tinc and voip

[Guus Sliepen]

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.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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