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.
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.
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.
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.
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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.
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.
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.
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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]
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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]
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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.
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.
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.
[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
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