RFC 3841 (rfc3841) - Page 2 of 26

Caller Preferences for the Session Initiation Protocol (SIP)

RFC 3841               Caller Preferences for SIP            August 2004


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Overview of Operation  . . . . . . . . . . . . . . . . . . . .  4
   5.  UAC Behavior . . . . . . . . . . . . . . . . . . . . . . . . .  5
       5.1.  Request Handling Preferences . . . . . . . . . . . . . .  6
       5.2.  Feature Set Preferences  . . . . . . . . . . . . . . . .  6
   6.  UAS Behavior . . . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . . .  9
       7.1.  Request-Disposition Processing . . . . . . . . . . . . .  9
       7.2.  Preference and Capability Matching . . . . . . . . . . .  9
             7.2.1. Extracting Explicit Preferences . . . . . . . . . 10
             7.2.2. Extracting Implicit Preferences . . . . . . . . . 10
                    7.2.2.1. Methods. . . . . . . . . . . . . . . . . 10
                    7.2.2.2. Event Packages . . . . . . . . . . . . . 11
             7.2.3. Constructing Contact Predicates . . . . . . . . . 11
             7.2.4. Matching. . . . . . . . . . . . . . . . . . . . . 12
             7.2.5. Example . . . . . . . . . . . . . . . . . . . . . 16
   8.  Mapping Feature Parameters to a Predicate. . . . . . . . . . . 17
   9.  Header Field Definitions . . . . . . . . . . . . . . . . . . . 19
       9.1.  Request Disposition  . . . . . . . . . . . . . . . . . . 20
       9.2.  Accept-Contact and Reject-Contact Header Fields  . . . . 21
   10. Augmented BNF  . . . . . . . . . . . . . . . . . . . . . . . . 22
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
   13. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 23
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
       14.1. Normative References . . . . . . . . . . . . . . . . . . 24
       14.2. Informative References . . . . . . . . . . . . . . . . . 24
   15. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 25
   16. Full Copyright Statements. . . . . . . . . . . . . . . . . . . 26

1.  Introduction

   When a Session Initiation Protocol (SIP) [1] server receives a
   request, there are a number of decisions it can make regarding the
   processing of the request.  These include:

   o  whether to proxy or redirect the request

   o  which URIs to proxy or redirect to

   o  whether to fork or not

   o  whether to search recursively or not




Rosenberg, et al.           Standards Track