<?xml version="1.0" encoding='ISO-8859-1'?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [

<!-- Include general documentation entities -->
<!ENTITY % docentities SYSTEM "../../../docbook/entities.xml">
%docentities;

]>

<!-- 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 rtpproxy.  Rtpproxies know to work with this module
		are Sippy RTPproxy <ulink url="http://www.rtpproxy.org"></ulink>
		and ngcp-rtpproxy-ng
		<ulink url="http://deb.sipwise.com/spce/2.6/pool/main/n/ngcp-mediaproxy-ng"></ulink>.
		Some features of the rtpproxy module apply only to one of the two rtpproxies.
	</para>
	</section>

	<section>
	<title>Multiple RTPProxy usage</title>
	<para>
		The rtpproxy module can support multiple rtpproxies 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>rtpproxy_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 rtpproxy from the set.
	</para>
	<para>
		The selection of the set is done from script prior using
		unforce_rtp_proxy(), rtpproxy_offer() or rtpproxy_answer()
		functions - see the set_rtp_proxy_set() 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
		unforce_rtp_proxy(), rtpproxy_offer() or rtpproxy_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 rtpproxy_offer()/rtpproxy_answer() and unforce_rtpproxy()!!
	</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 rtpproxy_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="rtpproxy.p.rtpproxy_sock">
		<title><varname>rtpproxy_sock</varname> (string)</title>
		<para>
		Used to define the list of RTPPRoxy instances to connect to.
		These can be UNIX sockets or IPv4/IPv6 UDP sockets.

		Each modparam entry will insert sockets into a single set. If no set ID is given, the default set ID '0' will be used. To define multiple sets add the set number at the beginning of each parameter followed by '=='.
		Sockets can be weighted by adding '=#' to a socket where # is an integer. A socket with a weight of 2 will be chosen twice as often as one with a weight of 1.
		</para>
		<para>
		<emphasis>
			Default value is <quote>NONE</quote> (disabled).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpproxy_sock</varname> parameter</title>
		<programlisting format="linespecific">
...
# single rtproxy
modparam("rtpproxy", "rtpproxy_sock", "udp:localhost:12221")

# multiple rtproxies for LB
modparam("rtpproxy", "rtpproxy_sock",
	"udp:localhost:12221 udp:localhost:12222")

# multiple sets of multiple rtproxies
modparam("rtpproxy", "rtpproxy_sock",
	"1 == udp:localhost:12221 udp:localhost:12222")
modparam("rtpproxy", "rtpproxy_sock",
	"2 == udp:localhost:12225")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.rtpproxy_disable_tout">
		<title><varname>rtpproxy_disable_tout</varname> (integer)</title>
		<para>
		Once RTPProxy was found unreachable and marked as disabled, the rtpproxy
		module will not attempt to establish communication to RTPProxy for
		rtpproxy_disable_tout seconds.
		</para>
		<para>
		<emphasis>
			Default value is <quote>60</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpproxy_disable_tout</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "rtpproxy_disable_tout", 20)
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.rtpproxy_tout">
		<title><varname>rtpproxy_tout</varname> (integer)</title>
		<para>
		Timeout value in waiting for reply from RTPProxy.
		</para>
		<para>
		<emphasis>
			Default value is <quote>1</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpproxy_tout</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "rtpproxy_tout", 2)
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.rtpproxy_retr">
		<title><varname>rtpproxy_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>rtpproxy_retr</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "rtpproxy_retr", 2)
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.nortpproxy_str">
		<title><varname>nortpproxy_str</varname> (string)</title>
		<para>
		This parameter sets the SDP attribute used by rtpproxy to mark
		the message's SDP attachemnt with information that it have
		already been changed.
		</para>
		<para>
		If empty string, no marker will be added or checked.
		</para>
		<note><para>
		The string must be a complete SDP line, including the EOH (\r\n).
		</para></note>
		<para>
		<emphasis>
			Default value is <quote>a=nortpproxy:yes\r\n</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>nortpproxy_str</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "nortpproxy_str", "a=sdpmangled:yes\r\n")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.timeout_socket">
		<title><varname>timeout_socket</varname> (string)</title>
		<para>
		The parameter sets the RTP timeout socket, which is transmitted to the RTP-Proxy.
		It will be used by the RTP proxy to signal back that a media stream timed
		out.
		</para>
		<para>
		If it is an empty string, no timeout socket will be transmitted to the RTP-Proxy.
		</para>
		<para>
		<emphasis>
			Default value is <quote></quote> (nothing).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>timeout_socket</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "timeout_socket", "xmlrpc:http://127.0.0.1:8000/RPC2")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.ice_candidate_priority_avp">
		<title><varname>ice_candidate_priority_avp</varname> (string)</title>
		<para>
		If specified and if value of the avp value is not 0,
		<function>rtpproxy_manage</function> function adds
		ICE relay candidate attributes
		to sdp stream(s) containing ICE candidate attributes.
		</para>
		<para>
		If value of the avp is 1, added candidates
		have high priority.  If value of the avp is 2 (default),
		added candidates have low priority.
		</para>
		<para>
		<emphasis>
		There is no default value meaning that no ICE relay
		candidates are added in any circumstance.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>ice_candidate_priority_avp</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "ice_candidate_priority_avp", "$avp(ice_priority)")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.extra_id_pv">
		<title><varname>extra_id_pv</varname> (string)</title>
		<para>
			The parameter sets the PV defination to use when the <quote>b</quote>
			parameter is used on unforce_rtp_proxy(), rtpproxy_offer(),
			rtpproxy_answer() or rtpproxy_manage() command.
		</para><para>
			Default is empty, the <quote>b</quote> parameter may not be used then.
		</para>
		<example>
		<title>Set <varname>extra_id_pv</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "extra_id_pv", "$avp(extra_id)")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.db_url">
		<title><varname>db_url</varname> (string)</title>
		<para>
			The database URL to load rtp_proxy sets from.
			If this parameter is set, the module will attempt to load the rtpproxy sets from the specified database and will ignore any 'rtpproxy_sock' modparams.
		</para>
		<para>
			Default is empty, a database will not be used.
		</para>
		<example>
		<title>Set <varname>db_url</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "db_url", "mysql://user:passwb@localhost/database")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.table_name">
		<title><varname>table_name</varname> (string)</title>
		<para>
			The name of the table containing the rtpproxy sets.
		</para>
		<para>
			Default value is <quote>rtpproxy</quote>.
		</para>
		<example>
		<title>Set <varname>table_name</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "table_name", "my_rtpp_sets")
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.p.rtp_inst_pvar">
		<title><varname>rtp_inst_pvar</varname> (string)</title>
		<para>
			A pseudo variable to store the chosen RTPProxy address.
			If this parameter is set, the instance URL will be stored in the given variable.
		</para>
		<para>
			By default, this parameter is not set.
		</para>
		<example>
		<title>Set <varname>rtp_inst_pvar</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpproxy", "rtp_inst_pvar", "$avp(RTP_INSTANCE)")
...
</programlisting>
		</example>
		<example>
		<title><varname>rtp_inst_pvar</varname> usage</title>
		<programlisting format="linespecific">
modparam("rtpproxy", "rtpproxy_sock",
	"udp:localhost:12221 udp:localhost:12222")
modparam("rtpproxy", "rtp_inst_pvar", "$var(RTP_INSTANCE)")
...
rtpproxy_manage("eiro");
xlog("L_INFO", "Chose rtpp instance $var(RTP_INSTANCE)\n");
# This will display 'udp:localhost:12222'
...
</programlisting>
		</example>
	</section>
	</section>

	<section>
	<title>Functions</title>
	<section id="rtpproxy.f.set_rtp_proxy_set">
		<title>
		<function moreinfo="none">set_rtp_proxy_set(setid)</function>
		</title>
		<para>
		Sets the Id of the rtpproxy set to be used for the next
		unforce_rtp_proxy(), rtpproxy_offer(), rtpproxy_answer()
		or rtpproxy_manage() command. The parameter can be an integer or
		a config variable holding an integer.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
		BRANCH_ROUTE.
		</para>
		<example>
		<title><function>set_rtp_proxy_set</function> usage</title>
		<programlisting format="linespecific">
...
set_rtp_proxy_set("2");
rtpproxy_offer();
...
</programlisting>
		</example>
	</section>
        <section id="rtpproxy.f.rtpproxy_ofrer">
                <title>
                <function moreinfo="none">rtpproxy_offer([flags [, ip_address]])</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 SDPs are in INVITE and 200 OK and on 200 OK
		when SDPs 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>
			<itemizedlist>
				<listitem><para>
				<emphasis>1</emphasis> - append first Via branch to Call-ID when sending
				command to rtpproxy. This can be used to create one media session per branch
				on the rtpproxy. When sending a subsequent <quote>delete</quote> command to
				the rtpproxy, you can then stop just the session for a specific branch when
				passing the flag '1' or '2' in the <quote>unforce_rtpproxy</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 rtpproxy
				gets an <quote>update</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>lookup</quote> for the
				new branch. <emphasis>This flag is only supported by the ngcp-mediaproxy-ng
				rtpproxy (now named rtpengine) at the moment!</emphasis>
				</para></listitem>
				<listitem><para>
				<emphasis>2</emphasis> - append second Via branch to Call-ID when sending
				command to rtpproxy. See flag '1' for its meaning.
				</para></listitem>
				<listitem><para>
				<emphasis>3</emphasis> - behave like flag 1 is set for a request and
				like flag 2 is set for a reply.
				</para></listitem>
				<listitem><para>
				<emphasis>a</emphasis> - flags that UA from which message is
				received doesn't support symmetric RTP. (automatically sets the 'r' flag)
				</para></listitem>
				<listitem><para>
				<emphasis>b</emphasis> - append branch specific variable to Call-ID when sending
				command to rtpproxy. This creates one rtpproxy session per unique variable.

				Works similar to the 1, 2 and 3 parameter, but is usefull when forking to multiple
				destinations on different address families or network segments, requiring different
				rtpproxy parameters.

				The variable value is taken from the <quote>extra_id_pv</quote>.

				When used, it must be used in every call to rtpproxy_manage(), rtpproxy_offer(),
				rtpproxy_answer() and rtpproxy_destroy() with the same contents of the PV.
				The b parameter may not be used in conjunction with the 1, 2 or 3 parameter
				to use the Via branch in the Call-ID.
				</para></listitem>
				<listitem><para>
				<emphasis>l</emphasis> - force <quote>lookup</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>i, e</emphasis> - these flags specify the direction of the SIP
				message. These flags only make sense when rtpproxy is running in bridge mode.
				'i' means internal network (LAN), 'e' means external network (WAN). 'i'
				corresponds to rtpproxy's first interface, 'e' corresponds to rtpproxy's
				second interface. You always have to specify two flags to define
				the incoming network and the outgoing network. For example, 'ie' should be
				used for SIP message received from the local interface and sent out on the
				external interface, and 'ei' vice versa. Other options are 'ii' and 'ee'.
				So, for example if a SIP requests is processed with 'ie' flags, the corresponding
				response must be processed with 'ie' flags.
				</para><para>
				Note: As rtpproxy in bridge mode s per default asymmetric, you have to specify
				the 'w' flag for clients behind NAT! See also above notes!
				</para></listitem>
				<listitem><para>
				<emphasis>x</emphasis> - this flag a shortcut for using the "ie" or "ei"-flags of RTP-Proxy,
				in order to do automatic bridging between IPv4 on the
				"internal network" and IPv6 on the "external network". The distinction is done by
				the given IP in the SDP, e.g. a IPv4 Address will always call "ie" to the RTPProxy
				(IPv4(i) to IPv6(e)) and an IPv6Address will always call "ei" to the RTPProxy (IPv6(e)
				to IPv4(i)).
				</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>f</emphasis> - instructs rtpproxy to ignore marks
				inserted by another rtpproxy in transit to indicate that the
				session is already goes through another proxy. Allows creating
				a chain of proxies.
				</para></listitem>
				<listitem><para>
				<emphasis>r</emphasis> - flags that IP address in SDP should
				be trusted. Without this flag, rtpproxy 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>o</emphasis> - flags that IP from the origin
				description (o=) should be also changed.
				</para></listitem>
				<listitem><para>
				<emphasis>c</emphasis> - flags to change the session-level
				SDP connection (c=) IP if media-description also includes
				connection information.
				</para></listitem>
				<listitem><para>
				<emphasis>w</emphasis> - flags that for the UA from which
				message is received, support symmetric RTP must be forced.
				</para></listitem>
				<listitem><para>
				<emphasis>zNN</emphasis> - requests the RTPproxy 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
				RTPproxy 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.
				</para></listitem>
			</itemizedlist>
		</listitem>
		<listitem><para>
		<emphasis>ip_address</emphasis> - new SDP IP address.
		</para></listitem>
		</itemizedlist>
		<para>
		This function can be used from ANY_ROUTE.
                </para>
		<example>
		<title><function>rtpproxy_offer</function> usage</title>
		<programlisting format="linespecific">
route {
...
    if (is_method("INVITE")) {
        if (has_body("application/sdp")) {
            if (rtpproxy_offer())
                t_on_reply("1");
        } else {
            t_on_reply("2");
        }
    }
    if (is_method("ACK") &amp;&amp; has_body("application/sdp"))
        rtpproxy_answer();
...
}

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

onreply_route[2]
{
...
    if (has_body("application/sdp"))
        rtpproxy_offer();
...
}
</programlisting>
                </example>
	</section>
        <section id="rtpproxy.f.rtpproxy_answer">
                <title>
                <function moreinfo="none">rtpproxy_answer([flags [, ip_address]])</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 SDPs are in INVITE and 200 OK and on ACK
		when SDPs are in 200 OK and ACK.
		</para>
		<para>
		See rtpproxy_answer() 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>rtpproxy_answer</function> usage</title>
		<para>
		See rtpproxy_offer() function example above for example.
		</para>
		</example>
        </section>
	<section id="rtpproxy.f.rtpproxy_destroy">
		<title>
		<function moreinfo="none">rtpproxy_destroy([flags])</function>
		</title>
		<para>
		Tears down the RTPProxy session for the current call.
		</para>
		<para>
		This function can be used from ANY_ROUTE.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>flags</emphasis> - flags to turn on some features.
			</para>
			<itemizedlist>
				<listitem><para>
				<emphasis>1</emphasis> - append first Via branch to Call-ID when sending
				command to rtpproxy. This can be used to create one media session per branch
				on the rtpproxy. When sending a subsequent <quote>delete</quote> command to
				the rtpproxy, you can then stop just the session for a specific branch when
				passing the flag '1' or '2' in the <quote>unforce_rtpproxy</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 rtpproxy
				gets an <quote>update</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>lookup</quote> for the
				new branch. <emphasis>This flag is only supported by the ngcp-mediaproxy-ng
				rtpproxy (now named rtpengine) at the moment!</emphasis>
				</para></listitem>
				<listitem><para>
				<emphasis>2</emphasis> - append second Via branch to Call-ID when sending
				command to rtpproxy. See flag '1' for its meaning.
				</para></listitem>
				<listitem><para>
				<emphasis>b</emphasis> - append branch specific variable to Call-ID when sending
				command to rtpproxy. See rtpproxy_offer() for details.
				<listitem><para>
				</para></listitem>
				<emphasis>t</emphasis> - do not include To tag to <quote>delete</quote> command to rtpproxy thus causing full call to be deleted. Useful for deleting unused rtpproxy call when 200 OK is received on a branch, where rtpproxy is not needed.
				</para></listitem>
			</itemizedlist>
		</listitem>
		</itemizedlist>
		<example>
		<title><function>rtpproxy_destroy</function> usage</title>
		<programlisting format="linespecific">
...
rtpproxy_destroy();
...
</programlisting>
		</example>
	</section>
	<section id="rtpproxy.f.unforce_rtp_proxy">
		<title>
		<function moreinfo="none">unforce_rtp_proxy()</function>
		</title>
		<para>
			Same as rtpproxy_destroy().
		</para>
	</section>

    <section id="rtpproxy.f.rtpproxy_manage">
        <title>
        <function moreinfo="none">rtpproxy_manage([flags [, ip_address]])</function>
        </title>
		<para>
		Manage the RTPProxy session - it combines the functionality of
		rtpproxy_offer(), rtpproxy_answer() and unforce_rtpproxy(), detecting
		internally based on message type and method which one to execute.
		</para>
		<para>
		It can take the same parameters as <function>rtpproxy_offer().</function>
		The flags parameter to rtpproxy_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>rtpproxy_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>rtpproxy_answer()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If ACK with SDP, then do <function>rtpproxy_answer()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If BYE or CANCEL, or called within a FAILURE_ROUTE[], then do <function>unforce_rtpproxy()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If reply to INVITE with code >= 300 do <function>unforce_rtpproxy()</function>
			</para>
		</listitem>
		<listitem>
			<para>
			If reply with SDP to INVITE having code 1xx and 2xx, then
			do <function>rtpproxy_answer()</function> if the request had SDP or tm is not loaded,
			otherwise do <function>rtpproxy_offer()</function>
			</para>
		</listitem>
	</itemizedlist>

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

	<section id="rtpproxy.f.rtpproxy_stream2uac">
	<title>
	    <function>rtpproxy_stream2uac(prompt_name, count)</function>,
	</title>
	<para>
	    Instruct the RTPproxy to stream prompt/announcement pre-encoded with
	    the makeann command from the RTPproxy distribution. The uac/uas
	    suffix selects who will hear the announcement relatively to the current
	    transaction - UAC or UAS. For example invoking the
	    <function>rtpproxy_stream2uac</function> in the request processing
	    block on ACK transaction will play the prompt to the UA that has
	    generated original INVITE and ACK while
	    <function>rtpproxy_stop_stream2uas</function> on 183 in reply
	    processing block will play the prompt to the UA that has generated 183.
	</para>
	<para>
	    Apart from generating announcements, another possible application
	    of this function is implementing music on hold (MOH) functionality.
	    When count is -1, the streaming will be in loop indefinitely until
	    the appropriate <function>rtpproxy_stop_stream2xxx</function> is issued.
	</para>
	<para>
	    In order to work correctly, these functions require that a session in the
	    RTPproxy already exists. Also those functions don't alter the SDP, so that
	    they are not a substitute for calling <function>rtpproxy_offer</function>
	    or <function>rtpproxy_answer</function>.
	</para>
	<para>
	    This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE.
	</para>
	<para>Meaning of the parameters is as follows:</para>
	<itemizedlist>
	    <listitem>
		<para>
		    <emphasis>prompt_name</emphasis> - name of the prompt to
		    stream. Should be either absolute pathname or pathname
		    relative to the directory where RTPproxy runs.
		</para>
	    </listitem>
	    <listitem>
		<para>
		    <emphasis>count</emphasis> - number of times the prompt
		    should be repeated. A value of -1 means that it will
		    be streaming in a loop indefinitely, until the appropriate
		    <function>rtpproxy_stop_stream2xxx</function> is issued.
		</para>
	    </listitem>
	</itemizedlist>
	<example>
	    <title><function>rtpproxy_stream2xxx</function> usage</title>
	    <programlisting>
...
    if (is_method("INVITE")) {
        rtpproxy_offer();
        if (detect_hold()) {
            rtpproxy_stream2uas("/var/rtpproxy/prompts/music_on_hold", "-1");
        } else {
            rtpproxy_stop_stream2uas();
        };
    };
...
	    </programlisting>
	</example>
	</section>
	<section id="rtpproxy.f.rtpproxy_stream2uas">
	<title>
	    <function>rtpproxy_stream2uas(prompt_name, count)</function>
	</title>
	<para>
		See function <function>rtpproxy_stream2uac(prompt_name, count)</function>.
	</para>
	</section>
	<section id="rtpproxy.f.rtpproxy_stop_stream2uac">
	<title>
	    <function>rtpproxy_stop_stream2uac()</function>,
	</title>
	<para>
	    Stop streaming of announcement/prompt/MOH started previously by the
	    respective <function>rtpproxy_stream2xxx</function>.  The uac/uas
	    suffix selects whose announcement relatively to tha current
	    transaction should be stopped - UAC or UAS.
	</para>
	<para>
	    These functions can be used from REQUEST_ROUTE, ONREPLY_ROUTE.
	</para>
	</section>
	<section id="rtpproxy.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 only supported by Sippy RTPproxy 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 id="rtpproxy.f.rtpproxy_stop_stream2uas">
	<title>
	    <function>rtpproxy_stop_stream2uas(prompt_name, count)</function>
	</title>
	<para>
		See function <function>rtpproxy_stop_stream2uac(prompt_name, count)</function>.
	</para>
	</section>


	</section>

	<section>
		<title>Exported Pseudo Variables</title>
		<section id="rtpproxy.pv.rtpstat">
			<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>unforce_rtpproxy()</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>
			<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 rtpproxy is defined multiple times (in the same or
			different sets), all of its instances will be enabled/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>
			<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>

