Tag-Archive for » Gateway «

06
Feb
IMS ARCHITECTURE
uchan

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

  • S-CSCF is the main point of the home network
  • I-CSCF providing topology hiding / interrogation
  • P-CSCF Entry point for IMS world
  • MS (media server) media hosting special resources
  • MGF (Media Gateway) for interworking with legacy network
  • PDF (Policy Decision Function) for QoS control using policies
  •  

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

local-sip

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"

multi-public-id

  1. 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 ;
  2. 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
  3. 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
  4. 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
Category: IMS  Tags: , , , , , , ,  One Comment