chuyển mạch

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n tt nghip i hc Chng 2. Tng quan v h thng CCS7

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 cung cp

mt s lng ln cc dch v khc nhau m trong cc ng dng khng b rng buc

ln nhau. TCAP l th tc ng dng ca h thng bo hiu s 7. TCAP cung cp kh

nng chuyn giao thng tin khng lin quan n knh trung k v cc dch v ca lpng dng.

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Cc dch v ca TCAP da trn nn dch v khng u ni. Hin nay lp phin,

lp trnh by, lp vn chuyn cha cung cp mt dch v no.TCAP giao tip trc tip

vi SCCP to kh nng s dng dch v khng u ni ca SCCP chuyn thng

tin gia cc TCAP (Hnh 2.8).

Hnh 2.8. V tr ca TCAP trong h thng bo hiu s 7

2.6.1. Cu trc ca TCAP

TCAP c chia thnh 2 phn lp: Phn lp giao dch v phn lp thnh phn

(Hnh 2.9).

Phn lp thnh phn c nhim v nhn cc thnh phn t cc ngi s dng TC

v phn chia cc thnh phn ny n cc ngi s dng TC pha i phng.Phn lp giao dch c nhim v qun tr s trao i cc bn tin gm cc thnh

phn gia cc thc th ca 2 TCAP. S trao i ny ca cc phn t thc hin mt

ng dng c gi l hi thoi.

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Hnh 2.9. Cu trc ca TCAP

a. Phn lp thnh phn (Component Sublayer CSL)

Phn lp thnh phn cung cp cho TC user kh nng gi cc yu cu thc hin

cho pha i phng v nhn tr li. Phn lp thnh phn li c chia thnh 2 chcnng nh l: Chc nng x l hi thoi (DHA) v chc nng x l thnh phn (CHA).

Hai chc nng ny lin lc vi TC user bng cch gi v nhn cc bn tin, c gi

l cc thnh phn v hi thoi nguyn thy.

Hnh 2.10. Cc phn lp ca TCAP

b. Phn lp giao dch (Transaction Sublayer TSL)

Phn lp giao dch cung cp kh nng gi cc bn tin gia cc TCAP. Cc bn

tin ny c th cha cc thnh phn t phn lp thnh phn. Phn lp ny s dng cc

dch v phi kt ni c cung cp bi NSP. TSL x l mt phn ca bn tin TCAP

c gi l phn giao dch (TP). Khi pht hin ra li trong thnh phn, bn tin s b

loi b v nu gp qu nhiu li th qu trnh giao dch s b loi b.

2.6.2. Cc hot ng ca TCAP

Hot ng ca TCAP l s trao i thng tin gia cc thc th trong lp TCAP

ny hoc l phc v s trao i thng tin ca lp trn nhm cung cp cc dch v

thng minh.

Qu trnh trao i thng tin c khi u khi mt qu trnh ng dng gi n

TCAP mt hm nguyn thy (primitive) v n kt thc do mt qu trnh ng dng gi

n TCAP mt hm nguyn thy khc. Trong mt qu trnh trao i c th c nhiu

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Chng 3.

TRUYN TI BO HIU S 7 QUA MNG IP SIGTRAN

3.1. GII THIU CHUNG

Cng nghip truyn thng ang tri qua mt giai on bng n theo hng hi t

ca cc dch v. D liu tr nn c ngha hn trong ton b lu lng truyn ti

trn mng so vi lu lng thoi. Cc nh khai thc ang tm cch kt hp gia lu

lng thoi v lu lng d liu, gia cc mng li v cc dch v. Trong s cc gii

php cng ngh c la chn, cng ngh IP hin ang c quan tm vi t cch l

gii php ha hn cho h tr a phng tin xy dng cc dch v tch hp mi.

Hin nay ang din ra s tch hp gia mng chuyn mch knh truyn thng vimng IP mi. Cc nh khai thc ang thay th cc mng in thoi c nh v di ng

theo kin trc ton IP v c c h tr giao thc bo hiu s 7. Cng nh IP cho php

cc nh khai thc mng c th m rng mng v xy dng cc dch v mi mt cch

c hiu qu. Thnh phn cc dch v b sung thng dng nh SMS, gp phn vo

s pht trin nhanh chng ca cc mng bo hiu.

Hnh 3.1 Truyn ti bo hiu n gin qua mi trng IP

Mng IP c cc u im ni bt so vi mng trn c s TDM nh sau:

D trin khai: Vi vic s dng gateway bo hiu s khng cn g b

mng SS7 hin c v cc tnh nng nng cao trong tng lai l trong sut.

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Gi thnh thit b thp hn: Khng cn u t nhiu i vi cc phn t

bo hiu hin c.

Hiu qu tt hn: S dng SIGTRAN qua IP khng yu cu cc lung

vt l E1/T1 qua mng truyn ti SDH. S dng cng ngh truyn ti IP quaSDH, IP qua cp quang, c th t thng lng cao hn nhiu.

Bng thng cao hn: Thng tin SIGTRAN qua IP khng buc phi c

lin kt nh trong SS7 v mng IP linh ng hn rt nhiu so vi mng TDM.

Cc dch v nng cao: Trin khai mng li IP to iu kin d dng cho s pht

trin hng lot cc gii php mi v cc dch v gi tr gia tng phong ph.

Cc nh khai thc mng ang mun chuyn dn mng vin thng tin n kin

trc mng IP. Trong khi cha th chuyn ngay ln kin trc mng ton IP th c mngIP v cc mng chuyn mch knh truyn thng u song song tn ti v cn phi

c kt hp li vo c s h tng mng thng nht. Chc chn rng mch chuyn

mch knh s cn tn ti trong nhiu nm na cng vi cc dch v IP. Kin trc kt

hp c th l gii php tt nht cho hu ht cc nh khai thc v n m bo mc

ri ro thp trong qu trnh pht trin mng hin ti trong khi vn cho php p ng

c cc dch v mi. y l mc ch ca nhiu nhm nghin cu chun ha m

SIGTRAN ca IETF l mt trong s . SIGTRAN a ra m hnh kin trc cho php

mng pht trin tin n mng ton IP. M hnh kin trc ny gm hai thnh phn

mi: SCTP v mt s cc giao thc tng thch ng ngi s dng (nh M2UA, M2PA,

M3UA, SUA) cho php p ng cc phng thc yu cu hi t hai mng ny.

Hnh 3.2. Kin trc mng s dng SIGTRAN

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3.2. GII THIU V SIGTRAN

Sigtran l mt nhm cng tc thuc t chc chun ha quc t cho lnh vc

Internet IETF. Mc ch chnh ca nhm l a ra gii php truyn ti bo hiu dng

gi trn mng PSTN qua mng IP, m bo c cc yu cu v chc nng v hiunng ca bo hiu PSTN. Nhm phi hp c vi PSTN, cc mng IP cn truyn ti

cc bn tin bo hiu nh bo hiu ng ISDN (Q.931) hay SS7 (nh ISUP, SCCP,

) gia cc nt IP nh gateway bo hiu (SG), b iu khin cng phng tin

(MGC) v cng phng tin (MG) hoc c s d liu IP. Nhm cng tc Sigtran xc

nh mc tiu l:

Cc yu cu v chc nng v hiu nng: Nhm a ra mt s cc lun

im (trong cc RFC) xc nh cc yu cu tnh nng v hiu nng h tr

bo hiu qua cc mng IP. Cc bn tin bo hiu (nht l SS7) c yu cu v

tr v mt gi rt cao phi c m bo nh trong mng in thoi hin

ti.

Cc vn v truyn ti: Nhm cng tc a ra RFC nh ngha cc

giao thc truyn ti bo hiu c s dng v nh ngha mi cc giao thc

truyn ti trn c s cc yu cu xc nh trn.

Hnh 3.3. M hnh chng giao thc SIGTRAN

SIGTRAN l mt tp cc tiu chun mi do IETF a ra nhm cung cp mt m

hnh kin trc truyn ti bo hiu s 7 qua mng IP. Kin trc giao thc SIGTRAN

c nh ngha gm ba thnh phn chnh (Hnh 3.3):

Chun IP.

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Giao thc truyn ti bo hiu chung SCTP: Giao thc h tr mt tp

chung cc tnh nng truyn ti tin cy cho vic truyn ti bo hiu. c bit,

SCTP l mt giao thc truyn ti mi do IETF a ra.

Cc phn lp thch ng: H tr cc hm nguyn thy xc nh c yucu bi mt giao thc ng dng bo hiu ring. Mt vi giao thc phn lp

thch ng mi c nh ngha bi IETF nh: M2UA, M2PA, M3UA, SUA.

3.3. NG LC PHT TRIN GIAO THC TRUYN TI MI

Nh chng ta bit, giao thc truyn ti d liu tin cy chnh i km giao thc

IP thng l TCP. Tuy nhin, do TCP ra i kh lu v c thit k theo kiu giao

thc hng gi nn TCP cng gp mt s hn ch khi s dng cho nhng ng dng

mi. Vi s lng ng dng mi ang tng ln ngy cng nhiu hin nay cho thyTCP c qu nhiu hn ch. Cc vn gii hn ca TCP th hin gm:

C ch tin cy: TCP cung cp c hai kiu chuyn giao d liu l c ch hi

p v c ch tun t. Mt vi ng dng yu cu chuyn giao thng tin tin

cy m khng cn duy tr th t gi tin, trong khi mt s khc li yu cu p

ng c v th t ca gi d liu. i vi TCP, c hai trng hp ny u gp

phi hin tng nghn u dng gy nn cc tr khng cn thit.

Vn thi gian thc: C ch hi p trong TCP yu cu c mt tr xc nhn gi tin, iu ny lm cho TCP khng p ng c cc ng dng

thi gian thc.

Cc vn bo mt: TCP rt d b tn cng do c ch bo mt trong TCP

khng cao.

Nhng gii hn cp trn y ca TCP l rt ng phi quan tm khi mun

truyn bo hiu s 7 qua mng IP v do , y l mt ng lc trc tip cho s ra i

ca giao thc SCTP mt giao thc truyn ti mi ca SIGTRAN. SCTP khng chgii quyt c vn truyn ti bo hiu trong SIGTRAN m cn c kh nng p

ng cho nhiu ng dng khc.

3.4. GIAO THC IU KHIN LUNG TRUYN TI SCTP

SCTP l mt giao thc truyn ti qua IP mi, tn ti ng mc vi TCP v UDP.

SCTP hin cung cp cc chc nng tng truyn ti cho nhiu ng dng trn c s

Internet. SCTP c IETF a ra v c t trong RFC 2960.

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3.4.1. Tng quan v kin trc ca SCTP

V kin trc, SCTP nm gia tng tng thch ngi dng SCTP v tng mng

chuyn gi phi kt ni nh IP, Dch v c bn ca SCTP l chuyn giao tin cy cc

bn tin ca ngi dng gia cc ngi dng SCTP ng mc. SCTP l giao thchng kt ni v vy, SCTP thit lp kt ni gia hai im u cui (gi l lin h

trong phin SCTP) trc khi truyn d liu ngi dng ca n.

3.4.2. Tng quan v chc nng ca SCTP

Dch v truyn ti SCTP c th c phn thnh mt s chc nng. Cc chc

nng ny c m t nh sau (Hnh 3.5):

Thit lp v hy b lin kt: Mt lin h c to ra bi mt yu cu t

ngi dng SCTP. C ch cookie c dng trong qu trnh khi to cungcp s h tr bo v chng li s tn cng.

Phn phi tun t theo cc lung: Ngi dng SCTP c th xc nh s

lng cc lung c h tr trong lin h ti thi im thit lp lin h .

Phn mnh d liu ngi dng: SCTP h tr phn mnh v ti hp cc bn

tin d liu ngi dng m bo cho cc gi tin SCTP truyn xung cc

tng thp hn ph hp vi MTU.

Pht hin v trnh tc nghn: SCTP gn cho mi bn tin d liu ngi dng

(c phn mnh hoc khng) mt s tun t truyn dn (TSN). u cui thu

s xc nhn ton b cc TSN v ngt on (nu c) thu c.

Chunk bundling: Gi tin SCTP c phn phi n tng thp hn bao gm

hai thnh phn l tiu chung v theo sau l mt hoc nhiu chunk. Hnh v

sau y m t kin trc chung ca mt gi SCTP:

Hnh 3.4. Cu trc gi SCTP

Hp thc ha gi tin: Trng Tag l bt buc v 32 bit ca trng

CheckSum nm trong tiu ca SCTP.

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Qun l tuyn: Chc nng qun l tuyn SCTP chn a ch truyn ti ch

cho mi gi tin SCTP u ra trn c s ch dn ca ngi dng SCTP v

trng thi hin thi ca cc a ch ch hin ti.

Hnh 3.5. Cc chc nng SCTP

3.4.3. Khun dng tiu chung ca SCTP

Hnh v sau y m t khun dng chung ca tiu gi tin SCTP:

Hnh 3.6. Khun dng tiu SCTP

Trng s th t cng ngun/ch: 16 bt. Ch th s th t cng ca SCTP

gi/nhn.

Trng Tag: 32 bt. Pha thu s dng trng ny xc nhn vi pha gi

v gi tin SCTP ny.

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Trng CheckSum: 32 bit. Cha tng kim tra ca gi tin SCTP. SCTP s

dng thut ton Adler-32 tnh ton tng kim tra.

3.5. M2PA

M2PA nh ngha giao thc h tr truyn ti cc bn tin MTP3 ca SS7 qua IP sdng cc dch v ca SCTP. M2PA cho php qun l cc bn tin MTP3 v kh nng

qun l mng gia hai nt SS7 bt k truyn thng vi nhau thng qua mng IP.

M2PA h tr:

Hot ng ca cc thc th giao thc MTP3 ng mc qua kt

ni mng IP.

Ranh gii giao tip MTP2/MTP3, qun l cc lin h truyn ti

SCTP v lu lng lin kt MTP2.

Thng bo khng ng b qun l s thay i trng thi.

c t MTP yu cu mi nt c tng MTP3 phi c mt m im SS7. V vy,

mi im bo hiu IP cng cn phi c m im SS7 ca n.

Hnh 3.7. Vai tr v v tr ca M2PA

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Hnh 3.8. Vai tr v v tr M2PA trong mng ton IP

Hnh 3.7 m t mt im bo hiu SS7 kt ni thng qua mt SG, c trang b

h tr cho c mng SS7 v IP, kt ni n mt im bo hiu IP. Hnh 3.8 l mt v d

khc, trong MTP3 c thch ng vi lp SCTP nh s dng M2PA trong kin trc

ton IP.

y, cc im bo hiu IP MTP3 s dng lp M2PA bn di n thay cho

MTP2. Giao tip gia hai lp MTP3 hoc M2PA c nh ngha bi cng cc hm

nguyn thu nh trong giao tip MTP3/MTP2. M2PA thc hin cc chc nng tng

t nh MTP2.

3.6. M2UA

M2UA nh ngha mt giao thc truyn ti cc bn tin bo hiu ca ng dng

MTP2 SS7 (v d MTP3) qua IP s dng SCTP. Ch c ng dng ca MTP2 l MTP3.

M2UA cung cp s h tr cho:

Ranh gii giao tip gia MTP2/MTP3.

Truyn thng gia cc modul qun l tng.

H tr cho qun l cc association tch cc.

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Hnh 3.9. Vai tr v v tr ca M2UA

SG mong mun nhn c bo hiu SS7 qua mt thit b kt cui mng SS7

chun, s dng MTP SS7 cung cp truyn ti cc bn tin bo hiu SS7 n v t

mt im du cui bo hiu SS7. Sau , SG cung cp s phi hp hot ng gia cc

chc nng truyn ti vi IP SIGTRAN nhm truyn ti cc bn tin bo hiu MTP3 n

im bo hiu IP ca MTP3 s dng MTP2 ca SG vi t cch l tng thp hn ca

n s dng cc hm nguyn thy tng ng c nh ngha gia cc tng. Truyn

thng MTP3/MTP2 c nh ngha l cc bn tin M2UA v gi qua kt ni IP.3.7. SO SNH M2PA V M2UA

Hnh 3.7 v 3.9 minh ha mt kin trc m t s khc nhau gia hai giao thc.

Bng 2.1. So snh M2PA v M2UA

c im so snh M2PA M2UA

Bn tin d liu MTP3 Truyn ti bn tin MTP3

Giao tip vi MTP3 a ra giao din pha trn vi MTP3

Cc hm nguyn thy

im bo hiu IP x l cc

hm nguyn thy MTP3

n MTP2

im bo hiu IP truyn ti cc

hm nguyn thy MTP3 n

MTP2 n SG ca MTP2 x

l (thng qua chc nng phi hp

hot ng)

Kiu lin kt

Kt ni im bo hiu IP

vi SG l lin kt bo hiu

SS7

Kt ni im bo hiu IP v SG

khng phi l kt ni bo hiu s

7. N l m rng ca MTP2 nmt node t xa.

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M imSG l mt node SS7 v c

m im

SG khng phi l mt node SS7

v khng c m im

Cc tng cao hnSG c cc tng SS7 cao hn

nh SCCP,

SG khng c tng SS7 cao hn v

n khng c MTP3

Qun lCc th tc qun l da vo

MTP3

S dng cc th tc qun l ca

M2UA

3.8. M3UA

M3UA nh ngha giao thc h tr truyn ti bo hiu ngi dng MTP3 (v d

nh cc bn tin ISUP/SCCP,) qua IP s dng cc dch v ca SCTP. Giao thc ny

thng c dng gia mt SG v mt MGC hoc c s d liu thng tr IP. M3UA

thch hp vi vic chuyn giao cc bn tin ca bt k phn ngi dng MTP3 no.Danh sch cc giao thc ny l khng gii hn v bao gm ISUP, SCCP v TUP. Ch

rng cc bn tin ca giao thc TCAP v RANAP c M3UA truyn ti trong sut

di dng ti SCCP bi v l cc giao thc ngi dng ca SCCP.

Tng M3UA cung cp mt tp cc hm nguyn thy tng ng ti tng trn

ca n n cc ngi dng MTP3 ging nh MTP3 cung cp cho cc ngi dng ca

n ti cc u cui bo hiu s 7. Theo cch ny, tng ISUP v/hoc SCCP khng bit

c rng cc dch v MTP3 yu cu c cung cp t xa bi tng MTP3 SG hay lbi chnh tng MTP3 di n. Tng MTP3 ti mt SG cng c th khng bit c

rng ngi dng ca n thc ra l ngi dng trn n hay l thnh phn ngi dng t

xa qua M3UA. Thc t th M3UA m rng truy nhp n cc dch v MTP3 thnh

ng dng trn c s IP t xa.

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Hnh 3.10. Vai tr v v tr ca M3UA

ASP MGC, IP SCP hay IP HLR

V d, hnh 3.10 m t mt SG cha mt thc th ca tng giao thc SS7 SCCP

thc hin chc nng bin dch tiu ton cc SCCP (GTT) i vi cc bn tin nh

a ch n SG SCCP. Nu kt qu ca GTT cho mt m im SS7 ch (DPC) hoc

DPC/a ch s phn h (SSN) ca mt SCCP ng mc t trong min IP, kt qu lyu cu gi n M3UA nh tuyn ra ngoi n IP ch s dng cc dch v ca

tng SCTP/IP.

Hnh 3.11 l v d trong mng ton IP, cc bn tin SCCP c trao i trc tip

gia hai im bo hiu IP bng cc thc th giao thc ngi dng SCCP nh RANAP

hoc TCAP. y khng c kt ni vi mng SS7 do khng quan tm n thng

tin qun l trng thi mng MTP3 cho SCCP v cc giao thc ngi dng SCCP.

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Hnh 3.11. Vai tr v v tr ca M3UA trong kin trc ton IP3.9. SUA

Hnh 3.12. Vai tr v v tr ca SUA

SUA nh ngha giao thc truyn ti bo hiu ngi dng SCCP SS7 (v d nhRANAP, TCAP,) qua mng IP s dng cc dch v ca SCTP. Giao thc ny c

thit k dng modul ha v i xng nn cho php lm vic c trong cc kin trc

khc nhau nh kin trc mt SG n im bo hiu IP cng nh kin trc im u

cui bo hiu IP ng mc. SUA h tr cc chc nng sau:

Chuyn giao cc bn tin phn ngi dng SCCP (TCAP, RANAP,).

Dch v phi kt ni SCCP.

Dch v hng kt ni SCCP.

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Qun l cc lin h truyn ti SCTP gia cc SG v mt hay nhiu nt

bo hiu IP.

Cc nt bo hiu IP phn tn.

Thng bo khng ng b qun l s thay i trng thi.

ASP-MGC, IP SCP hoc IP HLR

Trong kin trc ny, cc tng SUA v SCCP giao tip trong SG. Nhu cu ca

chng l phi hp gia cc tng SCCP v SUA cung cp ranh gii chuyn giao cc

bn tin ngi dng v bn tin qun l. i vi bn tin n ASP, c hai trng hp:

SG l im u cui: Trong trng hp ny, cc bn tin SCCP phi kt

ni c nh tuyn theo m im v SSN. Phn h xc nh bi SSN v pha

ngoi mng SS7 c xem nh thuc SG. iu ny ngha l nhn t im

SS7, ngi dng SCCP c t ti SG.

SG l im chuyn tip: Mt GTT phi c thc hin ti SG trc khi

c th xc nh c ch ca bn tin. V tr thc t ca ngi dng SCCP

khng lin quan n mng SS7.

Trong kin trc ton IP c th dng cho mt giao thc s dng cc dch v truyn

ti ca SCCP trong mt mng ton IP. iu ny cho php cc mng pht trin linh

ng hn, c bit l khi khng cn tng tc gia cc bo hiu hin thi. Hnh 3.13

m t trng hp ny.

Hnh 3.13. Vai tr v v tr ca SUA trong kin trc ton IP

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3.10. SO SNH M3UA V SUA

Nhn chung, chng giao thc s dng SUA l khng phc tp v hiu qu hn so

vi chng giao thc s dng SCCP v M3UA. Bi vy, SUA c th nng cao hiu qu

ca mng li v c th cung cp cc phng tin trin khai d dng hn.Bng 2.2. So snh gia M3UA v SUA

M3UA SUA

SCCP

Yu cu im bo hiu h tr

cho cc ng dng khc nhau ca

SCCP khi phi phi hp vi cc

h thng quc gia khc nhau.

Vn l khng c h tr khi

dng SUA.

phc tp

trong trin khaiM3UA cn cc dch v SCCP.

t nht c mt giao thc tngtrn. Gim phc tp ca nt

mng (trong trin khai cng nh

trong qun l), do , gim chi

ph.

V mt nh

tuyn

Trong M3UA, cc bn tin c

iu khin t m im n m

im.

SUA cho php mng IP nh

tuyn bn tin theo thng tin

trng tiu ton cc.

V mt a ch s dng M3UA, mi nt IPcn c gn c m im v a

ch IP.

S dng SUA, mi nt IP khng

cn c m im.

Cc dch v

ISUPC h tr. Khng th h tr c.

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