Media Gateway Control Protocol Fax Package
RFC 5347

Network Working Group                                       F. Andreasen
Request for Comments: 5347                                 Cisco Systems
Category: Informational                                       D. Hancock
                                                               CableLabs
                                                            October 2008

               Media Gateway Control Protocol Fax Package

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document defines a Media Gateway Control Protocol (MGCP) package
   to support fax calls.  The package allows for fax calls to be
   supported in two different ways.  The first one utilizes ITU-T
   Recommendation T.38 for fax relay under the control of the Call
   Agent.  The second one lets the gateway decide upon a method for fax
   transmission as well as handle the details of the fax call without
   Call Agent involvement.

Andreasen & Hancock          Informational                      [Page 1]
RFC 5347                    MGCP Fax Package                October 2008

Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................3
   2. Fax Package Definition ..........................................3
      2.1. LocalConnectionOptions .....................................3
           2.1.1. T.38 Procedure (Strict or Loose) ....................6
           2.1.2. Gateway Procedure ...................................8
           2.1.3. Off Procedure .......................................8
           2.1.4. Mode Operation ......................................8
           2.1.5. Detecting a Fax Call ...............................10
           2.1.6. Considerations for Determining Which
                  Procedures to Request ..............................11
      2.2. Events and Signals ........................................13
           2.2.1. Gateway Controlled Fax (gwfax) .....................13
           2.2.2. No Special Fax Handling (nopfax) ...................14
           2.2.3. T.38 Fax Relay (t38) ...............................14
      2.3. Connection Parameters .....................................15
      2.4. Negotiation of T.38 Parameters ............................16
      2.5. Implementation Considerations .............................18
           2.5.1. Media IP Address and Port for T.38 .................18
           2.5.2. Case Sensitivity ...................................18
           2.5.3. Boolean Indicator After T.38 Parameters ............19
   3. Call Flow Examples .............................................19
      3.1. Call Agent Controlled T.38 Strict .........................20
      3.2. Multiple and Different Options ............................29
      3.3. Interaction with SIP Endpoints ............................37
   4. Security Considerations ........................................44
   5. IANA Considerations ............................................44
   6. Normative References ...........................................44
   7. Informative References .........................................45

1.  Introduction

   This document defines a Media Gateway Control Protocol (MGCP)
   [RFC3435] package that enables MGCP controlled gateways to support
   fax calls.  The package enables fax calls to be supported in two
   different ways.  The first one utilizes ITU-T Recommendation T.38
   using either UDP Transport Layer (UDPTL) or TCP (see [T38]) for fax
   relay under the control of the Call Agent.  The second one lets the
   gateway decide upon a method for fax transmission as well as handle
   the details of the fax call without Call Agent involvement.

   The fax package definition is provided in Section 2, and in Section 3
   we provide three call flow examples showing how to use it.  Security
   considerations are found in Section 4, followed by the IANA
   considerations and references.

Andreasen & Hancock          Informational                      [Page 2]
RFC 5347                    MGCP Fax Package                October 2008

1.1.  Conventions Used in This Document

   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 BCP 14, RFC-2119
   [RFC2119].

2.  Fax Package Definition

   A package is defined for fax.  The package defines new