RFC 3968 BEST CURRENT PRACTICE SIP · IANA · REGISTRY
SIP Header Params: The Internet Assigned Number Authority (IANA) Header Field Parameter Registry for the Session Initiation Protocol (SIP)
The official list that keeps SIP header field parameter names from colliding.
RFC EDITOR
Camarillo, G., "The Internet Assigned Number Authority (IANA) Header Field Parameter Registry for the Session Initiation Protocol (SIP)", BCP 98, RFC 3968, DOI 10.17487/RFC3968, December 2004, <https://www.rfc-editor.org/info/rfc3968>.
BIBTEX
@misc{rfc3968,
series = {Request for Comments},
number = 3968,
howpublished = {RFC 3968},
publisher = {RFC Editor},
doi = {10.17487/RFC3968},
url = {https://www.rfc-editor.org/info/rfc3968},
author = {G. Camarillo},
title = {{The Internet Assigned Number Authority (IANA) Header Field Parameter Registry for the Session Initiation Protocol (SIP)}},
pagetotal = 8,
year = 2004,
month = dec,
} LINEAGE · FROM THE RFC INDEXOpen full graph →
RFC text
Contents
Network Working Group G. Camarillo
Request for Comments: 3968 Ericsson
Updates: 3427 December 2004
BCP: 98
Category: Best Current Practice
The Internet Assigned Number Authority (IANA)
Header Field 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) header field
parameters and parameter values. It also lists the already existing
parameters and parameter values to be used as the initial entries for
this registry.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Use of the Registry . . . . . . . . . . . . . . . . . . . . . 2
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4.1. Header Field Parameters Sub-Registry . . . . . . . . . . 3
4.2. Registration Policy for SIP Header Field Parameters. . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8
1. Introduction
RFC 3261 [3] allows new header field 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 [4] documents the process to extend SIP. This document
updates RFC 3427 by specifying how to define and register new SIP
header field parameters and parameter values.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations.
3. Use of the Registry
SIP header field parameters and parameter values MUST be documented
in an RFC in order to be registered by IANA. This documentation MUST
fully explain the syntax, intended usage, and semantics of the
parameter or parameter value. 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 [4] 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 header field parameters or parameter values MUST
register them with IANA as described below.
Registered SIP header field parameters and parameter values are to be
considered "reserved words". In order to preserve interoperability,
registered parameters and parameter values MUST be used in a manner
consistent with that described in their defining RFC.
Implementations MUST NOT utilize "private" or "locally defined" SIP
header field parameters or parameter values that conflict with
registered parameters.
Note that although unregistered SIP header field parameters and
parameter values may be used in implementations, developers are
cautioned that usage of such parameters is risky. New SIP header
field parameters and parameter values may be registered at any
time, and there is no assurance that these new registered
parameters or parameter values will not conflict with unregistered
parameters currently in use.
Some SIP header field 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
header field parameters of this type would require a large number of
subregistries. Instead, we have chosen to register parameter values
by reference. That is, the entry in the parameter registry for a
given header field parameter contains references to the RFCs defining
new values of the parameter. References to RFCs defining parameter
values appear in double brackets in the registry.
So, the header field 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 [3] creates an IANA registry for method names,
header field names, warning codes, status codes, and option tags.
This specification creates a new sub-registry for header field
parameters under the SIP Parameters registry.
4.1. Header Field Parameters Sub-Registry
The majority of the SIP header fields can be extended by defining new
parameters. New SIP header field parameters are registered by the
IANA. When registering a new parameter for a header field or a new
value for a parameter, the following information MUST be provided.
o Header field in which the parameter can appear.
o Name of the header field parameter being registered.
o Whether the parameter only accepts a set of predefined values.
o A reference to the RFC where the parameter is defined and to any
RFC that defines new values for the parameter. References to RFCs
defining parameter values appear in double brackets in the
registry.
Parameters that can appear in different header fields MAY have the
same name. However, parameters that can appear in the same header
field MUST have different names.
The following are the initial values for this sub-registry.
Header Field Parameter Name Predefined Reference
Values
_____________________________________________________________________
Accept q No [RFC 3261]
Accept-Encoding q No [RFC 3261]
Accept-Language q No [RFC 3261]
Authorization algorithm Yes [RFC 3261]
[[RFC 3310]]
Authorization auts No [RFC 3310]
Authorization cnonce No [RFC 3261]
Authorization nc No [RFC 3261]
Authorization nonce No [RFC 3261]
Authorization opaque No [RFC 3261]
Authorization qop Yes [RFC 3261]
Authorization realm No [RFC 3261]
Authorization response No [RFC 3261]
Authorization uri No [RFC 3261]
Authorization username No [RFC 3261]
Authentication-Info cnonce No [RFC 3261]
Authentication-Info nc No [RFC 3261]
Authentication-Info nextnonce No [RFC 3261]
Authentication-Info qop Yes [RFC 3261]
Authentication-Info rspauth No [RFC 3261]
Call-Info purpose Yes [RFC 3261]
Contact expires No [RFC 3261]
Contact q No [RFC 3261]
Content-Disposition handling Yes [RFC 3261]
Event id No [RFC 3265]
From tag No [RFC 3261]
P-Access-Network-Info cgi-3gpp No [RFC 3455]
P-Access-Network-Info utran-cell-id-3gpp No [RFC 3455]
P-Charging-Function-Addresses ccf No [RFC 3455]
P-Charging-Function-Addresses ecf No [RFC 3455]
P-Charging-Vector icid-value No [RFC 3455]
P-Charging-Vector icid-generated-at No [RFC 3455]
P-Charging-Vector orig-ioi No [RFC 3455]
P-Charging-Vector term-ioi No [RFC 3455]
P-DCS-Billing-Info called No [RFC 3603]
P-DCS-Billing-Info calling No [RFC 3603]
P-DCS-Billing-Info charge No [RFC 3603]
P-DCS-Billing-Info locroute No [RFC 3603]
P-DCS-Billing-Info rksgroup No [RFC 3603]
P-DCS-Billing-Info routing No [RFC 3603]
P-DCS-LAES content No [RFC 3603]
P-DCS-LAES key No [RFC 3603]
P-DCS-Redirect count No [RFC 3603]
P-DCS-Redirect redirector-uri No [RFC 3603]
Proxy-Authenticate algorithm Yes [RFC 3261]
[[RFC 3310]]
Proxy-Authenticate domain No [RFC 3261]
Proxy-Authenticate nonce No [RFC 3261]
Proxy-Authenticate opaque No [RFC 3261]
Proxy-Authenticate qop Yes [RFC 3261]
Proxy-Authenticate realm No [RFC 3261]
Proxy-Authenticate stale Yes [RFC 3261]
Proxy-Authorization algorithm Yes [RFC 3261]
[[RFC 3310]]
Proxy-Authorization auts No [RFC 3310]
Proxy-Authorization cnonce No [RFC 3261]
Proxy-Authorization nc No [RFC 3261]
Proxy-Authorization nonce No [RFC 3261]
Proxy-Authorization opaque No [RFC 3261]
Proxy-Authorization qop Yes [RFC 3261]
Proxy-Authorization realm No [RFC 3261]
Proxy-Authorization response No [RFC 3261]
Proxy-Authorization uri No [RFC 3261]
Proxy-Authorization username No [RFC 3261]
Reason cause Yes [RFC 3326]
Reason text No [RFC 3326]
Retry-After duration No [RFC 3261]
Security-Client alg Yes [RFC 3329]
Security-Client ealg Yes [RFC 3329]
Security-Client d-alg Yes [RFC 3329]
Security-Client d-qop Yes [RFC 3329]
Security-Client d-ver No [RFC 3329]
Security-Client mod Yes [RFC 3329]
Security-Client port1 No [RFC 3329]
Security-Client port2 No [RFC 3329]
Security-Client prot Yes [RFC 3329]
Security-Client q No [RFC 3329]
Security-Client spi No [RFC 3329]
Security-Server alg Yes [RFC 3329]
Security-Server ealg Yes [RFC 3329]
Security-Server d-alg Yes [RFC 3329]
Security-Server d-qop Yes [RFC 3329]
Security-Server d-ver No [RFC 3329]
Security-Server mod Yes [RFC 3329]
Security-Server port1 No [RFC 3329]
Security-Server port2 No [RFC 3329]
Security-Server prot Yes [RFC 3329]
Security-Server q No [RFC 3329]
Security-Server spi No [RFC 3329]
Security-Verify alg Yes [RFC 3329]
Security-Verify ealg Yes [RFC 3329]
Security-Verify d-alg Yes [RFC 3329]
Security-Verify d-qop Yes [RFC 3329]
Security-Verify d-ver No [RFC 3329]
Security-Verify mod Yes [RFC 3329]
Security-Verify port1 No [RFC 3329]
Security-Verify port2 No [RFC 3329]
Security-Verify prot Yes [RFC 3329]
Security-Verify q No [RFC 3329]
Security-Verify spi No [RFC 3329]
Subscription-State expires No [RFC 3265]
Subscription-State reason Yes [RFC 3265]
Subscription-State retry-after No [RFC 3265]
To tag No [RFC 3261]
Via branch No [RFC 3261]
Via comp Yes [RFC 3486]
Via maddr No [RFC 3261]
Via received No [RFC 3261]
Via rport No [RFC 3581]
Via ttl No [RFC 3261]
WWW-Authenticate algorithm Yes [RFC 3261]
[[RFC 3310]]
WWW-Authenticate domain Yes [RFC 3261]
WWW-Authenticate nonce No [RFC 3261]
WWW-Authenticate opaque No [RFC 3261]
WWW-Authenticate qop Yes [RFC 3261]
WWW-Authenticate realm No [RFC 3261]
WWW-Authenticate stale Yes [RFC 3261]
4.2. Registration Policy for SIP Header Field Parameters
As per the terminology in RFC 2434 [2], the registration policy for
SIP header field parameters and parameter values shall be "IETF
Consensus."
For the purposes of this registry, the parameter or the parameter
value for which IANA registration is requested MUST be defined by an
RFC. There is no requirement that this RFC be standards-track.
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, Aki
Niemi, Bill Marshall, Miguel A. Garcia-Martin, Jean Francois Mule,
and Allison Mankin provided useful comments on this document.
7. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[3] 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.
[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.
Author's Address
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
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
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.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
AI ELI5
On this page
PROBLEMSIP lets people define new header field parameters and parameter values, but RFC 3261 never created an IANA registry for them, so names could clash.
MECHANISMRFC 3968 creates a sub-registry of SIP header field parameters under the SIP Parameters registry. Anything registered must be defined in an RFC, and the registry starts with the parameters that already exist.
WHY IT MATTERSRegistered parameters become reserved words that implementations must use as their defining RFC describes. The document also updates RFC 3427.
§1Why a Parameter Registry
The Session Initiation Protocol (SIP) lets people define new header field parameters and new values for them. RFC 3261 allows this but left out an IANA registry for them. RFC 3968 creates that registry.
It also updates RFC 3427, which documents the process for extending SIP, by saying how to define and register new header field parameters and parameter values. The document uses the requirement words MUST, SHOULD and MAY as defined in BCP 14.
SIP messages have little labelled settings. Nobody kept a master list of the labels, so this RFC starts one.
§3Rules for Using the Registry
A SIP header field parameter or parameter value MUST be documented in an RFC before IANA will register it. The RFC MUST fully explain the syntax, intended usage and semantics. The goal is interoperability between independent implementations and no accidental name collisions between dissimilar features. Unlike other protocol registries, this one has no vendor-extension tree, because RFC 3427 raises concerns that new extensions may damage security or greatly increase the complexity of the protocol.
RFCs that define parameters MUST register them. Registered names are treated as reserved words: they MUST be used consistently with their defining RFC, and implementations MUST NOT use private or locally defined parameters that conflict with registered ones.
Unregistered parameters may still be used, but the RFC warns this is risky: a new registration can appear at any time and may conflict with one already in use.
If you want a name in the book, you must first write down exactly what it means. Once a name is in the book, nobody may use it for something else.
§4.1What a Registry Entry Contains
The registry is a sub-registry under the SIP Parameters registry that section 27 of RFC 3261 created for method names, header field names, warning codes, status codes and option tags. A registration MUST give four things: the header field the parameter appears in, the parameter name, whether the parameter accepts only a set of predefined values, and a reference to the RFC that defines it (plus any RFC that defines new values).
Parameters in different header fields MAY share a name. Parameters in the same header field MUST have different names.
Parameter values are registered by reference rather than in their own sub-registries. For a parameter marked Yes in the predefined-values column, implementers must read the referenced RFCs to find all valid values. References to RFCs that define values appear in double brackets, as with [[RFC 3310]] for the algorithm parameter.
The initial contents cover many header fields, including Accept, Authorization, Contact, From, To, Via, Reason, Security-Client and the P-header families, mostly pointing at RFC 3261 and a handful of other RFCs.
Each entry is a card with four lines: where the setting lives, its name, whether it has a fixed menu of choices, and which RFC explains it.
| Header field | Parameter | Predefined values | Reference |
|---|---|---|---|
| Via | branch | No | RFC 3261 |
| Via | rport | No | RFC 3581 |
| Via | comp | Yes | RFC 3486 |
| Reason | cause | Yes | RFC 3326 |
| Authorization | algorithm | Yes | RFC 3261, [[RFC 3310]] |
§4.2Registration Policy
Using the terminology of RFC 2434, the policy for SIP header field parameters and parameter values is IETF Consensus. The parameter or value MUST be defined by an RFC, but that RFC does not have to be on the standards track.
To get into the book, the community has to agree and the idea has to be written up in an RFC. It does not have to be the most official kind.
§5Security Considerations
The registry itself has no security considerations. However, as RFC 3427 notes, an important reason for the IETF to manage SIP extensions is to ensure that all extensions and parameters can be used securely. The RFCs that support parameter registrations MUST give detailed security considerations for them.
The book is harmless, but anyone adding a new entry has to explain how to use it safely.
§6References
[1]RFC 2119Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.March 1997[2]RFC 2434Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.October 1998[3]RFC 3261Rosenberg, J., et al., "SIP: Session Initiation Protocol", RFC 3261, June 2002.July 2002[4]RFC 3427Mankin, A., et al., "Change Process for the Session Initiation Protocol (SIP)", BCP 67, RFC 3427, December 2002.December 2002