qun l lu lng. thc hin cc chc nng ny cn rt

nhiu s truyn thng bn trong chuyn mch gia SM v cc khi chc nng khc.

- X l OA&M lp vt l

- OA&M lp ATM

- Qun l cu hnh cc thnh phn chuyn mch

- Kim sot bo mt cho cc c s d liu chuyn mch

- o lng mc s dng cc ti nguyn chuyn mch

- Qun l lu lng

- T chc thng tin qun l,

- Qun l khch hng - mng,

- Giao din vi h thng vn hnh

- H tr qun l mng.

d/ Khi chuyn mch t bo (CSF)

L phn trung tm ca h thng chuyn mch ATM, thc hin chc nng chnh l nh

tuyn cc t bo d liu (c th bao gm c cc t bo bo hiu v nh tuyn) t IM n OM

thch hp. V mt s chc nng khc bao gm:

- m t bo

- Multicast/Broadcast

- Dung sai, lp lch t bo trn c s cc u tin v tr.

- Gim st tc nghn v kch hot ch th tc nghn chuyn tip ngay lp tc (ECFI).

3.5. NGUYN TC CHUYN MCH V NH TUYN

3.5.1. Qu trnh chuyn mch v x l gi qua cc h thng chuyn mch 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 (hay knh o) cn c

thit lp trc khi nh tuyn cc t bo ATM. Cc t bo c nh tuyn da trn hai gi tr

quan trng cha trong 5 byte mo u t bo: nhn dng lung o (VPI) v nhn dng knh o

39

(VCI), trong mt lung o bao gm mt s cc knh o. S cc bit dnh cho VPI ph

thuc vo kiu giao din. Nu l giao din ngi s dng (UNI), gia ngi s dng v

chuyn mch ATM u tin, 8 bit c dnh cho VPI. iu ny c ngha l c ti 28 = 256

lung o sn c trong im truy nhp ngi s dng. Mt khc nu n l giao din node mng

(NNI), gia cc chuyn mch trung gian ATM, 12 bit s dnh cho VPI. iu ny cho thy c

212=4096 lung o c th c gia cc chuyn mch ATM. Trong c UNI v NNI, c 16 bit

dnh cho VCI. V th c 216=65 536 knh o cho mi lung o.

S kt hp c VPI v VCI to nn mt lin kt o gia hai u cui. Thay v c cng

VPI/VCI cho ton b lung nh tuyn, VPI/VCI c xc nh trn mi lin kt c s thay

i vi mi chuyn mch ATM. Mt cch c th, ti mi lin kt u vo n mt node

chuyn mch, mt VPI/VCI c th c thay th bng mt VPI/VCI khc ti u ra bng s

tham chiu ti mt bng gi l bng nh tuyn (Routing Information Table RIT) trong

chuyn mch ATM. 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, VPI/VCI mi, a ch cng u ra, v trng u tin (tu chn). Khi mt t bo ATM n

mt ng u vo ca chuyn mch, n b chia thnh 5 byte mo u v 48 byte ti trng.

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 a ch cng u ra tng ng v

trng u tin c nh km trong 48 byte ti trng trc khi n c gi n kt cu

chuyn mch. a ch cng u ra ch ti cng u ra no m t bo c nh tuyn. C ba

kiu nh tuyn trong kt cu chuyn mch: ch unicast l ch m mt t bo c

nh tuyn ti mt cng u ra xc nh, multicast l ch mt t bo c nh tuyn ti

mt s cc cng u ra, v broadcast l ch mt t bo c nh tuyn ti tt c cc cng

u ra. Trng u tin cho php chuyn mch truyn cc t bo mt cch c la chn ti cc

cng u ra hay loi chng khi b m b y, tu theo cc yu cu dch v.

Cc kt ni ATM c thit lp trc hoc thit lp mt cch linh ng theo bo hiu

c s dng, ging nh bo hiu UNI v bo hiu nh tuyn giao din mng mng ring

(PNNI). Thit lp trc c tham chiu ti cc kt ni o c nh (PVCs), thit lp linh ng

c tham chiu ti cc kt ni o chuyn mch (SVCs). Vi cc SVCs, bng nh tuyn

c cp nht bi b x l cuc gi trong sut qu trnh thit lp cuc gi. Qa trnh thit lp

cuc gi s tm mt ng nh tuyn ph hp gia ngun v ch. VPI/VCI ca mi ng

dn dc theo tuyn, cc a ch cng u ra ca cc b chuyn mch v trng u tin c

xc nh v c b x l cuc gi in vo bng. B x l cuc gi phi m bo rng ti

mi chuyn mch, VPI/VCI ca cc t bo ang n t cc cng u vo khc nhau c cng

mt cng u ra l khc nhau. Mi chuyn mch ATM c mt b x l cuc gi. Hnh 3.8 ch

ra mt b x l cuc gi cp nht bng nh tuyn trong chuyn mch.

40

B x l cuc gi

W

Y

Z

X

W X 100 P

RIT

RIT

RIT

100

X P10Y

Y Z 200 200

Ngi gi

Chuyn mch

ATM

Ngi

nhn

RIT: Bng nh tuyn

VPI/VCI

c

VPI/VCI

mi

a ch

u ra

Trng

u tin

Hnh 1.1 Bin dch VCI/VPI theo tuyn

10

Hnh 38 Qu trnh x l t bo

hnh v ny, khi mt cuc gi c thit lp thnh cng ngun bt u gi t bo c

VPI/VCI c ghi l W. Ngay khi t bo ny n chuyn mch ATM u tin, ng vo

bng nh tuyn c tm kim. Li vo thch hp c tm thy vi VPI/VCI mi c gi tr

X, thay th gi tr W. a ch cng u ra tng ng (c gi tr 100) v trng a ch c

nh km ti t bo v th t bo c th c nh tuyn ti cng u ra 100 ca chuyn mch

u tin. Ti chuyn mch ATM th hai, VPI/VCI ca t bo m gi tr X c cp nht vi

gi tr mi Y. Da vo a ch cng u ra t c t bng, t bo ang n c nh tuyn

ti cng u ra 10. Hot ng ny c lp li trong cc chuyn mch khc dc theo ng

ti ch. Khi kt ni kt thc, b x l cuc gi xo li vo lin kt trong bng dc theo ng

truyn.

Trong trng hp multicast, mt t bo c sao chp thnh nhiu bn, v mi bn sao

c nh tuyn ti mi cng u ra. V VPI/VCI ca mi bn sao ti cng u ra c th khc

nhau, s thay th VPI/VCI thng c thc hin ti cc cng u ra thay v cng u vo.

Kt qu l bng nh tuyn c chia lm 2 phn, mt ti u ra v mt ti u vo. Ti u

41

vo c hai trng trong bng nh tuyn: VPI/VCI c v N bit thng tin nh tuyn. Ti u ra

c ba trng trong bng nh tuyn: S cng u vo, VPI/VCI c, v VPI/VCI mi. S kt

hp ca s ca cng u vo v VPI/VCI c c th nhn dng duy nht kt ni multicast v

c s dng nh mt ch s nh v VPI/VCI mi ti cng u ra. Khi nhiu VPI/VCI t

cc cng u vo khc nhau c th hp li ti cng cng u ra v c gi tr VPI/VCI c

ging nhau, v th n phi s dng thng tin thm nh phn ca ch s cho bng nh tuyn.

S dng s cng u vo l hp l v l cch d dng.

3.5.2 . Nguyn tc nh tuyn trong chuyn mch ATM

C hai phng thc nh tuyn c s dng trong chuyn mch ATM, l nguyn

tc t nh tuyn v nh tuyn dng bng nh tuyn.

a/ Nguyn tc t nh tuyn

H nh 3.9 Nguyn tc t nh tuyn

Theo nguyn tc ny: Vic bin dch VPI/VCI cn phi thc hin ti u vo ca cc

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 ca t bo c t

trc nh ni dung ca bng bin dch, vic tng thm tiu t bo y yu cu tng thm

tc ni b ca ma trn chuyn mch. Ngay sau khi t bo c c nh danh ni b, n

c nh hng theo nguyn tc t nh hng. Mi cuc ni t u vo ti u ra c mt

tn ni b nm trong ma trn chuyn mch xc nh. Trong cc cuc ni a im VPI/VCI

c gn tn ni b nhiu chuyn mch do c kh nng cc t bo c nhn bn v nh

hng ti cc ch khc nhau ph thuc vo tn c gn.

Quy tc gn tiu cho t bo:

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

42

b/ Nguyn tc bng nh tuyn

Theo nguyn tc ny, VPI/VCI trong tiu t bo c bin dch ti mi phn t

chuyn mch thnh mt tiu mi v m s cng u ra thch hp nh mt bng nh tuyn

gn vi phn t chuyn mch ny. Trong giai on thit lp cuc ni, ni dung ca bng c

cp nht.

H nh 3.10 Nguyn tc bng iu khin

3.6. HOT NG CA MNG CHUYN MCH ATM

Ta hy xt mt v d ng dng 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) v

Qua knh o chuyn mch SVC (Switched virtual circuit)

PVC : Knh o c nh

Cc thnh phn c bn bao gm PABX l tng i ATM dng ring h tr cho cc

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. Ngi iu hnh mng

(Network Operator) c chc nng h tr cho vic thit lp/Gii phng cc knh o c nh.

43

H nh 3.11 PVC Mng ATM

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

1. Thu bao gi nh cung cp yu cu knh PVC

2. Thu bao a a ch ch, tc bit yu cu v thi gain s dng

3. in thoi vin (Network Operator) a cc thng tin ny qua thit b kt cui

(Terminal) thit lp knh tng t nh in thoi vin bnh thng

4. Knh ni c thit lp.

5. Thu bao tr tin theo qui 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 nhng n

c cc u im sau :

Gn nh thi gian thc

rng bng theo yu 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

SVC : Knh o chuyn mch

i vi phng thc ny, khi cuc gi thit lp, gi tr mc nh hoc theo nng lc

hay gn tc l 64 kb/s v ngay khi cuc gi thit lp mch s c gn cho ngi dng v

dnh ring cho ngi dng (in thoi thng thng). Hnh v di y minh hot hot ng

ca mng ATM phc v cho mt cuc gi.

44

Hnh 3.12 SVC mng ATM

Thu bao ch gi nhc my v quay s, cuc gi hng ti ATM-Hub (Trung tm

ATM), n thch ng cc thng tin bo hiu vo t bo ATM. ATM-Hub kim tra tc bit

yu cu, dng cc thng tin cha trong phn ti tin ca t bo ATM. Cc t bo ATM bo

hiu qua mng ti ch thit lp ni. Khi t bo ti ch, ATM Hub pha ch s gii cc t

bo ngc li vi cc thng tin v knh o thit lp knh n. Khi cc t 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 trong t bo cha VPI/VCI trong tiu

.

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 cc ch chng c kim tra, nu ng ch

thc s th ch s pht ngc li. Trn ng i s gn cc gi tr VPIi/VCIj v a vo phn

ti tin ca t bo ATM. T bo no tr v thu bao ch gi u tin chnh l ng i ngn

nht.

3.7. CC YU CU I VI H THNG CHUYN MCH BNG RNG ATM

Nh bit, mng ATM h tr cho cc dch v bng rng. Mi mt dch v c yu cu

tc bt khc nhau ( CBR,VBR), Tnh trong sut(T l mt mt t bo, li bt), v trong sut

v thi gian ( tr, trt thi gian). V vy chuyn mch ATM c thit k tho mn cc

yu cu i hi.

Tc bt yu cu cho cc dch v bng rng thay i theo tng dch v, thng thng

thay i t vi kb/s ti 150 Mb/s. Tc truyn dn ti thiu ca truyn dn SDH l

155Mb/s, v vy tc ti thiu ca ng dy h tr bi chuyn mch ATM l 155 Mb/s.

S lng cc cng h tr bi chuyn mch c gi l dung lng ng dy ca

chuyn mch. Trong mng cng cng B-ISDN, chuyn mch ATM c th yu cu ti thit

1000 cng cho cc u ni thu bao v trung k. Tch s ca tc ng V v dung lng

ng c gi l thng qua ca mt chuyn mch ( thng qua = VN). N rt d dng

tnh thng qua ca trng chuyn mch phi ln hn 150 Gb/s.

45

Trong mng B-ISDN mt s dch v yu cu phn b, v vy trng chuyn mch ATM

phi c c chc nng multicast v qung b.

Hiu nng ca trng chuyn mch c c trng bi kh nng nghn (phong to) u

ni v tr chuyn mch. Mt vi chuyn mch c tnh cht khng tc nghn hon ton, n th

hin khng c s tranh chp trong trng chuyn mch. Vi cc chuyn mch c nghn, kch

thc mng v, ch nh ngun ti nguyn l cc yu t quan trng trnh tc nghn. S mt

mt t bo cng do nguyn nhn trn b m. Thng thng, cc gi tr ca xc sut mt mt

t bo trong cc trng chuyn mch ATM cho php trong khong 10-8-10-11. Tr chuyn

mch nh hng ti tnh trong sut ca thi gian v thng thng t 10-1000 micro giy, vi

trt thi gian khong vi trm micro giy hoc nh hn. Di y l 3 tham s c bn

nh gi hiu nng ca trng chuyn mch ATM:

Kh nng thng qua ca trng chuyn mch : l lu lng truyn qua

trng chuyn mch, c nh ngha nh l xc sut mt gi tin truyn trong mt

khe qua trng chuyn mch ti u ra. thng qua ti a ca trng chuyn

mch thng c gi l dung lng chuyn mch, ch th mc ti thc hin c

khi u vo c mc ti cao nht.

tr trung bnh ca gi: S lng thi gian trung bnh yu cu ca chuyn

mch chuyn cc gi t u vo ti u ra theo yu cu.

Xc sut mt t bo : N c nh ngha nh l xc sut m cc gi nhn c

trong u vo mt trong trng chuyn mch v trn b m hoc do tranh chp.

Mt h thng chuyn mch l tng cn phi chuyn tt c cc gi m khng gy mt

mt vi tr truyn c th nh nht, vi th t gi n nh.

TM TT CHNG 3

Do h tng mng c s thay i , v vy cc h thng chuyn mch knh khng p ng

c nhng yu cu ca mng mi, n c thay th bng cc h thng tng i bng

rng s dng cng ngh chuyn mch ATM. y l mt h thng chuyn mch gi tc x

l cao, dung lng ln. Ni dung c bn ca chng 3 gii thiu cu trc, chc nng v qu

trnh x l gi tin qua h thng chuyn mch bng rng. Trong chng ny h thng chuyn

mch bng rng thng dng ang c s dng trong mng vin thng Vit nam

A1000E10MM cng c cp.

46

THUT NG VIT TT

Ch tt Thut ng Ting Anh Thut ng ting Vit

A

AAL ATM Adaptation Layer Lp thch ng ATM

ADSL Asymmetric Digital Subscriber Line ng dy thu bao bt i xng

AIS Alarm Indication Signal Tn hiu ch th cnh bo

ANSI American National Standards Institute Vin tiu chun quc gia M

API Application Programming Interface Giao din lp trnh ng dng

APS Automatic Protection Switching Chuyn mch bo v t ng

ARP Address Resolution Protocol Giao thc phn gii a ch

AS Application Server Server ng dng

ASCII American Standard Code for

Information Interchange

M tiu chun M cho trao i thng tin

ASIC Application Specific Integrated Circuit Mch tch hp ng dng ring bit

ATM Asynchronous Transfer Mode Phng thc truyn ti khng ng b

B

BERT Bit Error Rate Test Test t l li bit

BGP Border Gateway Protocol Giao thc cng bin

BOOTP BOOT strap Protocol

B-RAS Broadband -Remote Access Server Server truy nhp t xa bng rng

BS Base Station Trm gc

C

CBR Constant Bit Rate Tc bit khng i

CDMA Code Division Multiple Access a truy nhp theo m

CHAP Challenge Handshake Authentication

Protocol

Giao thc xc thc bt tay kch thch

CLI Command Line Interface Giao din dng lnh

CLP Cell Loss Priority Uu tin tn tht t bo

CLEC Competitive Local Exchange Carrier

CM Cable Modem Modem cp

47

CMTS Cable Modem Termination System H thng kt cui model cp

CO Central Office Trm trung tm

CoS Class of Service Lp dch v

CPE Customer Premises Equipment Thit b nh thu bao

CRC Cyclic Redundancy Check Kim tra chu k thng d

D

DA/SA Destination Address/Source Address a ch ngun/a ch ch

DC Direct Current Dng in mt chiu

DCE Data Communications Equipment Thit b truyn thng d liu

DHCP Dynamic Host Configuration Protocol Giao thc cu hnh host ng

DNS Domain Name System H thng tn min

DOCSIS Data-Over Cable Service Interface

Specifications

Cc c im k thut giao din dch v d liu qua cp

DS DiffServ Phn bit dch v

DSL Digital Subscriber Line ng dy thu bao s

DSLAM Digital Subscriber Line Access

Multiplexer

B ghp a truy nhp ng dy thu bao s

DSP Domain-Specific Part Phn min ring

DSCP Differentiated Service Code Point im m dch v phn bit

DSU Data Service Unit n v d liu dch v

DTE Data Terminal Equipment Thit b kt cui d liu

E

EBGP External Border Gateway Protocol Giao thc cng bin ngoi

EEPROM Electrically Erasable Programmable

Read-Only memory

B nh ch c c kh nng lp trnh bng xung in

EGP Exterior Gateway Protocol Giao thc cng bn ngoi

EMS Element Management System H thng qun l thnh phn

ESI End System Identifier Nhn dng h thng u cui

F

FE Fast Ethernet

FIFO First In First Out Vo trc ra trc

48

FR Frame Relay Chuyn tip khung

FT1 Fractional T1 Phn on T1

FTP File Transfer Protocol Giao thc truyn file

FTTC Fiber To The Curb

FTTH Fiber To The Home Cp quang ti nh

FTTS Fiber To The Subscriber Cp quang ti thu bao

G

GE Gigabit Ethernet

GSM Global System of Mobile H thng thng tn di ng ton cu

GPRS GSM Packet Radio System H thng v tuyn gi chung

GUI Graphical User Interface Giao din ngi dng bng ho

H

HDLC High-Level Data Link Control; High-

Speed Data Link Control

iu khin lin kt d liu mc cao; iu khin lin kt d liu tc cao

HDSL High-Data-rate Subscriber Line ng dy thu bao d liu tc cao

HSSI High-Speed Serial Interface

(abbreviation pronounced "hissy")

Giao din ni tip tc cao

I

I/O Input/Output u vo/u ra

IBGP Internal Border Gateway Protocol Giao thc cng bin ni b

ID Identification (Identifying; Identifier) Nhn dng

IDSL ISDN digital subscriber line ng dy thu bao s ISDN

IEEE Institute of Electrical and Electronics

Engineers

Vin cc nh thit k in v in t

IETF Internet Engineering Task Force Nhm thit k lin mng

IGMP Internet Group Management Protocol Giao thc qun l nhm lin mng

IGP Interior gateway protocol Giao thc cng bn trong

IIF Incoming Interface Giao din vo

IP Internet Protocol Giao thc lin mng

IPCP Internet Protocol Control Protocol Giao thc iu khin giao thc Internet

ISDN Integrated Services Digital Network Mng s lin kt a dch v

49

IS-IS Intermediate System-to-Intermediate

System

H thng trung gian - ni - H thng trung gian

ISM IPSec Service module Module dch v IPSec

ISO International Organization for

Standardization

T chc tiu chun th gii

ISP Internet Service Provider Nh cung cp dch v Internet

L

L2F Layer 2 Forwarding Chuyn gi lp 2

L2TP Layer 2 Tunneling Protocol Giao thc tunnel lp 2

LAC L2TP access concentrator B tp trung truy nhp giao thc L2TP

LAN Local Aea Network Mng vng ni b

LCP Link Control Protocol Giao thc iu khin ng lin kt

LED Light-Emitting Diode Diode pht quang

LER Label Edge Router H thng nh tuyn bin nhn

LSA Link State Advertisement Thng bo trng thi ng lin kt

LSP Link State Protocol Giao thc trng thi ng lin kt

LSR Label-Switching Router H thng nh tuyn chuyn mch nhn

M

MAC Media Access Control iu khin truy nhp truyn thng

MAN Metropolitan Area Network Mng th

MBGP Multicast Border Gateway Protocol Giao thc cng bin multicast

MDL Maintenance Data Link Bo dng ng lin kt d liu

MG Media Gateway Cng truyn thng

MGC Media Gateway Controller B iu khin cng truyn thng

MGCP Media Gateway Controller Protocol Giao thc iu khin cng truyn thng

MIB Management Information Base Qun l thng tin c s

MOTD Message of The Day Bn tin ca ngy

MP Multilink Point-to-Point Protocol Giao thc im - im a lin kt

MPLS Multiprotocol Label Switching Chuyn mch nhn a giao thc

MS Media Server Server truyn thng

MSO Multiservice Operator Nh iu hnh a dch v

50

N

NAS Network Access Server Server truy nhp mng

NCP Network Control Protocol Giao thc iu khin mng

NGN Next Generation Network Mng th h sau

NMC Network Management Center Trung tm qun l mng

NMS Network Management System H thng qun l mng

NSAP Network Service Access Point im truy nhp dch v mng

NVRAM Nonvolatile Random-Access Memory B nh RAM thay i c

NVS Nonvolatile Storage Lu gi thay i c

O

OAM Operations, Administration, and

Maintenance

Khai thc, qun l v bo dng

OIF Outgoing Interface Giao din ra

OSI Open Systems Interconnection M hnh u ni cc h thng m

OSPF Open Shortest Path First ng dn u tin ngn nht

OSS Operations Support System H thng h tr hot ng

P

PAP Password Authentication Protocol Giao thc xc thc mt khu

PBX Private Branch Exchange Tng i nhnh ring

PCMCIA Personal Computer Memory Card

International Association

Lin kt quc t card nh my tnh c nhn

PDM Packet Division Multiplexed Ghp knh phn chia theo gi

PIM Power Input Module Module ngun vo

PM Policy Manager Qun l chnh sch