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









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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",
  "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.






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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
  provided.

     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
        registry.



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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
  parameter.

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
  them.

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
  Ericsson
  Advanced Signalling Research Lab.
  FIN-02420 Jorvas
  Finland

  EMail:  [email protected]


























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Full Copyright Statement

  Copyright (C) The Internet Society (2004).

  This document is subject to the rights, licenses and restrictions
  contained in BCP 78, and except as set forth therein, the authors
  retain all their rights.

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Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.







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