SIP URI Params: The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)
Creates the IANA registry that keeps SIP and SIPS URI parameters from colliding.
Camarillo, G., "The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)", BCP 99, RFC 3969, DOI 10.17487/RFC3969, December 2004, <https://www.rfc-editor.org/info/rfc3969>.
@misc{rfc3969,
series = {Request for Comments},
number = 3969,
howpublished = {RFC 3969},
publisher = {RFC Editor},
doi = {10.17487/RFC3969},
url = {https://www.rfc-editor.org/info/rfc3969},
author = {G. Camarillo},
title = {{The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)}},
pagetotal = 6,
year = 2004,
month = dec,
} RFC text
Contents
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
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.
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.
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.
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: Gonzalo.Camarillo@ericsson.com
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.
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
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
AI ELI5
On this page
§1The Missing Registry
RFC 3261 allows new SIP URI and SIPS URI parameters, and new parameter values, to be defined. It omitted an IANA registry for them, and RFC 3969 creates it.
The document is a Best Current Practice and it updates RFC 3427, which documents the process for extending SIP. The update specifies how to define and register new SIP and SIPS URI parameters and their values.
The SIP rulebook said you may invent new address add-ons, but forgot to say where to write them down. This RFC adds the missing list.
§3Who Can Register a Parameter
SIP and SIPS URI parameters, and values for them, MUST be documented in a standards-track RFC to be registered by IANA. That documentation MUST fully explain the syntax, intended usage and semantics of the parameter. The aim is interoperability between independent implementations and no accidental namespace collisions between dissimilar features.
Unlike other protocol registries, this one has no vendor-extension tree. It only deals with parameters and values defined in RFCs. The reason given is the concerns in RFC 3427 about extensions that may damage security, greatly increase protocol complexity, or both.
RFCs that define SIP or SIPS URI parameters, or values, MUST register them with IANA.
To add a name to the list you must first write a proper standard explaining exactly what it does. No sneaking in your own private names.
§3.1Reserved Words and Unregistered Parameters
Registered parameters and their values are to be considered reserved words. To preserve interoperability, they MUST be used consistently with the RFC that defines them, and implementations MUST NOT use "private" or "locally defined" URI parameters that conflict with registered ones.
Unregistered parameters may still be used in implementations, but the RFC calls that risky. New parameters and values can be registered at any time, and nothing assures that they will not conflict with unregistered ones already in use.
Once a name is on the list it belongs to its official meaning. You may use a made-up name that is not listed, but someone may take it later and your thing could break.
§4.1The Sub-Registry and Its Initial Entries
RFC 3261 section 27 already creates IANA registries for method names, header field names, warning codes, status codes and option tags. This RFC adds a new sub-registry under the SIP Parameters registry, called SIP/SIPS URI Parameters.
Each registration MUST give the name of the parameter, whether it only accepts a set of predefined values, and a reference to the RFC defining the parameter plus any RFC defining new values for it. Because registering every value of every parameter would need many sub-registries, values are registered by reference: references to RFCs defining values appear in double brackets in the registry.
Every parameter is registered both as a SIP and as a SIPS URI parameter, even if it applies to only one scheme. That avoids two parameters with the same name but different semantics. The initial table has seven entries.
Each line on the list says the name, whether the choices are fixed, and which standard explains it. Fixed-choice names point to the standards that add choices.
| Parameter | 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 |
§4.2Registration Policy
Using the terminology of RFC 2434, the registration policy is Specification Required. For this registry, the parameter MUST be defined by a standards-track RFC.
The rule for getting on the list is: show a written standard first. Then you can be added.
§5Security Considerations
The registry itself has no security considerations. As RFC 3427 notes, though, an important reason for the IETF to manage SIP extensions is to ensure that all extensions and parameters can be used securely. The supporting RFCs for parameter registrations MUST therefore give detailed security considerations for their parameters.
The list is harmless on its own. But each standard that adds a name must explain how to use it safely.