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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>
	<para>
		From the current implementation point of view, the sets of rtpproxy nodes
		are shared memory(shm), so all processes can see a common list of nodes.
		There is no locking when setting the nodes enabled/disabled (to keep the
		memory access as fast as possible). Thus, problems related to node state
		might appear for concurent processes that might set the nodes
		enabled/disabled(e.g. by fifo command). This robustness problems are overcomed as follows.
	</para>

	<para>
		If the current process sees the selected node as disabled, the node is
		<emphasis>force tested</emphasis> before the current process actually
		takes the disabled decision. If the test succeeds, the process will set
		the node as enabled (but other concurrent process might still see it as disabled).
.
	</para>

	<para>
		If the current process sees the selected node as enabled, it does no additional checks
		and sends the command which will fail in case the machine is actually broken.
		The process will set the node as disabled (but other concurrent process might still see it as enabled).
	</para>

	<para>
		The 'kamctl fifo' commands (including rtpengin ones) are executed by an exclusive
		process which operate on the same shared memory node list.
	</para>

	<para>
		All the nodes are pinged in the beginning by all the processes,
		even if the node list is shared memory.
	</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 with weights (missing weight defaults to 1)
modparam("rtpengine", "rtpengine_sock",
	"udp:localhost:12221=2 udp:localhost:12222=1")
# 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_ms">
		<title><varname>rtpengine_tout_ms</varname> (integer)</title>
		<para>
		Timeout value expressed in milliseconds in waiting for reply from &rtp; proxy.
		</para>
		<para>
		<emphasis>
			Default value is <quote>1000</quote>.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_tout_ms</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "rtpengine_tout_ms", 2000)
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.rtpengine_allow_op">
		<title><varname>rtpengine_allow_op</varname> (integer)</title>
		<para>
		Enable this to allow finishing the current sessions while denying new sessions for the
		<emphasis>manually deactivated nodes </emphasis> via kamctl command i.e. "disabled(permanent)" nodes.
		Probably the manually deactivated machine is still running(did not crash).
		</para>
		<para>
		This is <emphasis>useful</emphasis> when deactivating a node for maintanance and reject new sessions but allow current ones to finish.
		</para>
		<para>
		The behaviour is the same for a rtpengine deleted table node.
		When the node is deleted from the table and the table reloaded (see nh_reload_rtpp) the node actually is disabled(permanent) and hidden for display.
		Next time the same node will be added in the table, and the content reloaded, it will be updated and re-displayed.
		</para>
		<para>
		<emphasis>
		Default value is <quote>0</quote> to keep the current behaviour.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>rtpengine_allow_op</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "rtpengine_allow_op", 1)
...
</programlisting>
		</example>
	</section>
	<section id="rtpengine.p.queried_nodes_limit">
		<title><varname>queried_nodes_limit</varname> (integer)</title>
		<para>
		The total number of nodes inside a set (sets are configurable via rtpengine_sock function) to be queried 
		before giving up establishing a session. This brings more flexibility in case checking all rtpengines
		would take too long. Max limit is 50.
		</para>
		<para>
		<emphasis>
			By default all nodes in a set are tried before giving up communicating with the rtpengines.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>queried_nodes_limit</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rtpengine", "queried_nodes_limit", 5)
...
</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_avp">
		<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 id="rtpengine.p.force_send_interface">
		<title><varname>force_send_interface</varname> (string)</title>
		<para>
			Forces all control messages between the &sip; proxy and
			the &rtp; proxy to be sent from the specified local
			interface. Both IPv4 and IPv6 addresses are supported. If
			not specified, the default interface selected by the
			operating system will be used.
			Note: when rtpengine_sock is a IPv6 link-local address,
			one _must_ set this parameter in order to successfully connect to RTP engine.
			This is necessarely because OS needs additional scope_id hint to communicate
			over IPv6 link locals. The scope_id is resolved based on the given IPv6.
		</para>
		<para>
			There is no default value.
		</para>
		<example>
		<title>Set <varname>force_send_interface</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "force_send_interface", "10.3.7.123")
modparam("rtpengine", "force_send_interface", "2001:8d8:1ff:10c0:9a90:96ff:fea8:fd99")
...
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.read_sdp_pv">
		<title><varname>read_sdp_pv</varname> (string)</title>
		<para>
			If this parameter is set to a valid AVP or script var specifier, rtpengine
			will take the input SDP from this pv instead of the message body.
		</para>
		<para>
			There is no default value.
		</para>
		<example>
		<title>Set <varname>read_sdp_pv</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "read_sdp_pv", "$var(sdp)")
...
route {
	...
	$var(sdp) = $rb + "a=foo:bar\r\n";
	rtpengine_manage();
}
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.write_sdp_pv">
		<title><varname>write_sdp_pv</varname> (string)</title>
		<para>
			If this parameter is set to a valid AVP or script var specifier, the
            SDP returned by rtpengine in the offer/answer operations
            is returned in the specified variable instead of the
            message body.
		</para>
		<para>
			There is no default value.
		</para>
		<example>
		<title>Set <varname>write_sdp_pv</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "write_sdp_pv", "$avp(sdp)")
...
route {
	...
	rtpengine_manage();
	set_body("$avp(sdp)a=baz123\r\n", "application/sdp");
}
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.rtp_inst_pvar">
		<title><varname>rtp_inst_pvar</varname> (string)</title>
		<para>
			A pseudo variable to store the chosen RTP Engine IP address.
			If this parameter is set, the IP address and port of the instance chosen 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("rtpengine", "rtp_inst_pvar", "$avp(RTP_INSTANCE)")
...
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.hash_table_size">
		<title><varname>hash_table_size</varname> (integer)</title>
		<para>
			Size of the hash table. Default value is 256.
		</para>
		<para>
			NOTE: If configured size is <emphasis>less than</emphasis> 1, the size will be defaulted to 1.
		</para>
		<example>
		<title>Set <varname>hash_table_size</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "hash_table_size", "123")
...
</programlisting>
		</example>
	</section>

	<section id="rtpengine.p.hash_table_tout">
		<title><varname>hash_table_tout</varname> (integer)</title>
		<para>
			Number of seconds after an rtpengine hash table entry is marked for deletion.
			By default, this parameter is set to 3600 (seconds).
		</para>
		<para>
			To maintain information about a selected rtp machine node, for a given call, entries are added in a hashtable of (callid, node) pairs.
			When command comes, lookup callid. If found, return chosen node. If not found, choose a new node, insert it in the hastable and return the chosen node.
		</para>
		<para>
			NOTE: In the current implementation, the actual deletion happens <emphasis>on the fly</emphasis>,
			while insert/remove/lookup the hastable, <emphasis>only</emphasis> for the entries in the insert/remove/lookup path.
		</para>
		<para>
			NOTE: When configuring this parameter, one should consider maximum call time VS share memory for unfinished calls.
		</para>
		<example>
		<title>Set <varname>hash_table_tout</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "hash_table_tout", "300")
...
</programlisting>
                </example>
        </section>




	<section id="rtpengine.p.db_url">
		<title><varname>db_url</varname> (string)</title>
		<para>
			The rtpengine datablase url. If present and valid, it activates database mode.
			Node information is read from database, not from config.
		</para>
		<para>
			By default, the datablase url is NULL (not set).
		</para>
		<example>
		<title>Set <varname>db_url</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "db_url", "mysql://pass@localhost/db")
...
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.table_name">
		<title><varname>table_name</varname> (string)</title>
		<para>
			The rtpengine table name. If database mode is activated (i.e. valid db_url),
			set the name of rtpengine table, on startup.
		</para>
		<para>
			By default, the rtpengine table name is "rtpengine".
		</para>
		<para>
			NOTE: One needs to add the version of the rtpengine table in the version table.
			The current version is version 1.
		</para>
		<example>
		<title>Set <varname>table_name</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "table_name", "rtpengine_table_name")
...
</programlisting>
		</example>

		<example>
		<title>Setup <varname>rtpengine</varname> table</title>
<programlisting format="linespecific">
mysql> describe rtpengine;
+----------+------------------+------+-----+---------+-------+
| Field    | Type             | Null | Key | Default | Extra |
+----------+------------------+------+-----+---------+-------+
| setid    | int(10) unsigned | NO   |     | NULL    |       |
| url      | varchar(256)     | NO   |     | NULL    |       |
| weight   | int(10) unsigned | NO   |     | NULL    |       |
| disabled | int(11)          | NO   |     | NULL    |       |
+----------+------------------+------+-----+---------+-------+

mysql> select * from rtpengine;
+-------+---------------------------+--------+----------+
| setid | url                       | weight | disabled |
+-------+---------------------------+--------+----------+
|     0 | udp:rtpproxy1.domain:8800 |    100 |        0 |
|     0 | udp:rtpproxy2.domain:8800 |    200 |        1 |
+-------+---------------------------+--------+----------+

mysql> select * from version;
+---------------------------+---------------+
| table_name                | table_version |
+---------------------------+---------------+
| rtpengine                 |             1 |
+---------------------------+---------------+
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.setid_col">
		<title><varname>setid_col</varname> (string)</title>
		<para>
			Column name in the rtpengine table. If database mode is activated (i.e. valid db_url),
			set the setid of rtp nodes according to this column, on startup.
			The MySQL value for this column should be INT UNSIGNED.
		</para>
		<para>
			By default, the column name is "setid".
		</para>
		<example>
		<title>Set <varname>setid_col</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "setid_col", "setid_column_name")
...
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.url_col">
		<title><varname>url_col</varname> (string)</title>
		<para>
			Column name in the rtpengine table. If database mode is activated (i.e. valid db_url),
			set the url of rtp nodes according to this column, on startup.
			The MySQL value for this column should be VARCHAR.
		</para>
		<para>
			By default, the column name is "url".
		</para>
		<example>
		<title>Set <varname>url_col</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "url_col", "url_column_name")
...
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.weight_col">
		<title><varname>weight_col</varname> (string)</title>
		<para>
			Column name in the rtpengine table. If database mode is activated (i.e. valid db_url),
			set the weight of rtp nodes according to this column, on startup. The column value has
			priority over the URL weight.
			The MySQL value for this column should be INT UNSIGNED.
		</para>
		<para>
			By default, the column name is "weight".
		</para>
		<example>
		<title>Set <varname>weight_col</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "weight_col", "weight_column_name")
...
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.disabled_col">
		<title><varname>disabled_col</varname> (string)</title>
		<para>
			Column name in the rtpengine table. If database mode is activated (i.e. valid db_url),
			set the state of rtp nodes according to this column, on startup.
			The MySQL value for this column should be INT.
		</para>
		<para>
			By default, the column name is "disabled".
		</para>
		<example>
		<title>Set <varname>disabled_col</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "disabled_col", "disabled_column_name")
...
</programlisting>
		</example>
	</section>


	<section id="rtpengine.p.setid_default">
		<title><varname>setid_default</varname> (string)</title>
		<para>
			The default set of nodes to be used.
		</para>
		<para>
			By default, the setid is 0.
		</para>
		<para>
			NOTE that if setid_avp is configured, this value will be ignored and
			the active set will be chosen according to the setid_avp.
		</para>
		<example>
		<title>Set <varname>setid_default</varname> parameter</title>
<programlisting format="linespecific">
...
modparam("rtpengine", "setid_default", 11)
...
</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. Starting with rtpengine 3.8, this is the default behaviour.
				In older versions, without this flag the &rtp; proxy ignores the 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>SIP-source-address</emphasis> - the opposite of
				<emphasis>trust-address</emphasis>. Restores the old default behaviour
				of ignoring endpoint addresses in the &sdp; body.
				</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>
				<listitem><para>
				<emphasis>delete-delay=...</emphasis> - override the default delay (in seconds)
				before a call is actually deleted from memory. Can be set to zero to effectuate
				immediate deletion. This option only makes sense for <emphasis>delete</emphasis>
				operations.
				</para></listitem>
				<listitem><para>
				<emphasis>strict-source</emphasis> - instructs the &rtp; proxy to check the
				source addresses of all incoming &rtp; packets and drop the packets if the
				address doesn't match.
				</para></listitem>
				<listitem><para>
				<emphasis>media-handover</emphasis> - the antithesis of
				<emphasis>strict-source</emphasis>. Instructs the &rtp; proxy not only to accept
				mismatching &rtp; source addresses (as it normally would), but also to accept
				them as the new endpoint address of the opposite media flow. Not recommended
				as it allows media streams to be hijacked by an attacker.
				</para></listitem>
				<listitem><para>
				<emphasis>DTLS=...</emphasis> - influence the behaviour of DTLS-SRTP. Possible
				values are <quote>no</quote> or <quote>off</quote> to suppress offering or
				accepting DTLS-SRTP, and <quote>passive</quote> to prefer participating in
				DTLS-SRTP in a passive role.
				</para></listitem>
				<listitem><para>
				<emphasis>SDES-off</emphasis> - don't offer SDES when it normally would. In an SRTP
				context, this leaves DTLS-SRTP as the only other option.
				</para></listitem>
				<listitem><para>
				<emphasis>SDES-unencrypted_srtp, SDES-unencrypted_srtcp,
				SDES-unauthenticated_srtp</emphasis> - these directly reflect the SDES session
				parameters from RFC 4568 and will make the &rtp; proxy offer these parameters
				when offering SDES.
				</para></listitem>
				<listitem><para>
				<emphasis>SDES-encrypted_srtp, SDES-encrypted_srtcp,
				SDES-authenticated_srtp</emphasis> - the opposites of the flags above. Useful
				if accepting these parameters is not desired and they should be rejected instead.
				</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 proxy_url/all 0/1</function></title>
			<para>
			Enables a &rtp; proxy if the second parameter value is greater than 0. Disables it if a zero value is given.
			The first parameter is either a specific &rtp; proxy url (exactly as defined in
			the config file) or the keyword <emphasis>all</emphasis>.
			The second parameter value must be a number in decimal.
			</para>
			<para>
            When try to enable the &rtp; proxy, an application ping command is sent to it.
            If it fails, the proxy is not enabled.
            Displays <emphasis>success</emphasis> or <emphasis>fail</emphasis> when try to enable/disable.
			</para>
			<para>
			NOTE: If a &rtp; proxy is defined multiple times (in the same or diferent sets), all of its instances will be enabled/disabled.
			</para>
			<para>
			NOTE: If a &rtp; proxy is in the disabled permanent state and one tries to enable it, even if the ping fails,
            it is moved to a disabled temporary state and a recheck_ticks are given to it.
            While the recheck_ticks are grater than 0, the proxy is considered disabled temporary, and it is not taken into consideration for sending data.
            When the recheck_ticks are 0, the proxy is retested <emphasis>when trying to send data</emphasis>(not automatically retested), and data can be send to it on success.
			</para>
			<para>
			NOTE: When specify the IPv6 &rtp; proxy url one must prefix it with <emphasis>::</emphasis>
            to escape the :: from the IPv6 address. See the example below.
			</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
$ &ctltool; fifo nh_enable_rtpp ::udp6:fe80::9a90:96ff:fea8:fd99:9999 1
$ &ctltool; fifo nh_enable_rtpp all 1
...
			</programlisting>
			</example>
		</section>

	    <section id="rtpengine.m.nh_show_rtpp">
			<title><function moreinfo="none">nh_show_rtpp proxy_url/all</function></title>
			<para>
			Displays all the &rtp; proxies and their information: set and
			status (disabled or not, weight and recheck_ticks). If a &rtp; proxy has been disabled by
            nh_enable_rtpp mi command a "(permanent)" quote will appear when printing the disabled status.
            This is to differentiate from a temporary disable due to the proxy being not found responsive
            by kamailio. In addition, when disabled permanent, recheck_ticks have no meaning and "N\A"
            is printed instead of the value.
			</para>
			<para>
            It takes either a specific &rtp; proxy url (exactly as defined in
			the config file) or the keyword <emphasis>all</emphasis> as a parameter.
			</para>
			<para>
			NOTE: When specify the IPv6 &rtp; proxy url one must prefix it with <emphasis>::</emphasis>
            to escape the :: from the IPv6 address. See the example below.
			</para>
			<example>
			<title>
				<function moreinfo="none">nh_show_rtpp</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_show_rtpp udp:192.168.2.133:8081
$ &ctltool; fifo nh_show_rtpp ::udp6:fe80::9a90:96ff:fea8:fd99:9999
$ &ctltool; fifo nh_show_rtpp all
...
			</programlisting>
			</example>
		</section>

	    <section id="rtpengine.m.nh_ping_rtpp">
			<title><function moreinfo="none">nh_ping_rtpp proxy_url/all</function></title>
			<para>
            Sends an application ping command to the &rtp; proxy. If the proxy does not respond,
            it will be disabled, but not permanent. If the proxy responds, no action is taken.
            Displays the ping result, i.e.
            <emphasis>success</emphasis> or <emphasis>fail</emphasis> when try to ping.
			</para>
			<para>
            It takes either a specific &rtp; proxy url (exactly as defined in
			the config file) or the keyword <emphasis>all</emphasis> as a parameter.
			</para>
			<para>
			NOTE: When specify the IPv6 &rtp; proxy url one must prefix it with <emphasis>::</emphasis>
            to escape the :: from the IPv6 address. See the example below.
			</para>
			<example>
			<title>
				<function moreinfo="none">nh_ping_rtpp</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_ping_rtpp udp:192.168.2.133:8081
$ &ctltool; fifo nh_ping_rtpp ::udp6:fe80::9a90:96ff:fea8:fd99:9999
$ &ctltool; fifo nh_ping_rtpp all
...
			</programlisting>
			</example>
		</section>


	    <section id="rtpengine.m.nh_reload_rtpp">
			<title><function moreinfo="none">nh_reload_rtpp</function></title>
			<para>
				Reloads the database node table content <emphasis>if configured</emphasis>.
				Returns specific message related to success, failure and no db_url configured.
			</para>
			<para>
				NOTE: The current behaviour updates the nodes state or creates new ones or
				hides old ones, based on the database content. If allow_op modparam is enabled,
				the sessions are still allowed to finish for the hidden old nodes.
			</para>
			<example>
			<title>
				<function moreinfo="none">nh_reload_rtpp</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_reload_rtpp
...
			</programlisting>
			</example>
		</section>


	    <section id="rtpengine.m.nh_show_hash_total">
			<title><function moreinfo="none">nh_show_hash_total</function></title>
			<para>
				Print the total number of hash entries in the hash table at a given moment.
			</para>
			<example>
			<title>
				<function moreinfo="none">nh_show_hash_total</function> usage</title>
			<programlisting format="linespecific">
...
$ &ctltool; fifo nh_show_hash_total
...
			</programlisting>
			</example>
		</section>

	</section>

</chapter>

