The papers talk about transport protocol for signaling, not media/RTP. I didn't hear of anyone who does RTP over TCP neither. I doubt even that the performance is a primary reason behind that, for media over TCP the client link must be virtually packet-loss free (due to TCP retransmissions), while over UDP sometimes up to 5% packet loss can be tolerated. TCP was not designed as transport for real-time media :-)
On 06/08/2012 12:35 AM, Yang Hong wrote:
Hello.
SIP over TCP would reduce server performance significantly when compared with SIP Over UDP.
Please read the following two papers. Combining RTP proxy with SIP over TCP would degrade SIP server performance even worse.
http://www.cs.columbia.edu/~hgs/papers/Shen1008_TLS.pdf
The Impact of TLS on SIP Server Performance
"Securing SIP is accomplished by using TLS instead of UDP as the transport protocol. We show that using TLS can reduce performance by up to a factor of 17 compared to the typical case of SIP-over-UDP."
"Network operators considering deploying SIP over TLS will need to consider the extra resources required to provide the same service quality as would be the case with UDP."
http://www.cs.columbia.edu/~hgs/nossdav/2007/files/file-27-session5-paper1-n...
Evaluating SIP Proxy Server Performance
"The next most signi cant performance feature is which transport protocol is used, TCP or UDP. Using TCP can reduce performance anywhere from 43 percent (the stateful proxying scenario with authentication) to 65 percent (state-less proxying without authentication).
Best regards,
Yang
Date: Thu, 7 Jun 2012 13:36:39 +0200 From: miconda@gmail.com To: sr-users@lists.sip-router.org Subject: Re: [SR-Users] Looking for RTP Proxy in TCP
Hello,
On 6/4/12 7:14 PM, Austin Einter wrote:
Hi All Now I am using Kamailio 3.1.5 and RTP proxy 1.1. Looks both are compatible and working fine.
The RTP Proxy basically sends/receives RTP packets over UDP. Is there any RTP Proxy available that does send/receive of RTP packets over TCP and also should be compatible with Kamailio 3.1.5.
If you have any information in this regard, kindly share.
RTP itself is specified over UDP, also I am not aware of any SIP phone doing RTP over TCP.
MSRP is a mechanism specified for sending message streams over TCP, we have a module for that, but I guess is not exactly what you are
looking for:
http://kamailio.org/docs/modules/devel/modules/msrp.html
Maybe based on it you can implement one that fits your needs.
Cheers, Daniel