- General presentation of the IMS
- General presentation of OpenIMSCore
- Installation of IMS network core
- IMS Client Installation
- Installation of AS
- Authors
- License
IMS (IP Multimedia Subsystem) is a new multimedia domain defined by 3GPP in release 5. IMS is embedded behind the packet domain (PS: Packet Switching) of the mobile core network and offers many services such as:
- Television over IP (IPTV)
- Video on demand (VoD)
- Presence (online, busy, ...)
- Instant messaging
- etc
The some entities of the IMS are:
- CSCF (Call Session Control Function)
- HSS (Home Subscriber Server)
- MRF (Media Resource Function)
- IM-MGW (IP MultiMedia Gateway)
- MGCF (Media Gateway Controller Function)
- AS (Application Servers) All these entities are software and can be installed on a single server or on several servers (distributed architecture).
The CSCF proxy is the first point of entry of the IMS core. It is connected to the GGSN/PGW (GGSN: Gateway GPRS Support Node, PGW: Packet Data Network Gateway) and BRAS (Broadband Access Server) entities.
The ICSCF is responsible for querying the HSS database to retrieve the name and address of the registration server (SCSCF). The ICSCF receives the requests, queries the HSS via the Diameter protocol, receives a response from the HSS and relays the received SIP messages to the appropriate SCSCF, hence the proxy function
Note: PCSCF and ICSCF are proxy servers.
The SCSCF is a "Registrar" or registration server. It is responsible for registering IMS subscribers (IMS clients) in the IP multimedia core. After receiving a SIP/Register request from the ICSCF, the SCSCF retrieves the authentication quintuplet (RAND, Kc, Ki, AUTN and XRES) from the HSS database. The SCSCF ensures the execution of calls and services in the IMS core.
The HSS stores the authentication quintuplet, profiles and subscription lists of IMS subscribers. The HSS uses the Cx interface to communicate with the SCSCF/ICSCF and the Sh interface for interconnection with the AS
The MRF ensures the storage of announcement tapes (examples: insufficient credit, voice mail, ...). The MRF allows to adapt the media streams and to mix them. The MRF is divided into two entities:
- MRFC (Media Resource Function Control)
- MRFP (Media Resource Function Processor)
Between MRFC and MRFP, the MEGACO protocol is used. The MRFC provides the control of the announcement band messages in the MRFP. The MRFP provides transport, storage and playback of the announcement tapes.
The AS provides an execution context for application components. There are several types of AS servers:
- SIP AS
- SSF AS
- OSA AS
AS are interconnected to the IMS core through Sh interfaces to the HSS, ISCSF and SCSCF. The AS allows to offer value-added services: Presence, IPTV, instant messaging, SMS/USSD, etc.
< 7440 div class="markdown-heading" dir="auto">