IMS Architecture

IMS Architecture

Layered Architecture comprises a set of interfaces, Sip proxies and servers(such as media servers) and media gateways(for connections to circuit core or the PSTN).

IMS Building Blocks

• Applications or service layer    ➡ OSA-GW, Telephony AS, Non-telephony AS

            AS (Application Servers) host and execute services and interface with the S-CSCF using SIP and which allow third party providers an easy integration and deployment of their value added service to the IMS infrastructure.

An example of services are:

- Lawful interception used by Police

- conference call services

-  MMS

- Instant messaging

- Voice call continuity and all basics features.

- Non-telephony based services eg: SIP  Offer a set of protocol built-in simple features, such as accept call, reject call, redirect call, proxy call request etc

- APIs for an enterprise to interact with each other.

• Session Control or core Layer ➡ CSCF,BGCF,MGCF &MRFC,HSS ( more detail in http://imsstudy.blogspot.in/2016/12/before-starting-ims-basics-thing-to-know.html)

       Several types of SIP servers known as CSCF are used to process SIP signaling packets in the IMS domain:

1. ·        Proxy CSCF
2. ·        Interrogating CSCF
3. ·        Serving CSCF

• Transport & Endpoint or AccessLayer ➡Media Gateway,Media Serve