MC LCMC LC .................................................................................................................. 1CHNG 1: TNG QUAN V CC H THNG BO HIU ................................ 3

1.1. KHI QUT ................................................................................................... 3

1.2 BO HIU NG DY THU BAO ......................................................... 31.3 BO HIU LIN TNG I ........................................................................ 4

1.3.1 Bo hiu knh lin kt (Channel Associated Signalling): ........................ 51.3.2 Bo hiu knh chung (Common Channel Signalling) .............................. 6

1.4 CHC NNG CA BO HIU ..................................................................... 71.4.1 Chc nng gim st ................................................................................... 71.4.2 Chc nng tm chn .................................................................................. 71.4.3 Chc nng vn hnh v qun l mng ..................................................... 7

CHNG 2: H THNG BO HIU S 7 .............................................................. 82.1. Khi nim chung .................................................................................................. 8

2.2.2 Cc kiu kin trc bo hiu .......................................................................... 102.2.3. Cc bn tin bo hiu trong mng bo hiu s 7........................................... 11

2.3. Chng giao thc bo hiu s 7 ......................................................................... 132.3.1. Phn truyn bn tin MTP ........................................................................... 152.3.2. Cc chc nng ngi s dng MTP ............................................................ 162.3.3. Ngi s dng SS7 (SS7 Users) ................................................................... 192.3.4. Cc phn ng dng INAP, MAP, OMAP.................................................... 20

2.4. V d v thit lp cuc gi n gin s dng h thng bo hiu s 7 ............. 222.5. X l bo hiu trong tng i ............................................................................. 24

2.5.1. Gii thiu ..................................................................................................... 242.5.2. S nh tuyn trong tng i ........................................................................ 252.5.3. Cc b thu pht bo hiu .............................................................................. 282.5.4. Cc b to tone v bn tin thng bo ............................................................ 29

Chng 3. TRUYN TI BO HIU S 7 QUA MNG IP SIGTRAN ............. 333.1. GII THIU CHUNG .................................................................................... 333.2. GII THIU V SIGTRAN ........................................................................... 343.3. NG LC PHT TRIN GIAO THC TRUYN TI MI ..................... 353.4. GIAO THC IU KHIN LUNG TRUYN TI SCTP ....................... 36

3.4.1. Tng quan v kin trc ca SCTP............................................................. 363.4.2. Tng quan v chc nng ca SCTP .......................................................... 363.4.3. Khun dng tiu chung ca SCTP........................................................ 38

3.5. M2PA ............................................................................................................. 38

3.6. M2UA............................................................................................................. 40

3.7. SO SNH M2PA V M2UA ......................................................................... 40

3.8. M3UA............................................................................................................. 41

3.9. SUA................................................................................................................ 43

3.10. SO SNH M3UA V SUA.......................................................................... 45

Chng 4: CC GIAO THC BO HIU V IU KHIN NGANG HNG...... 464.1. GIAO THC KHI TO PHIN SIP............................................................ 46

4.1.1. Cc c im v chc nng ca SIP.......................................................... 464.1.2. Cc khi nim v cc thnh phn ca h thng SIP................................... 474.1.3. Khi qut v hot ng ca SIP ................................................................ 534.1.4. Cc loi bn tin SIP .................................................................................. 574.1.5. nh gi SIP ............................................................................................ 60

4.2. H.323.............................................................................................................. 61

4.2.1. Tng quan v H.323 ................................................................................. 614.2.2. Kin trc mng v cc thnh phn ca H.323 ........................................... 624.2.3. Chng giao thc s dng trong H.323 ...................................................... 674.2.4. Thit lp v gii phng cuc gi H.323 trong trng hp n gin nht ... 714.2.5. So snh SIP v H.323 ............................................................................... 73

4.3. GIAO THC IU KHIN C LP KNH MANG BICC .................... 75Chng 5: CC GIAO THC BO HIU V IU KHIN CH T.................. 76

5.1. GIAO THC IU KHIN CNG PHNG TIN MGCP ..................... 765.1.1. Kin trc v cc thnh phn...................................................................... 765.1.2. Thit lp cuc gi thng qua MGCP......................................................... 785.1.3. So snh gia MGCP, SIP v H.323 .......................................................... 795.1.4. nh gi giao thc MGCP........................................................................ 79

5.2. MEGACO/H.248 ............................................................................................ 80

5.2.1. Tng quan v giao thc MEGACO/H.248 ................................................ 805.2.2. V tr ca giao thc MEGACO/H.248 trong m hnh OSI......................... 815.2.3. Cc chc nng ca MEGACO/H.248 ....................................................... 815.2.4. Cc khi nim trong giao thc MEGACO/H.248...................................... 825.2.5. Truyn dn cc bn tin ca giao thc MEGACO/H.248 ........................... 855.2.6. Cc lnh c nh ngha bi giao thc MEGACO/H.248 ....................... 855.2.7. Cu trc bn tin MEGACO/H.248 ............................................................ 885.2.8. Hot ng ca giao thc MEGACO/H.248............................................... 895.2.9. Cc u im ca MEGACO/H.248 so vi cc giao thc iu khin cngphng tin khc................................................................................................ 90

CHNG 1:

TNG QUAN V CC H THNG BO HIU

1.1. KHI QUT

Trong mng vin thng, bo hiu l vic trao i thng tin gia cc thnh phn tham gia vocuc ni thit lp, gim st v gii phng cuc gi. ng thi bo hiu cng c dng vnhnh v qun l mng vin thng.Thng thng bo hiu c chia thnh 2 loi chnh:

- Bo hiu ng dy thu bao (Subscriber Loop Signalling)- Bo hiu lin tng i (Inter - Exchange Signalling)

Hin nay, bo hiu lin tng i c 2 loi chnh:- Bo hiu knh lin kt CAS (Channel Associated Signalling)- Bo hiu knh chung CCS (Common Channel Signalling)

Hnh 1.1: Phn loi bo hiu trong mng vin thng1.2 BO HIU NG DY THU BAOL bo hiu c thc hin gia thu bao vi tng i hay gia tng i vi thu bao. thit lp cuc gi thu bao nhc t hp my. Trng thi nhc t hp c tng i phthin v n gi tn hiu mi quay s n thu bao. Lc ny thu bao c th quay s ca thubao cn gi. Khi quay s xong thu bao nhn c mt s tn hiu ca tng i tng ng vitrng thi nh tn hiu hi m chung, tn hiu bo bn hay mt s tn hiu c bit khc.

Hnh 1.2: v d v ng dy thu bao1.3 BO HIU LIN TNG IL bo hiu gia cc tng i vi nhau.Cc loi tn hiu trong bo hiu lin tng i c th l: tn hiu chim, tn hiu cng nhnchim (hay tn hiu xc nhn chim), s thu bao b gi, tnh trng tc nghn, xa thun, xangcTn hiu bo hiu lin tng i gm:

- Cc tn hiu thanh ghi (Register Signals): c s dng trong thi gian thit lpcuc gi chuyn giao a ch v thng tin th loi thu bao.

- Cc tn hiu bo ng dy (Line Signals): c s dng trong ton b thi giancuc gi gim st trng thi ca ng dy.

Hnh 1.3: V d v bo hiu lin tng iBo hiu lin tng i ngy nay c 2 phng php ang c s dng l: bo hiu knh linkt (ACS) v bo hiu knh chung (CCS).1.3.1 Bo hiu knh lin kt (Channel Associated Signalling):

a) Khi qut bo hiu knh lin kt:L bo hiu lin tng i m tn hiu bo hiu c truyn cng vi trung k ting. c

trng ca loi bo hiu ny l i vi mi knh thoi c ng tn hiu bo hiu xc nhkhng r rng. iu c ngha l:

- Tn hiu bo hiu c th chuyn giao trn knh thoi nu s dng tn hiu bo hiutrong bng tn thoi.

- Tn hiu bo hiu c chuyn giao trong mt knh bo hiu ring bit nh sp xpa khung trong PCM, cc tn hiu bo hiu ng dy c chuyn giao trong khethi gian TS16

b) Cc h thng bo hiu knh lin kt:

* H thng bo hiu CCITT 1: y l h thng bo hiu lu i nht v ngy nay khngcn c s dng na. H thng bo hiu ny s dng tn s 500Hz, ngt qung 20Hz.

* H thng bo hiu CCITT 2: y l h thng bo hiu s dng tn s 600Hz, ngtZealand v Nam M.

* H thng bo hiu CCITT 3: y l h thng bo hiu bng u tin s dng tn s2280Hz cho c bo hiu ng dy v bo hiu thanh ghi. Ngy nay vn cn s dng Php,o, Phn Lan v Hungary.

* H thng bo hiu CCITT 4: y l mt bin th ca h thng bo hiu CCITT 3nhng s dng tn s 2040Hz v 2400Hz cho bo hiu ng dy v bo hiu thanh ghi.

* H thng bo hiu CCITT 5: y l h thng bo hiu c s dng kh rng ri vibo hiu ng dy s dng tn s 2400Hz v 2600Hz, bo hiu thanh ghi s dng t hp 2trong 6 tn s 700Hz, 900Hz, 1100Hz, 1300Hz, 1500Hz v 1700Hz.

* H thng bo hiu R1: y l h thng bo hiu gn ging vi h thng bo hiu s 5,nhng ch s dng mt tn s 2600 cho bo hiu ng dy. Bo hiu thanh ghi ging nhtrong bo hiu s 5.

* H thng bo hiu R2: y l h thng bo hiu s dng tn s 3825Hz cho bo hiung dy (vi phin bn analog) v cc tn s 540Hz ti 1140Hz cho hng v, tn s t1380 n 1980 cho hng i vi bc tn s 120Hz.

c) u im v nhc im ca bo hiu knh lin kt:* u im: do bo hiu knh lin kt tng i c lp vi nhau nn khi c s c

mt knh bo hiu no th cc knh cn li t b nh hng.* Nhc im:- Thi gian thit lp cuc gi lu do tc trao i thng tin bo hiu chm.- Dung lng ca bo hiu knh lin kt nh do c s ng dy trung k gii hn.- tin cy ca bo hiu knh lin kt khng cao do khng c ng dy trung k

d phng.1.3.2 Bo hiu knh chung (Common Channel Signalling)

a) Khi qut bo hiu knh chung:L bo hiu lin tng i m tn hiu bo hiu c truyn trn mt ng s liu tc

cao c lp vi trung k ting. Bo hiu c thc hin c 2 hng i v v vi mt knhbo hiu cho mi hng.Thng tin bo hiu cn gi i c nhm thnh nhng gi d liu. Bn cnh nhng thng tindnh cho vic bo hiu cn c thm mt s thng tin nhn dng knh thoi m n bo hiucho, thng tin a ch (nhn) v thng tin iu chnh li.

Cc tng i iu khin bng chng trnh lu tr (SPC) cng vi cc knh bo hiu sto thnh mng bo hiu chuyn mch gi.

b) Cc h thng bo hiu knh chung:* H thng bo hiu CCITT 6: ra i nm 1968, c s dng dnh cho cc ng dy

analog v cho lu thoi quc t.

* H thng bo hiu CCITT 7: ra i vo nhng nm 1979-1980 dnh cho c mngchuyn mch s trong nc v quc t, h thng truyn dn s tc cao (64Kb/s).

c) u im ca h thng bo hiu knh chung:- Thi gian thit lp cuc gi nhanh do s dng ng truyn s liu tc cao.

Trong hu ht cc trng hp, thi gian thit lp cuc gi gim di mt giy.- Dung lng ca bo hiu knh chung ln do mi knh bo hiu c th x l tn hiu

bo hiu cho vi nghn cuc gi cng lc.- tin cy ca bo hiu knh chung cao nh s dng cc tuyn bo hiu linh ng.- Bo hiu knh chung c linh hot cao v h thng c th mang thng tin ca

nhiu loi tn hiu khc nhau, c th s dng cho nhiu mc ch, khng ch phcv cho ring thoi.

1.4 CHC NNG CA BO HIUBo hiu trong mng vin thng bao gm 3 chc nng c bn:

- Chc nng gim st- Chc nng tm chn.- Chc nng vn hnh v qun l mng.

1.4.1 Chc nng gim stChc nng ny c s dng gim st v pht hin s thay i trng thi ca cc

phn t (ng dy thu bao, ng dy trung k) a ra cc quyt nh x l chnh xcv kp thi.1.4.2 Chc nng tm chn

Chc nng ny lin quan n th tc thit lp cuc gi, l vic truyn s liu thubao b gi v tm tuyn ti u ti thu bao b gi. iu ny ph thuc vo kiu bo hiu vphng php bo hiu.Yu cu t ra cho chc nng tm chn cho tng i l phi c tn hiu qu, tin cy cao thc hin chnh xc chc nng chuyn mch, thit lp cuc gi thnh cng, gim thi gian trquay s.1.4.3 Chc nng vn hnh v qun l mng

Khc vi hai chc nng trn, chc nng vn hnh v qun l mng gip cho vic sdng mng mt cch hiu qu v ti u nht. N thu thp cc thng tin bo cnh, tn hiu olng kim tra thng xuyn thng bo tnh hnh ca cc thit b phn t trong toang b hthng c quyt nh x l ng.

CHNG 2.H THNG BO HIU S 7

2.1. Khi nim chungBo hiu s 7 c quc t cng nhn l h thng bo hiu knh chung (CCS) gia cc

tng i s dng trong mng quc gia v quc t. Thng tin bo hiu c truyn i trnmt khe thi gian c phn pht trn 1 trong cc tuyn PCM mang cc knh thoi.

Hnh 2.1. S tiu biu h thng bo hiu s 7V d nh hai tng i trao i vi nhau bng 2 lung 2 Mbps, nh vy, kh nng dng

lng knh thng tin gia 2 tng i ny l 60 knh, trong , 1 lung 2 Mbps mang bo hius 7 trong TS16 ca n. Thng tin bo hiu c tch, ghp qua trng chuyn mch ca tngi hoc DLTU (Digital Line Terminal Unit).

Thng tin bo hiu c gi t tng i ny sang tng i khc c xc nh bi hthng iu khin qua S/R CCS cho bo hiu s 7. S/R CCS bao gm 3 phn h trn c s cacc b x l. Thng tin t h thng iu hin tng i nhn t phn h iu khin bo hiudi dng thc thch hp. Cc bn tin c xp hng y, cho n khi c th c truyn i.Khi khng c cc bn tin truyn i th phn h iu khin bo hiu pht cc bn tin chn lc gi tuyn lun trng thi tch cc.

Cc bn tin c gi qua phn h u cui bo hiu, s dng cc bits kim tra cpht i t phn h iu khin li to thnh cc n v bo hiu s 7 hon chnh. Ti tng ithu, qu trnh ngc li c thc hin.2.2. Cu trc h thng mng bo hiu s 72.2.1. Cc thnh phn chnh ca mng bo hiu s 7a. im bo hiu (Signalling Points)

Mng bo hiu s 7 hot ng song song vi mng truyn ti. Kin trc mng bo hius 7 nh ngha ba tp cc node gi l cc im bo hiu (SPs), c kt ni vi nhau bi cc

tuyn bo hiu. Mi mt im bo hiu SP c phn bit vi nhau bi mt m im bo hiunh phn duy nht. Tu theo v tr ca n c th l m im gc OPC (Originating Point Code)hay m im ch DPC (Destination Point Code).

Hnh 2.2. Cc thnh phn ca mng bo hiu s 7- im chuyn mch dch v (Service Switching Point SSP)

SSP c kt hp vi cc node chuyn mch ca mng truyn ti v l giao din giamng bo hiu s 7 v mng truyn ti. Trong mng truyn ti c iu khin bi bo hiu s7, tt c cc tng i, k c tng i trung tm v qu giang, u c kt ni ti mng bohiu s 7 thng qua cc SSP. Mt SSP ch kt ni trc tip vi cc nt gn k v vic lin lcvi cc im bo hiu xa ph thuc hon ton vo kh nng nh a ch v nh tuyn camng. V mt vt l, SSP l mt my tnh to ra cc bn tin gi n cc thnh phn khcca mng bo hiu s 7 v nhn cc bn tin tr li.- im chuyn tip bo hiu (Signal Transfer Point)

STP l cc node chuyn mch c thm chc nng bin dch nhn nh tuyn v nhtuyn lu lng mng SS7 gia cc SP khng k nhau. STP cng nh tuyn cc bn tin SS7n cc im iu khin dch v (Service Control Point SCP) m ti lu gi c s dliu. Ton b qu trnh thng tin trong mng SS7 u c thc hin qua STP ngay c i vicc node k nhau. Cui cng, STP cung cp cc dch v gateway, phn phi v nhn cc cucgi SS7 t cc mng khc, bao gm c cc nh cung cp dch v quc t v v tuyn m c thtrin khai SS7 mt cch khc nhau. Trong thc t, STP thng c trin khai theo tng cp nng cao hiu nng h thng v tin cy ca mng.- im iu khin dch v (Service Control Point)

SCP cho php truy nhp vo c s d liu thng tin cn thit cho qu trnh hot ng camng, thng l bin dch s v ch dn ng dng, nhng cng bao gm ngy cng nhiu ccd liu cn thit cho cc dch v v tuyn v thng minh. Cc STP c th truy nhp nhng dliu ny thng qua cc tuyn khng phi l ca SS7, v d nh X.25, v tr li thng tin chonh tuyn cuc gi gia cc SSP, kt hp s quay vi ch n thc t, cung cp hng dn chuyn tip cuc gi..v.v.. SCP cng cho php kt ni ti cc thnh phn mng thng minh

nh H thng qun l dch v v Ngoi vi thng minh. SCP thng c d phng kp nng cao hiu nng h thng v tin cy ca mng.b. Cc kiu tuyn bo hiu

Hnh 2.3. Cc tuyn bo hiu trong mng bo hiu s 7Cc tuyn bo hiu trong mng bo hiu s 7 c phn chia ph thuc vo ng dng

ca chng trong mng bo hiu. Thc t chng khng c g khc nhau v mt vt l, u l cctuyn d liu song hng 56kbps hoc 64kbps. Cc tuyn bo hiu ny c phn loi nhsau:

- Tuyn A (Access): kt ni gia mt STP v mt SSP hay mt SCP. Tuyn A c s dngcho mc ch duy nht l phn pht bo hiu xut pht t hay n cc im cui bo hiu (SSPhay SCP).

- Tuyn C (Cross): kt ni cc STP vi nhau. Chng c s dng tng tin cy ca mngbo hiu trong trng hp mt hay vi tuyn bo hiu gp s c.- Tuyn E (Extend): trong khi mt SSP c kt ni vi STP nh ca n bng mt s cctuyn A th c th tng tin cy bng cch trin khai thm mt s cc tuyn ni ti mt cpSTP th hai. Nhng tuyn ny c gi l tuyn E, thc cht l cc tuyn kt ni d phngtrong trng hp khng th kt ni c vi SSP nh qua cc tuyn A. Tuyn E c th ctrin khai hay khng hon ton ph thuc vo nh cung cp mng.- Tuyn F (Fully associated): y l cc tuyn m kt ni trc tip hai im bo hiu vi nhau.Cc tuyn F ch c cho php thc hin trong kin trc mng bo hiu kiu kt hp v vic ctrin khai cc tuyn F hay khng l ph thuc vo nh cung cp mng.

Ngoi cc tuyn bo hiu trn cn c mt s tuyn bo hiu khc nh: tuyn B (Bridge),tuyn D (Diagonal). D tn c khc nhau nhng chc nng chung ca chng u l truyn ticc bn tin bo hiu t im khi u vo mng n ng a ch ch.2.2.2 Cc kiu kin trc bo hiu

Trong thut ng ca CCS No.7, khi hai nt bo hiu c kh nng trao i cc bn tinbo hiu vi nhau thng qua mng bo hiu ta ni gia chng tn ti mt lin kt bo hiu. Cc

mng bo hiu c th s dng 3 kiu bo hiu khc nhau, trong ta hiu kiu l mi quanh gia ng i ca bn tin bo hiu v ng ting c lin quan.

Kiu kt hp: Trong kiu kt hp cc bn tin bo hiu v cc ng ting gia haiim c truyn trn mt tp hp ng u ni trc tip gia hai im ny vi nhau.

Kiu khng kt hp: Trong kiu ny cc bn tin bo hiu c lin quan n cc ngting gia hai im bo hiu c truyn trn mt hoc nhiu tp hp ng qu giang, quamt hoc nhiu im chuyn tip bo hiu.

Kiu ta kt hp: Kiu bo hiu ny l trng hp c bit ca kiu bo hiu khngkt hp, trong cc ng i ca bn tin bo hiu c xc nh trc v c nh, tr trnghp nh tuyn li v c li.2.2.3. Cc bn tin bo hiu trong mng bo hiu s 7

Trong mng bo hiu s 7, cc node thng tin vi nhau bng cc bn tin di dng gigi l cc n v bo hiu (Signal unit SU). C ba kiu bn tin bo hiu c phn bit vinhau bi trng ch th di (LI Length Indicator), l:

n v tn hiu bn tin MSU: y l bn tin quan trng v phc tp nht trong ba loibn tin. Khng ging nh FISU v LSSU ch c th c nh a ch ti node ln cnv do ch h tr nhng lp thp nht trong chng giao thc SS7, MSU cha nhnnh tuyn v trng thng tin bo hiu. Do chng cung cp phng tin mangthng tin iu khin knh v bn tin thc hin s dng bi cc lp cao hn ca chnggiao thc SS7. Cc trng thng tin ca MSU cng c th mang thng tin bo dngv qun l mng.

n v tn hiu trng thi ng LSSU: LSSU c s dng cung cp cc ch th vtrng thi ng ti u kia ca ng s liu. Cc thng tin v trng thi ng c thl: bnh thng, khng hot ng, mt tn hiu ng chnh, trng thi khn.., trong c th tc ng chnh ban u, c s dng khi khi to ln u cc ng bo hiuv khi phc li sau s c.

n v tn hiu thay th FISU: FISU c truyn khi trn ng truyn s liu khngtruyn cc bn tin MSU v LSSU, mc ch l nhn cc thng bo tc thi v s cca ng bo hiu.

Cc trng trong n v bo hiu:- F (C): Mu ring bit 8 bit ny c s dng bt u v kt thc mt n v bo

hiu v c gi l c. N khng xut hin bt c ni no khc trong n v bo hiu. Ngita phi a ra cc phng php o lng, kim tra trnh c gi xut hin trong n v bohiu. C c c trng bng t m 01111110.

- CK (m kim tra d vng): CK l mt con s tng (ChechSum) c truyn trongtng n v bo hiu. Nu ti im bo hiu thu nhn c Checksum khng ph hp th nv bo hiu c coi l c li v phi loi b.

- SIF (Trng thng tin bo hiu): Trng ny ch tn ti trong bn tin MSU. N gmcc thng tin v nh tuyn v thng tin thc v bo hiu ca bn tin.

Cu trc ca SIF gm c 2 phn: nhn nh tuyn (mc 3) v thng tin ngi s dng(mc 4)

Nhn nh tuyn: im ch ca mt n v tn hiu c xc nh trong mt nhn nhtuyn. Nhn nh tuyn trong mt n v tn hiu bn tin bao gm cc trng m im ch(DPC), m im gc (OPC) v la chn tuyn bo hiu (SLS).

Mt m c gn cho mi im bo hiu trong mng bo hiu ph thuc vo mt khoch nh s. Phn truyn bn tin s dng m nh tuyn bn tin. DPC xc nh im bohiu m bn tin c truyn n . OPC xc nh im bo hiu m t bn tin ctruyn.

Ni dung ca trng SLS xc nh tuyn bo hiu m theo bn tin c truyn. Bngcch ny, trng SLS c s dng chia ti trong cc tuyn bo hiu gia hai im bohiu.

Thng tin ngi s dng: thng tin ngi s dng cha d liu c to ra bi phnngi s dng im gc v d liu c c lng ca phn ngi s dng im ch.

- SIO (Octet thng tin dch v): Trng ny ch tn ti trong bn tin LSSU. Octet nygm ch th dch v v phn ch th mng.

Ch th dch v c s dng phi hp bn tin bo hiu vi mt Ngi dng ring bitca MTP ti mt im bo hiu, c ngha l cc chc nng lp 3 phn phi bn tin ti cc phnngi s dng tng ng, vi s tr gip ca ch th dch v.

Trng ch th mng gm ch th v mng c s dng phn bit gia cc cuc gitrong mng quc gia v quc t hoc gia cc s nh tuyn khc nhau trong mt mng. Chth mng cng xc nh mng tng ng trong c ni gi v nhn bn tin.

NAT0 = mng ch.NAT1 = mng bo hiu chung vi cc nh cung cp mng trong nc khc.INAT0 = mng bo hiu chung vi cc nh cung cp mng quc t khc.INAT1 = khng s dng.- ERROR CORRECTION c dng kim tra li tun t v yu cu truyn li, n

gm:+ BSN (S th t hng v): Trng BSN c s dng cng nhn cc n v bo

hiu m u cui ca ng bo hiu pha i phng nhn c. BSN l s th t n v bohiu c cng nhn (7 bits)

+ BIB (Bt ch th hng v): BIB c s dng khi phc li bn tin khi c li (1 bit)+ FSN (S th t hng i): FSN l con s th t hng i ca n v bo hiu mang n

(7 bits)

+ FIB (Bt ch th hng i): FIB c s dng khi phc li cc bn tin khi c li (1bit)

+ LI (Ch th di): Trng LI ch ra s lng Octet c trong mt n v bo hiu tnht sau trng LI n trc trng CK.

Trong : LI = 0 : n v bo hiu thay th (FISU) LI = 1 hoc 2 : n v bo hiu trng thi ng (LSSU) LI thuc (2;63) : n v bo hiu bn tin (MSU)

2.3. Chng giao thc bo hiu s 7Chng giao thc bo hiu s 7 c 4 mc : 3 mc ca phn truyn bn tin MTP cung

cp mt h thng truyn dn tin cy cho tt c ngi s dng ; v mc th t bao gm ccngi s dng ca MTP (MTP User). C hai ngi s dng MTP: th nht, l phn ngi sdng ISDN (ISDN User Part) cung cp bo hiu iu khin cuc gi chuyn mch knh c bnv h tr cc dch v ph ca ISDN. Ngi dng MTP th hai l Phn iu khin kt ni bohiu SCCP, cung cp cc dch v nh tuyn v nh a ch mng khng phi l chuyn mchknh, thng qua giao thc Cc kh nng bin dch TC ti ngi s dng ca SS7 tc l ccng dng. Cc ng dng ca SS7 yu cu phi truy nhp n c s d liu xa v cc node, do yu cu kh nng nh a ch mng.

Kin trc chng giao thc bo hiu ny c ch ra hnh sau :

Mc d ITU T nh ngha chng giao thc SS7 trc khi ISO/OSI m t m hnh bylp, nhng n cng c th c so snh i th vi m hnh OSI by lp nh c ch ra hnh sau :

S kt hp ca MTP v cc kh nng nh a ch ca SCCP to nn Phn dch vmng SS7 (SS7 Network Service Part) cung cp cc dch v nh tuyn v nh ach lp 3 ca m hnh OSI cho cc ng ng.

Cc lp t 4 n 6 ca m hnh OSI ng vi Phn dch v ngi s dng ca SS7(Application Service Part) nhng hin thi cha c nh ngha. tin cy m nhnggiao thc hng kt ni trong m hnh OSI ny cung cp c thc hin bng ccphng thc khc trong cc giao thc ca phn Cc kh nng bin dch TC.

Mc d ISUP thng c biu din m rng t lp 3 n lp 7 nhng iu khngc ngha l tt c cc lp gia c xc nh. Thc t, n ch cho thy l ISUP linquan n vic bin dch cc tn hiu thit lp cuc gi ban u ca ngi s dng thnh

cc giao thc bo hiu thit lp cuc gi SS7, v cng tng tc vi cc giao thctruyn bn tin mc thp hn ca MTP.

2.3.1. Phn truyn bn tin MTPa. MTP mc 1

Mc mt trong phn chuyn bn tin MTP gi l ng s liu bo hiu, n tng ngvi mc vt l trong m hnh OSI. ng s liu bo hiu l mt ng truyn dn s liu haichiu. N bao gm hai knh s liu hot ng ng thi trn hai hng ngc nhau vi cngmt tc .

ng s liu bo hiu c th l ng tn hiu s hoc tng t . ng s liu bohiu s c xy dng trn knh truyn dn s (64 Kb/s) v tng i chuyn mch s. ngs liu bo hiu tng t c xy dng trn knh truyn dn tng t tn s thoi (4Khz ) vModem.

Giao thc mc 1 nh ngha cc c tnh vt l, cc c tnh in v cc c tnh chcnng ca cc ng bo hiu u ni vi cc thnh phn CCS N07. Cc c tnh ny c mt chi tit trong khuyn ngh CCITT G703, G732 v G734.

Cc tc ca MTP mc 1 c th l DS-1 (1.544Mbps), DS-0 (64kbps) v DS-0A(56kbps) theo chun Bc M hay theo cc giao din chun ca th gii nh V.35 (64kbps).b. MTP mc 2

MTP mc 2 tng ng vi lp 2 trong m hnh phn lp OSI. N thc hin chc nngng bo hiu, cng vi ng s liu bo hiu (MTP mc 1) cung cp mt ng s liucho chuyn giao tin cy cc bn tin bo hiu gia hai im bo hiu c u ni trc tip .

MTP mc 2 nh ngha cc giao thc cn thit xc nh mt v hu gi tin trn ccng d liu ring bit v sp th t cc gi d liu c phn pht. MTP mc 2 s dngcc bn tin FISU xc nh v sa li v s dng cc bn tin LSSU iu khin khi phcng s liu. MTP mc 2 thc hin chc nng ny m khng lm nh hng n cc lp caohn.c. MTP mc 3

MTP mc 3 c th c coi nh tng ng vi lp mng trong m hnh OSI. N chutrch nhim x l bn tin v qun tr mng. MTP mc 3 s thc hin cc chc nng phn bit,nh tuyn, v phn phi cc bn tin qua cc ng s liu c to bi cc giao thc mc 2.

- Mc 3 phn tch a ch ca cc bn tin n v t phn bit cc bn tin c a ch la ch node hin ti vi cc bn tin c a ch l node khc.

- Cc bn tin c a ch l node hin ti c chuyn ti cc qu trnh tip theo xc nhbi trng SIO trong bn tin.

- Nu a ch ca bn tin n khng phi l a ch node hin ti, mc 3 s chuyn tip tchc nng phn loi sang chc nng nh tuyn. Chc nng ny s kim tra bng nhtuyn, nh tuyn bn tin mt cch thch hp v phn pht n tr v cho cc giao thcmc 2 truyn i.

MTP mc 3 thc hin chc nng nh tuyn ca n da trn m im (Point Codes) cghi trong a ch bn tin. M im ny xc nh duy nht v tr ca im khi u v kt thc

ca ng s liu. Tuy nhin MTP ch c th nh tuyn theo kiu theo tng ng mt (link by link). y khng phi l vn i vi bo hiu chuyn mch knh. Tuy nhin, vi bohiu khng phi l chuyn mch knh ti cc c s d liu v cc ng dng c th khp nitrn mng, MTP mc 3 ti cc tng i chuyn mch c th khng c bng nh tuyn yu cu.Do , n lp y cc trng cha bit vi s 0 v chuyn tip n n STP ni c bng nhtuyn tp trung. Cc giao thc lp trn ti STP s thc hin chc nng bin dch tiu chung(Global Title Translation), thm vo d liu nh tuyn cn thit v tr bn tin li cho MTPmc 3 tip tc truyn i.

Bn cnh chc nng phn bit, phn pht v nh tuyn bn tin, MTP mc 3 cng thchin mt s chc nng qun l. N iu khin vic s dng LSSU cho qun l ng s liumc 2. Quan st trng thi ng mc 3 bao gm c iu kin ca im cui, chng hn nhcc card giao din mng, sao cho mt ng s liu c th hot ng mc 2 nhng khngcung cp dch v mc 3. Chc nng qun l ng mc 3 thng a nhng ng s liu liny sang trng thi khng phc v, thc hin xc nh li v ng chnh li, v a chng trli phc v m khng lm gin on qu trnh hot ng. Chc nng qun l mc 3 cng khito lu lng lp cao hn v qun l nh tuyn bn tin s dng cc bn tin MSU c xcnh qun l. Khi mt node b nghn hay khng phc v c v mt l do no , mc 3c th gim lu lng qua node hay nh tuyn li lu lng. Trong c hai trng hp uthng bo cho cc node ln cn trn mng. Mc 3 cng cung cp thng tin bo dng cho cctrung tm OA&M nh qun l c th can thip.2.3.2. Cc chc nng ngi s dng MTP

Cc chc nng ngi s dng MTP (MTP User Functions) cho php tip cn ti ngis dng MTP (MTP User). C hai ngi s dng MTP :

- Th nht l Phn ngi s dng ISDN (ISUP) s dng MTP mang cc bn tin iukhin thip lp v hu b cuc gi link by linh.

- Th hai l Phn iu khin kt ni bo hiu (SCCP) cho php nh tuyn mng mtcch mm do cc bn tin bin dch ng dng c s dng bi cc mng thng minh, ccdch v di ng cng nh OA&M.a. Phn ngi s dng ISDN (ISUP)

ISUP cung cp cc chc nng bo hiu cn thit h tr cc dch v mang c bn vcc dch v ph tr cho cc ng dng thoi v phi thoi. N iu khin qu trnh thit lp vhu b cuc gi thoi v s liu cho c cc cuc gi ISDN v khng phi l ISDN thng quaMTP. Nhim v ISUP c bn l thit lp mt kt ni knh truyn dn gia cc node, dn tibn b gi ph thuc vo bng nh tuyn chun t ti im chuyn mch. ISUP cng h trcc dch v ph tr ISDN bng cch mang cc c im hay thng tin ch gi kt hp vi cucgi m c thit lp nh l mt phn ca Trng thng tin dch v ISDN SIF.

ISUP chp nhn c cc bn tin thit lp cuc gi ISDN v khng phi l ISDN, sp xpchng vo Bn tin a ch khi to ISUP IAM ca chnh n. Do , ISUP thng c miu tl m rng n c lp ng dng (lp 7) ca m hnh OSI, ni m cc bn tin thit lp cuc giny c khi to.

Khun dng cc bn tin ISUP c mang trong trng SIF ca mt bn tin MSU ISUP.ISUP SIF cha mt nhn nh tuyn, mt m nhn dng knh v thng tin bo hiu. Nhn nhtuyn cung cp cc m im cho a ch bt u v a ch ch. M nhn dng knh CIC lmt m (khng c xc nh trong cc khuyn ngh ca ITU T) m xc nh knh mang li tng ca bn tin. Thng tin bo hiu bao gm kiu bn tin v cc thng s bt buc/lachn c xc nh bi bn tin . C 43 kiu bn tin ISUP c ITU T nh ngha, v dnh l Bn tin a ch khi to IMA, bn tin qun l cuc gi nh CPG

Cu trc ca bn tin ISUP SIF nh sau :

b. Phn iu khin kt ni bo hiu SCCPKhng ging ISUP c s dng thit lp v hu b knh mang vt l, SCCP tn ti

mang lu lng Cc ng dng ngi s dng SS7 v qun l. V n mang thng tin ngdng gia hai im m c th khng lin quan n bt c knh mang no, SCCP phi c khnng bin dch v cung cp thng tin nh tuyn v nh a ch mm do hn qua cc giaodin ti MTP. SCCP thc hin chc nng bin dch tiu chung GT (Global TitleTranslation) v nh tuyn cho cc m im xut pht v m im ch m khng gn vi imxut pht v im ch thc t, cng nh l cc s phn h m cung cp cc a ch logic chocc phn h ng dng ring bit trong node c nh a ch. SCCP cng iu khin chia sti MTP mc 3 gia cc im bo hiu d phng.

Giao thc SCCP c bn chc nng c bn nh c ch ra hnh sau :

SCRC

SCLC

SCMG

SCOC

Ti lp 2

Ti lp 4T lp 2

Ti lp 2

Hnh 2.8. Chc nng ca SCCPChc nng quan trng nht l iu khin nh tuyn SCCP (SCCP Routing Control -

SCRC). SCRC bin dch gia node duy nht v m im i ch phn h v tiu chung cn gin ho cha trong hu ht cc bn tin SCCP. Da trn kh nng bin dc ny, SCCP thchin chc nng phn loi bn tin, phn phi cc bn tin c nh a ch node ny ti cc

phn h, v chuyn nhng bn tin m khng c nh a ch tr li MTP. SCCP nh tuynbn tin ti mt trong ba chc nng sau phn pht ti cc phn h: chc nng iu khinkhng kt ni SCCP (SCCP Conectionless Control - SCLC), chc nng qun l SCCP (SCCPManagement - SCMG), v chc nng iu khin hng kt ni SCCP (SCCP ConectionOriented Control - SCOC). SCCP c nh ngha cho c cc dch v hng kt ni v khngkt ni. Dch v khng kt ni SCCP rt tt v c th cnh tranh vi cc c tnh vi dch vhng kt ni n mc thng tin kiu hi p c th c thc hin mt cch tin cy.

SCCP cung cp hai mc dch v khng kt ni : lp 0 l dch v datagram, v lp 1 ldch v nh th t. Khi mt ngi s dng la chn dch v lp 0, SCCP phn phi bn tinmt cch ngu nhin qua bt c ng s liu d phng no kh dng nh l mt phng thcqun l duy tr s cn bng lu lng. Lp 1 c chn khi di ca mt phin lm vicln hn 273 octet c php trong trng SIF ca mt bn tin MSU. Khi SCCP lp 1 phthin ra rng mt phin giao dch b phn on, n yu cu tt c cc on s phi c truynqua cng mt tuyn vt l, do bo m rng ngi nhn s nhn tt c cc on theo ngth t m n c truyn i.

Bn cnh vic iu khin th t c cung cp bi s la chn hai lp dch v, SCCPcung cp hai thng s cht lng dch v QoS khc nhau. La chn quay li cho php MTPhu b bn tin li hay yu cu tr li SCCP nh l mt bn tin li. Mc u tin ca bn tinc gn bi MTP cho bn tin SCCP ph thuc vo cc tiu ch c pht trin t bn ngoi.

SCCP cho php qun l nh tuyn v lu lng mng mt cch t ng. Khng gingnh qun l MTP ch chu trch nhim cho cc ng s liu ring bit ni cc node, qun lSCCP h tr cc ng dng v phn h m c th c phn phi qua vi node. SCCP nhnthng tin gc v tnh trng node trc tip t im bo hiu MTP cng nh trng thi phn h tnode xa. Da trn nhng thng tin ny, SCCP c th cu hnh li mng bo hiu; SCCP loi blu lng hay nh tuyn cc bn tin i vng qua cc node m thng bo l chng b nghn, vqun l s khc nhau v nh tuyn gia dch v lp 0 v lp 1. Thm vo , SCCP c thc s dng h tr OAMP trong tnh trng cnh bo.

Ging nh ISUP, bn tin SCCP c mang trong trng SIF ca bn tin MSU. TrngSIF ny mang mt nhn nh tuyn ging nh ca ISUP, xc nh im khi to v im chca cuc gi. Phn th hai ca SCCP SIF cha loi bn tin v cc thng s la chn hay btbuc nh ngha cho loi bn tin . Khng ging nh ISUP, SCCP cung cp mt dch v vnchuyn v trng th ba cha bt c bn tin no c truyn, thng l mt bn tin Cc khnng ngi s dng TC.

Cu trc ca bn tin SCCP SIF nh sau :

2.3.3. Ngi s dng SS7 (SS7 Users)Ngi s dng SS7 chng ta cp n y l nhng ng dng tn ti ti lp 7 ca m

hnh OSI (lp ng dng). Ngi s dng SS7 c th c chia thnh hai loi : Nhng ngi s dng ng dng h tr lu lng chuyn mch knh (Phn ngi s

dng iu khin knh), s dng ISUP truy nhp ti MTP Nhng ngi s dng ng dng m truy nhp ti MTP thng qua Cc kh nng bin

dch SS7 v SCCP m h tr lu lng khng phi l chuyn mch knh vi c sd liu ti SCP ; bn cnh cho php vn chuyn cc d liu ng dng.

a. Phn ngi s dng ISDNISUP - iu khin thit lp v hu b knh nh l mt giao thc lp 4 trong m hnh

OSI, cng l mt giao thc lp ng dng OSI. V ISUP coi mt bn tin thit lp gi ca ngis dng nh l mt bn tin ng dng c bin dch sang khun dng ISUP ca chnh n,ISUP thng c m t trong chng giao thc SS7 nh l mt " ng ng" t lp 4 n lp7, s dng bi cc ng dng chuyn mch knh.b. Cc kh nng bin dch TC

TC h tr cc tin trnh ng dng lp 7 ca m hnh OSI khng phi l chuyn mchknh. Nhng tin trnh ny ph thuc vo mt kh nng no ca SS7 thc hin hi - p,cc dch v mng thng minh, hay cc bn tin truyn d liu... Tt c u c th c coi nhl cc "giao dch". Tt c cc giao dch ny yu cu bn tin phi c nh tuyn gia ngi sdng v c s d liu hay gia ngi s dng vi nhau. Thng tin ny khng p dng cho iukhin knh, v nh tuyn th khng c thc hin bng phng thc link to link nhISUP. TC l mt Thnh phn dch v ng dng (ASE) chung m c th h tr mt s cc ngdng SS7. Tuy nhin, hu ht cc ng dng, chng hn nh Phn ng dng Qun l, iu hnhv bo dng OAMP, yu cu phi c thm cc chc nng ASE xc nh m khng c cp bi SS7.

ITU T nh ngha TC l mt ASE chung nm gia Ngi s dng TC (trn lp 7 OSI)v SCCP. TC bao gm Phn ng dng (TCAP) v Phn dch v ng dng cha xc nh(ASP). ASP thuc t lp 4 n lp 6 OSI v h tr dch v hng kt ni. Tuy nhin c cckhuyn ngh ca ITU T v cc chun T1 ca M u cha nghin cu c th vn ny. Dovy, c ITU T v T1 u coi TC trng vi TCAP.

TCAP gm 3 phn lp: Bin dch, Hi thoi v Thnh phn. Phn lp Bin dch xc nhv phn phi lu lng ti phin xc nh v cc thnh phn ng dng nh, do h tr victhc hin cc dch v hng kt ni. Phn lp Hi thoi v Thnh phn h tr hi/p v nhucu truyn ti lu lng d liu n hng ca cc ng dng.

Ging nh tt c cc bn tin SS7 lp cao hn, TCAP ph thuc vo MSU, to mttrng TCAP trong trng SCCP SIF bao gm phn xc nh bin dch v d liu (thnh phn,d liu, hay hi thoi) cn thit cho bin dch. Trng xc nh bin dch xc nh kiu bn tinv cc thng s yu cu.

Cu trc ca trng TCAP trong SCCP SIF nh sau:

2.3.4. Cc phn ng dng INAP, MAP, OMAPa. Phn ng dng mng thng minh INAP

INAP (Intelligent Network Application Part) cho php thc hin mt c s h tng bohiu, phn cp nh cung cp t c mt th trng in thoi c nh rng khp ton cu.INAP l mt giao thc bo hiu gia mt SSP, cc ngun phng tin mng (ngoi vi thngminh), v c s d liu tp trung ca SCP. SCP bao gm cc d liu v chng trnh dch vcung cp bi nh khai thc mng hay bn th ba no . Thng qua INAP, nh khai thc mngc th t c s c lp ti a t cc chng trnh phn mm cung cp bi cc nh cung cptng i. Mng thng minh (IN) l mt kin trc mng in thoi m tch bit dch v ra khithit b chuyn mch, cho php cc dch v mi c th c thm vo m khng phi thit kli phn mm chuyn mch. Vi mng IN, nh khai thc c th thc hin cc dch v gi tr giatng khc nhau, to cho chng cc u im cnh tranh trn th trng v n cho php thm vocc dch v mi mt cch d dng hn v cung cp cho cc khch hng nhiu s la chn hn.IN c tnh c lp ng dng, c ngha l n cung cp cc chc nng c th ti s dng v tngqut m c th c tch hp hay ti kt hp cung cp cho mt dch v mi.

SCP lu tr cc d liu v thng tin v nh cung cp dch v nh hng cho hot ngx l chuyn mch v iu khin cuc gi. Ti mt im nh trc trong qu trnh x l mtcuc gi n hay i, tng i tm dng tin trnh ang thc hin, ng gi thng tin lin quann x l cuc gi, a vo hng i v i lnh tip theo. SCP thc hin cc chng trnh

c nh ngha bi ngi s dng m phn tch trng thi hin ti ca cuc gi v thng tinnhn t tng i. Chng trnh khi c th chnh sa hay to d liu cuc gi c gi trli cho tng i. Sau tng i phn tch thng tin nhn c t SCP v thc hin theo nhnghng dn c cung cp cho qu trnh x l cuc gi tip theo.

c pht trin bi ITU, IN c xc nh nh l mt chun ton cu. Ton b cc chcnng ca IN c xc nh v thc hin trong cc phn gi l cc tp kh nng (CS). Phinbn u tin c pht hnh l CS-1. Hin nay cng xc nh v c CS-2. Phn ng dngCAMEL (CAP) l mt phn tch ra t INAP v cho php s dng INAP trong mng di ngGSM.

Cch thc hot ng ca INAP: Thu bao ch gi quay s. Nhng con s quay ny c gi n tng i. Tng i thng c bit n trong mng bo hiu l SSP chuyn tip cuc gi

qua mng bo hiu s 7 ti SCP, ni lu tr c s d liu v thng tin logic dch v. SCP xc nh dch v c yu cu t cc s c quay v tr li thng tin v cch

thc x l cuc gi cho SSP. Trong mt s trng hp, cuc gi c th c x l nhanh hn bng ngoi vi

thng minh c u ni vi SSP thng qua cc ng ISDN tc cao. V d, mtthng bo thoi tu chn c th c pht tr li cho s quay hay mt cuc githoi c th c phn tch v xc nh.

Thm vo , cc thit b b tr c th c thm trc tip vo SSP vi cc kt nitc cao cho cc dch v gia tng cha xc nh.

Cc dch v c th c cung cp bi INAP bao gm: Dch v s n: mt s quay c th ti mt s ni ht cng vi dch v. Dch v truy nhp c nhn: cho php ngi s dng qun l cuc gi n. Dch v khi phc thm ho: cho php lu tr d phng a ch cuc gi trong

trng hp c thm ha. Dch v chuyn tip cuc gi Dch v quay s m rng mng ring o

b. Phn ng dng di ng GSM MAPPhn ng dng di ng GSM (GSM MAP) cho php thc hin c s h tng bo hiu

mng di ng, phn cp nh cung cp dch v hng ti mng GSM v l nn tng cungcp cc c tnh di ng ca n. Tin to ra GSM MAP l kt ni cc thnh phn chuynmch phn tn, c gi l cc MSC vi mt c s d liu chnh l HLR. HLR lu tr mtcch ng v tr hin ti v thuc tnh ca mt thu bao di ng. HLR c tham kho trongqa trnh x l mt cuc gi n. Ngc li, HLR c cp nht khi thu bao di chuyn trongmng v do c phc v bi cc tng i khc nhau.

GSM MAP v ang pht trin khi mng v tuyn m rng, t h tr n thun thoi,ti cc dch v d liu gi. GSM MAP cng c th c kt ni ti cc thnh phn ca mngNGN chng hn nh GGSN hay SGSN.

GSM MAP c mt s chc nng c bn. N cung cp:

C ch cho mt GMSC tip cn c mt s nh tuyn cho cuc gi n. C ch cho mt MSC cp nht tnh trng thu bao v s nh tuyn qua VLR tch

hp. D liu v cc thuc tnh dch v b sung ca thu bao ti cc thnh phn chuyn

mch thng qua VLR.GSM MAP cng vi CAMEL cho php thc hin khi nim mng ch v khch, t

cho php nh khai thc mng c th cung cp cng mt s cc dch v nh nhau m khngquan tm n vic thu bao c l thu bao ca mng ch khng, hay n ang c chuynvng mng khch.c. Phn iu hnh, qun l v bo dng OAMP.

OMAP cung cp phng tin nh khai thc mng bo dng mng ca h. Cng vicduy tr v bo dng bao gm vic qun l bn ngoi chc nng qun l c thc hin mtcch t ng bi cc giao thc SS7.

OMAP hon ton p ng ba yu cu chnh ca cc giao thc SS7 v mng bo hiu kthp.

N cung cp mt giao din gia nh khai thc v mng bng cch s dng cc khinim chun c nh ngha bi cc khuyn ngh v qun l mng vin thng caITU T.

N cung cp phng tin chun ha cch tip cn ti ton b mng vin thng (baogm cc knh mang v cc mng khc). iu ny c ngha l cc i tng cqun l bi OMAP ph hp vi cc i tng c nh ngha qun l bi ITU T.OMAP thc hin vic iu khin nhng i tng ny bng cch s dng mt Cs thng tin qun l TMN (TMN MIB), thng qua mt giao din cha xc nh.Mi mc giao thc cha mt s Thc th qun l lp (LME) m cc i tng cqun l t .

OMAP m rng cc chc nng qun l t ng ca cc giao thc SS7 thnh mt hthng duy nht trn ton th gii.

OMAP cho php qun l li v hiu nng, qun l cu hnh li, gim st hiu nng mngv s thnh cng ca cc th tc qun l t ng ca SS7. OMAP cng cho php ngi iuhnh c th ch ng can thip tm dng hot ng mng bo dng.

OMAP hot ng thng qua 3 chc nng l: kim tra tnh hp l nh tuyn MTP, kimtra tnh hp l nh tuyn SCCP, kim tra tnh hp l knh. Nhng kim tra ny v mt khinim thuc v Ngi s dng thnh phn ng dng OMAP (OMASE) ca OMAP. OMASEthng tin vi SCCP v MTP thng qua OMASE c bit v ASE, TC chung.2.4. V d v thit lp cuc gi n gin s dng h thng bo hiu s 7

Chng ta xem xt mt th tc gi cho mt cuc gi t mt thu bao ca tng i A timt thu bao ca tng i B v qua thy c vai tr ca mng bo hiu s 7.

STP W STP X

Bchuynmch A

Bchuynmch B

14. R

EL

3.IA

M

16. RLC

11. ANM

7. ACM

8. ACM

12. ANM

17. RLC

14. REL4. IAM

Voice Trunk

Signaling Link

Subscriber Line

Hnh 2.11. V d thit lp cuc gi n gin s dng SS7

1. Tng i A phn tch cc con s c quay v xc nh rng n cn phi chuyncuc gi n tng i B

2. Tng i A chn mt knh trung k ri gia n v tng i B v to mt bn tina ch khi u IMA bn tin c bn u tin thit lp mt cuc gi. IMA ca ch l tng i B. N xc nh tng i khi to (tng i A), tng i nhn(tng i B), trung k c chn, s b gi v s ch gi cng nh l cc thngtin khc.

3. Tng i A chn mt trong nhng tuyn bo hiu loi A ca n (v d AW) vtruyn bn tin qua tuyn bo hiu nh tuyn n tng i B.

4. STP W nhn bn tin, c nhn nh tuyn, v xc nh rng bn tin c nhtuyn n tng i B. N chuyn tip bn tin trn tuyn bo hiu WB n B.

5. Tng i B nhn bn tin. Nh phn tch bn tin, n xc nh rng thu bao b ginm trong s phc v ca n v thu bao b gi ang ri.

6. Tng i B to mt bn tin hon thnh a ch ACM ch ra rng IAM nc a ch thch hp. Bn tin xc nh tng i nhn (tng i A), tng i gi(tng i B) v trung k c chn.

7. Tng i B chn mt trong nhng tuyn bo hiu loi A ca n (v d l BX) vtruyn bn tin ACM qua tuyn nh tuyn n tng i A. Cng mt thiim, n hon thnh ng i cho cuc gi hng ngc li (hng v tng iA), gi hi m chung qua trung k n A, v gi tn hiu chung cho ngdy thu bao b gi.

8. STP X nhn bn tin, c nhn nh tuyn ca n v xc nh rng bn tin cgi n tng i A. N chuyn tip bn tin trn tuyn XA.

9. Khi nhn c ACM, tng i A kt ni ng dy thu bao ch gi ti trung k c chn theo hng ngc li ( ngi gi c th nghe thy tn hiu him chung c gi t tng i B).

10. Khi thu bao ch gi nhc my, tng i B to mt bn tin tr li ANM, xc nhtng i nhn (A), tng i gi (B) v trung k c chn.

11. Tng i B chn tuyn bo hiu dng gi bn tin ACM (tuyn BX) gibn tin ANM. Ti thi im ny, trung k cng phi c kt ni ti ng dyb gi theo c hai hng ( cho php hi thoi).

12. STP X nhn dng bn tin ANM, xc nh a ch tng i nhn l tng i A vchuyn tip n qua tuyn bo hiu XA.

13. Tng i A m bo chc chn rng thu bao ch gi c kt ni vi trung k c hai hng v cuc m thoi c th c thc hin.

14. Nu nh thu bao ch gi h my trc (sau khi hi thoi), tng i A s to mtbn tin gii phng REL c a ch l tng i B, xc nh trung k phc v cucgi. N gi bn tin ny i qua tuyn bo hiu AW.

15. STP W nhn bn tin REL, xc nh a ch ca n l tng i B, v chuyn tipn bng tuyn bo hiu B.

16. Tng i B nhn bn tin REL, ngt kt ni trung k khi ng thu bao, tr litrung k v trng thi ri, to mt bn tin hon ton gii phng RLC c a ch ltng i A, v truyn n trn tuyn bo hiu BX. RLC cng ch r trung k c s dng phc v cuc gi.

17. STP X nhn bn tin RLC, xc nh a ch tng i nhn (A) v chuyn bn tin iqua tuyn XA.

18. Khi nhn c bn tin RLC, tng i A a trung k c ch ra v trng thiri, sn sng phc v cuc gi mi.

2.5. X l bo hiu trong tng i2.5.1. Gii thiu

H thng bo hiu c s dng nh mt ngn ng cho 2 thit b trong h thng chuynmch trao i vi nhau thit lp tuyn ni cho cuc gi. Ging nh bt k ngn ng no,chng cng c t vng vi nhng chiu di khc nhau v chnh xc khc nhau. Tc l ccbo hiu cng c th thay i v kch thc v dng c php ca n theo cc quy lut ghpni v to thng tin bo hiu.

X l bo hiu trong tng i l s x l cc dng tn hiu bo hiu thu bao v tng itrn cc ng dy thu bao v trung k trong tng i. Bo hiu trong tng i in thoi baogm khng ch l bo hiu gia tng i vi thu bao v bo hiu lin i m cn mang ccthng tin v trng thi cuc gi bng cc tones v cc bn tin thng bo khc

Hnh 2.12. Tng quan x l bo hiu trong tng iNh vy, ta thy rng qu trnh x l bo hiu bao gm cc phn chnh sau:

- nh tuyn trong tng i.- Cc b thu pht bo hiu.- To tones v cc bn tin thng bo.

2.5.2. S nh tuyn trong tng iBo hiu tng i - thu bao: Trong tng i SPC c kh nng cho php hai loi thu bao

tng t v thu bao s ng vi mi loi, ta c cc tn hiu, phng php nh tuyn khcnhau.

o Thu bao tng t: Trn mng in thoi hin nay, v l do kinh t thng s dngthu bao tng t. S nh tuyn thu bao tng t nh hnh di y. S nh tuyngm hai thnh phn bo hiu:

- Tn hiu bo hiu ng dy (gim st): mang trng thi ca mch in.- Tn hiu bo hiu a ch (chn s): ch th s thu bao b gi.

Hnh 2.13. nh tuyn bo hiu ca thu bao tng t n thit b thu tng ngTn hiu bo hiu ng dy c nhim v gim st mch in ng dy thu bao. Vi

cc thu bao tng t, dng tn hiu ny dng LD (ct mch vng). Tn hiu bo hiu chn s(a ch) c th c thu bao pht bng 2 cch: LD hoc MF (m a tn). i vi in thoidng a quay s, c bo hiu ng dy v chn s u c thc hin theo kiu ct mchvng (Loop disconnection). Cc tn hiu bo hiu ny c tch ra t ng dy thu bao biSLTU. Sau , chng c thu thp ti khi iu khin SLTU bin i t trng thi LDsang cc tn hiu trng thi v ch s a ch ri gi n h thng iu khin taeng i x lv t a ra nhng thao tc thch hp. i vi in thoi n phm, tn hiu ng dy ctin hnh theo kiu LD cn tn hiu chn s theo kiu MF. Nh vy, tn hiu ng dy ctch ra khi SLTU v qua b SLTU n h thng iu khin tng i nh in thoi a quays. S truy cp n b thu MF thng thng qua khi chuyn mch tp trung thu bao. B thuMF c th dng chung cho 1 s ln ng dy thu bao vi mc ch gim chi ph thit b.

o Thu bao s: y l s nh tuyn bo hiu n 2 kiu thu bao s ISDN v ISPBXtrn s truy cp ng dy s cp v th cp. Trong s truy cp s cp, 1 knh bohiu 16Kbps kt hp vi 2 knh giao thng 64Kbps to thnh tc 144kbps dng(2B+D) cho mi hng. Knh bo hiu mang thng tin bo hiu ng dy v chns cho c 2 knh giao thng nh thng tin x l cuc gi v cc thng tin bo dng.Trong s truy cp th cp bao gm 1 ng dn 2Mbps t 1 ISPBX, 1 knh bo hiuknh chung tc 64kbps cho 30 knh giao thng 64Kbps c mang trong TS16.

Hnh 2.14. nh tuyn ca thu bao sBo hiu lin tng i: Cc h thng bo hiu khc nhau trn cc ng trung k c

nh tuyn n cc b thu pht bo hiu tng ng c thc hin nh b chuyn i tn hiuhoc kt hp trong ATTU (Analogue Trunk Terminalting Unit) cho cc kiu bo hiu LD, DCv 1VF. H thng bo hiu 1VF l h thng bo hiu n tn trong bng, n c th l bo hiung dy hoc bo hiu a ch (nhng ch yu l ng dy). S chuyn i bo hiu trongbng sang dng thch hp a n cc b thu pht bo hiu (thng l CAS) c th cthc hin bi mt thit b kt hp mi li vo tng t n 1 ATTU hoc s dng mt n vn gin m n tch cc tones t dng s 2Mbps. Phng thc th 2 thng c s dngnhiu hn v tnh kinh t ca n. B chuyn i thc hin chia mt li vo 2Mbps cha 30knh vi m bo hiu n tn 1VF thnh li ra 2Mbps vi bo hiu mang trong TS16. Thit bdo phi c kh nng tm kim s xut hin ca cc tones c m ha s (v d 2280). iuny c thc hin bi k thut lc s. i vi hng ngc li, thit b chuyn i cc bitsCAS trong TS16 thnh cc tones tng ng chn vo lung 2Mbps. Bo hiu MF c nhtuyn trn c s call-by-call qua khi chuyn mch nhm t ng dy ang gi n b thupht MF bng ni kt thi gian gi ngn (short-holding-time). Ni kt thi gian gi ngn lmt ni kt trong thi gian rt ngn thng vi mc ch thu nhn cc ch s a ch, ni ktny c gii phng ngay sau khi tn hiu a ch kt thc. Lc ny mt ng dn thoic thit lp qua trng chuyn mch n li ra yu cu. Ty theo phng thc truyn thngtin bo hiu m c phng php bin i khc nhau. truy nhp ti b thu pht bo hiuCAS l cc ng ni bn c nh. Cn cc ng ni ti cc b thu pht MF l cc tuyn cnh thc hin nguyn tc trao i gia cc khe thi gian TS16 vi nhau v ni dung cc TSny c cha thng tin bo hiu. i vi bo hiu knh chung, thng tin bo hiu c chatrong cc TS16 ca cc lung 2Mbps truy nhp n b thu pht CCS qua ng ni bnvnh vin (semi-permanent) qua trng chuyn mch. Ni kt ny cho php cc khe thi giant lung 2Mbps truy cp n CCS S/R qua 1 cng 2Mbps. Ni kt ny l bn vnh vin v n

duy tr trong mt thi gian di (c th l vi nm) cho n khi c s c hoc c s thay i lntrong tng i th h thng iu khin s thit lp tr li.

Hnh 2.15. nh tuyn bo hiu vi cc ng trung k2.5.3. Cc b thu pht bo hiuThu pht MF

nh tuyn bo hiu MF t thu bao hoc cc ng trung k ti b thu pht MF, yucu mi b thu pht cn phi giao tip vi 30 knh thoi v s b thu pht yu cu ph thucvo tc s dng v thi gian chim dng ca mi cuc gi. i vi bo hiu thu bao, mtng dn n hng c thit lp qua b tp trung thu bao gia SLTU ang gi v 1 khethi gian ri trong ng cao tc ti b thu pht MF, trong khi tone mi quay s c a nthu bao qua 1 ng thoi n hng khc qua b tp trung. n vTH MF phi c kh nngxc nhn c ch s u trong tone mi quay s. Khi cc s quay l y , h thng iukhin tng i s gii phng ng dn qua b tp trung thu bao ny. Khe thi gian trongng cao tc lc ny l ri v c th c s dng cho cc cuc gi khc. Qu trnh bo hiulin i cng din ra tng t.B thu pht MF c th s dng k thut tng t hoc k thut s.

B thu pht MF dng tng t: Phng php ny s dng nhiu trong cc tng ith h u v tnh kinh t cao. 30 b thu pht MF c ni v bin i ti PMUX(MUX th cp) to ra lung s 2,048Mbps theo cu trc khung. Trong , TS0 chctn hiu ng b khung v TS16 bo hiu cho cc knh cn li.

Hnh 2.16. Cc b thu MF tng t B thu pht bo hiu MF dng s: B thu lm vic theo nguyn tc phn chia theo

thi gian cho mt s knh ( y l 4). Cc s thu c t mi knh qua b thu n nv iu khin, , chng c nh dng vo trong mt bn tin ri gi n h thngiu khin taeng i. B pht MF th lm vic mt cch n gin hn, mnh n c sdng cho tt c cc knh thoi v trong TS16 ca lung 2Mbps.

Hnh 2.17. Cc b thu MF sVi kiu thu pht MF s, ch cn 8 b thu MF cho 30 knh u vo v mt b pht chott c cc knh. B thu MF s da trn c s b lc s. Yu cu kh nng nhn bit vphn tch 2 tone t mt t hp a tn (2 tn s), b qua cc tn hiu ngoi bng tn4Khz xc nh c cc tn hiu bo hiu khc nhau suy ra ngha ca n. Sau, b thu s tm ra tn hiu c t hp tn s tng ng gi n b iu khin thu phtMF a n h thng iu khin tng i c nhng x l thch hp. B pht MF cth thc hin bng cc t hp tn s c m ha v lu tr trong ROM v c c ra cc ng vo thi im thch hp.

2.5.4. Cc b to tone v bn tin thng boa. S nh tuyn tones v cc bn tin thng bo:

Tng i cn phi bo cho thu bao v trng thi cuc gi cng nh cc tin trnh ca nt khi bt u n khi kt thc. Tc l mt thu bao bnh thng mun trao i thng tin thphi c p ng m xc nhn yu cu hoc yu cu khng c chp thun v nhiu m

khc nhau trong tin trnh x l cuc gi nh thng bo, tr gip... Thng thng, thng tintrng thi c th nghe thy c dng tones hoc li thoi thng bo. Do , mi thu baocng nh cc ng trung k v cc n v khc thuc tng i phi c truy nhp n cc bto tone v thng bo.

Hnh 2.18. S nh tuyn cho Tone v bn tin thng bo t hiu qu kinh t v k thut cho vic phn phi cc m bo n tng thu bao, cn

phi phn loi theo chc nng ca tng dng m m phn b v tr ca cc b to m. V d:cc tnh trng thng thng c bo hiu bng cc tones, cn cc trng hp c bit th bngcc bn tin. Trong tng i SPC, cc b m bo thng c phn b ti cc b tp trung thubao theo phng php 1 ng phn b ti nhiu ng. Cn b lu tr bn tin thng boc phn b ti khi chuyn mch chnh, v cc bn tin ny mang tnh cht dch v, t linquan n tin trnh x l cuc gi.

Vic nh tuyn cho cc m bo ti cc thu bao c thc hin bng lung s PCM.Nh vy, ti u ra ca thit b to m l cc tn hiu s, mi 1 m bo khc nhau c chatrong mt TS ring v n c qua khi chuyn mch tp trung thu bao hay khi chuynmch nhm nh qu trnh chuyn i tn hiu thai. S khc bit y l tn hiu t b to mphi m bo v ln n thc hin chuyn mch ti nhiu u ra c yu cu cng lc.

Vi cc bn tin thng bo, thng thng n c truy cp ti khe thi gian trung gianca khi chuyn mch chnh v c thc hin chuyn mch nh tn hiu thai.b. Cc tones x l cuc gi

Trong tng i s, c hai cch to tones x l cuc gi a vo ng dn thai, l:

- Pht lin tc cc tones dng tng t, ri sau a qua b chuyn i A/D.- Pht lin lc cc tn hiu s tng ng vi cc tones bo hiu khc nhau.

Phng thc u tin c s dng cho cc h tng i trc y v n khai thc thit bto tones trong tng i tng t m cha thay bng k thut s c. S lai tp gia cc bpht tones c-in t trong taeng i in t s gy nn s cng knh v kch thc v kmhiu qu v mt kinh t. Khi k thut s l pht trin th phng thc th 2 c s dng nhiuhn vi cc tnh nng cao hn.

Cc b to tones phc v cho chuyn mch tp trung thu bao c yu cu trong thigian u trc thit lp cuc gi, cn b to tone phc v chuyn mch nhm dng mangp ng ca thu bao trong thi gian thit lp cuc gi.c. B to tone v cc bn tin thng bo

Dng k thut tng t: C nhiu loi cu trc b to tone. Vi cc tng i analog thta c cc b to tone analog vi cu trc n gin l cc b to dao ng vi cc mchiu khin ngt nhp khc nhau nh rle hoc cc cng in t. Cc tn hiu bo hiuny phi c chuyn i sang dng s chn vo cc khe thi gian trong cc tuynPCM a n cc u cui qua trng chuyn mch. Nhc im: Kch thc ln,cng knh, khng kinh t, khng c tin cy cao.

Hnh 2.19. S dng k thut tng t Dng k thut s:

o To tones: i vi tng i SPC hin nay th cc b to m thng l b totone s. Cc b to tone ny c kh nng cho ra nhiu loi tone khc nhau. Vicphn bit cho cc loi tone ny cho tin trnh x l cuc gi c thc hinbng cch thit lp cc di ngt nhp khc nhau cho cc tone. Cu trc nyph thuc vo cch qun l khc nhau. Cc phn t b to tone s bao gm: Ccb nh ROM dng lu tr cc loi tone tng ng bng cc tn hiu s,mch iu khin tone theo chu k, b iu khin c ROM v cc thit b iukhin khc.

Hnh 2.20. S b to m bo s

Cc b nh ROM lu cc loi tones tng ng m ha v c ra vi a ch dobm chu k xc nh. Thi im pht tones qua trng chuyn mch do n v iukhin iu khin b SELECTOR. B SELECTOR bao gm cc b ghp knh logics m chuyn mch gia li vo v li ra ph thuc vo a ch c cung cp bin v iu khin. Nh vy, cc tones khc nhau c s ha (vi tn s ly mu l8Khz) v np vo ROM, sau c c ra thi im thch hp theo yu cu cathu bao. i vi tn hiu c chu k th ch cn np vo chu k l . i vi tnhiu khng c chu k th phi np tt c tn hiu . iu ny lm gim dung lngca ROM, do , tnh kinh t phng pht ny rt cao.

To cc bn tin thng bo: Mt trong kh nng cung cp dch v ca tng i SPC lvic cung cp cc bn tin thng bo vi nhng ni dung mang tnh cht thng bo chdn Cc bn tin thng bo c lu tr trong cc thit b bng t, a t, b nhsao cho kh nng truy cp c d dng. Trn thc t c hai phng php lu trsau:

- Phng php 1: Tt c cc bn tin c s ha vi tng bit nh phn v ghi vo thitb lu tr.- Phng php 2 : Kiu ca bn tin thng bo c dng cc cu, cc t hp ch ci cchung nht mt m tit, cc t vng chung c ghi vo vi mch ROM, RAM truyxut theo mt a ch thch hp.

Phng php 1 n gin nhng tn km v khng gian b nh, phng php 2 kinh t hn,nhng vn iu khin li phc tp hn rt nhiu. Cc bn tin c nh th c th lu vo trongROM, cn cc bn tin c th thay i hoc cc dch v mi th thng c lu vo RAM tng tnh linh hat, thun tin trong vic sa i b sung.

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 tca cc dch v. D liu tr nn c ngha hn trong ton b lu lng truyn titrn mng so vi lu lng thoi. Cc nh khai thc ang tm cch kt hp gia lulng thoi v lu lng d liu, gia cc mng li v cc dch v. Trong s cc giiphp cng ngh c la chn, cng ngh IP hin ang c quan tm vi t cch lgii 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 vi mngIP mi. Cc nh khai thc ang thay th cc mng in thoi c nh v di ng theokin trc ton IP v c c h tr giao thc bo hiu s 7. Cng nh IP cho php cc nhkhai thc mng c th m rng mng v xy dng cc dch v mi mt cch c hiuqu. Thnh phn cc dch v b sung thng dng nh SMS, gp phn vo s phttrin 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 mngSS7 hin c v cc tnh nng nng cao trong tng lai l trong sut.

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

Hiu qu tt hn: S dng SIGTRAN qua IP khng yu cu cc lung vt lE1/T1 qua mng truyn ti SDH. S dng cng ngh truyn ti IP qua SDH, IPqua cp quang, c th t thng lng cao hn nhiu.

Bng thng cao hn: Thng tin SIGTRAN qua IP khng buc phi c lin ktnh 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 phttrin 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 kintrc 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 ckt hp li vo c s h tng mng thng nht. Chc chn rng mch chuyn mchknh s cn tn ti trong nhiu nm na cng vi cc dch v IP. Kin trc kt hp cth l gii php tt nht cho hu ht cc nh khai thc v n m bo mc ri ro thptrong qu trnh pht trin mng hin ti trong khi vn cho php p ng c cc dchv mi. y l mc ch ca nhiu nhm nghin cu chun ha m SIGTRAN caIETF l mt trong s . SIGTRAN a ra m hnh kin trc cho php mng pht trintin n mng ton IP. M hnh kin trc ny gm hai thnh phn mi: SCTP v mt scc giao thc tng thch ng ngi s dng (nh M2UA, M2PA, M3UA, SUA) chophp p ng cc phng thc yu cu hi t hai mng ny.

Hnh 3.2. Kin trc mng s dng SIGTRAN

3.2. GII THIU V SIGTRAN

Sigtran l mt nhm cng tc thuc t chc chun ha quc t cho lnh vcInternet IETF. Mc ch chnh ca nhm l a ra gii php truyn ti bo hiu dnggi 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 ticc 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) vcng phng tin (MG) hoc c s d liu IP. Nhm cng tc Sigtran xc nh mctiu 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 bohiu qua cc mng IP. Cc bn tin bo hiu (nht l SS7) c yu cu v trv 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 giaothc truyn ti bo hiu c s dng v nh ngha mi cc giao thc truynti 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 mhnh kin trc truyn ti bo hiu s 7 qua mng IP. Kin trc giao thc SIGTRANc nh ngha gm ba thnh phn chnh (Hnh 3.3):

Chun IP.

Giao thc truyn ti bo hiu chung SCTP: Giao thc h tr mt tp chung cctnh nng truyn ti tin cy cho vic truyn ti bo hiu. c bit, SCTP l mtgiao thc truyn ti mi do IETF a ra.

Cc phn lp thch ng: H tr cc hm nguyn thy xc nh c yu cubi mt giao thc ng dng bo hiu ring. Mt vi giao thc phn lp thchng 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 IPthng l TCP. Tuy nhin, do TCP ra i kh lu v c thit k theo kiu giaothc 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 pv c ch tun t. Mt vi ng dng yu cu chuyn giao thng tin tin cy mkhng cn duy tr th t gi tin, trong khi mt s khc li yu cu p ng cv th t ca gi d liu. i vi TCP, c hai trng hp ny u gp phihin 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 xcnhn gi tin, iu ny lm cho TCP khng p ng c cc ng dng thigian thc.

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

Nhng gii hn cp trn y ca TCP l rt ng phi quan tm khi muntruyn bo hiu s 7 qua mng IP v do , y l mt ng lc trc tip cho s ra ica 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 png 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 sInternet. SCTP c IETF a ra v c t trong RFC 2960.

3.4.1. Tng quan v kin trc ca SCTP

V kin trc, SCTP nm gia tng tng thch ngi dng SCTP v tng mngchuyn gi phi kt ni nh IP, Dch v c bn ca SCTP l chuyn giao tin cy ccbn tin ca ngi dng gia cc ngi dng SCTP ng mc. SCTP l giao thc hngkt ni v vy, SCTP thit lp kt ni gia hai im u cui (gi l lin h trong phinSCTP) 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 nngny 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 ngidng SCTP. C ch cookie c dng trong qu trnh khi to cung cp sh tr bo v chng li s tn cng.

Phn phi tun t theo cc lung: Ngi dng SCTP c th xc nh s lngcc 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 tind liu ngi dng m bo cho cc gi tin SCTP truyn xung cc tngthp 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 thus 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 haithnh phn l tiu chung v theo sau l mt hoc nhiu chunk. Hnh v sauy 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 CheckSumnm trong tiu ca SCTP.

Qun l tuyn: Chc nng qun l tuyn SCTP chn a ch truyn ti ch chomi gi tin SCTP u ra trn c s ch dn ca ngi dng SCTP v trng thihin 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 SCTPgi/nhn.

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

Trng CheckSum: 32 bit. Cha tng kim tra ca gi tin SCTP. SCTP sdng 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. M2PAh 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 lulng 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

Hnh 3.8. Vai tr v v tr M2PA trong mng ton IPHnh 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 dkhc, trong MTP3 c thch ng vi lp SCTP nh s dng M2PA trong kin trcton IP.

y, cc im bo hiu IP MTP3 s dng lp M2PA bn di n thay choMTP2. Giao tip gia hai lp MTP3 hoc M2PA c nh ngha bi cng cc hmnguyn thu nh trong giao tip MTP3/MTP2. M2PA thc hin cc chc nng tng tnh MTP2.

3.6. M2UA

M2UA nh ngha mt giao thc truyn ti cc bn tin bo hiu ca ng dngMTP2 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.

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 SS7chun, s dng MTP SS7 cung cp truyn ti cc bn tin bo hiu SS7 n v t mtim du cui bo hiu SS7. Sau , SG cung cp s phi hp hot ng gia cc chcnng truyn ti vi IP SIGTRAN nhm truyn ti cc bn tin bo hiu MTP3 n imbo hiu IP ca MTP3 s dng MTP2 ca SG vi t cch l tng thp hn ca n sdng cc hm nguyn thy tng ng c nh ngha gia cc tng. Truyn thngMTP3/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 thyim bo hiu IP x l cchm nguyn thy MTP3n MTP2

im bo hiu IP truyn ti cchm nguyn thy MTP3 nMTP2 n SG ca MTP2 xl (thng qua chc nng phihp hot ng)

Kiu lin ktKt ni im bo hiu IPvi SG l lin kt bo hiuSS7

Kt ni im bo hiu IP v SGkhng phi l kt ni bo hiu s7. N l m rng ca MTP2 nmt node t xa.

M imSG l mt node SS7 v cm im

SG khng phi l mt node SS7v khng c m im

Cc tng cao hnSG c cc tng SS7 cao hnnh SCCP,

SG khng c tng SS7 cao hn vn khng c MTP3

Qun lCc th tc qun l da voMTP3

S dng cc th tc qun l caM2UA

3.8. M3UA

M3UA nh ngha giao thc h tr truyn ti bo hiu ngi dng MTP3 (v dnh cc bn tin ISUP/SCCP,) qua IP s dng cc dch v ca SCTP. Giao thc nythng c dng gia mt SG v mt MGC hoc c s d liu thng tr IP. M3UAthch 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 sutdi 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 can n cc ngi dng MTP3 ging nh MTP3 cung cp cho cc ngi dng ca n ticc u cui bo hiu s 7. Theo cch ny, tng ISUP v/hoc SCCP khng bit crng cc dch v MTP3 yu cu c cung cp t xa bi tng MTP3 SG hay l bichnh tng MTP3 di n. Tng MTP3 ti mt SG cng c th khng bit c rngngi dng ca n thc ra l ngi dng trn n hay l thnh phn ngi dng t xaqua M3UA. Thc t th M3UA m rng truy nhp n cc dch v MTP3 thnh ngdng trn c s IP t xa.

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 SCCPthc hin chc nng bin dch tiu ton cc SCCP (GTT) i vi cc bn tin nha ch n SG SCCP. Nu kt qu ca GTT cho mt m im SS7 ch (DPC) hocDPC/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 tngSCTP/IP.

Hnh 3.11 l v d trong mng ton IP, cc bn tin SCCP c trao i trc tipgia hai im bo hiu IP bng cc thc th giao thc ngi dng SCCP nh RANAPhoc TCAP. y khng c kt ni vi mng SS7 do khng quan tm n thng tinqun l trng thi mng MTP3 cho SCCP v cc giao thc ngi dng SCCP.

Hnh 3.11. Vai tr v v tr ca M3UA trong kin trc ton IP

3.9. 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 cthit k dng modul ha v i xng nn cho php lm vic c trong cc kin trckhc nhau nh kin trc mt SG n im bo hiu IP cng nh kin trc im ucui 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.

Qun l cc lin h truyn ti SCTP gia cc SG v mt hay nhiu nt bohiu 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 cachng l phi hp gia cc tng SCCP v SUA cung cp ranh gii chuyn giao ccbn 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 cnh tuyn theo m im v SSN. Phn h xc nh bi SSN v pha ngoimng SS7 c xem nh thuc SG. iu ny ngha l nhn t im SS7, ngidng SCCP c t ti SG.

SG l im chuyn tip: Mt GTT phi c thc hin ti SG trc khi c thxc nh c ch ca bn tin. V tr thc t ca ngi dng SCCP khng linquan n mng SS7.

Trong kin trc ton IP c th dng cho mt giao thc s dng cc dch v truynti ca SCCP trong mt mng ton IP. iu ny cho php cc mng pht trin linh nghn, c bit l khi khng cn tng tc gia cc bo hiu hin thi. Hnh 3.13 m ttrng hp ny.

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

3.10. SO SNH M3UA V SUA

Nhn chung, chng giao thc s dng SUA l khng phc tp v hiu qu hn sovi chng giao thc s dng SCCP v M3UA. Bi vy, SUA c th nng cao hiu quca 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 trcho cc ng dng khc nhau caSCCP khi phi phi hp vi cch thng quc gia khc nhau.

Vn l khng c h tr khidng SUA.

phc tptrong trin khai

M3UA cn cc dch v SCCP.

t nht c mt giao thc tngtrn. Gim phc tp ca ntmng (trong trin khai cng nhtrong qun l), do , gim chiph.

V mt nhtuyn

Trong M3UA, cc bn tin ciu khin t m im n mim.

SUA cho php mng IP nhtuyn bn tin theo thng tintrng tiu ton cc.

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

S dng SUA, mi nt IP khngcn c m im.

Cc dch vISUP

C h tr. Khng th h tr c.

Chng 4.

CC GIAO THC BO HIU V IU KHIN NGANG HNG

4.1. GIAO THC KHI TO PHIN SIP

4.1.1. Cc c im v chc nng ca SIP

4.1.1.1. Cc c im

Theo nh ngha ca IETF, Giao thc khi to phin SIP (Session InitiationProtocol) l giao thc bo hiu lp ng dng m t vic khi to, thay i v giiphng cc phin kt ni tng tc a phng tin gia nhng ngi s dng. SIP cth s dng cho rt nhiu dch v khc nhau trong mng IP nh dch v thng ipthoi, hi ngh thoi, E-mail, dy hc t xa, qung b (MPEG, MP3...), truy nhpHTML, XML, hi ngh video...

SIP da trn tng v cu trc ca HTTP (HyperText Transfer Protocol) - giaothc trao i thng tin ca World Wide Web. N c nh ngha nh mt giao thcClient-Server, trong cc yu cu c ch gi (Client) a ra v bn b gi (Server)tr li. SIP s dng mt s kiu bn tin v cc trng mo u ca HTTP, xc nh nidung lung thng tin theo mo u thc th (m t ni dung - kiu loi) v cho phpxc nhn cc phng php s dng ging nhau c s dng trn Web. Kinh nghimtrong s dng cc giao thc Internet mail (SMTP) cung cp rt nhiu cho vic phttrin SIP, trong tp trung vo kh nng thch ng ca bo hiu trong tng lai.

SIP nh ngha cc bn tin INVITE v ACK ging nh bn tin Setup v Connecttrong H.225, trong c hai u nh ngha qu trnh m mt knh ng tin cy mthng qua cuc gi c th i qua. Tuy nhin khc vi H.225, tin cy ca knhny khng ph thuc vo TCP. Vic tch hp tin cy vo lp ng dng ny chophp kt hp mt cch cht ch cc gi tr iu chnh ng dng, c th ti u hoVoIP.

Cui cng, SIP da vo giao thc m t phin SDP, mt tiu chun khc caIETF, thc hin s sp xp tng t theo c cu chuyn i dung lng ca H.245.SDP c dng nhn dng m tng i trong nhng cuc gi s dng mt m tnguyn bn n. SDP cng c s dng chuyn cc phn t thng tin ca giaothc bo hiu thi gian thc RTSP sp xp cc tham s hi ngh a im v nhngha khun dng chung cho nhiu loi thng tin khi c chuyn trong SIP.

Giao thc SIP c thit k vi nhng tiu ch h tr ti a cho cc giao thckhc ra i trc . Giao thc SIP n c tch hp vi cc giao thc c ca

t chc IETF, n c kh nng m rng, h tr u cui v vi SIP th vic cung cpdch v mi tr nn d dng v nhanh chng khi trin khai. SIP c 5 tnh nng sau:

Tch hp vi cc giao thc c ca IETF.

n gin v c kh nng m rng.

H tr ti a s di ng ca u cui.

D dng to tnh nng mi cho dch v v dch v mi.

Kh nng lin kt hot ng vi mng in thoi hin ti.

4.1.1.2. Cc chc nng

SIP l mt giao thc iu khin lp ng dng m n c th thit lp, sa i vkt thc cc phin truyn thng a phng tin (cc hi ngh) hay cc cuc gi inthoi qua Internet. SIP c th mi cc thnh vin tham gia vo cc phin truyn thngn hng hoc a hng; bn khi to phin khng nht thit phi l thnh vin caphin . Phng tin v cc thnh vin c th c b sung vo mt phin ang tnti.

SIP h tr vic nh x tn v cc dch v chuyn tip mt cch trong sut, v thn cho php thc hin cc dch v thu bao in thoi ca mng thng minh v mngISDN. Nhng tin ch ny cng cho php thc hin cc dch v ca cc thu bao ding.

SIP h tr 5 kha cnh ca vic thit lp v kt thc cc truyn thng a phngtin sau:

nh v ngi dng (User location): xc nh h thng u cui c s dngtrong truyn thng.

Cc kh nng ngi dng (User capabilities): xc nh phng tin v ccthng s phng tin c s dng.

Tnh kh dng ngi dng (User Availability): xc nh s sn sng ca bnc gi tin hnh truyn thng.

Thit lp cuc gi (Call setup): chung, thit lp cc thng s ca cucgi ti c hai pha b gi v ch gi.

X l cuc gi (Call handling): bao gm chuyn ti v kt thc cuc gi.

4.1.2. Cc khi nim v cc thnh phn ca h thng SIP

4.1.2.1. Cc khi nim

Phn ny a ra mt s thut ng lin quan n cc quy tc c s dng bi ccthnh vin trong cc truyn thng SIP:

Call: Mt cuc gi bao gm tt c cc thnh vin s dng mt ti nguyn chung trongmt hi ngh. Mt cuc gi SIP c nhn dng bi mt nhn dng cuc gi (call ID) duy nht. Do , mt v d l nu mt ngi s dng c mi vo phintruyn thng a hng bi ng thi mt vi ngi, th mi mt li mi ny s lmt cuc gi duy nht.

Call leg: Mt call leg c nhn dng bng s kt hp ca trng mo u Call IDv a ch xc nh, th ca cc trng mo u To v From.

Client: l mt chng trnh ng dng gi cc yu cu SIP. Cc Client c th hockhng th tng tc mt cch trc tip vi mt ngi s dng. Cc User agent(UA) v cc Proxy cha cc client (v cc Server).

Conference (hi ngh): l mt phin truyn thng a phng tin c nhn bit bimt s m t phin chung. Mt hi ngh c th khng c hoc c nhiu thnhvin v bao gm nhng trng hp ca mt hi ngh a phng, hi ngh nhiumt li (full mesh) v mt cuc gi in thoi hai bn, cng nh cc hnhp ca cc trng hp ny. Bao nhiu cuc gi cng c th c s dng tora mt hi ngh.

Downstream (lung xung): gm cc yu cu c gi trc tip t pha ch gi npha b gi (ngha l t UA Client n UA Server).

Final response (phc p cui cng): l mt phc p kt thc mt phin giao dchSIP, tri li mt phc p tm thi khng kt thc mt phin giao dch SIP. Ttc cc phc p: 2xx, 3xx, 4xx, 5xx v 6xx u l cc phc p cui cng.

Initiator, calling party, caller (Bn khi to, bn ang gi, ngi gi): L bn khito mt li mi phin. Ch rng bn ang gi khng phi l bn to ra hi ngh.

Invitation (li mi): L mt yu cu c gi n mt ngi s dng (hay mt dchv) yu cu tham gia vo mt phin. Mt li mi SIP thnh cng gm 2 giaodch: mt yu cu INVITE c theo sau bi mt yu cu ACK.

Invitee, invited user, called party, callee (bn c mi, ngi b gi): L ngi haydch v m bn ang gi ang mi tham gia vo mt hi ngh.

Yu cu hay phc p ng hnh: Hai yu cu hoc hai phc p c nh ngha lng hnh theo cc ca ti liu ny nu chng c cng cc gi tr trong cctrng mo u ca Call ID, To, From v Cseq. Thm vo , cc yu cu

ng hnh phi c cng Request URI v cng thng s nhnh trong trng mou Via ca chng.

Location server (my ch nh v): chi tit phn dch v nh v.

Location service (dch v nh v): Mt dch v nh v c s dng bi mt SIPredirect hay proxy server c c thng tin v cc v tr c th c ca ngi bgi. Cc v d v cc ti nguyn ca thng tin nh v gm cc ng k SIP, ccc s d liu hay cc giao thc ng k di ng. Cc dch v nh v c a rabi cc my ch nh v. Cc my ch nh v c th l mt phn ca mt mych SIP, nhng cch thc m mt my ch SIP yu cu cc dch v nh v nmngoi phm vi ca ti liu ny.

Outbound proxy: L mt proxy nm gn ni to ra cc yu cu. N nhn tt c ccyu cu i ra t mt UAC c th, cc Request URL ca cc yu cu ny nhndng mt host khng phi l outbound proxy. Sau bt k mt x l cc b no,outbound proxy s gi nhng yu cu ny n cc a ch c ch ra trongRequest URL. (Tt c cc proxy server khc u c xem xt mt cch ngin nh l cc proxy, ch khng phi l cc inbound proxy).

Parallel search (tm kim song song): Trong mt tm kim song song, mt proxy ara mt vi yu cu n cc v tr c th c ca ngi s dng trong khi nhn mtyu cu u vo. Hn l a ra mt yu cu v sau i cho n khi nhn cphc p cui cng trc khi a ra mt yu cu k tip nh trong mt tm kimtun t, mt tm kim song song a ra cc yu cu m khng cn i kt quca cc yu cu trc .

Provisional response (phc p tm thi): L mt phc p c s dng bi mych ch th tin trnh nhng n khng kt thc mt giao dch SIP. Phc p1xx l phc p tm thi, cc phc p khc l cc phc p cui cng.

Proxy, proxy server: L mt chng trnh trung gian hot ng c nh l mt mych v mt my khch cho mc ch to ra cc yu cu vi t cch ca cc mykhch khc. Cc yu cu c cung cp mt cch ni b hoc a chng qua ccmy ch khc sau nhng bin dch cn thit. Mt proxy bin dch v nu cn thitn ghi li mt bn tin yu cu trc khi chuyn tip bn tin . V d, cc proxyserver c s dng nh tuyn cc yu cu, thc thi cc chnh sch, iukhin cc tng la.

Redirect server: Mt redirect server l mt my ch m n nhn mt yu cu SIP,nh x a ch hin c thnh mt s a ch mi v gi tr li cc a ch ny chomy khch. Khng ging nh mt proxy server, n khng khai bo yu cu SIP

ca bn thn n. Khng ging nh mt UA Server, n khng chp nhn cc cucgi.

Registrar (trm ng k): Mt trm ng k l mt my ch m n nhn cc yu cuREGISTER. Mt trm ng k c nh v chung vi mt proxy hoc redirectserver v c th to ra sn sng thng tin ca n thng qua my ch nh v(location server).

Ringback (hi m chung): Hi m chung l chung bo hiu c to ra bi ngdng ca my khch pha gi ch ra rng bn b gi ang c thng bo (chung).

Server (my ch): Mt my ch l mt chng trnh ng dng m n nhn cc yucu x l v gi tr li cc p ng cho nhng yu cu . Cc my ch l ccproxy, redirect, UAS hoc registrar.

Session (phin): T nh ngha SDP: Mt phin truyn thng a phng tin l mttp cc pha gi v nhn a phng tin v cc lung d liu t pha gi n phanhn. Mt hi ngh a phng tin l mt v d ca mt phin truyn thng aphng tin. Nh c nh ngha, mt bn b gi c th c mi tham giacng 1 phin mt vi ln bi cc cuc gi khc nhau. Nu SDP c s dng,mt phin c nh ngha bng s ghp ni ca cc phn t: tn ngi dng, IDca phin, kiu mng, kiu a ch v a ch trong cc trng gc.

(SIP) transaction (giao dch SIP): Mt giao dch SIP xut hin gia mt my khchv mt my ch v bao gm tt c cc bn tin t yu cu u tin c gi tmy khch n my ch cho n phc p cui cng c gi t my ch vmy khch. Mt giao dch c nhn bit bi chui s Cseq trong mt call legn l. Yu cu ACK c cng chui s Cseq vi yu cu INVITE tng ng,nhng bao gm mt giao dch ca ring n.

Stateless Proxy (proxy phi trng thi): L mt thc th logic m n khng duy trtrng thi ca mt phin giao dch SIP. Mt proxy phi trng thi chuyn tip ttc cc yu cu n nhn ng xung v tt c cc phc p n nhn ngln.

Stateful Proxy (proxy trng thi): L mt thc th logic duy tr thng tin trng thica t nht mt giao dch SIP.

Upstream (ng ln): Cc phc p c gi trc tip t my ch UA n mykhch UA.

URL encoded (m URL): L mt chui k t c m ho theo RFC 1738.

User agent client (UAC): Mt UAC l mt ng dng khch khi u mt yu cu SIP

User agent server (UAS): Mt UAS l mt ng dng ch m n giao tip vi ngis dng khi mt yu cu SIP c nhn v n gi tr li mt phc p cho ngis dng . Phc p chp nhn, t chi hoc chuyn tip yu cu .

User agent (UA): Mt ng dng hot ng c nh UAC v UAS.

Cc Proxy, Redirect, Location v Registrar Server c nh ngha trn l ccthc th logic; cc s thc thi c th kt hp chng thnh mt chng trnh ng dngn nht. Cc thuc tnh ca cc kiu my ch SIP khc nhau c cho trong bng 4.1.

Bng 4.1. Cc thuc tnh ca cc kiu my ch SIP khc nhau

4.1.2.2. Cc thnh phn ca h thng SIP

Xt trn quan im Client / Server, cc thnh phn chnh ca mt h thng SIPbao gm (Hnh 4.1):

u cui SIP (UAC/UAS).

Proxy server.

Location server.

Redirect server.

Registrar server.

Hnh 4.1. Cu trc ca h thng SIP

User Agent l thit b u cui trong mng SIP, n c th l mt my in thoiSIP hay mt my tnh chy phn mm u cui SIP. UA c th khi to, thay i haygii phng cuc gi. Trong phn bit hai loi UA: UAC (User Agent Client) vUAS (User Agent Server). UAC l mt thc th thc hin vic khi to mt cuc gicn UAS l mt thc th thc hin vic nhn cuc gi. Nhng c UAC v UAS u cth gii phng cuc gi.

Proxy Server l phn mm trung gian hot ng c nh Server v c nh Client thc hin cc yu cu thay th cho cc u cui khc. Tt c cc yu cu c x lti ch bi Proxy Server (nu c th) hoc n chuyn n cho cc my ch khc.Trong trng hp Proxy Server khng trc tip p ng cc yu cu ny th ProxyServer s thc hin khu chuyn i hoc dch sang khun dng thch hp trc khichuyn i.

Location Server l phn mm nh v thu bao, cung cp thng tin v nhng vtr c th ca pha b gi cho cc phn mm Proxy Server v Redirect Server.

Redirect Server l phn mm nhn yu cu SIP v chuyn i a ch SIP sangmt s a ch khc v gi li nhng a ch ny cho u cui. Khng ging nh ProxyServer, Redirect Server khng bao gi hot ng nh mt u cui, tc l khng gii bt c mt yu cu no. Redirect Server cng khng thc hin vic chp nhn hayhu cuc gi.

Registrar Server l phn mm nhn cc yu cu ng k Register. Trong nhiutrng hp Registrar Server m nhim lun mt s chc nng an ninh nh xc nhnngi s dng. Thng thng Registrar Server c ci t cng vi Proxy hocRedirect Server hoc cung cp dch v nh v thu bao. Mi ln u cui c bt

ln (th d my in thoi hoc phn mm SIP) th u cui li ng k vi Server.Nu u cui cn thng bo vi Server v a im ca mnh th bn tin Registerc gi i. Ni chung cc u cui u thc hin vic ng k li mt cch nh k.

4.1.3. Khi qut v hot ng ca SIP

Trong hi thoi SIP, mi bn tham gia (bn ch gi v bn b gi) c gn mta ch SIP hay cn gi l SIP URL. Ngi s dng phi ng k v tr ca h vi SIPServer. to mt cuc gi SIP, pha ch gi nh v ti my phc v thch ng vsau gi mt yu cu SIP. Hot ng SIP thng xuyn nht l li mi cc thnhvin tham gia hi thoi. Thnh phn Register ng vai tr tip nhn cc yu cu ngk t UA v lu tr cc thng tin ny ti mt dch v phi SIP (Non-SIP).

4.1.3.1. a ch SIP

Cc i tng c nh a ch bi SIP l cc ngi s dng ti cc trm,nhng ngi s dng ny dc nh danh bng mt SIP URL. SIP URL c dnguser@host. Phn user l mt tn ca ngi s dng hay tn ca mt my in thoi.Phn host c th l mt tn min hoc mt a ch mng.

SIP URL c dng trong cc bn tin SIP thng bo v ni gi (From), chhin thi (Request URI) v ni nhn cui cng (To) ca mt yu cu SIP v ch r ach gin tip. Mt SIP URL c th gn vo mt trang Web hoc nhng siu lin kt(Hyperlink) khc thng bo rng ngi dng hoc dch v c th gi thng qua SIP.

Mt a ch SIP URL c th ch r mt c nhn (c th c nh v ti mt trongcc h thng u cui), ngi kh dng u tin t mt nhm cc c nhn hoc tonb mt nhm. V d, khun dng a ch: sip: sales@example.com ni chung l khng quyt nh mc ch ca ngi gi.

4.1.3.2. Qu trnh nh v ti my ch SIP

Khi mt Client mun gi i mt yu cu, Client s gi bn tin yu cu ti SIPProxy Server (nh trong HTTP), hoc ti a ch IP v cng tng ng trong a chca yu cu SIP (Request-URI). Trng hp u, yu cu c gi ti SIP ProxyServer khng ph thuc vo a ch ca yu cu l nh th no. Vi trng hpsau, Client phi xc nh giao thc, cng v a ch IP ca Server m yu cu c gin.

Mt Client thc hin cc bc tip theo c c nhng thng tin ny. Ti mibc, tr cc trng thi khc, Client c gng lin lc vi Server theo s cng c chra trong a ch yu cu SIP (Request-URI). Nu khng c s cng no ch ra trongRequest-URI, Client s s dng a ch cng mc nh l 5060. Nu Request-URI ch

mailto:user@hostmailto:sales@example.com

r l s dng giao thc TCP hay UDP, Client s lm vic vi Server theo giao thc .Nu khng c giao thc no c ch ra th Client c gng dng giao thc UDP (nukhng h tr TCP) hoc s dng giao thc TCP cho hot ng ca mnh (ch c htr TCP m khng c h tr UDP).

Client c gng tm mt hay nhiu a ch cho SIP Server bng vic truy vn DNS(Domain Name System) theo cc th tc sau:

1) Nu a ch Host trong a ch Request-URI l mt a ch IP th Client lmvic vi Server bng a ch c a ra. Nu khng phi l mt a chIP, Client thc hin bc tip theo.

2) Client a ra cu hi ti DNS Server v bn ghi a ch cho a ch Host tronga ch Request-URI. DSN s tr v mt bn ghi danh sch cc a ch. Lc vic la chn mt trong cc a ch ny l ty . Cn nu DNS Server khnga ra bn ghi a ch, Client s kt thc hot ng, c ngha n khng thchin c vic nh v my ch. Nh bn ghi a ch, s la chn tip theocho giao thc mng ca Client c nhiu kh nng thnh cng hn. Mt qutrnh thc hin thnh cng l qu trnh c mt bn ghi cha trong phn tr liv Server lm vic mt trong nhng a ch cha trong tr li .

4.1.3.3. Giao dch SIP

Khi c a ch IP ca SIP Server th yu cu s c gi i theo tng vn chuyngiao thc TDP hay UDP. Client gi mt hoc nhiu yu cu SIP n my ch vnhn li mt hoc nhiu cc phc p t my ch. Mt yu cu cng vi cc phc pc to ra bi yu cu to thnh mt giao dch SIP. Tt c cc phc p cho mtyu cu mang cng cc gi tr trong cc trng: Call ID, Cseq, To, v From. Yucu ACK xc nh s nhn mt phc p INVITE khng l mt phn ca giao dch vn c th di chuyn gia mt tp cc host khc nhau. Mi cuc gi trong SIP cnh danh bi mt trng nh danh cuc gi (Call-ID).

Mt yu cu phi cn c thng tin gi i t u (From) v ti u (To). TrngFrom v To u c cu trc theo khun dng SIP-URL. Trng CSeq lu tr thng tinv phng thc s dng trong phin, trng CSeq c dng:

CSeq = CSeq: DIGIT Method

Trong DIGIT l s nguyn khng du 32 bit.

Nu mt giao thc iu khin lung tin cy c s dng, yu cu v cc phcp trong mt giao dch n l c mang trn cng kt ni. Mt vi yu cu SIP t

cng my khch n cng my ch c th s dng cng kt ni hoc c th s dngmt kt ni mi cho mi yu cu.

Nu mt client gi yu cu thng qua mt giao thc datagram n hng nhUDP th cc UA thu s nh hng phc p theo thng tin cha trong cc trng mou Via. Mi proxy server trong tuyn chuyn tip ca yu cu chuyn tip phc ps dng cc trng mo u Via ny.

4.1.3.4. Li mi SIP

Mt li mi SIP thnh cng gm hai yu cu INVITE v ACK. Yu cu INVITEthc hin li mi mt thnh vin tham gia hi thoi. Khi pha b gi ng tham gia,pha ch gi xc nhn nhn mt bn tin p ng bng cch gi i mt yu cuACK. Nu pha ch gi khng mun mi thnh vin tham gia cuc gi na n s giyu cu BYE thay cho ACK.

Thng ip INVITE cha thnh phn m t phin (SDP) v phng thc tinhnh trao i ng vi phin . Vi cc phin a hng, phn m t phin lit k kiuv khun dng ca cc phng tin (Media) phn phi cho phin hi thoi. Vi mtphin n hng, phn m t phin lit k kiu v khun dng ca cc phng tin mpha ch gi mun s dng v ni nhng d liu mun gi i.

Trng hp my phc v y quyn (Proxy Server):

Proxy Server (PS) tip nhn li mi INVITE.

PS tra cu thng tin dch v nh v ngoi SIP.

PS nhn thng tin to ra a ch chnh xc.

PS to li INVITE trong trng Request URI v chuyn tip.

UAS thng bo b gi.

PS nhn p ng chp nhn 200 OK t UAS.

PS tr v kt qu thnh cng cho ch gi.

Ch gi gi thng bo xc nhn ACK.

Yu cu xc nhn c chuyn tip qua PS.

Ch : Mt ACK c th c gi trc tip n User c gi qua Proxy. Ttc cc yu cu v p ng phi c cng Call-ID.

Trng hp my phc v gin tip (Redirect Server):

PS tip nhn li mi INVITE.

Lin lc vi dch v nh v.

Tr li a ch ch gi.

Ch gi gi thng bo xc nhn ACK n PS.

Ch gi to mt yu cu mi cng mt Call-ID nhng c CSeq cao hnti a ch tr li bi Server u tin.

B gi gi p ng chp nhn 200 OK.

Ch gi gi thng bo xc nhn ACK.

4.1.3.5. nh v ngi dng

Mt i tng b gi c th di chuyn gia mt s cc h thng u cui khcnhau theo thi gian. Mt my ch nh v cng c th s dng mt hay nhiu giao thckhc nhau xc nh h thng u cui m ti mt ngi s dng c th lin lc.Mt my ch nh v c th a ra mt vi v tr v ngi s dng c ng nhp voti mt vi host ng thi hoc bi v my ch nh v li. My ch SIP kt hp cckt qu a ra mt danh sch cc v tr.

i vi tng kiu SIP Server th hot ng sau khi nhn c danh sch cc v trkhc nhau l khc nhau. Mt SIP Redirect Server s tr li danh sch a ch choClient vi cc mo u Contact. Mt SIP proxy server c th th ln lt hoc songsong cc a ch cho n khi cuc gi thnh cng (phc p 2xx) hoc bn b gi tchi cuc gi (phc p 6xx).

Nu mt proxy server chuyn tip mt yu cu SIP, n phi b sung a ch can vo v tr bt u ca danh sch cc trm chuyn tip c ghi trong cc mo uVia. Du vt Via m bo rng cc tr li c th i theo cng tuyn theo hngngc li, vic m bo hot ng chnh xc nh tun theo cc tng la v trnh lpli yu cu. hng phc p, mi host phi xo b Via ca n, do thng tin nhtuyn ni b c che khut i vi pha b gi v cc mng bn ngoi.

4.1.3.6. Thay i mt phin hin ti

Trong mt vi trng hp, cn phi thay i cc thng s ca phin hi thoihin ti. Vic c thc hin bi vic pht li cc yu cu INVITE. Cc yu cuINVITE c cng trng Call-ID nhng c trng mo u v trng bn tin khcvi yu cu ban u mang thng tin mi. Cc bn tin INVITE phi c ch sCSeq cao hn cc yu cu trc. V d: c hai thnh vin ang hi thoi v mun cthm mt ngi th ba tham gia. Mt trong hai thnh vin s mi thnh vin th batham gia vi mt a ch a hng (Multicast) mi v ng thi gi mt bn tin

INVITE n thnh vin th hai vi trng miu t phin a hng nhng c trngCall-ID c.

4.1.4. Cc loi bn tin SIP

SIP l giao thc dng Text s dng b k t ISO 10646 trong m ho UTF-8(RFC 2279). iu ny to cho SIP tnh linh hot, m rng v d thc thi cc ngn nglp trnh cp cao nh Java, Tol, Perl. C php ca SIP gn ging vi giao thc HTTP,n cho php dng li m v n gin ha s lin kt ca cc my phc v SIP vi ccmy phc v Web. Tuy nhin, SIP khng phi l mt dng m rng ca HTTP. Khcvi HTTP, SIP c th s dng giao thc UDP.

Bn tin SIP c chia lm hai loi: Bn tin yu cu t Client ti Server v bn tinp ng t Server tr li cho Client:

SIP-message = Request/ Response

4.1.4.1. Bn tin yu cu (Request)

Bn tin Request c khun dng gm hai phn c bn: Request-line v phn mou-header (vi 3 loi header):

Request=Request-line*(General-header/Request-header/ Entity-header)CLRF[message-body]

Trong thnh phn Request-line cha tn phng thc, mt Request URI vs phin bn ca giao thc. Cc thnh phn c ngn cch vi nhau bng mt khongtrng (SP). Cng nh cc dng khc, dng khi u c kt thc bng mt k txung dng (CRLF).

Request-line = Method SP Request-URI SP SIP-Version

Trong :

Method (Phng thc SIP): SIP nh ngha 6 phng thc c bn nh trongbng 4.2.

Request-URI: Trng Request-URI c khun dng theo SIP URL. N thngbo cho User hoc dch v v a ch hin ti. Khc vi trng To,Request-URI c th c ghi li bi Proxy (trng hp my phc v yquyn).

SIP Version: Phin bn SIP l cc bn SIP c a ra cc ln khc nhau. Chai bn tin Request v Response u cha phin bn ca SIP c s dngSIP Version. Hin ti phin bn SIP l 2.0.

Bng 4.2. Cc phng thc SIPINVITE Mi thnh vin tham gia hi thoi.

ACKYu cu xc nhn nhn c p ng chp nhn(OK) cho yu cu INVITE.

OPTIONS Hi kh nng ca my phc v SIP.

BYE Yu cu gii phng cuc gi

CANCEL

Hy b yu cu sp c thc hin vi cng gi trtrong cc trng Call_ID, From, To, Cseq ca yu cu bng cch ngng qu trnh tm kim bo hiu.

REGISTERng k danh sch a ch lin h ca ngi dng vimy phc v.

4.1.4.2. Bn tin phc p (Response)

Sau khi nhn v thng dch mt bn tin yu cu, pha nhn thc hin tr li bngmt bn tin phc p.

Khun dng bn tin cng gm hai phn c bn: Status-line v phn mo uheader (vi 3 loi header):

Response = Status-line *(General-header/ Response-header/ Entity-header)CLRF[message-body]

Trong thnh phn Status-line c cu trc sau: (SP l k t phn cch):

Status-line = SIP-Version SP status-code SP Reason-phrase

SIP Version: Cng ging nh trong bn tin Request.

Status-code v Reason-phrase: Status-code l mt m kt qu nguyn gm 3digit, ch ra kt qu ca vic c gng thc hin v mc tha mn yu cu.Reason-Phrase th dng a ra mt li gii thch ngn cho Status-code.Status-code mc ch l s dng cho Server cn Reason-phrase l dngcho User. Client khng th yu cu hin th hay kim tra Reason-phrase.

Status-code gm 3 digit. Digit u tin nh ngha loi p ng, hai digit saukhng c vai tr phn loi. SIP 2.0 nh ngha 6 gi tr ca digit u tin nh sau:

Bng 4.3. Cc m trng thi SIP

1xx Tm kim, bo hiu, sp hng i

2xx Thnh cng

3xx Chuyn tip yu cu

4xx Li pha ngi dng

5xx Li pha Server

6xx Li chung: ng dy ang bn, t chi,.

M p ng SIP c th m rng c. Cc ng dng SIP khng yu cu phihiu r v ngha ca tt c m p ng c ng k m ch cn hiu cc loi mp ng, ngha ca digit u tin.

4.1.4.3. Cu trc bn tin SIP

C hai loi bn tin trn u s dng chung mt nh dng c bn c quy nhtrong RFC 2822 vi cu trc gm mt dng khi u (start line), mt s trng tiu v mt phn thn bn tin tu chn (hnh 4.2). Cu trc ny c tm tt nh sau:

generic-message = start-line*message-headerCRLF[ message-body ]

Vistart-line = Request-Line / Status-Line