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Network Working Group                                       G. CamarilloRequest for Comments: 3969                                      EricssonUpdates:3427                                              December 2004BCP: 99Category: Best Current PracticeThe Internet Assigned Number Authority (IANA)Uniform Resource Identifier (URI) Parameter Registryfor 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 Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .22.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .23.  Use of the Registry. . . . . . . . . . . . . . . . . . . . . .24.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .34.1.  SIP and SIPS URI Parameters Sub-Registry . . . . . . . .34.2.  Registration Policy for SIP and SIPS URI Parameters. . .45.  Security Considerations. . . . . . . . . . . . . . . . . . . .46.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .47.  Normative References . . . . . . . . . . . . . . . . . . . . .5       Author's Address . . . . . . . . . . . . . . . . . . . . . . .5       Full Copyright Statement . . . . . . . . . . . . . . . . . . .6Camarillo                Best Current Practice                  [Page 1]

RFC 3969          IANA URI Parameter Registry for SIP      December 20041.  IntroductionRFC 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   updatesRFC 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 inBCP 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   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 ConsiderationsSection 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 Parameters4.1.  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.Camarillo                Best Current Practice                  [Page 3]

RFC 3969          IANA URI Parameter Registry for SIP      December 2004   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 inRFC 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 inRFC 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.Camarillo                Best Current Practice                  [Page 4]

RFC 3969          IANA URI Parameter Registry for SIP      December 20047.  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:  Gonzalo.Camarillo@ericsson.comCamarillo                Best Current Practice                  [Page 5]

RFC 3969          IANA URI Parameter Registry for SIP      December 2004Full Copyright Statement   Copyright (C) The Internet Society (2004).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the IETF's procedures with respect to rights in IETF Documents can   be found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Camarillo                Best Current Practice                  [Page 6]