The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)
RFC 3969

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Network Working Group                                       G. Camarillo
Request for Comments: 3969                                      Ericsson
Updates: 3427                                              December 2004
BCP: 99
Category: Best Current Practice

             The Internet Assigned Number Authority (IANA)
         Uniform Resource Identifier (URI) Parameter Registry
               for the Session Initiation Protocol (SIP)

Status of This Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document creates an Internet Assigned Number Authority (IANA)
   registry for the Session Initiation Protocol (SIP) and SIPS Uniform
   Resource Identifier (URI) parameters, and their values.  It also
   lists the already existing parameters to be used as initial values
   for that registry.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3.  Use of the Registry. . . . . . . . . . . . . . . . . . . . . .  2
   4.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  3
       4.1.  SIP and SIPS URI Parameters Sub-Registry . . . . . . . .  3
       4.2.  Registration Policy for SIP and SIPS URI Parameters. . .  4
   5.  Security Considerations. . . . . . . . . . . . . . . . . . . .  4
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  4
   7.  Normative References . . . . . . . . . . . . . . . . . . . . .  5
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  5
       Full Copyright Statement . . . . . . . . . . . . . . . . . . .  6

Camarillo                Best Current Practice                  [Page 1]
RFC 3969          IANA URI Parameter Registry for SIP      December 2004

1.  Introduction

   RFC 3261 [1] allows new SIP URI and SIPS URI parameters, and new
   parameter values to be defined.  However, RFC 3261 omitted an IANA
   registry for them.  This document creates such a registry.

   RFC 3427 [2] documents the process to extend SIP.  This document
   updates RFC 3427 by specifying how to define and register new SIP and
   SIP URI parameters and their values.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [3] and indicate requirement levels for compliant SIP
   implementations.

3.  Use of the Registry

   SIP and SIPS URI parameters and values for these parameters MUST be
   documented in a standards-track RFC in order to be registered by
   IANA.  This documentation MUST fully explain the syntax, intended
   usage, and semantics of the parameter.  The intent of this
   requirement is to assure interoperability between independent
   implementations, and to prevent accidental namespace collisions
   between implementations of dissimilar features.

      Note that this registry, unlike other protocol registries, only
      deals with parameters and parameter values defined in RFCs (i.e.,
      it lacks a vendor-extension tree).  RFC 3427 [2] documents
      concerns with regards to new SIP extensions which may damage
      security, greatly increase the complexity of the protocol, or
      both.  New parameters and parameter values need to be documented
      in RFCs as a result of these concerns.

   RFCs defining SIP URI, SIPS URI parameters, or parameter values MUST
   register them with IANA as described below.

   Registered SIP and SIPS URI parameters and their values are to be
   considered "reserved words".  In order to preserve interoperability,
   registered parameters MUST be used in a manner consistent with that
   described in their defining RFC.  Implementations MUST NOT utilize
   "private" or "locally defined" URI parameters that conflict with
   registered parameters.

Camarillo                Best Current Practice                  [Page 2]
RFC 3969          IANA URI Parameter Registry for SIP      December 2004

      Note that although unregistered SIP and SIPS URI parameters may be
      used in implementations, developers are cautioned that usage of
      such parameters is risky.  New SIP and SIPS URI parameters and new
      values for them may be registered at any time, and there is no
      assurance that these new registered URI parameters will not
      conflict with unregistered parameters currently in use.

   Some SIP and SIPS URI parameters only accept a set of predefined
   parameter values.  For example, a parameter indicating the transport
   protocol in use may only accept the predefined tokens TCP, UDP, and
   SCTP as valid values.  Registering all parameter values for all SIP