Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)
draft-hanes-dispatch-fax-capability-00

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Last updated 2012-08-14
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DISPATCH                                                        D. Hanes
Internet-Draft                                              G. Salgueiro
Intended status: Standards Track                           Cisco Systems
Expires: February 15, 2013                                    K. Fleming
                                                            Digium, Inc.
                                                         August 14, 2012

                   Indicating Fax over IP Capability
                in the Session Initiation Protocol (SIP)
                 draft-hanes-dispatch-fax-capability-00

Abstract

   This document defines and registers with IANA the new 'fax' media
   feature tag for use with the Session Initialization Protocol (SIP).
   Currently, fax calls are indistinguishable from voice at call setup.
   Consequently, fax calls can be routed to SIP user agents that are not
   fax capable.  A 'fax' media feature tag implemented in conjunction
   with RFC 3841 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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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on February 15, 2013.

Copyright Notice

   Copyright (c) 2012 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
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   (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.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7

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1.  Introduction

   Fax communications in the Session Initiation Protocol (SIP) are
   handled in a "voice first" manner.  Indications that a user desires
   to use a fax transport protocol, such as ITU-T T.38, to send a fax
   are not known during the call setup.  The call is set up as a voice
   call first and then only after it is connected, does a switchover to
   the T.38 protocol occur.  This is problematic in that fax calls can
   be routed inadvertently to SIP user agents 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 is
   necessary.  Feature preferences are a part of RFC 3841 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 land at 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 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 [RFC2119].

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