1RTPPROXY(8) RTPPROXY(8)
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6 rtpproxy - RTP (Real-time Transport Protocol) Proxy Server
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9 rtpproxy [-?] [-2] [-f] [-v] [-R] [-l addr1[/addr2]] [-6 addr1[/addr2]]
10 [-s ctrl_socket] [-t tos] [-p pidfile] [-T max_ttl]
11 [-r rdir [-S sdir]]
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15 rtpproxy is a symmetric RTP proxy designed to be used in conjunction
16 with the SIP Express Router (SER) or any other SIP proxy capable of
17 rewriting SDP bodies in SIP messages that it processes.
18 The main purpose of rtpproxy is to make the communication between SIP
21 user agents behind NAT(s) (Network Address Translator) possible. Sever‐
22 al cases exists when direct end-to-end communication is not possible
23 and RTP streams have to be relayed through another host. Rtpproxy can
24 be used to setup such a relaying host.
25 When two listen interfaces have been specified using the command line
28 parameters described below then rtpproxy will enter so called bridging
29 mode. In briding mode rtpproxy forwards RTP packets received on one in‐
30 terface to the other interface and vice versa. This mode can be used to
31 forward RTP packets between networks without direct network level con‐
32 nectivy (provided that the host running rtpproxy has one interface in
33 both of them). One particular application of bridging mode is IPv4/IPv6
34 traversal of RTP packets.
35 When instructured by SER rtpproxy can also record the entire RTP ses‐
38 sion in a file on a local harddisk or play a pre-recorded file to the
39 user agent (so called Music-on-Hold).
40
43 -? Show summary of options.
44 -2 Send every RTP packet twice in sessions that use low-bitrate
47 codecs. Only packets that are smaller than 128 bytes will be
48 sent twice. This option can improve audio quality on lossy
49 links.
50 -f Rtpproxy will stay in foreground mode if this option is set.
53 -v Show version of program.
56 -l addr1[/addr2]
59 IPv4 listen IP address(es). You can specify either one or two
60 addresses. If two addresses have been specified then rtpproxy
61 will work in bridging mode.
62 -6 addr1[/addr2]
65 IPv6 listen IP address(es). You can specify either one or two
66 addresses. If two addresses have been specified then rtpproxy
67 will work in bridging mode.
68 -s ctrl_socket
71 This parameter configures rtpproxy control socket. The control
72 socket is used by nathelper module of SER to create/modi‐
73 fy/delete RTP sessions to be relayed. Format of ctrl_socket is
74 <type>:<socket>. Following types are supported:
75 ·
78 udp: Create UDP control socket. In this mode RTPProxy will
79 listen on UDP for control messages from SER/nathelper.
80 Example: -s udp:127.0.0.1:9000
82 IP address can be '*' in which case rtpproxy will listen on
84 all local interfaces. If omitted port 22222 is used.
85 Note
88 RTPProxy control protocol has no built-in security mecha‐
90 nisms. Make sure that you protect the listening IP and port
91 properly when using RTPProxy with UDP control socket.
92 ·
95 udp6: Create IPv6 UDP control socket. In this mode RTPProxy
96 will listen on UDP/IPv6 for control messages from
97 SER/nathelper.
98 Example: -s udp6:::1:9000
100 ·
102 unix: Create UNIX domain socket for control interface. In
103 this mode SER/nathelper and RTPProxy must be running on the
104 same host. This is the default setting for both SER/nathelper
105 and rtpproxy.
106 Example: -s unix:/var/run/rtpproxy.sock
108 Default value is /var/run/rtpproxy.sock.
110 -t tos Set this ToS (Type of Service) in outgoing packets. Default val‐
112 ue is 0xB8.
113 -r rec_dir
116 Directory where recorded RTP sessions will be stored.
117 -S spool_dir
120 Spool directory for RTP sessions being recorded. The file will
121 be moved to directory configured in-r option after the session
122 finishes.
123 -R Do not record RTCP when recording an RTP session. This option is
126 disabled (rtpproxy will record RTCP) by default.
127 -p pid_file
130 This parameter configures the name of the file where PID of run‐
131 ning rtpproxy will be stored. Default is/var/run/rtpproxy.pid.
132 -T max_ttl
135 Limit the maximum TTL (Time To Live) of outgoing IP packets to
136 the value of max_ttl.
137
140 When SER receives an INVITE request, it extracts Call-ID from it and
141 communicates it to rtpproxy via Unix domain socket or UDP. Rtproxy
142 looks for an existing session with such Call-ID. If the session exists
143 it returns UDP port for that session, if not, then it creates a new
144 session, binds to a first empty UDP port from the range specified at
145 the compile time and returns number of that port to a SER. After re‐
146 ceiving reply from the proxy, SER replaces media ip:port in the SDP to
147 point to the proxy and forwards request as usually.
148 When SER receives a non-negative SIP reply with SDP it again extracts
151 Call-ID from it and communicates it to the proxy. In this case the
152 proxy does not allocate a new session if it doesn't exist, but simply
153 performs a lookup among existing sessions and returns either a port
154 number if the session is found, or error code indicating that there is
155 no session with such id. After receiving positive reply from the proxy,
156 SER replaces media ip:port in the SIP reply to point to the proxy and
157 forwards reply as usually.
158 After the session has been created, the proxy listens on the port it
161 has allocated for that session and waits for receiving at least one UDP
162 packet from each of two parties participating in the call. Once such
163 packet is received, the proxy fills one of two ip:port structures asso‐
164 ciated with each call with source ip:port of that packet. When both
165 structures are filled in, the proxy starts relaying UDP packets between
166 parties.
167 The proxy tracks idle time for each of existing sessions (i.e. the time
170 within which there were no packets relayed), and automatically cleans
171 up a sessions whose idle times exceed the value specified at compile
172 time (60 seconds by default).
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176 /usr/sbin/rtpproxy
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180 This program is licensed under the BSD license. See COPYING file in the
181 rtpproxy sources for details.
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185 The latest version of this program can be found at http://ftp.ip‐
186 tel.org/pub/rtpproxy: http://ftp.iptel.org/pub/rtpproxy.
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190 ser(8).
191
194 Maxim Sobolev.
195 Feb 20, 2006 RTPPROXY(8)