John Waclawsky, part of the Mobile Wireless Group at Cisco Systems, provides some background:
Out of the wireless standards consortium called 3rd Generation Partnership Project (3GPP) comes a slow-growing and complicated collection of carrier network functions and processes that collectively are referred to as IMS, which stands for the IP (or Internet) Multimedia Subsystem. The IMS standards promise an operator-friendly environment for real-time, packet-based calls and services that not only will preserve traditional carrier controls over user signaling and usage-based billing, but also will generate new revenue via deep packet inspection of protocols, URI and content.
IMS was conceived for the evolution of cellular telephony networks, but the benefits of user signaling and billing controls have attracted the endorsement and involvement of wireline network operators and standards makers.
IMS is only a part of such a system, as defined by 3GPP. The entire 3G system can be briefly summarized in five pieces:
1. The IMS, or SIP/SDP control plane, at the core.
2. The media and signal conversion layer wrapped around the core.
3. The embedded walled garden, defined by the applications or services the operator offers to its subscribers and the limits it also sets on their behavior and signaling.
4. The billing and back office function layer.
5. An array of network, systems management and operations tools.
IMS is a result of the telephony carriers growing interest (at 3GPP) in data applications, the Internet in general and the emerging wireless Internet in particular. IMS is part of a huge 3G gamble by the mobile telephony operators around the world, with assistance from traditional telephony vendors, to obtain control of the vast new Internet medium and monetize it.
TechTip adds about SIP:
SIP [Session Initiation Protocol] is the real-time communication protocol for VoIP [Voice over IP]. SIP has been expanded to support video and instant-messaging applications. SIP is designed to perform basic call-control tasks, such as session call set up and tear down and signaling for features such as call hold, caller ID, conferencing and call transferring.
“Presence” is an all-encompassing term used to describe reachability control over how, where, when and by whom they can be contacted (reached). Presence covers any concept such as “buddy lists” (desired contacts) or the means (wireless/wireline), device (pager, cell, PDA, TV, etc.) or media (voice, data, music, multi-media) and yet-to-be-defined means of communication.
Tomorrow: The Future
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