[Asterisk-Users] IAX2 Channels & Bandwidth

[Leif Madsen]

On Sat, 15 Jan 2005 19:58:15 -0000, Derek Conniffe <derek at rivertower.ie> wrote:
> I have read many times that IAX2 has a signaling overhead (30 or 40kbps?)
> and then every channel uses the codec bandwidth.

This is true if you are using IAX2 trunking.  This can be enabled with
trunk=yes in your peer  configuration.  The other end must also
support the trunking as well.

> Does Asterisk automatically know to use one overhead bandwidth management
> for IAX2 remote peer gateways?  I'm afraid of the possibility that I have
> not configured the VOIPJET IAX2 link correcty and that I'm making lots of
> single connections to them and thus duplicating the IAX2 overhead bandwidth
> requirement for every call?  I don't know though - The next steps are to 1)
> hear back for you ;) and 2) put in mrtg bandwidth logging to get an idea of
> my usage.

It does not do it automatically.  As I mentioned previously, you must
enable it via the trunk command.  Having never used VoipJet however,
I'm not sure if they allow it or not.  I would assume that if they are
using Asterisk they would want it enabled?

Your next step should be to turn on something like Ethereal or
tethereal (or tcpdump, etc..) and just look at the network traffic. 
Filter it for IAX2 traffic and just look to see what is going on.  If
you've never used it, LEARN IT!!!

> I have VOIPJET setup as a peer in iax2.conf and then my extensions.conf dial
> command just looks like: exten => _00.,2,Dial,IAX2/xx at voipjet/011${EXTEN:2}
> ; Make Call - (In Ireland we use 00 as the International prefix but US
> people (and VOIPJET) like 011 as the international dial prefix)

You should be able to set it up so that you have a peer definition in
your iax.conf file and use the provider like so:

exten => _9NXXNXXXXXX,1,Dial(IAX2/provider/${EXTEN:1})  <-- note that
the "provider" should be replaced with whatever you name the peer
definition in iax.conf.

HTH,
Leif Madsen.
http://www.leifmadsen.com