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<chapter>
  <header>
    <copyright>
      <year>2000</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.
    
    </legalnotice>

    <title>Introduction</title>
    <prepared>H&aring;kan Mattsson</prepared>
    <responsible>H&aring;kan Mattsson</responsible>
    <docno></docno>
    <approved>H&aring;kan Mattsson</approved>
    <checked></checked>
    <date>2007-06-15</date>
    <rev>%VSN%</rev>
    <file>megaco_intro.xml</file>
  </header>
  <p>Megaco/H.248 is a protocol for control of elements in a
    physically decomposed multimedia gateway, enabling separation of
    call control from media conversion. A Media Gateway Controller
    (MGC) controls one or more Media Gateways (MG).</p>
  <p>This version of the stack supports version 1, 2 and 3 as 
    defined by:</p>
  <list type="bulleted">
    <item>
      <p>version 1 - RFC 3525 and H.248-IG (v10-v13)</p>
    </item>
    <item>
      <p>version 2 - draft-ietf-megaco-h248v2-04 &amp; H.248.1 
        v2 Corrigendum 1 (03/2004)</p>
    </item>
    <item>
      <p>version 3: </p>
      <list type="bulleted">
        <item>
          <p>prev3a - as defined by TD-33 (except segments)</p>
        </item>
        <item>
          <p>prev3b - TD-33 updated to be backward compatible with v2 
            (except segments)</p>
        </item>
        <item>
          <p>prev3c - As defined by ITU H.248.1 (09/2005) 
            (except segments)</p>
        </item>
        <item>
          <p>v3 - Full version 3 as defined by ITU H.248.1 (09/2005) 
            (including segments)</p>
        </item>
      </list>
    </item>
  </list>
  <p>The semantics of the protocol has jointly been defined by two
    standardization bodies:</p>
  <list type="bulleted">
    <item>
      <p>IETF - which calls the protocol Megaco</p>
    </item>
    <item>
      <p>ITU  - which calls the protocol H.248</p>
    </item>
  </list>

  <section>
    <title>Scope and Purpose</title>
    <p>This manual describes the Megaco application, as a component
      of the Erlang/Open Telecom Platform development environment. It
      is assumed that the reader is familiar with the Erlang
      Development Environment, which is described in a separate User's
      Guide.</p>
  </section>

  <section>
    <title>Prerequisites</title>
    <p>The following prerequisites is required for understanding the
      material in the Megaco User's Guide:</p>
    <list type="bulleted">
      <item>
        <p>the basics of the Megaco/H.248 protocol</p>
      </item>
      <item>
        <p>the basics of the Abstract Syntax Notation One (ASN.1)</p>
      </item>
      <item>
        <p>familiarity with the Erlang system and Erlang programming</p>
      </item>
    </list>
    <p>The application requires Erlang/OTP release R10B or later.</p>
  </section>

  <section>
    <title>About This Manual</title>
    <p>In addition to this introductory chapter, the Megaco User's
      Guide contains the following chapters:</p>
    <list type="bulleted">
      <item>
        <p>Chapter 2: "Architecture" describes the architecture
          and typical usage of the application.</p>
      </item>
      <item>
        <p>Chapter 3: "Internal form and its encodings" describes
          the internal form of Megaco/H.248 messages and its various
          encodings.</p>
      </item>
      <item>
        <p>Chapter 4: "Transport mechanisms" describes how
          different mechanisms can be used to transport the
          Megaco/H.248 messages.</p>
      </item>
      <item>
        <p>Chapter 5: "Debugging" describes tracing and debugging.</p>
      </item>
    </list>
  </section>

  <section>
    <title>Where to Find More Information</title>
    <p>Refer to the following documentation for more information about
      Megaco/H.248 and about the Erlang/OTP development system:</p>
    <list type="bulleted">
      <item>
        <p><url href="http://www.erlang.org/project/megaco/standard/rfc3525.txt">version 1, RFC 3525</url></p>
      </item>
      <item>
        <p><url href="http://www.ietf.org/rfc/rfc3015.txt">old version 1, RFC 3015</url></p>
      </item>
      <item>
        <p><url href="http://www.erlang.org/project/megaco/standard/H.248.1-Corr1-200403.doc">Version 2 Corrigendum 1</url></p>
      </item>
      <item>
        <p><url href="http://www.erlang.org/project/megaco/standard/draft-ietf-megaco-h248v2-04.txt">version 2, draft-ietf-megaco-h248v2-04</url></p>
      </item>
      <item>
        <p><url href="http://www.itu.int/">TD-33 (Draft H.248.1 version 3)</url></p>
      </item>
      <item>
        <p><url href="http://www.itu.int/">H.248.1 version 3</url></p>
      </item>
      <item>
        <p>the ASN.1 application User's Guide</p>
      </item>
      <item>
        <p>the Megaco application Reference Manual</p>
      </item>
      <item>
        <p>Concurrent Programming in Erlang, 2nd Edition (1996),
          Prentice-Hall, ISBN 0-13-508301-X.</p>
      </item>
    </list>
  </section>
</chapter>

