RTP Blog Articles & Resources

Asterisk MulticastRTP channels

Posted: September 17, 2011

MulticastRTP Asterisk 1.8: A new RTP engine and channel driver have been added which supports Multicast RTP. The channel driver can be used with the Page application to perform multicast RTP paging. The dial string format is: MulticastRTP/<type>/<destination>/<control…

ZRTP

Posted: May 4, 2009

ZRTP is key exchange protocol designed to enable VoIP devices to agree keys for encrypting media streams (voice or video) using SRTP. ZRTP is defined in an Internet draft https://datatracker.ietf.org/doc/html/draft-zimmermann-avt-zrtp. The authors of ZRTP describe it as “Media…

Kamailio 1.5.x and RTPProxy

Posted: February 15, 2009

This is a basic configuration file for Kamailio (OpenSER) v1.5.x to do VoIP NAT traversal using RTPProxy. valid for Kamailio (OpenSER) 1.5.x # # sample config file to be used with nathelper/rtpproxy # # start RTPProxy with:…

Asterisk sip directrtpsetup

Posted: September 13, 2008

Version Introduced in Asterisk 1.4 Description directrtpsetup=yes is similar to directmedia=, except the audio is redirected in the initial INVITEs rather than reinviting the media a few RTP packets in. Note: canreinvite= was renamed to directmedia= in Asterisk…

About RTPproxy

Posted: June 5, 2007

The RTPproxy is a high-performance software proxy for RTP streams that can work together with SIP Express Router or OpenSER. Originally created for handling NAT scenarious it can also act as a generic media relay as well as…

Asterisk SRTP

Posted: February 13, 2007

General info about SRTP can be found here Asterisk 1.8 has native support for SRTP ! Ref. http://bugs.digium.com/view.php?id=5413 Review board http://reviewboard.digium.com/r/191/, http://lists.digium.com/pipermail/asterisk-dev/2009-January/036029.html You MUST secure signaling because SRTP keys are exchanged in plaintext with SDES. Use TLS –…

RTP Ports

Posted: August 31, 2005

Realtime Transport Protocol. RTP in general is described in RFC 3550. This range is not registered (it never could be, being so broad) but it seems to be somewhat common. See Are there specific ports assigned to RTP?…

Converting RTP to audio

Posted: August 8, 2005

For debugging and troubleshooting it is often desirable to convert a stream of captured RTP packets to playable audio (e.g. a WAV file). A major difficulty in doing this is decoding the many different types of Codecs that…

SRTP

Posted: February 2, 2005

SRTP is a security profile for RTP that adds confidentiality, message authentication, and replay protection to that protocol. It is an action item in the IETF Audio-Video Transport Working Group, where it is an Internet Draft and is…

RTP

Posted: December 30, 2004

RTP opens two ports for communication. One for the media stream (an even port number) and one for control (QoS feedback and media control) – RTCP. The port numbers are not hard defined, it depends very much upon…

Asterisk sip rtptimeout

Posted: September 27, 2004

rtptimeout Terminate call if 60 seconds of no RTP activity when we’re not on hold. Added in June 2004 to CVS-HEAD Example rtptimeout=60 See also >Asterisk sip rtpholdtimeout AbsoluteTimeout Note from MarkSter’s writing on bugtrack: However, I’ve added…

RTP Silence Suppression

Posted: September 27, 2004

Endpoints sending audio as an RTP stream are not required to send packets during silent periods. The capability to stop sending RTP packets during silent periods is known as “Silence Suppression” or VAD (Voice Activity Detection). Whether to…

RTP Symmetric

Posted: July 8, 2004

Symmetric RTP means that the UA uses the same socket/port for sending and receiving the RTP stream. How to set it up is defined in the SDP part of a SIP Invite. An IETF Internet draft for connection-oriented…

Asterisk config rtp.conf

Posted: May 15, 2004

rtp.conf Configuration of Asterisk Real Time Protocol, RTP, media channels. RTP is used for SIP communication. Details On your router you might want to arrange both traffic shaping (QoS) and port forwarding (in case of NAT) for the…