general.sgml

SIP Express Router, Linux下的SIP代理服务器,小巧实用,开发测试VoIP设备和应用的必备.

		</para>
		<para>
		    The SIP Express Router scales from SOHOs to large, international enterprises. 
		    Even a single installation on a common PC is able to serve VoIP signaling of any 
		    world's enterprise. Its policy-based routing language makes implementation of numbering 
		    plans of companies spread across the world very easy. ACL features allow for protection of 
		    PSTN gateway from unauthorized callers.
		</para>
		<para>
		    SIP Express Router's support for programmable routing and accounting efficiently allows for 
		    implementation of such a scenario.
		</para>
	    </section>
	</section> <!-- Use Cases -->
	<section id="aboutsip">
	    <title>About SIP Technology</title>
	    <para>
		The SIP protocol family is the technology which integrates services. 
		With SIP, Internet users can easily contact each other; figure out 
		willingness to have a conversation and couple different applications such as VoIP, video 
		and instant messaging. Integration with added-value services is seamless and easy. Examples 
		include integration with web (click-to-dial), E-mail (voice2email, UMS), and PSTN-like 
		services (conditional forwarding).
	    </para>
	    <para>
		The core piece of the technology is the Session Initiation Protocol (SIP, RFC3261) standardized by IETF. 
		Its main function is to establish communication sessions between users connected to the public 
		Internet and identified by e-mail-like addresses. One of SIP's greatest features is its transparent 
		support for multiple applications: the same infrastructure may be used for voice, video, gaming 
		or instant messaging as well as any other communication application.
	    </para>
	    <para>
		There are numerous scenarios in which SIP is already deployed: PBX replacement allows for 
		deployment of single inexpensive infrastructure in enterprises; PC-2-phone long-distance 
		services (e.g., Deltathree) cut callers long-distance expenses; instant messaging offered 
		by public severs (e.g., iptel.org) combines voice and text services with presence information. 
		New deployment scenarios are underway: SIP is a part of UMTS networks and research publications 
		suggest the use of SIP for virtual home environments or distributed network games.
	    </para>
	</section> <!-- about sip -->
	<section id="serlimitations">
	    <title>Known SER Limitations</title>
	    <para>
		The following items are not part of current distribution and are planned for next releases:
		<itemizedlist>
		    <listitem>
			<para>
			    Script processing of multiple branches on forking
			</para>

			<warning>
			    <para>
				<application>ser</application>'s request processing language allows 
				to make request decisions based on current URI. 
				When a request if forked to multiple destinations, only the first branch's URI is used as 
				input for script processing. This might lead to unexpected results. Whenever a URI resolves 
				to multiple different next-hop URIs, only the first is processed which may result in handling 
				not appropriate for the other branch. For example, a URI might resolve to an IP phone SIP 
				address and PSTN gateway SIP address. If the IP phone address is the first, then script 
				execution ignores the second branch. If a script includes checking gateway address in
				request URI, the checks never match. That might result in ignoring of 
				gateway admission control rules or applying them unnecessarily to non-gateway 
				destinations.
			    </para>
			</warning>
		    </listitem>
		</itemizedlist>
	    </para>
	    <para>
		List of known problems is publicly available at the 
		<application>ser</application> webpage at
		<ulink url="http://www.iptel.org/ser/">
		    http://www.iptel.org/ser/
		</ulink>. See the "ISSUES" link.
	    </para>
	</section> <!-- limitations -->
	<section id="licensing">
	    <title>Licensing</title>
	    <para>
		<application>ser</application> is freely available under terms and
		conditions of the GNU General Public License.
	    </para>	
	    <!-- COPYING -->
	    <screen>
	    	    &gpllicense;
	    </screen>
	    
	</section>
	<section id="support">
	    <title>Obtaining Technical Assistance</title>
		<para>
			iptel.org offers qualified professional services. We help you to 
			plan your network, configure your server, build applications, 
			integrate SIP components with each other, and set up advanced features
			such as redundancy, multidomain support, CLID interworking and others
			not described in this document. Our customer alert services
			notifies you on all new features and code fixes. We help you to
			solve operational troubles in short time and keep you updated on
			latest operational practices. Ask [e-mail] for
			information on enrollment in our support program.
		</para>

	    <para>
		Additionally, help may be obtained from our user forum. The community
		of <application>SER</application> users is subscribed to the
		[e-mail] mailing list and discusses issues related to
		<application>SER</application> operation.
	    </para>
	    <itemizedlist>
		<title>Mailing List Instructions</title>
		<listitem>
		    <para>
			Public archives and subscription form:
			<ulink url="http://mail.iptel.org/mailman/listinfo/serusers">
			    http://mail.iptel.org/mailman/listinfo/serusers
			</ulink>			
		    </para>
		</listitem>
		<listitem>
		    <para>
			To post, send an email to [e-mail]
		    </para>
		</listitem>
		<listitem>
		    <para>
			If you think you encountered an error, please submit the
			following information to avoid unnecessary round-trip times:			
			<itemizedlist>
			    <listitem>
				<para>
				    Name and version of your operating system --
				    you can obtain it by calling
				    <command>uname -a</command>
				</para>
			    </listitem>
			    <listitem>
				<para>
				    <application>ser</application> distribution: 
				    release number and package				    
				</para>
			    </listitem>
			    <listitem>
				<para>
				    <application>ser</application> build -- 
				    you can obtain it by calling 
				    <command moreinfo="none">ser -V</command>
				</para>
			    </listitem>
			    <listitem>
				<para>
				    Your <application>ser</application> configuration file
				</para>
			    </listitem>
			    <listitem>
				<para>
				    <application>ser</application> logs -- with default settings
				    few logs are printed to <command>syslog</command> facility which
				    typically dumps them to 
				    <filename moreinfo="none">/var/log/messages</filename>. To 
				    enable detailed logs dumped to <filename>stderr</filename>,
				    apply the following configuration options: <command moreinfo="none">
				    debug=8, log_stderror=yes, fork=no</command>.
				</para>
			    </listitem>
			    <listitem>
				<para>
				    Captured SIP messages -- you can obtain them 
				    using tools such as <application>ngrep</application>
				    or <application moreinfo="none">ethereal</application>.
				</para>
			    </listitem>
			</itemizedlist>
		    </para>
		    
		</listitem>
	    </itemizedlist>	    
	
	    <para>
		If you are concerned about your privacy and do not wish your
		queries to be posted and archived publicly, you may post to
		[e-mail]. E-mails to this address are only forwarded
		to iptel.org's <application>ser</application> development team.
		However, as the team is quite busy you should not be surprised
		to get replies with considerable delay.

	    </para>
	</section>
        
	<section id="moreinfo">
	    <title>More Information</title>
	    <para>
		Most up-to-date information including latest and most complete version
		of this documentation is always available at our website,
		<ulink url="http://www.iptel.org/ser/">http://www.iptel.org/ser/</ulink>.
		The site includes links to other important information about
		<application moreinfo="none">ser</application>, such
		as installation guidelines (INSTALL), download links,
		development pages, programmer's manual, etc.
	    </para>
	    <para>
		A SIP tutorial (slide set) is available at 
		<ulink url="http://www.iptel.org/sip/">http://www.iptel.org/sip/</ulink> .
	    </para>
	</section> <!-- info -->

	<section>
	    <title>Release Notes</title>
	    <literallayout format="linespecific" class="normal">
&releasenotes;
	    </literallayout>
	</section> <!-- release notes -->


    </chapter> <!-- general -->