6.Multimedia Resource Function Controller (MFRC)
The Multimedia Resource Function (MRFC) is need to support bearer-related services, such as conferencing, announcement to a user or bearer transcoding. the MRFC interprets SIP signaling receive via S-CSCF and uses the Media Gateway Control Protocol (MEGACO) or H.248 instruction to control the Multimedia Resource Function Processor (MRFP). for charging purchasing, the MFRC is able to send accounting information to the CCF and OCF
the multimedia Resource Function Processor (MRFP) allocates user-plane resource as instructed by the MFRC
7.Media Gateway Control Function (MGCF)
the Media Gateway Control Function (MGCF) connect IMS communications to legacy CS user. all incoming CS call control signaling ex: ISDN,User Part (ISUP) or the Bearer Independent Call Control (BICC) message are converted into SIP and vice versa
for the lower signaling layer, a Signaling Gateway (SGW) convert standard SS7 MTP or IP-base SCTP (Stream control Transmission Protocol ) message into the TCP or UDP format and forwards them to MGCF
8.Breakout Gateway Control Function (BGCF)
the Breakout Gateway Control Function (BGCF) determines where signaling breakout to the CS domain occurs, if the breakout occurs in the same network, BGCF select an MGCF in the same network to convert SIP signaling into ISUP/BICC signaling to CS domain. if the breakout come in another network, BGCF select an BGCF in an different network, then other BGCF select own MGCF to convert SIP signaling to ISUP/BICC to CS domain
We continue this discuses… about IMS, and now we talk about the architecture of IMS network
In IMS network there is overlay session/service control architecture on top of the package switch domain (GPRS,UMTS,WLAN..etc) based on IP technologies and IETF protocols (like SIP) in IMS there include some element like :
IMS CORE
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S-CSCF is the main point of the home network
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I-CSCF providing topology hiding / interrogation
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P-CSCF Entry point for IMS world
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MS (media server) media hosting special resources
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MGF (Media Gateway) for interworking with legacy network
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PDF (Policy Decision Function) for QoS control using policies
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IMS Application
- HSS (Home Subscriber system) for maintaining subscriber and the AS profile
- AS (Application Server Function) for hosting application
- IMS enabler as a specific with generic function
- IMS endpoint for client the IMS system
IDENTIFICATION in the IMS
Identification is one of the most important abilities of a network, the user must be identified in any kind of network, in IMS have own way to identified the users and provide mechanisms to identified the service ,such as when the call be directed to the appropriated user, and the service need to be identified when they are provided, typically user a special number
Private User Identities each IMS subscriber has one a private user identities with the format NAI (Network Access Identifier) /RFC 2486 "user@operator.com" and it use for subscription identification and authentication
Public User Identification each IMS user can be allocated one or more public user identity,and it be a SIP URI or a TEL URI
SIP URI ex: "sip:first.last@operator.com"
TEL URI ex:"sip:+62-212-55-7695@operator.com; user=phone"
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PSTNGateway it use for gateway interface with PSTN circuit switch (CS) network, it make IMS client to call the PSTN user or receive a call from PSTN user… there are is ;
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MGCF (Media Gateway Control Function) is the main rule of PSTN/CS gateway, it does call control protocol conversation and maps SIP to ISUP, it also control the resources in an MGW with H.248 interface
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SGW (Signaling Gateway) provide an interface toward the signaling plane of the CS network, it transform lower layer protocol as SCTP (which is IP protocol) into MTP (which is a SS7 protocol), to Pass the ISUP from MGCF network
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MGW use for interface whit media plane of the PSTN/CS network, the MGW can send or receive IMS media and can transcode when the codec cannot match
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