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+---
+Author: János Kövesdi
+Version: 1551-CNL 113 789, Rev. A
+Date: 2016-11-17
+
+---
+= The Generic Routing Encapsulation (GRE) Protocol Module for TTCN-3 Toolset with TITAN, Description
+:author: János Kövesdi
+:revnumber: 1551-CNL 113 789, Rev. A
+:revdate: 2016-11-17
+:toc:
+
+*Copyright*
+
+Copyright (c) 2000-2016 Ericsson Telecom AB. +
+All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License v1.0 that accompanies this distribution, and is available at +
+http://www.eclipse.org/legal/epl-v10.html.
+
+== How to Read This Document
+
+This is the Description for the The Generic Routing Encapsulation (GRE) protocol module. The GRE protocol module is developed for the TTCN-3 Toolset with TITAN.
+
+== Presumed Knowledge
+
+To use this protocol module the knowledge of the TTCN-3 language <<_3, [3]>> is essential.
+
+= Functionality
+
+The protocol module implements the message structure of the Generic Routing Encapsulation (GRE) using the standard specification language TTCNv3. This allows defining of test data in the TTCNv3 language <<_3, [3]>> and correctly encoding/decoding these messages when executing test suites using the TITAN TTCNv3 test environment.
+
+== Protocol Version Implemented
+
+This set of protocol modules implements protocol messages and constants of https://tools.ietf.org/html/rfc1701[RFC 1701].
+
+For example of GRE used over IPv4 networks, please read https://tools.ietf.org/html/rfc1701[RFC 1702].
+
+== Routing Functionality
+
+The payload (a packet that needs to be encapsulated and routed) is first encapsulated in a GRE packet and the GRE packet can be encapsulated in some other protocol and then forwarded.
+
+== Modified and Non-Implemented Protocol Elements
+
+=== Relaxed conditions
+
+There is no constraint between received and sent messages.
+
+== Ericsson-Specific Changes
+
+There is no Ericsson specific change in this product.
+
+== Backward Incompatibilities
+
+None.
+
+== System Requirements
+
+Protocol modules are a set of TTCN-3 source code files that can be used as part of TTCN-3 test suites only. Hence, protocol modules alone do not put specific requirements on the system used. However in order to compile and execute a TTCN-3 test suite using the set of protocol modules the following system requirements must be satisfied:
+
+* TITAN TTCN-3 Test Executor version R7A (1.7.pl0) or higher installed. For installation guide see <<_4, [4]>>.
+
+NOTE: This version of the protocol module is not compatible with TITAN releases earlier than R7A.
+
+= Feature List
+
+[[encoding-decoding-and-other-related-functions]]
+== Encoding/Decoding and Other Related Functions
+
+This product also contains encoding/decoding functions that assure correct encoding of messages when sent from TITAN and correct decoding of messages when received by TITAN. Implemented encoding/decoding functions:
+
+[cols=3*,options=header]
+|===
+
+|Name |Type of formal parameters |Type of return value
+|`enc_GRE_PDU` |(in PDU_GRE pdu) |octetstring
+|`dec_GRE_PDU` |(in octetstring stream) |PDU_GRE
+|===
+
+= Protocol Modules
+
+== Overview
+
+Protocol modules implement the message structure of the related protocol in a formalized way, using the standard specification language TTCN-3. This allows defining of test data (templates) in the TTCN-3 language <<_3, [3]>> and correctly encoding/decoding messages when executing test suites using the Titan TTCN-3 test environment.
+
+== Installation
+
+The set of protocol modules can be used for developing TTCN-3 test suites using any text editor. However to make the work more efficient a TTCN-3- enabled text editor is recommended (e.g. `nedit`, `xemacs`). Since the GRE protocol is used as a part of a TTCN-3 test suite, this requires Titan TTCN-3 Test Executor be installed before the module can be compiled and executed together with other parts of the test suite. For more details on the installation of TTCN-3 Test Executor see the relevant section of <<_4, [4]>>.
+
+== Configuration
+
+== Module parameters
+
+No module parameters are used in the ICAP protocol module.
+
+= Terminology
+
+No specific terminology used.
+
+= Abbreviations
+
+ETSI:: European Telecommunications Standards Institute
+
+IETF:: Internet Engineering Task Force
+
+GRE:: Generic Routing Encapsulation
+
+TTCNv3:: Testing and Test Control Notation version 3
+
+= References
+
+[[_1]]
+[1] https://tools.ietf.org/html/rfc1701[RFC 1701] +
+Generic Routing Encapsulation (GRE)
+
+[[_2]]
+[2] https://tools.ietf.org/html/rfc1702[RFC 1702] +
+Generic Routing Encapsulation over IPv4 networks
+
+[[_3]]
+[3] ETSI ES 201 873-1 v.3.2.1 (02/2007) +
+The Testing and Test Control Notation version 3. Part 1: Core Language
+
+[[_4]]
+[4] User Guide for the TITAN TTCN-3 Test Executor
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