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Chng 2.

TNG QUAN V H THNG BO HIU S 7

2.1. VAI TR CA H THNG BO HIU S 7 (CCS7)

H thng bo hiu knh chung s 6 (CCS6) c hn ch so vi CCS7 l: cc

trung k lm vic vi tc thp (2,4 kb/s). di ca cc bn tin b hn ch v

khng c cu trc phn mc m c cu trc n nn h thng ny khng p ng c

vi s pht trin ca mng li.

H thng CCS7 c thit k ti u cho mng quc gia v quc t s dng trung

k s. Tc t 64 kb/s, c cu trc phn lp. H thng bo hiu s 7 cng c th sdng trn cc ng dy tng t (analog).

H thng CCS7 c thit k khng ch cho iu khin thit lp, gim st cc

cuc gi in thoi m cho c cc dch v phi thoi.

SS7 l h thng bo hiu knh chung ti u iu hnh trong mng vin thng

s, n c s phi hp vi cc tng i SPC.

SS7 c th tho mn cc yu cu hin ti v trong tng lai cho cc hot ng

giao dch gia cc b vi x l trong mng vin thng bo hiu iu khin cuc gi,iu khin t xa, bo hiu qun l v bo dng.

SS7 cung cp cc phng tin tin cy truyn thng tin theo trnh t chnh xc,

khng b mt hoc lp li thng tin.

Hin nay v trong tng lai, CCS7 s ng vai tr rt quan trng i vi cc dch

v trong cc mng nh:

Mng in thoi cng cng PSTN.

Mng s tch hp a dch v ISDN.

Mng thng minh IN.

Mng thng tin di ng mt t PLMN.

2.2. CC KHI NIM C BN CA H THNG CCS7

Mng bo hiu CCS7 c cc khi nim c bn sau:

im bo hiu (SP: Signalling Point): l mt nt chuyn mch hoc nt x ltrong mng bo hiu c ci t chc nng bo hiu s 7 ca CCITT. Mt

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tng i in thoi hot ng nh mt im bo hiu phi l tng i c

iu khin bng chng trnh lu tr SPC v bo hiu s 7 l dng thng tin

s gia cc b vi x l. SP c th l im kt cui bo hiu khi n c kh

nng x l cc bn tin bo hiu c lin quan.

im chuyn tip bo hiu (STP: Signalling Transfer Point): l cc im bo

hiu c kh nng nh tuyn cho cc bn tin, chuyn cc bn tin CCS7 ti cc

tuyn bo hiu mt cch chnh xc da trn cc thng tin cha trong trng

a ch ca bn tin .

Knh bo hiu/chm knh bo hiu: Knh bo hiu l mt ng truyn dn

64 kb/s kt ni gia cc im bo hiu chuyn ti cc thng tin bo hiu.

Chm knh bo hiu l mt tp gm mt s knh bo hiu (ti a 16 knh)

hot ng chia s ti cho nhau nng cao an ton cho h thng.

Bn tin bo hiu: l mt tp hp cc thng tin thuc v mt cuc gi, c

nh ngha ti lp 3 hay lp 4, sau c chuyn nh mt thc th bi chc

nng chuyn tip bn tin.

Tuyn bo hiu/nhm tuyn bo hiu: Tuyn bo hiu l mt ng c

xc nh trc bn tin i qua mng bo hiu t im bo hiu ngun n

im bo hiu ch. N gm mt chui cc SP/STP c u ni vi nhau

bng cc knh bo hiu. Nhm tuyn bo hiu l tt c cc tuyn bo hiu m

thng tin bo hiu c th s dng i qua mng bo hiu.

M im bo hiu: l mt m nh phn c gn cho mi mt SP hoc STP.

2.3. CC KHI CHC NNG CHNH CA CCS7

2.3.1. S khi chc nng

H thng CCS7 c chia thnh mt s khi chc nng chnh sau (Hnh 2.1):

Hnh 2.1. Cu trc c bn ca h thng CCS7

Phn truyn bn tin (MTP: Message Transfer Part): y l h thng vn

chuyn chung truyn cc bn tin bo hiu gia hai SP. MTP truyn cc bn

tin bo hiu gia cc UP khc nhau v hon ton c lp vi ni dung cc bntin c truyn. MTP chu trch nhim chuyn chnh xc bn tin t mt UP

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ny ti mt UP khc. iu ny c ngha l bn tin bo hiu c chuyn s

c kim tra chnh xc trc khi chuyn cho UP.

Phn ngi s dng (UP: User Part): y thc cht l mt s nh ngha

phn ngi s dng khc nhau tu thuc vo kiu s dng ca h thng bohiu.

UP l phn to ra v phn tch bn tin bo hiu. Chng s dng MTP

chuyn thng tin bo hiu n mt UP khc cng loi. Hin ang tn ti mt

s UP trn mng li:

TUP (Telephone User Part): phn ngi s dng cho mng thoi.

DUP (Data User Part): phn ngi s dng cho mng s liu.

ISUP (ISDN User Part): phn ngi s dng cho mng ISDN.

MTUP (Mobile Telephone User Part): Phn ngi s dng cho

mng in thoi di ng.

2.3.2. Mi tng quan gia CCS7 v m hnh OSI

H thng CCS7 l mt kiu thng tin s liu chuyn mch gi, n c cu trc

theo kiu module, rt ging vi m hnh OSI nhng n ch c 4 mc. Trong 3 mc

thp nht hp thnh phn chuyn bn tin (MTP), mc th t gm cc phn ng dng

(Hnh 2.2).

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Hnh 2.2. Mi tng quan gia CCS7 v m hnh OSI

2.4. PHN CHUYN GIAO BN TIN MTP

MTP l phn chung cho tt c cc UP khc nhau. N bao gm ng s liu bo

hiu (MTP mc 1), u ni gia 2 tng i v h thng bo hiu bn tin.

H thng iu khin chuyn bn tin c chia lm 2 phn: Chc nng ng bo

hiu (MTP mc 2) v chc nng mng bo hiu (MTP mc 3).

Hnh 2.3. Cu trc chung ca MTP

Chc nng ng bo hiu: chc nng ny thc hin gim st ng bo hiu

nh pht hin cc bn tin li, iu khin vic gi v nhn cc bn tin mt cch

tun t, khng mt hoc lp bn tin.

Chc nng mng bo hiu: bao gm cc chc nng x l bn tin bo hiu v

qun l mng bo hiu.

X l bn tin bo hiu: bao gm cc chc nng to tuyn cho cc bn tin

v phn phi chnh xc cc bn tin nhn c cho cc UP.

Qun l mng bo hiu: chc nng ny c kh nng cu hnh li v hot

ha ng bo hiu duy tr cc dch v trong cc trng hp c s c.

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2.4.1. MTP mc 1 (ng s liu bo hiu)

Hnh 2.4. Cu trc MTP 1

ng s liu bo hiu l mt ng truyn dn s liu hai chiu. N bao gm 2

knh s liu hot ng ng thi trn hai hng ngc nhau vi cng mt tc (Hnh 2.4).

ng s liu bo hiu c th l ng tn hiu s hoc tng t. ng s liu

bo hiu c xy dng trn knh truyn dn s (64 kb/s) v tng i chuyn mch s.

ng s liu bo hiu tng t c xy dng trn knh truyn dn tng t tn s

thoi (4 kHz) v Modem.

2.4.2. MTP mc 2 (chc nng ng bo hiu)

MTP mc 2 cng vi MTP mc 1 cung cp 1 ng s liu cho chuyn giao tincy cc bn tin bo hiu gia 2 im bo hiu c u ni trc tip. Chc nng

ng bo hiu bao gm:

Chc nng iu khin ng bo hiu.

Cc trng iu khin c x l trong mc 2 chuyn chnh xc cc

bn tin.

S phn nh ranh gii cc n v bo hiu.

Pht hin li.

Sa sai.

ng chnh ban u.

X l ngng hot ng.

iu khin lu lng mc 2.

Ch th hin tng tc nghn ln mc 3. Gim st li ng bo hiu.

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2.4.3. MTP mc 3 (chc nng mng bo hiu)

Cc chc nng ca MTP mc 3 c phn chia thnh 2 loi c bn l cc chc

nng x l bn tin bo hiu v cc chc nng qun tr mng bo hiu (Hnh 2.5).

a. X l bn tin bo hiu

Mc ch ca chc nng x l bn tin bo hiu l m bo cho cc bn tin bo

hiu bt ngun t mt UP ti mt im bo hiu pht c chuyn n UP ti im

bo hiu thu. Chc nng ny gm:

nh tuyn bn tin bo hiu.

Phn bit bn tin bo hiu.

Phn phi bn tin bo hiu.b. Qun tr mng bo hiu

Mc ch ca cc chc nng qun tr mng bo hiu l hot ha cc ng bo

hiu mi, duy tr cc dch v bo hiu, iu khin lu lng khi xy ra tc nghn

v cu hnh li mng bo hiu nu c s c. Trong trng hp ng bo hiu b

h hng, lu lng s c chuyn n cc ng khc trong cng mt nhm knh

bo hiu vi ng hng. Cc chc nng ny gm:

Qun tr mng bo hiu. Qun tr tuyn bo hiu.

Qun tr lu lng bo hiu.

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Hnh 2.5. Cc chc nng mng bo hiu

2.5. PHN IU KHIN U NI BO HIU SCCP

2.5.1. Cc dch v ca SCCP

Phin dch, nh a ch ca SCCP.

Dch v phi kt ni.

Dch v hng kt ni.

2.5.2. Cu trc chc nng ca SCCP

Chc nng SCCP bao gm 4 chc nng chnh (Hnh 2.6):

iu khin hng kt ni SCCP (SCOC): cung cp cc th tc cho thit

lp, chuyn giao v gii phng 1 u ni bo hiu tm thi. N cng iu

khin cng vic truyn s liu trn cc u ni ny.

iu khin phi kt ni SCCP (SCLC): cung cp cc th tc chuyn giao s

liu phi kt ni gia cc ngi dng; phn phi v tip nhn cc bn tin qun

tr.

nh tuyn SCCP (SCR): l chc nng da vo MTP to tuyn vt l

t im bo hiu ny n im bo hiu khc.

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Qun tr SCCP (SCM): cung cp cc th tc m bo duy tr s hot ng

ca mng bng phng php nh tuyn d phng hoc iu chnh li lu

lng nu xy ra s c, tc nghn,

Hnh 2.6. Cu trc chc nng ca SCCP

2.5.3. Cc th tc bo hiu

a. Cc th tc hng kt ni Giao thc mc 2 v 3

Cc th tc hng kt ni bao gm cc pha: thit lp kt ni, truyn s liu v

gii phng u ni (Hnh 2.7).

Thit lp kt ni: bao gm cc chc nng yu cu thit lp kt

ni bo hiu tm thi gia 2 ngi s dng SCCP. Th tc ny c ngi s

dng SCCP khi to bng cch a ra yu cu kt ni (N CONNECT

REQUEST). Trc tin, SCCP gc pht i bn tin CR yu cu kt ni. Bn

tin ny cha mt con s th t (do SCCP gc chn), mc giao thc v a ch

ca SCCP nhn. Bn tin CR c th cha nhng thng tin a ch ca SCCP

pht v d liu ca ngi s dng.

Khi nhn c bn tin CR, SCCP nhn tr li bng mt bn tin xc nhn CC.

Bn tin ny mang con s th t c chn bi SCCP pht, mt con s th

t khc v mc giao thc c chn bi SCCP nhn. Khi SCCP pht nhn

c bn tin CC, ng kt ni bo hiu c thit lp.

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Truyn s liu: s liu c chuyn i trong cc bn tin s liu

DT1 hoc DT2.

Gii phng kt ni: ng kt ni bo hiu c gii phng

bng cc bn tin gii phng RLSD v gii phng hon ton RLC.b. Cc th tc phi kt ni Giao thc mc 0 v 1

Hnh 2.7. Th tc hng kt ni SCCP

Cc th tc phi kt ni cho php ngi s dng SCCP yu cu truyn dn s liu

m khng cn thit lp ng u ni.

Yu cu N UNIT DATA c ngi s dng SCCP a ra yu cu thc

hin chc nng truyn s liu. Yu cu ny cng c SCCP thu s dng phn phtcc bn tin s liu ti nhng ngi s dng cui cng. S liu c truyn i trong cc

bn tin UDT.

2.6. PHN NG DNG KH NNG GIAO DCH TCAP

CCITT nh ngha khi nim kh nng giao dch, vit tt l TC