tinc and voip

[Perry Couprie]

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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>    

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