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Keywords: SIP, Call-Info, header field, Instant Messaging, Presence
Internet Engineering Task Force (IETF) P. Saint-Andre
Request for Comments: 6993 Cisco Systems, Inc.
Category: Informational July 2013
ISSN: 2070-1721
Instant Messaging and Presence Purpose for the
Call-Info Header Field in the Session Initiation Protocol (SIP)
Abstract
This document defines and registers a value of "impp" ("instant
messaging and presence protocol") for the "purpose" header field
parameter of the Call-Info header field in the Session Initiation
Protocol (SIP).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6993.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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RFC 6993 Call-Info Purpose: IMPP July 2013
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Security Considerations . . . . . . . . . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Normative References . . . . . . . . . . . . . . . . . . 3
4.2. Informative References . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Some real-time communication endpoints support the combined use of
the Session Initiation Protocol (SIP) [RFC3261] and the Extensible
Messaging and Presence Protocol (XMPP) [RFC6120]. To improve
interoperability among such "CUSAX" endpoints [CUSAX], it can be
helpful to advertise each endpoint's SIP address over XMPP and each
endpoint's XMPP address over SIP, thus providing hints about the
communication capabilities of the endpoints. The former feature is
enabled by an XMPP extension protocol called Reachability Addresses
[XEP-0152]. As to the latter feature, discussion in the SIP
community led to the conclusion that it would be best to use the
Call-Info header field [RFC3261] with a value of "impp" ("instant
messaging and presence protocol") for the "purpose" header field
parameter. An example follows.
Call-Info: <xmpp:juliet@example.com> ;purpose=impp
Although CUSAX endpoints constitute the primary use case for the
"impp" purpose, a Uniform Resource Identifier (URI) [RFC3986] for an
instant messaging and presence protocol other than XMPP could be
included in the Call-Info header field.
2. Security Considerations
Advertising an endpoint's XMPP address over SIP could inform
malicious entities about an alternative attack vector. Because the
"purpose" header field parameter could be spoofed, the receiving
endpoint ought to check the value against an authoritative source
such as a user directory. Clients can integrity protect and encrypt
this header field using end-to-end mechanisms such as S/MIME or hop-
by-hop mechanisms such as Transport Layer Security (TLS).
This specification provides a new way to correlate otherwise possibly
unconnected identifiers. Because such correlations can be privacy
sensitive, user agents ought to provide a means for users to control
whether or not these values are sent.
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RFC 6993 Call-Info Purpose: IMPP July 2013
3. IANA Considerations
This document defines and registers a new predefined value "impp" for
the "purpose" header field parameter of the Call-Info header field.
The IANA has completed this action by adding this RFC as a reference
to the line for the header field "Call-Info" and parameter name
"purpose" in the "Header Field Parameters and Parameter Values"
section of the "Session Initiation Protocol (SIP) Parameters"
registry as follows:
Header Field: Call-Info
Parameter Name: purpose
Predefined Values: Yes
Reference: [RFC3261][RFC5367][RFC6910][RFC6993]
4. References
4.1. Normative References
[RFC3261] 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.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
4.2. Informative References
[CUSAX] Ivov, E., Saint-Andre, P., and E. Marocco, "CUSAX:
Combined Use of the Session Initiation Protocol (SIP) and
the Extensible Messaging and Presence Protocol (XMPP)",
Work in Progress, June 2013.
[XEP-0152] Saint-Andre, P. and J. Hildebrand, "Reachability
Addresses", XSF XEP 0152, February 2013.
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RFC 6993 Call-Info Purpose: IMPP July 2013
5. Acknowledgements
Thanks to Gonzalo Camarillo, Keith Drage, Saul Ibarra, Emil Ivov,
Cullen Jennings, Olle Johanssen, Paul Kyzivat, Gonzalo Salgueiro,
Dean Willis, and Dale Worley for their input. Elwyn Davies,
Salvatore Loreto, Glen Zorn, and Mehmet Ersue completed reviews on
behalf of the General Area Review Team, Applications Area
Directorate, Security Directorate, and Operations and Management
Directorate, respectively. Stephen Farrell and Pete Resnick provided
substantive feedback during IESG review. Thanks to Yana Stamcheva
for her helpful comments and for shepherding the document.
Author's Address
Peter Saint-Andre
Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600
Denver, CO 80202
USA
Phone: +1-303-308-3282
EMail: psaintan@cisco.com
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