[SR-Users] Looking for RTP Proxy in TCP

[Aft nix]

On Fri, Jun 8, 2012 at 2:18 PM, Andrew Pogrebennyk
<apogrebennyk at sipwise.com> wrote:
> 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-nahum.pdf
>>
>> 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 at gmail.com
>>> To: sr-users at 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
>>>
>
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These things are wild attempt to escape some telcos blocking UDP
packets suspecting VOIP for pushing their own IP telephony product.
Sometimes even encrypted media is blocked because their DPI use some
heuristic methods for detecting media packet. Like payload size in
different codecs can give a clue about the packet. Although This bites
in the a** of whole "net neutrality" campaign, They don't bother.

These practices force VOIP providers for "obsfucation" techniques for
escaping the DPI. Interesting thing is i know of some situation when
they blocked VPN because people were using it to make VOIP calls. Now
you can use VPN for other purposes!

Some telco even went to lengths to block UDP "streams" by calculating
some "threshold" bandwidth consumption.

The DPI vendors are making a business case, but it all comes at price
of making Provider inventing non standard schemes to do ordinary
stuffs.

Media over TCP is the worst idea in the history of worst ideas. But
sometimes you have no choice.

I guess big web companies should push these telcos who are afraid of
losing their traditional TDM market share and going at lengths to stop
media over IP.

Cheers.

-- 
-aft