tinc and voip

[Ramses II]

Perry, with what codec are you working?

Try to work with gsm codec or g729 and try again.


Best regards,

Ramses

________________________________________
De: tinc-bounces at tinc-vpn.org [mailto:tinc-bounces at tinc-vpn.org] En nombre
de Perry Couprie
Enviado el: viernes, 06 de agosto de 2010 11:54
Para: tinc at tinc-vpn.org
Asunto: Re: tinc and voip

Thanks for your help :-) 

Here some results.

We did a test with 3 voip phones, the extra traffic was about 600kbits/s.
Then with 2 phones en 1 phone.

The result was that each phone adds 200kbits of tinc traffic.

Then we measured the other interface on wich the phones where connected.

We found that the traffic was 160kbits/s for each phone, sothat the overhead
added by tinc is 25%.

Then we increased compression to 11, at wich we gain no extra compression,
but then we had sounds problems.
Which is logical because voip is already compressed data.

After that we switched of the compression complety and stil the same result.
But a lower system load on the computers.

The final conclusion, the overhead that tinc adds is arround 25%.

I hope that these results are to some use to you.

Greeting from Amsterdam, Perry

ps: Tinc is super, keep up the good work ;-) 


On 08/04/2010 11:08 PM, Guus Sliepen wrote: 
On Wed, Aug 04, 2010 at 10:44:36PM +0200, Perry Couprie wrote:

  
I want to use tinc for voip phones.

How can i measure the overhead ?
Compared to a direct connection ?

How can i reduce overhead when tunneling voip over tinc ?
    

You can use tcpdump to see what packets are sent on an interface and how big
they are. If you want to know latency, just use the ping command.

Tinc will typically add one or a few milliseconds to the latency, and add
around 80 bytes to each packet. You can decrease the size overhead slightly
by
changing the Cipher to something that can handle partial blocks, like
blowfish-ofb for example. This will save you 4.5 bytes on average. You can
also
disable the Digest, this will save you another 4 bytes. So it is probably
not
worth it.

Although in principle tinc adds only a millisecond or so to latency, it is a
user-space program, and the operating system's scheduler can add more
latency if
other programs are running at the same time. So jitter is increased. You can
minimise that by running tinc at a higher priority level (with the
ProcessPriority option), or on Linux, you could in principle run it as a
real-time process with the chrt command from the util-linux package.

  


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