Media Gateway Controller

NI DUNG

NI DUNG...........................................................................................................1 PHN 1.................................................................................................................2 TNG QUAN V MGC......................................................................................2 Khi nim MGC...................................................................................................2 Chc nng ca MGC............................................................................................3 Cu trc ca MGC................................................................................................5 Cch thc tin hnh cuc gi trong MGC............................................................7 1.4.1 Giao thc Peer to Peer...........................................................................11 1.4.1.1 Giao thc BICC (Bearer Independent call control)........................11 1.4.1.2 Giao thc SIP (Sesson Initiation Protocol).....................................12 1.4.2 Giao thc iu khin truyn thng.........................................................13 1.4.2.1 Giao thc MGCP (Media Gateway Control Protocol)...................14 1.4.2.2 Giao thc Megaco/H.248................................................................14 VI DU M PHONG NG DUNG MGC...........................................................15 PHN 3...............................................................................................................19 KT LUN.........................................................................................................19

Media Gateway Controller

Page 1

PHN 1 TNG QUAN V MGC Khi nim MGCMGC l vit tt ca cm t Media Gateway Controller, cn c gi l Call Agent hay b iu khin cng (Gateway Controller). MGC l thnh phn chnh (thnh phn chc nng c bn) ca chuyn mch mm (Softswitch). MGC chnh l chic cu ni gia cc mng c c tnh khc nhau nh PSTN, SS7, mng IP. N chu trch nhim qun l lu lng thoi v d liu qua cc mng khc nhau. MGC iu khin x l cuc gi, cn MG v SG s thc hin truyn thng. MGC iu khin SG thit lp v kt thc cuc gi. Ngoi ra cn giao tip vi h thng OSS v BSS. MGC iu khin x l cuc gi, cn MG v SG s thc hin truyn thng. MGC iu khin SG thit lp v kt thc cuc gi. Ngoi ra cn giao tip vi h thng OSS v BSS. Trong Softswitch, MGC kt hp vi MG (Media Gateway) v SG (Signalling Gateway) to thnh cu hnh c bn cho chuyn mch mm c tnh h thng ca MGC bao gm L mt CPU c hiu, yu cu h thng a x l, c kh nng m rng theo chiu ngang. Cn b nh ln lu tr c s d liu. iu ny cng rt cn thit cho cc qu trnh x l. Media Gateway Controller Page 2

Ch yu lm vic vi lu lng IP, do yu cu cc kt ni vi tc co. H tr nhiu loi giao thc. sn sng cao.

Chc nng ca MGCTrong chuyn mch mm Softswitch, MGC ng vai tr quan trng, thc hin cc chc nng sau iu khin cuc gi, duy tr trng thi ca mi cuc gi trn mt MG. iu khin v h tr hot ng ca MG v SG. Trao i cc bn tin c bn gia 2 MG-F. X l bn tin bo hiu SS7 (khi s dng SIGTRAN). X l bn tin lin quan QoS nh RTCP. Thc hin nh tuyn cuc gi (bao gm bng nh tuyn v bin dch). Ghi li cc thng tin chi tit ca cuc gi tnh cc (CDR- Call Detail Record). iu khin qun l bng thng. ng k Gatekeeper. i vi Media Gateway, MGC c chc nng sau: Xc nh v cu hnh thi gian cho cc DSP. Phn b knh DS0. Media Gateway Controller Page 3

Truyn dn thoi (m ha, nn, ng gi). i vi Sinalling Gateway, MGC cung cp: Cc loi SS7. Cc b x l thi gian. Cu hnh cc kt ni. M ca nt mng hay thng tinh cu hnh. Chc nng c bn ca MGC s c trnh by chi tit trong s hnh 1.1 di y Trong : MS F: Media Server Function, cung cp cc dch v tng cng cho x l cuc gi. N hot ng nh 1 server x l cc yu cu t AS-F hoc MGC F. AS F: Application Server Function, l thc th thi hnh cc ng dng nn nhim v chnh l cung cp cc logic dch v v thi hnh mt hay nhiu ng dng / dch v MGC F: Media Gateway Control Function, cung cp logic cuc gi v tn hiu x l cuc gi cho mt hay nhiu Media Gateway CA F: Call Agent Function, l mt thnh phn chc nng ca MGS F. Thc th ny c kch hot khi MGC F thc hin vic iu khin gi SG F: Signalling Gateway Function, dng chuyn cc thng tin bo hiu ca mng PSTN qua IP


Page 4

MG F: Media Gateway Function, dng chuyn thng tin t trng thi truyn dn ny sang trng thi truyn dn khc

Hnh 1.1 S chc nng ca MGC

Cu trc ca MGCS cu trc ca MGC c th hin trong hnh 1.2


Page 5

Hnh 1.2 S cu trc ca MGC Giao thc s dng gia MGC v cc thnh phn khc trong chuyn mch mm c miu t trong hnh 1.3

Hnh 1.3 Giao thc s dng gia MGC v cc thnh phn khc Media Gateway Controller Page 6

Theo hnh 1.2, MGC giao tip vi cc thnh phn khc trong Softswitch thng qua cc giao thc SIGNTRAN, SIP, Megaco, MGCP, ENUM/TRIP. Cch thc hot ng ca cc giao tip ny c trnh by chi tit trong mc 1.4.

Cch thc tin hnh cuc gi trong MGCMGC lm nhim v iu khin cuc gi, bo hiu v cc tnh nng to mt cuc gi trong mng NGN hoc xuyn qua nhiu mng khc (PSTN, ISDN). MGC iu khin cuc gi thng qua cc bo hiu, c 2 loi chnh l Peer to peer: giao tip SW v SW, giao thc s dng BICC hay SIP. iu khin truyn thng (ch/t): giao tip SW v Gateway, giao thc s dng MGCP hay Megaco/H.248 So snh gia 2 giao thc th hin trong bng 1.1 Ni dung Khai thc Ch/t - Thit b cng n gin. - Cc ng dng c ci t ti cc Server. Ngang hng - Thit b cng thng minh, phc tp. - Tng tc ngang hng Trin khai dch v - Ch trin khai dch v trn cc Server. - Thi gian trin khai dch v trn mng ngn. - Ch nng cp cc Server iu khin. - Trin khai trn tng thit b. - Thi gian trin khai trn mng ln. - Phi nng cp ton b cc thit b Media Gateway Controller Page 7

- Qun l dch v linh hot trn ton mng.

cng khi trin khai 1 dch v mi trn ton mng

Chi ph

- Thit b cng c ti u v chi ph dn ti tng chi ph gim. - Vng i sn phm ca cc thit b cng di hn.

- Thit b cng c gi thnh cao lm cho chi ph tng th ln. - Theo thi gian, thit b cng phi thng xuyn nng cp.

V d v giao thc

- Megaco/H.248. - MGCP.

- SIP. - H.323.

Bng 1.1 So snh gia 2 giao thc Peer to Peer v Ch/T S khc nhau gia 2 giao thc ny c th hin nh trong hnh 1.4 di y


Page 8

Hnh 1.4: Cc giao thc bo hiu s dng trong NGN S khc nhau c bn gia 2 giao thc ny l kh nng thng minh (Intelligent) c phn b nh th no gia cc thit b bin ca mng v cc Server. S la chn giao thc no ph thuc vo chi ph h thng, cch thc trin khai dch v, kh thi. C th xem xt gii php tng th kt hp s dng c 2 phng thc. Qa trnh thc hin 1 cuc gi thng qua Softswitch c m t trong hnh 1.5 di y:


Page 9

Hnh 1.5a Lin kt gia cc thnh phn trong mng NGN qua IP network

Hnh 1.5b Qa trnh thc hin 1 cuc gi thng qua Softswitch Trong IAM: Initial Address Message: cha nhng ch s u tin ca s b gi BSAM (Subsequent Access Message) ACM: Address Complete Message: Bn tin a ch y , bao gm trng thi thu bao b gi bn hay ri CPG: Call Process Message: Bn tin cho bit qu trnh cuc gi ang din ra nh th no?


Page 10

ANM: Answer Message: Bn tin tr li CRCX: Create Connection: to kt ni ti thu bao b gi MDCX: Modify Connection: iu chnh kt ni ph hp1.4.1 Giao thc Peer to Peer

Peer to Peer cn gi l mng ngang hng hay mng ng ng, l 1 mng my tnh trong hot ng ca mng ch yu da vo kh nng tnh ton v bng thng ca cc my tham gia ch khng tp trung vo mt s nh cc my ch trung tm nh cc mng thng thng. Mng ng ng thng c s dng kt ni cc my thng qua mt lng kt ni dng ad hoc. Mng ng ng c nhiu ng dng. ng dng thng xuyn gp nht l chia s tp tin, tt c cc dng nh m thanh, hnh nh, d liu,... hoc truyn d liu thi gian thc nh in thoi VOIP.1.4.1.1 Giao thc BICC (Bearer Independent call control)

L giao thc bo hiu gia 2 MGC, c th t cc nh cung cp khc nhau, nhm mc ch m bo lu lng thoi dng k thut gi (VoP). BICC h tr cc dch v bng hp (PSTN, ISDN) mt cch c lp vi ng truyn v k thut chuyn ti bn tin tn hiu. Thng qua bo hiu BICC, mng NGN vi nn tng chuyn mch gi IP c th cung cp y cc dch v bng hp. Trong BICC, giao thc bo hiu iu khin ng truyn ph thuc vo cng ngh ng truyn lp di nh ATM, IP/MPLS. M t ng dng ca BICC trong vic lin kt hot ng ca cc mng truyn thng (PSTN, ISDN) v mng NGN c miu t trong hnh 1.6


Page 11

Hnh 1.6 M t ng dng BICC Theo hnh trn, 2 thu bao in thoi truyn thng lin lc vi nhau thng qua s iu khin ca Softswitch theo bo hiu ca BICC.1.4.1.2 Giao thc SIP (Sesson Initiation Protocol)

L giao thc iu khin lp ng dng c thit k v pht trin bi IETF. Giao thc SIP c s dng khi to, iu chnh v chm dt cc phin lm vic vi mt hay nhiu yu t tham d. L giao thc bo hiu m, mm do v c kh nng m rng, SIP khai thc ti a cng c Internet to ra nhiu dch v mi trong NGN. SIP cn dng lm bo hiu gia hai SW. Media Gateway Controller Page 12

Hin nay, SIP ang tr thnh s la chn thay th H.323 tr thnh mt giao thc im ni im (end to end) trong cng ngh SW Hot ng c bn ca SIP c m t trong hnh 1.7 di y:

Hnh 1.7 Hot ng c bn ca SIP Bao gm cc bc sau: Tm v v ngi dng hin ti gi bn tin mi. Mi tham gia phin thoi. Mang thng tin phin thoi. Trong SIP ngi dng c nh a ch nh a ch email1.4.2 Giao thc iu khin truyn thng

Giao thc iu khin truyn thng c thc hin qua cng truyn thng (Media Gateway) c nhim v chuyn i t nh dng truyn thng ny sang nh dng truyn thng khc.


Page 13

1.4.2.1 Giao thc MGCP (Media Gateway Control Protocol)

MGCP l giao thc iu khin cc cng VoIP t cc thit b iu khin MGC. L giao thc ch /t (Client/Server), s dng SDP m t phng thc truyn thng v s dng RTP/RCTP cho vic vn chuyn v gim st thng tin. Cc hot ng ca MGCP l cc bo hiu (Signal S) gi t MGC ti MG v cc kt qu (Event E) do MG gi ti MGC. Quan h gia MG v MGC c th hin trong hnh 1.8

Hnh 1.8 Quan h gia MG v MGC1.4.2.2 Giao thc Megaco/H.248

Megaco l giao thc iu khin cng phng tin ni chung, bao gm cng ni ht, trung k trong mng PSTN, giao din ATM, giao din in thoi v ng dy Analog in thoi IP v cc loi Server. Kin trc iu khin ca Megaco cho trong hnh 1.9 di y:


Page 14

Hnh 1.9 Kin trc iu khin Megaco/H.248 Megaco tng t nh MGCP nhng n h tr a dng hn cc loi mng.

PHN 2 VI DU M PHONG NG DUNG MGC

M t ng dng s dng MGC c th hin trong hnh 2.1


Page 15

Hnh 2.1 V d s dng MGC Qua trnh thc hin cuc gi qua MGC c thc hin tun t qua cc bc di y: Thu bao nhc my chun b thc hin cuc gi, tng i ni ht qun l thu bao s nhn bit trng thi off-hook ca thu bao.SG ni vi tng i ny thng qua mng SS7 cng nhn bit c trng thi mi ca n. SG s bo cho MGC trc tip qun l mnh CA-F ng thi cung cp tn hiu Dial-tone cho thu bao.Ta gi MGC ny l Caller-MGC. Caller-MGC gi yu cu to kt ni n MG ni vi tng i ni ht ban u nh MGC-F. Cc s do thu bao nhn s c SG thu nhn v chuyn ti Caller-MGC.


Page 16

Caller-MGC s dng s ny quyt nh cng vic tip theo s thc hin.Cc s ny s c chuyn ti chc nng R-F v R-F s dng thng tin lu tr ca cc server quyt nh tuyn cuc gi. Nu thu bao b gi cng thuc s qun l ca Caller-MGC th thc hin bc 7, cn nu thu bao b gi thuc MGC khc th thc hin bc 6. Caller-MGC gi yu cu thit lp cuc gi n 1 MGC khc.Nu cha n ng MGC ca thu bao b gi (Callee-MGC) th MGC ny s tip tc chuyn yu cu n ng Callee-MGC.V MGC trung gian lun gi li phn hi n MGC gi yu cu n n, vic ny c thc hin nh CA-F. Callee-MGC (Calleer-MGC) yu cu to kt ni vi MG ni vi tng i ni ht ca thu bao b gi Callee-MG (Calleer-MG). Callee-MGC (Calleer-MGC) gi thng ip n Callee-SG(Calleer-SG) thng qua mng SS7 lm rung chung thu bao b gi. Khi Callee-SG(Calleer-SG) nhn c bn tin bo trng thi ca thu bao b gi (gi s ri) n s gi thng tin ny tr v Callee-MGC (CallerMGC). V Callee MGC s phn hi v Calleer MGC bo mnh ang lin lc vi ngi c gi. Callee-MGC gi thng tin cung cp tn hiu ring back tone cho Calleer MGC qua Calleer SG n ngi gi. Khi thu bao b nhc my th qu trnh thng bo tng t cc bc trn xy ra: qua nt bo hiu s 7, thng tin nhc my qua Callee SG, ri n Callee MGC, ri n Calleer MGC, qua Calleer SG ri n thu bao th hin cuc gi. Media Gateway Controller Page 17

Kt ni thwe bao gi i v thu bao b gi c hnh thnh thng qua Callee MG v Calleer MG. Khi kt thc cuc gi th qu trnh din ra tng t nh lc thit lp.


Page 18

PHN 3 KT LUN

MGC ng mt vai tr ct li trong chuyn mch mm Softswitch. Thng qua ti, chng em tm hiu c bn v khi nim MGC, cc chc nng ca MGC, cu trc ca MGC v cch thc tin hnh cuc gi trong MGC. Phn v d minh ha ng dng MGC trang b mt ci nhn c bn v cch thc 1 cuc gi c trin khai trong MGC nh th no? Chng em xin cm n nhng kin thc nn tng ca thy qua cc bi ging trn lp. Chng em mong nhn c nhng kin ng gp qu bu ca thy chng em c th hon thin ti. Chng em xin chn thnh cm n! H Ni, ngy 03, thng 05, nm 2012 Nhm sinh vin


Page 19

Documents

Media Gateway Controller