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
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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
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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
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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:
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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?
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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
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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.
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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:
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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
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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.
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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
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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.
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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
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