serfaq.sgml

用来作为linux中SIP SERVER,完成VOIP网络电话中服务器的功能

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<book>
    <bookinfo>
	<title>&ser; Frequently Asked Questions</title>
	<authorgroup>
	    <editor>
		<firstname>Jan</firstname>
		<surname>Janak</surname>
		<email>[e-mail]</email>
	    </editor>
	</authorgroup>
	<copyright>
	    <year>2003</year>
	    <holder>&fhg;</holder>
	</copyright>
	<abstract>
	    <para>
		A compilation of questions and answers from <email>[e-mail]</email>,
		<email>[e-mail]</email>, and <email>[e-mail]</email> mailing
		lists.
	    </para>
	</abstract>
    </bookinfo>
    <toc></toc>
    
    <chapter>
	<title>General</title>
	<qandaset>
	    <qandaentry>
		<question>
		    <simpara>
			Is it possible to use &ser; as a &sip; user agent (both of User Agent Client
			(&uac;) and User Agent Server (&uas;)?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Not easily. &ser; has built-in some functions that allow to use it as user
			agent, but our primary goal is to develop a server so this is without
			guarantee and can even disappear in future versions.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Can &ser; work well together with some of the location server (e. g.LDAP or DNS) ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			&ser;'s built-in location server uses in-<acronym>RAM</acronym> database for
			high performance and optionally MySQL for persistence. More database
			protocols may be supplied on contractual basis. As far as I know,
			<acronym>DNS</acronym> is not used in the industry for user location.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			What is a proxy server ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			A proxy server is an entity that routes &sip; messages. See &sip
			introduction which is part of the distribution.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    What is the difference between proxy server and back to back user agent (B2BUA) ?
		</question>
		<answer>
		    <simpara>
			The main difference is that proxy servers are transaction-stateful, while
			B2BUAs are call stateful. That means proxy servers keep state only during
			&sip; transactions (that is at the beginning and and of a call) and do not
			keep any state during the whole call.
		    </simpara>
		    <simpara>
			A B2BUA acts merely as connection of two or more user agents which are
			connected through some means. B2BUAs keep some state (usually some structures
			in the memory) during the whole call.
		    </simpara>
		    <para>
			This property gives B2BUA some interesting features that proxies don't
			have. For example B2BUA can tear down and existing call--proxies can't do
			that. On the other hand B2BUAs can easily become a bottleneck in terms of
			scalability.
		    </para>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			So is &ser; proxy or B2BUA ? Can it terminate an existing call ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			&ser; is a proxy. I can't terminate existing call.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I'd like to know if &ser; supports <acronym>CPL</acronym> and
			servlets. Where can I find any documentation about this, or any link ?
		    </simpara>
		    </question>
		    <answer>
		    <simpara>
			Yes, <acronym>CPL</acronym> is supported through cpl module, the module
			needs an external <acronym>CPL</acronym> interpreter written in Java. A C
			version is under development. There is no support for Java servlets. The
			documentation can be found at <ulink
			url="http://iptel.org/ser/doc">http://iptel.org/ser/doc</ulink>.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I wanted to know whether &lt;PUT_YOUR_FAVOURITE_METHOD_HERE&gt; is supported
			by &ser;.
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Proxy server are indifferent of non-INVITEs methods. &lt;METHOD&gt; works as
			good as BYE, INFO, and FOOBAR.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I was wondering if &ser; has been tested and is supported on FreeBSD ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Yes.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Does &ser; support <acronym>TCP</acronym> ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Yes.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I think I found a bug that should be fixed, what information should I send
			and where should I send it?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Please send us as much info as possible. We would like see the following:
		    </simpara>
		    <itemizedlist>
			<listitem>
			    <simpara>&ser; version (ser -V).</simpara>
			</listitem>
		    </itemizedlist>
		    <itemizedlist>
			<listitem>
			    <simpara>Configuration file.</simpara>
			</listitem>
		    </itemizedlist>
		    <itemizedlist>
			<listitem>
			    <simpara>&sip; message dumps.</simpara>
			</listitem>
		    </itemizedlist>
		    <itemizedlist>
			<listitem>
			    <simpara>Coredump (if any, if not please generate it).</simpara>
			</listitem>
		    </itemizedlist>
		    <itemizedlist>
			<listitem>
			    <simpara>Anything else you think might help us.</simpara>
			</listitem>
		    </itemizedlist>
		    <itemizedlist>
			<listitem>
			    <simpara>The whole compiled source tree.</simpara>
			</listitem>
		    </itemizedlist>
		    <simpara>
			Please send it to <email>[e-mail]</email>.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			How does &ser; scale ?
		    </simpara>
		    <simpara>
			&ser; is able to handle thousands calls per second on a regular
			<acronym>PC</acronym>.
		    </simpara>
		</question>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I read <quote>Throughput thousands of calls per second
			    (<acronym>CPS</acronym>) on a dual-<acronym>CPU</acronym>
			    <acronym>PC</acronym></quote> on your webpage. How fast is it really ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Last time we have  checked ~4900cps on a dual Athlon MP2000.
		    </simpara>
		    <simpara>
			This was ser 0.8.9 running statefully (stateless is should be much faster),
			with 4 processes and 256 Mb shared mem.  It was compiled with: STATS:Off,
			USE_IPV6, NO_DEBUG, SHM_MEM, SHM_MMAP, PKG_MALLOC, F_MALLOC,
			FAST_LOCK-ADAPTIVE_WAIT ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE
			262144, MAX_LISTEN 16, MAX_URI_SIZE 1024, BUF_SIZE 3040
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Do you think that &ser; is suitable for a commercial environment in your opinion ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Sure.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Do you have any recommendations on additional open source or developer
			community resources to round out my platform?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			I'm a &ser; believer and think that other servers simply don't compare :) If
			you wish more detailed propaganda, check our website and if that is not
			enough I will send you some more.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Do you have any thoughts on how it compares in deployability and features to
			the Vovida stuff or other options ? Also, are there any issues I should be
			thinking of that would make a commercial venture with &ser; difficult
			(licensing, scaling, etc..)
		    </simpara>
		</question>
		<answer>
		    <simpara>
			&ser; is licensed under &gnu; &gpl;. I would be surprised if any &sip;
			server available today would scale a bit better--we spent lot of work on
			performance, achieved thousands of <acronym>CPS</acronym> on a
			<acronym>PC</acronym>--I guess it will take lot of time until your demand
			hits this capacity.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Does &ser; have the capability to automatically send an INVITE from one
			number to another?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Yes if the phones support REFER. There is an application called
			Click-To-Dial which can connect two phones.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Is it necessary to have a <acronym>DNS SVR</acronym> Resource Record, as
			mentioned in the ser-Howto guide for connecting to &ser; ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			No. It's nice to have it, but you can work around it setting a normal A
			record for your domain. The <acronym>SRV</acronym> lookup will fall back to
			normal A lookup.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			What would you charge to help get us started?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			See <ulink url="http://iptel.org/support">http://iptel.org/support</ulink>.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Are you going to provide integration support from &sip; to H.323 and vice
			versa ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			No, we are not going to provide the integration.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			I've gone thru the &ser; Admin's Guide and the module documentation
			(sip_router/modules/). Is there additional documentation on how to use the
			modules?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			Each module has a doc subdirectory which contains complete documentation of
			the module in docbook format. <acronym>PS</acronym>, <acronym>PDF</acronym>
			and <acronym>HTML</acronym> renderings can be obtained through our web page,
			see <ulink url="http://iptel.org/ser/doc">http://iptel.org/ser/doc</ulink>.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			What functions would I use in my ser.cfg to log <quote>missed calls</quote>?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			FIXME.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Are there some additional requirements for using the acc.so module?  Radius?
			I want to be able to view dialed calls from serweb.
		    </simpara>
		</question>
		<answer>
		    <simpara>
			FIXME.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Do you have any example configs that use nathelper?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			FIXME.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Who are the people behind &ser; ?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			FIXME.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			How successful has nathelper been with <acronym>NAT</acronym>/firewall transversal?
		    </simpara>
		</question>
		<answer>
		    <simpara>
			I only know that users reported success with nathelper and ATAs.
		    </simpara>
		</answer>
	    </qandaentry>
	    <qandaentry>
		<question>
		    <simpara>
			Does ser support <acronym>LDAP</acronym> ?
		    </simpara>