1 Introduction
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).
This version of the stack supports version 1, 2 and 3 as defined by:
- 
      version 1 - RFC 3525 and H.248-IG (v10-v13) 
- 
      version 2 - draft-ietf-megaco-h248v2-04 & H.248.1 v2 Corrigendum 1 (03/2004) 
- 
      version 3: - 
          prev3a - as defined by TD-33 (except segments) 
- 
          prev3b - TD-33 updated to be backward compatible with v2 (except segments) 
- 
          prev3c - As defined by ITU H.248.1 (09/2005) (except segments) 
- 
          v3 - Full version 3 as defined by ITU H.248.1 (09/2005) (including segments) 
 
- 
          
The semantics of the protocol has jointly been defined by two standardization bodies:
- 
      IETF - which calls the protocol Megaco 
- 
      ITU - which calls the protocol H.248 
1.1 Scope and Purpose
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.
1.2 Prerequisites
The following prerequisites is required for understanding the material in the Megaco User's Guide:
- 
        the basics of the Megaco/H.248 protocol 
- 
        the basics of the Abstract Syntax Notation One (ASN.1) 
- 
        familiarity with the Erlang system and Erlang programming 
The application requires Erlang/OTP release R10B or later.
1.3 About This Manual
In addition to this introductory chapter, the Megaco User's Guide contains the following chapters:
- 
        Chapter 2: "Architecture" describes the architecture and typical usage of the application. 
- 
        Chapter 3: "Internal form and its encodings" describes the internal form of Megaco/H.248 messages and its various encodings. 
- 
        Chapter 4: "Transport mechanisms" describes how different mechanisms can be used to transport the Megaco/H.248 messages. 
- 
        Chapter 5: "Debugging" describes tracing and debugging. 
1.4 Where to Find More Information
Refer to the following documentation for more information about Megaco/H.248 and about the Erlang/OTP development system:
- 
        the ASN.1 application User's Guide 
- 
        the Megaco application Reference Manual 
- 
        Concurrent Programming in Erlang, 2nd Edition (1996), Prentice-Hall, ISBN 0-13-508301-X. 
