Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)
RFC 6913
Document | Type |
RFC - Proposed Standard
(March 2013; No errata)
Was draft-hanes-dispatch-fax-capability (individual in rai area)
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Authors | David Hanes , Gonzalo Salgueiro , Kevin Fleming | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6913 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Gonzalo Camarillo | ||
IESG note | Mary Barnes (mary.ietf.barnes@gmail.com) is the document shepherd. | ||
Send notices to | mary.ietf.barnes@gmail.com |
Internet Engineering Task Force (IETF) D. Hanes Request for Comments: 6913 G. Salgueiro Category: Standards Track Cisco Systems ISSN: 2070-1721 K. Fleming Digium, Inc. March 2013 Indicating Fax over IP Capability in the Session Initiation Protocol (SIP) Abstract This document defines and registers with IANA the new "fax" media feature tag for use with the Session Initiation Protocol (SIP). Currently, fax calls are indistinguishable from voice calls at call initiation. Consequently, fax calls can be routed to SIP user agents that are not fax capable. A "fax" media feature tag implemented in conjunction with caller preferences allows for more accurate fax call routing. Status of This Memo This is an Internet Standards Track document. 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). Further information on Internet Standards is available in 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/rfc6913. Hanes, et al. Standards Track [Page 1] RFC 6913 Fax Media Feature Tag March 2013 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Usage of the "sip.fax" Parameter . . . . . . . . . . . . . . . 4 5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 1. Introduction Fax communications in the Session Initiation Protocol (SIP) [RFC3261] are handled in a "voice first" manner. Indications that a user desires to use a fax transport protocol, such as ITU-T T.38 [T38], to send a fax are not known when the initial INVITE message is sent. The call is set up as a voice call first, and then, only after it is connected, does a switchover to the T.38 [T38] protocol occur. This is problematic in that fax calls can be routed inadvertently to SIP user agents (UAs) that are not fax capable. To ensure that fax calls are routed to fax-capable SIP UAs, an implementation of caller preferences defined in RFC 3841 [RFC3841] can be used. Feature preferences are a part of RFC 3841 [RFC3841] that would allow UAs to express their preference for receiving fax communications. Subsequently, SIP servers take these preferences into account to increase the likelihood that fax calls are routed to fax-capable SIP UAs. Hanes, et al. Standards Track [Page 2] RFC 6913 Fax Media Feature Tag March 2013 This document defines the "fax" media feature tag for use in the SIP tree, as per Section 12.1 of RFC 3840 [RFC3840]. This feature tag will be applied per RFC 3841 [RFC3841] as a feature preference for fax-capable UAs. 2. 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 RFC 2119 [RFC2119]. 3. Motivation In the majority of circumstances, it is preferred that capabilities be handled in the Session Description Protocol (SDP) portion of theShow full document text