IMS – IP Multimedia Subsystem

IMS is defined as part of the 3GPP standards. IMS is an architecture based on internet standards. SIP is one of the main protocols used to enable IMS functionality. With the wide range of end-user applications in use today simultaneously, IMS can provide a common IP interface for singalling, traffic and applications. The Voice over LTE (VoLTE) scheme for providing voice over an LTE system utilizes IMS enabling it to become part of a rich media solution. It was the option chosen by the GSMA for use on LTE and is the standardized method for providing SMS and voice over LTE.


XML Configuration Access Protocol
XCAP is an application layer protocol that allows a client to read, write, and modify application configuration data stored in XML format on a server. XCAP maps XML document sub-trees and element attributes to HTTP URIs, so that these components can be directly accessed by clients using HTTP protocol. An XCAP server is used by XCAP clients to store data such as buddy lists and presence policy in combination with a SIP Presence server that supports PUBLISH, XCAP can support configuration of a number of applications. It is used in IMS to facilitate the management of subscriber information related to services and settings XCAP supports the following operations:
  • Retrieve an item
  • Delete an item
  • Modify an item
  • Add an item
These operation can be run on
  • Document
  • ¬†Element
  • Attribute
  • There are various application usages. These are provided using specific application unique IDs auid.

Message Session Relay Protocol MSRP is a protocol for transmitting a series of related instant messages in the context of a communications session. It Is a session-oriented instant message transport protocol An application instantiates the session with the Session Description Protocol (SDP) over Session Initiation Protocol (SIP) It is used as part of RCS, Rich Communication Services, as based on IMS. It is used to perform instant messaging for attachment file transfer or for photo sharing. The syntax of MSRP is similar to that of SIP, HTTP etc. A message can either be a request or a response. Each message contains headers and a body. The first 2 headers must be To-Path and From-Path. The last header is Content-Type. MSRP is carried over a reliable transport layer.

Additional Protocols Used in IMS

Diameter SIP MGCP