RFC3969: The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)

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Related keywords:  (session initiation protocol) (SIP)

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).


   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

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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",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [3] and indicate requirement levels for compliant SIP

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.

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      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
   and SIPS URI parameters of this type would require a large number of
   subregistries.  Instead, we have chosen to register URI parameter
   values by reference.  That is, the entry in the URI parameter
   registry for a given URI parameter contains references to the RFCs
   defining new values of that parameter.  References to RFCs defining
   parameter values appear in double brackets in the registry.

   So, the SIP and SIPS URI parameter registry contains a column that
   indicates whether or not each parameter only accepts a set of
   predefined values.  Implementers of parameters with a "yes" in that
   column need to find all the valid parameter values in the RFCs
   provided as references.

4.  IANA Considerations

   Section 27 of RFC 3261 [1] creates an IANA registry for method names,
   header field names, warning codes, status codes, and option tags.
   This specification creates a new sub-registry under the SIP
   Parameters registry.

      o  SIP/SIPS URI Parameters

4.1.  SIP and SIPS URI Parameters Sub-Registry

   New SIP and SIPS URI parameters and new parameter values are
   registered by the IANA.  When registering a new SIP or SIPS parameter
   or a new value for a parameter, the following information MUST be

      o  Name of the parameter.

      o  Whether the parameter only accepts a set of predefined values.

      o  Reference to the RFC defining the parameter and to any RFC that
         defines new values for the parameter.  References to RFCs
         defining parameter values appear in double brackets in the

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   Table 1 contains the initial values for this sub-registry.

      Parameter Name  Predefined Values  Reference
      comp                   Yes        [RFC 3486]
      lr                      No        [RFC 3261]
      maddr                   No        [RFC 3261]
      method                 Yes        [RFC 3261]
      transport              Yes        [RFC 3261]
      ttl                     No        [RFC 3261]
      user                   Yes        [RFC 3261]

   Table 1: IANA SIP and SIPS URI parameter sub-registry

   Note that any given parameter name is registered both as a SIP and as
   a SIPS URI parameter.  Still, some parameters may not apply to one of
   the schemes.  We have chosen to register any parameter as both a SIP
   and SIPS URI parameter anyway to avoid having two parameters with the
   same name, one applicable to SIP URIs and one to SIPS URIs, but with
   different semantics.  Implementors are urged to read the parameter
   specifications for a detailed description of the semantics of any

4.2.  Registration Policy for SIP and SIPS URI Parameters

   As per the terminology in RFC 2434 [4], the registration policy for
   SIP and SIPS URI parameters shall be "Specification Required".

   For the purposes of this registry, the parameter for which IANA
   registration is requested MUST be defined by a standards-track RFC.

5.  Security Considerations

   The registry in this document does not in itself have security
   considerations.  However, as mentioned in RFC 3427, an important
   reason for the IETF to manage the extensions of SIP is to ensure that
   all extensions and parameters are able to provide secure usage.  The
   supporting RFC publications for parameter registrations described
   this specification MUST provide detailed security considerations for

6.  Acknowledgements

   Jonathan Rosenberg, Henning Schulzrinne, Rohan Mahy, Dean Willis, and
   Allison Mankin provided useful comments on this document.

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7.  Normative References

   [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
       Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
       Session Initiation Protocol", RFC 3261, June 2002.

   [2] Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J., and B.
       Rosen, "Change Process for the Session Initiation Protocol
       (SIP)", BCP 67, RFC 3427, December 2002.

   [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [4] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
       Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

Author's Address

   Gonzalo Camarillo
   Advanced Signalling Research Lab.
   FIN-02420 Jorvas

   EMail:  Gonzalo.Camarillo@ericsson.com

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Full Copyright Statement

   Copyright (C) The Internet Society (2004).

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   retain all their rights.

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