kamailio/modules/rtpengine

rtpengine Module

Maxim Sobolev

Sippy Software, Inc.

Juha Heinanen

TuTPro, Inc.

Edited by

Maxim Sobolev

Edited by

Bogdan-Andrei Iancu

Edited by

Juha Heinanen

Edited by

Sas Ovidiu

Edited by

Carsten Bock

ng-voice GmbH

Edited by

Richard Fuchs

Sipwise GmbH

Copyright (c) 2003-2008 Sippy Software, Inc.

Copyright (c) 2005 Voice Sistem SRL

Copyright (c) 2009-2014 TuTPro Inc.

Copyright (c) 2010 VoIPEmbedded Inc.

Copyright (c) 2013-2014 Sipwise GmbH
__________________________________________________________________

Table of Contents

1. Admin Guide

1. Overview
2. Multiple RTP proxy usage
3. Dependencies

3.1. Kamailio Modules
3.2. External Libraries or Applications

4. Parameters

4.1. rtpengine_sock (string)
4.2. rtpengine_disable_tout (integer)
4.3. rtpengine_tout (integer)
4.4. rtpengine_retr (integer)
4.5. extra_id_pv (string)
4.6. setid_avp (string)

5. Functions

5.1. set_rtpengine_set(setid[, setid])
5.2. rtpengine_offer([flags])
5.3. rtpengine_answer([flags])
5.4. rtpengine_delete([flags])
5.5. rtpengine_manage([flags])
5.6. start_recording()

6. Exported Pseudo Variables

6.1. $rtpstat

7. MI Commands

7.1. nh_enable_rtpp
7.2. nh_show_rtpp

2. Frequently Asked Questions

List of Examples

1.1. Set rtpengine_sock parameter
1.2. Set rtpengine_disable_tout parameter
1.3. Set rtpengine_tout parameter
1.4. Set rtpengine_retr parameter
1.5. Set extra_id_pv parameter
1.6. Set setid_avp parameter
1.7. set_rtpengine_set usage
1.8. rtpengine_offer usage
1.9. rtpengine_answer usage
1.10. rtpengine_delete usage
1.11. rtpengine_manage usage
1.12. start_recording usage
1.13. $rtpstat Usage
1.14. nh_enable_rtpp usage
1.15. nh_show_rtpp usage

Chapter 1. Admin Guide

Table of Contents

1. Overview
2. Multiple RTP proxy usage
3. Dependencies

3.1. Kamailio Modules
3.2. External Libraries or Applications

4. Parameters

4.1. rtpengine_sock (string)
4.2. rtpengine_disable_tout (integer)
4.3. rtpengine_tout (integer)
4.4. rtpengine_retr (integer)
4.5. extra_id_pv (string)
4.6. setid_avp (string)

5. Functions

5.1. set_rtpengine_set(setid[, setid])
5.2. rtpengine_offer([flags])
5.3. rtpengine_answer([flags])
5.4. rtpengine_delete([flags])
5.5. rtpengine_manage([flags])
5.6. start_recording()

6. Exported Pseudo Variables

6.1. $rtpstat

7. MI Commands

7.1. nh_enable_rtpp
7.2. nh_show_rtpp

1. Overview

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 https://github.com/sipwise/rtpengine. 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.

2. Multiple RTP proxy usage

The rtpengine module can support multiple RTP proxies for
balancing/distribution and control/selection purposes.

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 "rtpengine_sock"
module parameter definition for syntax description.

The balancing inside a set is done automatically by the module based on
the weight of each RTP proxy from the set.

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.

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.

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.

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.

3. Dependencies

3.1. Kamailio Modules
3.2. External Libraries or Applications

3.1. Kamailio Modules

The following modules must be loaded before this module:
* tm module - (optional) if you want to have rtpengine_manage() fully
functional

3.2. External Libraries or Applications

The following libraries or applications must be installed before
running Kamailio with this module loaded:
* None.

4. Parameters

4.1. rtpengine_sock (string)
4.2. rtpengine_disable_tout (integer)
4.3. rtpengine_tout (integer)
4.4. rtpengine_retr (integer)
4.5. extra_id_pv (string)
4.6. setid_avp (string)

4.1. rtpengine_sock (string)

Definition of socket(s) used to connect to (a set) RTP proxy. It may
specify a UNIX socket or an IPv4/IPv6 UDP socket.

Default value is "NONE" (disabled).

Example 1.1. Set rtpengine_sock parameter
...
# 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")
...

4.2. rtpengine_disable_tout (integer)

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.

Default value is "60".

Example 1.2. Set rtpengine_disable_tout parameter
...
modparam("rtpengine", "rtpengine_disable_tout", 20)
...

4.3. rtpengine_tout (integer)

Timeout value in waiting for reply from RTP proxy.

Default value is "1".

Example 1.3. Set rtpengine_tout parameter
...
modparam("rtpengine", "rtpengine_tout", 2)
...

4.4. rtpengine_retr (integer)

How many times the module should retry to send and receive after
timeout was generated.

Default value is "5".

Example 1.4. Set rtpengine_retr parameter
...
modparam("rtpengine", "rtpengine_retr", 2)
...

4.5. extra_id_pv (string)

The parameter sets the PV defination to use when the "b" parameter is
used on rtpengine_delete(), rtpengine_offer(), rtpengine_answer() or
rtpengine_manage() command.

Default is empty, the "b" parameter may not be used then.

Example 1.5. Set extra_id_pv parameter
...
modparam("rtpengine", "extra_id_pv", "$avp(extra_id)")
...

4.6. setid_avp (string)

The parameter defines an AVP that, if set, determines which RTP proxy
set rtpengine_offer(), rtpengine_answer(), rtpengine_delete(), and
rtpengine_manage() functions use.

There is no default value.

Example 1.6. Set setid_avp parameter
...
modparam("rtpengine", "setid_avp", "$avp(setid)")
...

5. Functions

5.1. set_rtpengine_set(setid[, setid])
5.2. rtpengine_offer([flags])
5.3. rtpengine_answer([flags])
5.4. rtpengine_delete([flags])
5.5. rtpengine_manage([flags])
5.6. start_recording()

5.1. set_rtpengine_set(setid[, setid])

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.

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().

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
BRANCH_ROUTE.

Example 1.7. set_rtpengine_set usage
...
set_rtpengine_set("2");
rtpengine_offer();
...

5.2. rtpengine_offer([flags])

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.

Meaning of the parameters is as follows:
* flags - flags to turn on some features.
The "flags" string is a list of space-separated items. Each item is
either an individual token, or a token in "key=value" format. The
possible tokens are described below.
+ via-branch=... - Include the "branch" value of one of the
"Via" headers in the request to the RTP proxy. Possible values
are: "1" - use the first "Via" header; "2" - use the second
"Via" header; "auto" - use the first "Via" header if this is a
request, or the second one if this is a reply; "extra" - don't
take the value from a header, but instead use the value of the
"extra_id_pv" variable. This can be used to create one media
session per branch on the RTP proxy. When sending a subsequent
"delete" 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 "rtpengine_delete", 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 "offer" command for a new branch,
and then a "delete" command for the previous branch, which
would otherwise delete the full call, breaking the subsequent
"answer" for the new branch. This flag is only supported by
the Sipwise rtpengine RTP proxy at the moment!
+ asymmetric - flags that UA from which message is received
doesn't support symmetric RTP. Disables learning of endpoint
addresses in the Sipwise rtpengine proxy.
+ force-answer - force "answer", 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.
+ direction=... - 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 "direction=priv direction=pub" if those two logical
network interfaces were called "priv" and "pub" 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.
+ internal, external - shorthand for "direction=internal" and
"direction=external" respectively. Useful for brevity or as
legacy option if the RTP proxy only supports two network
interfaces instead of multiple, arbitrarily named ones.
+ auto-bridge - this flag an alternative to the "internal" and
"external" 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.
+ address-family=... - instructs the RTP proxy that the
recipient of this SDP body expects to see addresses of a
particular family. Possible values are "IP4" and "IP6". For
example, if the SDP body contains IPv4 addresses but the
recipient only speaks IPv6, you would use "address-family=IP6"
to bridge between the two address families.
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 "offer", but not in the "answer".
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.
+ force - 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.
+ trust-address - 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.
+ replace-origin - flags that IP from the origin description
(o=) should be also changed.
+ replace-session-connection - flags to change the session-level
SDP connection (c=) IP if media description also includes
connection information.
+ symmetric - 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.
+ repacketize=NN - 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.
+ ICE=... - controls the RTP proxy's behaviour regarding ICE
attributes within the SDP body. Possible values are: "force" -
discard any ICE attributes already present in the SDP body and
then generate and insert new ICE data, leaving itself as the
only ICE candidates; "force-relay" - discard any "relay" type
ICE attributes already present in the SDP body and then
generate and insert itself as the only ICE "relay" candidates;
"remove" instructs the RTP proxy to discard any ICE attributes
and not insert any new ones into the SDP. The default (if no
"ICE=..." 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 additional
ICE candidate. Other SDP substitutions (c=, m=, etc) are
unaffected by this flag.
+ RTP, SRTP, AVP, AVPF - 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 "SRTP" flag indicates that
SRTP should be used, while "RTP" indicates that SRTP should
not be used. "AVPF" indicates that the advanced RTCP profile
with feedback messages should be used, and "AVP" indicates
that the regular RTCP profile should be used. See also the
next set of flags below.
+ RTP/AVP, RTP/SAVP, RTP/AVPF, RTP/SAVPF - 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 "RTP/SAVPF" has the same effect as
giving the two flags "SRTP AVPF".
+ to-tag - force inclusion of the "To" tag. Normally, the "To"
tag is always included when present, except for "delete"
messages. Including the "To" tag in a "delete" messages allows
you to be more selective about which dialogues within a call
are being torn down.
+ rtcp-mux-demux - if rtcp-mux (RFC 5761) was offered, make the
RTP proxy accept the offer, but not offer it to the recipient
of this message.
+ rtcp-mux-reject - if rtcp-mux was offered, make the RTP proxy
reject the offer, but still offer it to the recipient. Can be
combined with "rtcp-mux-offer" to always offer it.
+ rtcp-mux-offer - make the RTP proxy offer rtcp-mux to the
recipient of this message, regardless of whether it was
offered originally or not.
+ rtcp-mux-accept - 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 "rtcp-mux-offer" to always offer
it.
+ media-address=... - force a particular media address to be
used in the SDP body. Address family is detected
automatically.
+ TOS=... - change the IP TOS value for all outgoing RTP packets
within the entire call in both directions. Only honoured in an
"offer", ignored for an "answer". 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.

This function can be used from ANY_ROUTE.

Example 1.8. rtpengine_offer usage
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") && 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();
...
}

5.3. rtpengine_answer([flags])

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.

See rtpengine_offer() function description above for the meaning of the
parameters.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
FAILURE_ROUTE, BRANCH_ROUTE.

Example 1.9. rtpengine_answer usage

See rtpengine_offer() function example above for example.

5.4. rtpengine_delete([flags])

Tears down the RTPProxy session for the current call.

See rtpengine_offer() function description above for the meaning of the
parameters. Note that not all flags make sense for a "delete".

This function can be used from ANY_ROUTE.

Example 1.10. rtpengine_delete usage
...
rtpengine_delete();
...

5.5. rtpengine_manage([flags])

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.

It can take the same parameters as rtpengine_offer(). The flags
parameter to rtpengine_manage() can be a configuration variable
containing the flags as a string.

Functionality:
* If INVITE with SDP, then do rtpengine_offer()
* 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
rtpengine_answer()
* If ACK with SDP, then do rtpengine_answer()
* If BYE or CANCEL, or called within a FAILURE_ROUTE[], then do
rtpengine_delete()
* If reply to INVITE with code >= 300 do rtpengine_delete()
* If reply with SDP to INVITE having code 1xx and 2xx, then do
rtpengine_answer() if the request had SDP or tm is not loaded,
otherwise do rtpengine_offer()

This function can be used from ANY_ROUTE.

Example 1.11. rtpengine_manage usage
...
rtpengine_manage();
...

5.6. start_recording()

This function will send a signal to the RTP proxy to record the RTP
stream on the RTP proxy. This function is not supported by Sipwise
rtpengine at the moment!

This function can be used from REQUEST_ROUTE and ONREPLY_ROUTE.

Example 1.12. start_recording usage
...
start_recording();
...

6. Exported Pseudo Variables

6.1. $rtpstat

6.1. $rtpstat

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 rtpengine_delete()).

Example 1.13. $rtpstat Usage
...
append_hf("X-RTP-Statistics: $rtpstat\r\n");
...

7. MI Commands

7.1. nh_enable_rtpp
7.2. nh_show_rtpp

7.1. nh_enable_rtpp

Enables a RTP proxy if parameter value is greater than 0. Disables it
if a zero value is given.

The first parameter is the RTP proxy url (exactly as defined in the
config file).

The second parameter value must be a number in decimal.

NOTE: if a RTP proxy is defined multiple times (in the same or
diferente sete), all of its instances will be enables/disabled.

Example 1.14. nh_enable_rtpp usage
...
$ kamctl fifo nh_enable_rtpp udp:192.168.2.133:8081 0
...

7.2. nh_show_rtpp

Displays all the RTP proxies and their information: set and status
(disabled or not, weight and recheck_ticks).

No parameter.

Example 1.15. nh_show_rtpp usage
...
$ kamctl fifo nh_show_rtpp
...

Chapter 2. Frequently Asked Questions

2.1. How do I migrate from "rtpproxy" or "rtpproxy-ng" to "rtpengine"?
2.2. Where can I find more about Kamailio?
2.3. Where can I post a question about this module?
2.4. How can I report a bug?

2.1.

How do I migrate from "rtpproxy" or "rtpproxy-ng" to "rtpengine"?

For the most part, only the names of the functions have changed, with
"rtpproxy" in each name replaced with "rtpengine". For example,
"rtpproxy_manage()" has become "rtpengine_manage()". A few name
duplications have also been resolved, for example there is now a single
"rtpengine_delete()" instead of "unforce_rtp_proxy()" and the identical
"rtpproxy_destroy()".

The largest difference to the old module is how flags are passed to
"rtpengine_offer()", "rtpengine_answer()", "rtpengine_manage()" and
"rtpengine_delete()". Instead of having a string of single-letter
flags, they now take a string of space-separated items, with each item
being either a single token (word) or a "key=value" pair.

For example, if you had a call "rtpproxy_offer("FRWOC+PS");", this
would then become:
rtpengine_offer("force trust-address symmetric replace-origin replace-session-co
nnection ICE=force RTP/SAVPF");

Finally, if you were using the second paramater (explicit media
address) to any of these functions, this has been replaced by the
"media-address=..." option within the first string of flags.

2.2.

Where can I find more about Kamailio?

Take a look at http://www.kamailio.org/.

2.3.

Where can I post a question about this module?

First at all check if your question was already answered on one of our
mailing lists:
* User Mailing List -
http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
* Developer Mailing List -
http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-dev

E-mails regarding any stable Kamailio release should be sent to
and e-mails regarding development
versions should be sent to .

If you want to keep the mail private, send it to
.

2.4.

How can I report a bug?

Please follow the guidelines provided at:
http://sip-router.org/tracker.