The IP multimedia subsystem is an architectural framework for the delivery of IP multimedia services. It was initially developed by the Wireless Standards Body 3rd Generation Partnership Project (3GPP) as part of a vision for mobile network evolution beyond the Global System for Mobile Communication (GSM) standard.

IMS uses Internet Engineering Task Force protocols to provide access to voice applications and multimedia from wireless and wire-line terminals. IMS also supports services enabled and based on Session Initiation Protocol (SIP). Multimedia subsystems deliver multimedia services, which can be accessed by users from various devices through an IP network or a traditional telephony system.

The network architecture is divided into the following layers:

• Device layer
• Transport layer
• Control layer
• Service layer