<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" 
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<section id="nathelper" xmlns:xi="http://www.w3.org/2001/XInclude">
    <sectioninfo>
	<authorgroup>
	    <author>
		<firstname>Maxim</firstname>
		<surname>Sobolev</surname>
		<affiliation><orgname>Sippy Software, Inc.</orgname></affiliation>
		<address>
		    <email>sobomax@sippysoft.com</email>
		</address>
	    </author>
	</authorgroup>
	<copyright>
	    <year>2003-2008</year>
	    <holder>Sippy Software, Inc.</holder>
	</copyright>

    </sectioninfo>

    <title>Nathelper Module</title>

    <section id="nathelper.overview">
	<title>Overview</title>
	<para>
	    This is a module to help with NAT traversal. In particular, it
	    helps symmetric UAs that don't advertise they are symmetric and are
	    not able to determine their public address. fix_nated_contact
	    rewrites Contact header field with request's source address:port
	    pair. fix_nated_sdp adds the active direction indication to SDP
	    (flag 0x01) and updates source IP address too (flag 0x02).
	</para>
	<para>
	    Known devices that get along over NATs with nathelper are ATAs (as clients) and Cisco
	    Gateways (since 12.2(T)) as servers.  See <ulink
		url="http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080110bf9.html">
		http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080110bf9.html"></ulink>
	</para>
    </section>

    <xi:include href="params.xml"/>
    <xi:include href="functions.xml"/>

</section>



