RFC5341

Network Working Group C. Jennings Request for Comments: 5341 Cisco Systems Updates: 3966 V. Gurbani Category: Standards Track Bell Laboratories, Alcatel-Lucent

                                                      September 2008

         The Internet Assigned Number Authority (IANA)
    tel Uniform Resource Identifier (URI) Parameter Registry

Status of This Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Abstract

This document creates an Internet Assigned Number Authority (IANA) registry for tel Uniform Resource Identifier (URI) parameters and their values. It populates the registry with the parameters defined in the tel URI specification, along with the parameters in tel URI extensions defined for number portability and trunk groups.

Introduction

The tel URI (RFC 3966 [1]), defines a URI that can be used to represent resources identified by telephone numbers. The tel URI, like many other URIs, provides extensibility through the definition of new URI parameters and new values for existing parameters. However, RFC 3966 did not specify an IANA registry where such parameters and values can be listed and standardized. This specification creates such a registry.

Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [2].

Use of the Registry

The tel URI parameters and values for these parameters MUST be documented in a RFC or other permanent and readily available public specification 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.

Documents defining tel URI parameters or parameter values MUST register them with IANA, as described in Section 4. The IANA registration policy for such parameters is "Specification Required, Designated Expert," and is further discussed in Section 4.2.

Some tel URI parameters only accept a set of predefined parameter values while others can take any value. There are also parameters that do not have any value; they are used as flags.

Those URI parameters that take on predefined values typically take on a large number of values. Registering each of those values, or creating a sub-registry for each such parameter is not appropriate. 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.

Accordingly, the tel URI parameter registry contains a column that indicates whether or not each parameter accepts a value. The column may contain "No value" or "Constrained". A "Constrained" in the column implies that certain predefined values exist for this

parameter and the accompanying RFC or other permanent and readily available public specification should be consulted to find out the accepted set of values. A "No Value" in the column implies that the parameter is used either as a flag, or does not have a set of predefined values. The accompanying RFC or other permanent and readily available public specification should provide more information on the semantics of the parameter.

IANA Considerations

The specification creates a new IANA registry named "tel URI Parameters".

tel URI Parameters Registry

New tel URI parameters and new values for existing tel URI parameters MUST be registered with IANA.

When registering a new tel URI 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 or other permanent and readily available

  public specification defining the parameter and new values.

When registering a new value for an existing tel URI parameter, the following information MUST be provided:

o Name of the parameter.

o Reference to the RFC or other permanent and readily available

  public specification providing the new value.

Table 1 contains the initial values for this registry.

Parameter Name Predefined Values Reference

---

----------------- ---------

isub Constrained RFC3966 isub-encoding Constrained RFC4715 ext Constrained RFC3966 phone-context Constrained RFC3966 enumdi No value RFC4759 npdi No value RFC4694 rn Constrained RFC4694 rn-context Constrained RFC4694 cic Constrained RFC4694 cic-context Constrained RFC4694 tgrp Constrained RFC4904 trunk-context Constrained RFC4904

Table 1: IANA tel URI parameter registry

Registration Policy for tel URI Parameters

As per the terminology in [3] and actions accorded to such a role, the registration policy for tel URI parameters shall be "Specification Required, Designated Expert" (the former implicitly implies the latter).

The Designated Expert, when deliberating on whether to include a new parameter in the tel URI registry, may use the criteria provided below to reach a decision (this is not an exhaustive list but representative of the issues to consider when rendering an equitable decision):

o If the tel URI -- with the parameter under consideration -- will

  be converted to a URI used by other signaling protocols such as
  the Session Initiation Protocol (SIP [5]) or H.323 [7], then the
  expert must consider whether this parameter merely encapsulates
  signaling information that is not meaningful to the processing of
  requests in the domain of the converted URI.  For example, certain
  Integrated Services Digital Network (ISDN) User Part (ISUP, [8])
  parameters have no equivalent corollary in SIP; thus, their
  presence or absence in a SIP URI will not hinder the normal rules
  for processing that URI.  Other parameters may affect the normal
  processing rules associated with the URI; in such cases, the
  expert must carefully consider the ramifications, if any, of the
  presence of such parameters.

o Certain parameters of a tel URI can be optional. These parameters

  act as metadata about the identifier in the tel URI.  Optional
  parameters should provide additional information to a service for
  which they apply instead of acting as enablers of that service in

  the first place.  The service must continue to be invoked and
  operate normally even in the absence of these parameters.

Security Considerations

The registry in this document does not in itself have security considerations. However, as mentioned in [4], 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 in this specification MUST provide detailed security considerations for them.

Acknowledgments

The structure of this document comes from [6], which is the equivalent work done in the SIP domain to establish a registry. Ted Hardie, Alfred Hoenes, Jon Peterson, and Jonathan Rosenberg provided substantive comments that have improved this document.

Brian Carpenter, Lars Eggert, Pasi Eronen, Chris Newman, and Glen Zorn provided feedback during IESG review and Gen-ART review.

References

Normative References

[1] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,

    December 2004.

[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement

    Levels", BCP 14, RFC 2119, March 1997.

[3] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA

    Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.

Informative References

[4] 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.

[5] 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.

[6] Camarillo, G., "The Internet Assigned Number Authority (IANA)

    Uniform Resource Identifier (URI) Parameter Registry for the
    Session Initiation Protocol (SIP)", BCP 99, RFC 3969,
    December 2004.

[7] ITU-T H.323, "H.323: Packet-based multimedia communications

    systems", June 2006.

[8] ITU-T Q.764, "Signaling System No. 7: ISDN User Part Signaling

    Procedures", December 1999.

Authors' Addresses

Cullen Jennings Cisco Systems 170 West Tasman Drive Mailstop SJC-21/2 San Jose, CA 95134 USA

Phone: +1 408 902-3341 EMail: [email protected]

Vijay K. Gurbani Bell Laboratories, Alcatel-Lucent 2701 Lucent Lane Room 9F-546 Lisle, IL 60532 USA

Phone: +1 630 224-0216 EMail: [email protected]

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