Guidelines for Usage of the Session Initiation Protocol (SIP) Caller Preferences Extension

This document contains guidelines for usage of the Caller Preferences Extension to the Session Initiation Protocol (SIP). It demonstrates the benefits of caller preferences with specific example applications, provides use cases to show proper operation, provides guidance on the applicability of the registered feature tags, and describes a straightforward implementation of the preference and capability matching algorithm specified in Section 7.2 of RFC 3841. This memo provides information for the Internet community.