Provided by: rtpproxy_1.2.1-2.2ubuntu1_amd64 
NAME
rtpproxy - RTP (Real-time Transport Protocol) Proxy Server
SYNOPSIS
rtpproxy [-?] [-2] [-f] [-v] [-R] [-l addr1[/addr2]] [-6 addr1[/addr2]] [-s ctrl_socket] [-t tos]
[-p pidfile] [-T max_ttl] [-r rdir [-S sdir]] [-m min_port] [-M max_port] [-u uname[:gname]]
[-F] [-i] [-n timeout_socket] [-P] [-a] [-d log_level[:log_facility]]
DESCRIPTION
rtpproxy is a symmetric RTP proxy designed to be used in conjunction with the SIP Express Router (SER) or
any other SIP proxy or SIP B2BUA capable of rewriting SDP bodies in SIP messages that it processes.
The main purpose of rtpproxy is to make the communication between SIP user agents behind NAT(s) (Network
Address Translator) possible. Several cases exists when direct end-to-end communication is not possible
and RTP streams have to be relayed through another host. Rtpproxy can be used to setup such a relaying
host.
When two listen interfaces have been specified using the command line parameters described below then
rtpproxy will enter so called bridging mode. In briding mode rtpproxy forwards RTP packets received on
one interface to the other interface and vice versa. This mode can be used to forward RTP packets between
networks without direct network level connectivy (provided that the host running rtpproxy has one
interface in both of them). One particular application of bridging mode is IPv4/IPv6 traversal of RTP
packets.
When instructured by SER rtpproxy can also record the entire RTP session in a file on a local harddisk or
play a pre-recorded file to the user agent (so called Music-on-Hold).
OPTIONS
-?
Show summary of options.
-2
Send every RTP packet twice in sessions that use low-bitrate codecs. Only packets that are smaller
than 128 bytes will be sent twice. This option can improve audio quality on lossy links.
-f
Rtpproxy will stay in foreground mode if this option is set.
-v
Show version of program.
-l addr1[/addr2]
IPv4 listen IP address(es). You can specify either one or two addresses. If two addresses have been
specified then rtpproxy will work in bridging mode.
-6 addr1[/addr2]
IPv6 listen IP address(es). You can specify either one or two addresses. If two addresses have been
specified then rtpproxy will work in bridging mode.
-s ctrl_socket
This parameter configures rtpproxy control socket. The control socket is used by nathelper module of
SER to create/modify/delete RTP sessions to be relayed. Format of ctrl_socket is <type>:<socket>.
Following types are supported:
• udp: Create UDP control socket. In this mode RTPProxy will listen on UDP for control messages
from SER/nathelper.
Example: -s udp:127.0.0.1:9000
IP address can be ´*´ in which case rtpproxy will listen on all local interfaces. If omitted port
22222 is used.
Note
RTPProxy control protocol has no built-in security mechanisms. Make sure that you protect the
listening IP and port properly when using RTPProxy with UDP control socket.
• udp6: Create IPv6 UDP control socket. In this mode RTPProxy will listen on UDP/IPv6 for control
messages from SER/nathelper.
Example: -s udp6:::1:9000
• unix: Create UNIX domain socket for control interface. In this mode SER/nathelper and RTPProxy
must be running on the same host. This is the default setting for both SER/nathelper and
rtpproxy.
Example: -s unix:/var/run/rtpproxy.sock
Default value is /var/run/rtpproxy.sock.
-t tos
Set ToS (Type of Service) in the outgoing UDP packets to this value. Default value is 0xB8.
Setting this parameter to -1 disables setting ToS resulting in operating system default ToS being
used instead.
-r rec_dir
Directory where recorded RTP sessions will be stored.
-S spool_dir
Spool directory for RTP sessions being recorded. The file will be moved to directory configured
in -r option after the session finishes.
-R
Do not record RTCP when recording an RTP session. This option is disabled (rtpproxy will record
RTCP) by default.
-p pid_file
This parameter configures the name of the file where PID of running rtpproxy will be stored.
Default is /var/run/rtpproxy.pid.
-T max_ttl
Limit the maximum TTL (Time To Live) of outgoing IP packets to the value of max_ttl.
-m min_port
Set lower limit on UDP ports range that the RTPproxy uses for RTP/RTCP sessions to min_port.
Default is 35000.
-M max_port
Set upper limit on UDP ports range that the RTPproxy uses for RTP/RTCP sessions to max_port.
Default is 65000.
-u uname[:gname]
Switch RTPproxy to UID identified by the uname and optional GID identified by gname when proxy is
up and running.
-F
By default the RTPproxy will warn user if running as superuser (UID 0) in local control mode and
refuse to run in remote control mode at all. This switch removes the check.
-i
Enable independent timeout mode. By default, a timeout (which results in automatic destruction of
the session) can only occur if no RTP packets are received on any of the session´s ports. This
option if set varies that behaviour, such that a timeout will occur if packets are still being
received on one port but not the other. The option should be used with caution since in some
cases it´s perfectly fine to have packets coming from only one side of conversation (i.e. when
the second party has muted its audio).
-n timeout_socket
This parameter configures the optional timeout notification socket. The socket should be created
by another application, preferably before starting rtpproxy. For those sessions where the timeout
mechanism is enabled, notifications are sent on this socket if the session times out.
Example: -n unix:/var/run/rtpproxy_timeout.sock
There is no default value, notifications are not sent and not permitted unless a value is
specified explicitly.
-P
Record sessions using PCAP file format instead of non-standard ad-hoc format. The PCAP format,
which is the de-facto standard for packet capturing software, has the advantage of being
compatible with numerous third-party tools and utilities, such as Wireshark (Ethereal) for
example. The drawback of PCAP is sligtly larger overhead (extra 12 bytes for every saved RTP
packet for IPv4). Also, recording IPv6 sessions in PCAP format is not supported at the moment.
-a
Record all sessions going through the RTPproxy unconditionally. By default the RTPproxy requires
call control software (i.e. SER, OpenSER or B2BUA) to enable recording explicitly on per-session
basis by sending appropriate record command.
-d log_level[:log_facility]
This parameter configures the verbosity level of the log output. Possible log_level values in the
order from the most verboe to the least verbose are: DBUG, INFO, WARN, ERR and CRIT.
The optional log_facility parameter sets syslog(3) facility assigned to log messages.
Example: -d WARN:LOG_LOCAL5
The default level in foreground mode is is DBUG, in background - WARN and facility is LOG_DAEMON.
HOWITWORKS
When SER receives an INVITE request, it extracts Call-ID from it and communicates it to rtpproxy via Unix
domain socket or UDP. Rtproxy looks for an existing session with such Call-ID. If the session exists it
returns UDP port for that session, if not, then it creates a new session, binds to a first empty UDP port
from the range specified at the compile time and returns number of that port to a SER. After receiving
reply from the proxy, SER replaces media ip:port in the SDP to point to the proxy and forwards request as
usually.
When SER receives a non-negative SIP reply with SDP it again extracts Call-ID from it and communicates it
to the proxy. In this case the proxy does not allocate a new session if it doesn´t exist, but simply
performs a lookup among existing sessions and returns either a port number if the session is found, or
error code indicating that there is no session with such id. After receiving positive reply from the
proxy, SER replaces media ip:port in the SIP reply to point to the proxy and forwards reply as usually.
After the session has been created, the proxy listens on the port it has allocated for that session and
waits for receiving at least one UDP packet from each of two parties participating in the call. Once such
packet is received, the proxy fills one of two ip:port structures associated with each call with source
ip:port of that packet. When both structures are filled in, the proxy starts relaying UDP packets between
parties.
The proxy tracks idle time for each of existing sessions (i.e. the time within which there were no
packets relayed), and automatically cleans up a sessions whose idle times exceed the value specified at
compile time (60 seconds by default).
FILES
/usr/sbin/rtpproxy
LICENSE
This program is licensed under the BSD license. See COPYING file in the rtpproxy sources for details.
AVAILABILITY
The latest version of this program can be found at http://www.rtpproxy.org/.
SEEALSO
ser(8).
AUTHOR
Maxim Sobolev
Author.
COPYRIGHT
CopyrightCopyright © 2006 janakj
[FIXME: source] Jun 16, 2008 RTPPROXY(8)