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<!-- Module User's Guide -->

<chapter>

	<title>&adminguide;</title>

	<section>
	<title>Overview</title>
	<para>
		This is a module that enables media streams to be proxied
		via an &rtp; proxy. The only &rtp; proxy currently known to work
		with this module is the Sipwise rtpengine
		<ulink url="https://github.com/sipwise/rtpengine"></ulink>.
		The rtpengine module is a modified version of the original
		rtpproxy module using a new control protocol. The module is
		designed to be a drop-in replacement for the old module from
		a configuration file point of view, however due to the
		incompatible control protocol, it only works with &rtp; proxies
		which specifically support it.
	</para>
	</section>

	<section>
	<title>Multiple &rtp; proxy usage</title>
	<para>
		The rtpengine module can support multiple &rtp; proxies for
		balancing/distribution and control/selection purposes.
	</para>
	<para>
		The module allows definition of several sets of rtpproxies.
		Load-balancing will be performed over a set and the admin has the
		ability to choose what set should be used. The set is selected via
		its id - the id being defined with the set. Refer to the
		<quote>rtpengine_sock</quote> module parameter definition for syntax
		description.
	</para>
	<para>
		The balancing inside a set is done automatically by the module based on
		the weight of each &rtp; proxy from the set.
	</para>
	<para>
		The selection of the set is done from script prior using
		rtpengine_delete(), rtpengine_offer() or rtpengine_answer()
		functions - see the set_rtpengine_set() function.
	</para>
	<para>
	        Another way to select the set is to define setid_avp
	        module parameter and assign setid to the defined avp
	        before calling rtpengine_offer() or rtpengine_manage()
	        function.  If forwarding of the requests fails and
	        there is another branch to try, remember to unset the
	        avp after calling rtpengine_delete() function.
	</para>
	<para>
		For backward compatibility reasons, a set with no id take by default
		the id 0. Also if no set is explicitly set before
		rtpengine_delete(), rtpengine_offer() or rtpengine_answer()
		the 0 id set will be used.
	</para>
	<para>
		IMPORTANT: if you use multiple sets, take care and use the same set for
		both rtpengine_offer()/rtpengine_answer() and rtpengine_delete()!!
		If the set was selected using setid_avp, the avp needs to be
		set only once before rtpengine_offer() or rtpengine_manage() call.
	</para>
	</section>

	<section>
	<title>Dependencies</title>
	<section>
		<title>&kamailio; Modules</title>
		<para>
		The following modules must be loaded before this module:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>tm module</emphasis> - (optional) if you want to
				have rtpengine_manage() fully functional
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries or applications must be installed before
		running &kamailio; with this module loaded:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>None</emphasis>.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	</section>

	<section>
	<title>Parameters</title>
	<section id="rtpengine.p.rtpengine_sock">
		<title><varname>rtpengine_sock</varname> (string)</title>
		<para>
		Definition of socket(s) used to connect to (a set) &rtp; proxy. It may
		specify a UNIX socket or an IPv4/IPv6 UDP socket.
		</para>
		<para>
		<emphasis>
			Default value is <quote>NONE</quote> (disabled).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_sock</varname> parameter</title>
		<programlisting format="linespecific">
...
# single rtproxy
modparam("rtpengine", "rtpengine_sock", "udp:localhost:12221")
# multiple rtproxies for LB
modparam("rtpengine", "rtpengine_sock",
	"udp:localhost:12221 udp:localhost:12222")
# multiple sets of multiple rtproxies
modparam("rtpengine", "rtpengine_sock",
	"1 == udp:localhost:12221 udp:localhost:12222")
modparam("rtpengine", "rtpengine_sock",
	"2 == udp:localhost:12225")
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.rtpengine_disable_tout">
		<title><varname>rtpengine_disable_tout</varname> (integer)</title>
		<para>
		Once an &rtp; proxy was found unreachable and marked as disabled, the rtpengine
		module will not attempt to establish communication to that &rtp; proxy for
		rtpengine_disable_tout seconds.
		</para>
		<para>
		<emphasis>
			Default value is <quote>60</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_disable_tout</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "rtpengine_disable_tout", 20)
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.rtpengine_tout">
		<title><varname>rtpengine_tout</varname> (integer)</title>
		<para>
		Timeout value in waiting for reply from &rtp; proxy.
		</para>
		<para>
		<emphasis>
			Default value is <quote>1</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_tout</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "rtpengine_tout", 2)
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.rtpengine_retr">
		<title><varname>rtpengine_retr</varname> (integer)</title>
		<para>
		How many times the module should retry to send and receive after
		timeout was generated.
		</para>
		<para>
		<emphasis>
			Default value is <quote>5</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_retr</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "rtpengine_retr", 2)
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.extra_id_pv">
		<title><varname>extra_id_pv</varname> (string)</title>
		<para>
			The parameter sets the PV defination to use when the <quote>b</quote>
			parameter is used on rtpengine_delete(), rtpengine_offer(),
			rtpengine_answer() or rtpengine_manage() command.
		</para><para>
			Default is empty, the <quote>b</quote> parameter may not be used then.
		</para>
		<example>
		<title>Set <varname>extra_id_pv</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "extra_id_pv", "$avp(extra_id)")
...
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.setid_pv">
		<title><varname>setid_avp</varname> (string)</title>
		<para>
			The parameter defines an AVP that, if set,
			determines which &rtp; proxy set
			rtpengine_offer(), rtpengine_answer(),
			rtpengine_delete(), and rtpengine_manage()
			functions use.
		</para>
		<para>
			There is no default value.
		</para>
		<example>
		<title>Set <varname>setid_avp</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "setid_avp", "$avp(setid)")
...
</programlisting>
		</example>
	</section>

	</section>

	<section>
	<title>Functions</title>
	<section id="rtpengine.f.set_rtpengine_set">
		<title>
		<function moreinfo="none">set_rtpengine_set(setid[, setid])</function>
		</title>
		<para>
		Sets the ID of the &rtp; proxy set to be used for the next
		rtpengine_delete(), rtpengine_offer(), rtpengine_answer()
		or rtpengine_manage() command. The parameter can be an integer or
		a config variable holding an integer.
		</para>
		<para>
		A second set ID can be specified to daisy-chain two &rtp; proxies.
		The two set IDs must be distinct from each other and there must not
		be any overlap in the proxies present in both sets. In this use case,
		the request (offer, answer, etc) is first sent to an &rtp; proxy from
		the first set, which rewrites the &sdp; body and sends it back to the
		module. The rewritten &sdp; body is then used to make another request
		to an &rtp; proxy from the second set, which rewrites the &sdp; body
		another time and sends it back to the module to be placed back into the
		&sip; message. This is useful if you have a set of &rtp; proxies that
		the caller must use, and another distinct set of &rtp; proxies that the
		callee must use. This is supported by all rtpengine commands except
		rtpengine_manage().
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
		BRANCH_ROUTE.
		</para>
		<example>
		<title><function>set_rtpengine_set</function> usage</title>
		<programlisting format="linespecific">
...
set_rtpengine_set("2");
rtpengine_offer();
...
</programlisting>
		</example>
	</section>
        <section id="rtpengine.f.rtpengine_offer">
                <title>
                <function moreinfo="none">rtpengine_offer([flags])</function>
                </title>
                <para>
                Rewrites &sdp; body to ensure that media is passed through
                an &rtp; proxy. To be invoked
		on INVITE for the cases the &sdp; bodies are in INVITE and 200 OK and on 200 OK
		when &sdp; bodies are in 200 OK and ACK.
                </para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>flags</emphasis> - flags to turn on some features.
			</para>
			<para>The <quote>flags</quote> string is a list of space-separated items. Each item
			is either an individual token, or a token in <quote>key=value</quote> format. The
			possible tokens are described below.</para>
			<itemizedlist>
				<listitem><para>
				<emphasis>via-branch=...</emphasis> - Include the <quote>branch</quote>
				value of one of the <quote>Via</quote> headers in the request to the
				&rtp; proxy. Possible values are:
				<quote>1</quote> - use the first <quote>Via</quote> header;
				<quote>2</quote> - use the second <quote>Via</quote> header;
				<quote>auto</quote> - use the first <quote>Via</quote> header if this is
				a request, or the second one if this is a reply;
				<quote>extra</quote> - don't take the value from a header, but instead use
				the value of the <quote>extra_id_pv</quote> variable.
				This can be used to create one media session per branch
				on the &rtp; proxy. When sending a subsequent <quote>delete</quote> command to
				the &rtp; proxy, you can then stop just the session for a specific branch when
				passing the flag '1' or '2' in the <quote>rtpengine_delete</quote>, or stop
				all sessions for a call when not passing one of those two flags there. This is
				especially useful if you have serially forked call scenarios where the &rtp; proxy
				gets an <quote>offer</quote> command for a new branch, and then a
				<quote>delete</quote> command for the previous branch, which would otherwise
				delete the full call, breaking the subsequent <quote>answer</quote> for the
				new branch. <emphasis>This flag is only supported by the Sipwise rtpengine
				&rtp; proxy at the moment!</emphasis>
				</para></listitem>
				<listitem><para>
				<emphasis>asymmetric</emphasis> - flags that UA from which message is
				received doesn't support symmetric &rtp;. Disables learning of endpoint addresses
				in the Sipwise rtpengine proxy.
				</para></listitem>
				<listitem><para>
				<emphasis>force-answer</emphasis> - force <quote>answer</quote>, that is,
				only rewrite &sdp; when corresponding session already exists
				in the &rtp; proxy. By default is on when the session is to be
				completed.
				</para></listitem>
				<listitem><para>
				<emphasis>direction=...</emphasis> - this option specifies a logical network
				interface and should be given exactly twice. It enables &rtp; bridging between
				different addresses or networks of the same family (e.g. IPv4 to IPv4). The
				first instance of the option
				specifies the interface that the originator of this message should be using,
				while the second instance specifies the interface that the target should be
				using. For example, if the &sip; message was sent by an endpoint on a private
				network and will be sent to an endpoint on the public internet, you would use
				<quote>direction=priv direction=pub</quote> if those two logical network
				interfaces were called <quote>priv</quote> and <quote>pub</quote> in your
				&rtp; proxy's configuration respectively. The direction must only be specified
				in for initial &sdp; offer; answers or subsequent offers can omit this option.
				</para></listitem>
				<listitem><para>
				<emphasis>internal, external</emphasis> - shorthand for
				<quote>direction=internal</quote> and <quote>direction=external</quote>
				respectively. Useful for brevity or as legacy option if the &rtp; proxy only
				supports two network interfaces instead of multiple, arbitrarily named ones.
				</para></listitem>
				<listitem><para>
				<emphasis>auto-bridge</emphasis> - this flag an alternative to the
				<quote>internal</quote> and <quote>external</quote> flags
				in order to do automatic bridging between IPv4 on the
				"internal network" and IPv6 on the "external network". Instead of
				explicitly instructing the &rtp; proxy to select a particular address
				family, the distinction is done by the given IP in the &sdp; body by
				the &rtp; proxy itself. Not supported by Sipwise rtpengine.
				</para></listitem>
				<listitem><para>
				<emphasis>address-family=...</emphasis> - instructs the &rtp; proxy that the
				recipient of this &sdp; body expects to see addresses of a particular family.
				Possible values are <quote>IP4</quote> and <quote>IP6</quote>. For example,
				if the &sdp; body contains IPv4 addresses but the recipient only speaks IPv6,
				you would use <quote>address-family=IP6</quote> to bridge between the two
				address families.
				</para><para>
				Sipwise rtpengine remembers the address family preference of each party after
				it has seen an &sdp; body from them. This means that normally it is only
				necessary to explicitly specify the address family in the <quote>offer</quote>,
				but not in the <quote>answer</quote>.
				</para><para>
				Note: Please note, that this will only work properly with non-dual-stack user-agents or with
				dual-stack clients according to RFC6157 (which suggest ICE for Dual-Stack implementations).
				This short-cut will not work properly with RFC4091 (ANAT) compatible clients, which suggests
				having different m-lines with different IP-protocols grouped together.
				</para></listitem>
				<listitem><para>
				<emphasis>force</emphasis> - instructs the &rtp; proxy to ignore marks
				inserted by another &rtp; proxy in transit to indicate that the
				session is already goes through another proxy. Allows creating
				a chain of proxies. Not supported and ignored by Sipwise rtpengine.
				</para></listitem>
				<listitem><para>
				<emphasis>trust-address</emphasis> - flags that IP address in &sdp; should
				be trusted. Without this flag, the &rtp; proxy ignores address in
				the &sdp; and uses source address of the &sip; message as media
				address which is passed to the &rtp; proxy.
				</para></listitem>
				<listitem><para>
				<emphasis>replace-origin</emphasis> - flags that IP from the origin
				description (o=) should be also changed.
				</para></listitem>
				<listitem><para>
				<emphasis>replace-session-connection</emphasis> - flags to change the session-level
				&sdp; connection (c=) IP if media description also includes
				connection information.
				</para></listitem>
				<listitem><para>
				<emphasis>symmetric</emphasis> - flags that for the UA from which
				message is received, support symmetric &rtp; must be forced. Does nothing with
				the Sipwise rtpengine proxy as it is the default.
				</para></listitem>
				<listitem><para>
				<emphasis>repacketize=NN</emphasis> - requests the &rtp; proxy to perform
				re-packetization of &rtp; traffic coming from the UA which
				has sent the current message to increase or decrease payload
				size per each &rtp; packet forwarded if possible.  The NN is the
				target payload size in ms, for the most codecs its value should
				be in 10ms increments, however for some codecs the increment
				could differ (e.g. 30ms for GSM or 20ms for G.723).  The
				&rtp; proxy would select the closest value supported by the codec.
				This feature could be used for significantly reducing bandwith
				overhead for low bitrate codecs, for example with G.729 going
				from 10ms to 100ms saves two thirds of the network bandwith.
				Not supported by Sipwise rtpengine.
				</para></listitem>
				<listitem><para>
				<emphasis>ICE=...</emphasis> - controls the &rtp; proxy's behaviour
				regarding ICE attributes within the &sdp; body. Possible values
				are: <quote>force</quote> -
				discard any ICE attributes already present in the &sdp; body
				and then generate and insert new ICE data, leaving itself
				as the <emphasis>only</emphasis> ICE candidates;
				<quote>force-relay</quote> -
				discard any <quote>relay</quote> type ICE attributes already present
				in the &sdp; body and then generate and insert itself
				as the <emphasis>only</emphasis> ICE <quote>relay</quote> candidates;
				<quote>remove</quote> instructs the &rtp; proxy to discard
				any ICE attributes and not insert any new ones into the &sdp;.
				The default (if no <quote>ICE=...</quote> is given at all),
				new ICE data will only be generated
				if no ICE was present in the &sdp; originally; otherwise
				the &rtp; proxy will only insert itself as
				<emphasis>additional</emphasis> ICE candidate. Other
				&sdp; substitutions (c=, m=, etc) are unaffected by this flag.
				</para></listitem>
				<listitem><para>
				<emphasis>RTP, SRTP, AVP, AVPF</emphasis> - These flags control the &rtp;
				transport protocol that should be used towards the recipient of
				the &sdp;. If none of them are specified, the protocol given in
				the &sdp; is left untouched. Otherwise, the <quote>SRTP</quote> flag indicates that
				SRTP should be used, while <quote>RTP</quote> indicates that SRTP should not be used.
				<quote>AVPF</quote> indicates that the advanced RTCP profile with feedback messages
				should be used, and <quote>AVP</quote> indicates that the regular RTCP profile
				should be used. See also the next set of flags below.
				</para></listitem>
				<listitem><para>
				<emphasis>RTP/AVP, RTP/SAVP, RTP/AVPF, RTP/SAVPF</emphasis> - these serve as
				an alternative, more explicit way to select between the different &rtp; protocols
				and profiles supported by the &rtp; proxy. For example, giving the flag
				<quote>RTP/SAVPF</quote> has the same effect as giving the two flags
				<quote>SRTP AVPF</quote>.
				</para></listitem>
				<listitem><para>
				<emphasis>to-tag</emphasis> - force inclusion of the <quote>To</quote> tag.
				Normally, the <quote>To</quote> tag is always included when present, except
				for <quote>delete</quote> messages. Including the <quote>To</quote> tag in
				a <quote>delete</quote> messages allows you to be more selective about which
				dialogues within a call are being torn down.
				</para></listitem>
				<listitem><para>
				<emphasis>rtcp-mux-demux</emphasis> - if rtcp-mux (RFC 5761) was
				offered, make the &rtp; proxy accept the offer, but not offer it to the
				recipient of this message.
				</para></listitem>
				<listitem><para>
				<emphasis>rtcp-mux-reject</emphasis> - if rtcp-mux was offered, make the
				&rtp; proxy reject the offer, but still offer it to the recipient. Can be
				combined with <quote>rtcp-mux-offer</quote> to always offer it.
				</para></listitem>
				<listitem><para>
				<emphasis>rtcp-mux-offer</emphasis> - make the &rtp; proxy offer rtcp-mux
				to the recipient of this message, regardless of whether it was offered
				originally or not.
				</para></listitem>
				<listitem><para>
				<emphasis>rtcp-mux-accept</emphasis> - if rtcp-mux was offered, make the
				&rtp; proxy accept the offer and also offer it to the recipient of this
				message. Can be combined with <quote>rtcp-mux-offer</quote> to always offer it.
				</para></listitem>
				<listitem><para>
				<emphasis>media-address=...</emphasis> - force a particular media address to
				be used in the &sdp; body. Address family is detected automatically.
				</para></listitem>
				<listitem><para>
				<emphasis>TOS=...</emphasis> - change the IP TOS value for all outgoing &rtp;
				packets within the entire call in both directions. Only honoured in an
				<quote>offer</quote>, ignored for an <quote>answer</quote>. Valid values are
				0 through 255, given in decimal. If this option is not specified, the TOS
				value will revert to the default TOS (normally 184). A value of -1 may be used
				to leave the currently used TOS unchanged.
				</para></listitem>
			</itemizedlist>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from ANY_ROUTE.
                </para>
		<example>
		<title><function>rtpengine_offer</function> usage</title>
		<programlisting format="linespecific">
route {
...
    if (is_method("INVITE")) {
        if (has_body("application/sdp")) {
            if (rtpengine_offer())
                t_on_reply("1");
        } else {
            t_on_reply("2");
        }
    }
    if (is_method("ACK") &amp;&amp; has_body("application/sdp"))
        rtpengine_answer();
...
}

onreply_route[1]
{
...
    if (has_body("application/sdp"))
        rtpengine_answer();
...
}

onreply_route[2]
{
...
    if (has_body("application/sdp"))
        rtpengine_offer();
...
}
</programlisting>
                </example>
	</section>
        <section id="rtpengine.f.rtpengine_answer">
                <title>
                <function moreinfo="none">rtpengine_answer([flags])</function>
                </title>
		<para>
		Rewrites &sdp; body to ensure that media is passed through
		an &rtp; proxy. To be invoked
		on 200 OK for the cases the &sdp; bodies are in INVITE and 200 OK and on ACK
		when &sdp; bodies are in 200 OK and ACK.
		</para>
		<para>
		See rtpengine_offer() function description above for the meaning of the
		parameters.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
		FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		 <title><function>rtpengine_answer</function> usage</title>
		<para>
		See rtpengine_offer() function example above for example.
		</para>
		</example>
        </section>
	<section id="rtpengine.f.rtpengine_delete">
		<title>
		<function moreinfo="none">rtpengine_delete([flags])</function>
		</title>
		<para>
		Tears down the RTPProxy session for the current call.
		</para>
		<para>
		See rtpengine_offer() function description above for the meaning of the
		parameters. Note that not all flags make sense for a <quote>delete</quote>.
		</para>
		<para>
		This function can be used from ANY_ROUTE.
		</para>
		<example>
		<title><function>rtpengine_delete</function> usage</title>
		<programlisting format="linespecific">
...
rtpengine_delete();
...
</programlisting>
		</example>
	</section>

    <section id="rtpengine.f.rtpengine_manage">
        <title>
        <function moreinfo="none">rtpengine_manage([flags])</function>
        </title>
		<para>
		Manage the RTPProxy session - it combines the functionality of
		rtpengine_offer(), rtpengine_answer() and rtpengine_delete(), detecting
		internally based on message type and method which one to execute.
		</para>
		<para>
		It can take the same parameters as <function>rtpengine_offer().</function>
		The flags parameter to rtpengine_manage() can be a configuration variable
		containing the flags as a string.
		</para>
		<para>
		Functionality:
		</para>
		<itemizedlist>
		<listitem>
			<para>
			If INVITE with &sdp;, then do <function>rtpengine_offer()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If INVITE with &sdp;, when the tm module is loaded, mark transaction with
			internal flag FL_SDP_BODY to know that the 1xx and 2xx are for
			<function>rtpengine_answer()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If ACK with &sdp;, then do <function>rtpengine_answer()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If BYE or CANCEL, or called within a FAILURE_ROUTE[], then do <function>rtpengine_delete()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If reply to INVITE with code >= 300 do <function>rtpengine_delete()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If reply with &sdp; to INVITE having code 1xx and 2xx, then
			do <function>rtpengine_answer()</function> if the request had &sdp; or tm is not loaded,
			otherwise do <function>rtpengine_offer()</function>
			</para>
		</listitem>
	</itemizedlist>

		<para>
		This function can be used from ANY_ROUTE.
		</para>
		<example>
		 <title><function>rtpengine_manage</function> usage</title>
		<programlisting format="linespecific">
...
rtpengine_manage();
...
</programlisting>
		</example>
        </section>

	<section id="rtpengine.f.start_recording">
		<title>
		<function moreinfo="none">start_recording()</function>
		</title>
		<para>
		This function will send a signal to the &rtp; proxy to record
		the &rtp; stream on the &rtp; proxy.
		<emphasis>This function is not supported by Sipwise rtpengine at the moment!</emphasis>
		</para>
		<para>
		This function can be used from REQUEST_ROUTE and ONREPLY_ROUTE.
		</para>
		<example>
		<title><function>start_recording</function> usage</title>
		<programlisting format="linespecific">
...
start_recording();
...
		</programlisting>
		</example>
	</section>


	</section>

	<section>
		<title>Exported Pseudo Variables</title>
		<section>
			<title><function moreinfo="none">$rtpstat</function></title>
			<para>
			Returns the &rtp; statistics from the &rtp; proxy. The &rtp; statistics from the &rtp; proxy
			are provided as a string and it does contain several packet counters. The statistics
			must be retrieved before the session is deleted	(before <function>rtpengine_delete()</function>).
			</para>

		<example>
		<title>$rtpstat Usage</title>
		<programlisting format="linespecific">
...
    append_hf("X-RTP-Statistics: $rtpstat\r\n");
...
		</programlisting>
		</example>
	        </section>

	</section>

	<section>
		<title><acronym>MI</acronym> Commands</title>
		<section id="rtpengine.m.nh_enable_rtpp">
			<title><function moreinfo="none">nh_enable_rtpp</function></title>
			<para>
			Enables a &rtp; proxy if parameter value is greater than 0.
			Disables it if a zero value is given.
			</para>
			<para>
			The first parameter is the &rtp; proxy url (exactly as defined in
			the config file).
			</para>
			<para>
			The second parameter value must be a number in decimal.
			</para>
			<para>
			NOTE: if a &rtp; proxy is defined multiple times (in the same or
			diferente sete), all of its instances will be enables/disabled.
			</para>
			<example>
			<title>
			<function moreinfo="none">nh_enable_rtpp</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_enable_rtpp udp:192.168.2.133:8081 0
...
			</programlisting>
			</example>
		</section>

			<section id="rtpengine.m.nh_show_rtpp">
			<title><function moreinfo="none">nh_show_rtpp</function></title>
			<para>
			Displays all the &rtp; proxies and their information: set and
			status (disabled or not, weight and recheck_ticks).
			</para>
			<para>
			No parameter.
			</para>
			<example>
			<title>
				<function moreinfo="none">nh_show_rtpp</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_show_rtpp
...
			</programlisting>
			</example>
		</section>
	</section>

</chapter>