3GPP has selected SIP [2] as the protocol to establish and tear down multimedia sessions in the IP Multimedia Subsystem (IMS). 3GPP Technical Specification 23.228 [28] describes the IMS. 3GPP Technical Specification 24.228 [29] contains a comprehensive set of session flows. 3GPP Technical Specification 24.229 [30] describes the usage of SIP by the various IMS nodes.
This document is an effort to define the requirements applicable to the usage of the SIP protocol suite in cellular networks, particularly in the 3GPP IMS for Release 5 of the 3GPP specifications. Further releases of the 3GPP specifications may contain additional SIP requirements. This document focuses on the requirements identified for the 3GPP Release 5 IMS.
The rest of this document is structured as follows:
o Section 3 offers an overview of the 3GPP IMS. Readers who are not familiar with it should carefully read this section.
o Section 4 contains the 3GPP requirements to SIP. Requirements are grouped by category. Some requirements include statements on possible solutions that would be able to fulfill them. Note that, as a particular requirement might be fulfilled by different solutions, not all the solutions might have an impact on SIP.
This document is advisory in nature. Its primary purpose is to help the IETF understand the IMS environment. Given this better understanding, we expect that the IETF can more effectively evolve the SIP protocol. The IETF will not respond to the requirements given in this document on a point-for-point basis. Some requirements have been and/or will be met by extensions to the SIP protocol. Others may be addressed by effectively using existing capabilities in
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