Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)
draft-hanes-dispatch-fax-capability-07

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Document Type Active Internet-Draft (individual in rai area)
Last updated 2013-01-24 (latest revision 2013-01-15)
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Send notices to dhanes@cisco.com, gsalguei@cisco.com, kevin@kpfleming.us, draft-hanes-dispatch-fax-capability@tools.ietf.org, mary.ietf.barnes@gmail.com
DISPATCH                                                        D. Hanes
Internet-Draft                                              G. Salgueiro
Intended status: Standards Track                           Cisco Systems
Expires: July 19, 2013                                        K. Fleming
                                                            Digium, Inc.
                                                        January 15, 2013

                   Indicating Fax over IP Capability
                in the Session Initiation Protocol (SIP)
                 draft-hanes-dispatch-fax-capability-07

Abstract

   This document defines and registers with IANA the new 'fax' media
   feature tag for use with SIP.  Currently, fax calls are
   indistinguishable from voice 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 Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on July 19, 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

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   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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Usage of the sip.fax Parameter  . . . . . . . . . . . . . . . . 4
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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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 user agents,
   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 user agents.

   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
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