[Freeswitch-users] IAX Trunking

[David Villasmil]

Very interesting... We're doing about 40 calls per trunk so i'm saving
a lot by not sendind all ip headers. Plus i'm using g.729 and g.723,
which cosume low bandwidth.

But what you say about using 120ms instead of the usual 20/30 is very
interesting indeed. I must try that.

thanks a lot.

d

On 6/18/08, Daniel Swarbrick <freeswitch at pressure.net.nz> wrote:
> You would probably save more bandwidth by switching to a lower bandwidth
> codec. IAX trunking only reduces bandwidth wasted by IP headers of
> individual RTP streams, by combining multiple small RTP packets (from
> different RTP streams) into larger packets. It does not do anything
> magical to the RTP data itself.
>
> This is only useful if all those RTP streams are going to the same
> destination of course.
>
> With SIP, you could try increasing the packetization delay from the
> usual 20 or 30ms up to something like 120ms. This means more RTP data
> gets packed into a single packet, and hence fewer of them are required
> in any given RTP stream. It does have side effects however - if your
> link is not reliable enough, and you lose the occasional packet, that's
> 120 ms of audio you just lost - probably quite noticeable. Depending on
> the jitter buffer being used, it may also want at least a few packets in
> the buffer before it starts playing audio. If 3 x 120ms packets is what
> it wants, there will be a 360ms delay at the start of the call before
> the first audio is heard.
>
> On Wed, 2008-06-18 at 11:36 +0200, David Villasmil wrote:
>> Thanks for the reply,
>>
>>      I was just curious because we have many gws doing IAX trunking to
>> save bandwidth as the gws are behind ADSL.
>>
>> Thank you again.
>>
>> d
>>
>> On Wed, Jun 18, 2008 at 11:18 AM, David Knell <dave at 3c.co.uk> wrote:
>>         Hi David,
>>
>>         I believe the answer to be 'no' - the workaround we use is to
>>         run * and FS on the same
>>         box, and have * act as an IAX<->SIP gateway.  Works fine, but
>>         probably restricts capacity
>>         in the limit.
>>
>>         Cheers --
>>
>>         Dave
>>         > Can FS do IAX Trunking?
>>         >
>>         > David
>>         >
>>         >
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>>         --
>>         David Knell, Director, 3C Limited
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>>         http://www.3c.co.uk
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