[Asterisk-Users] IAX2 Channels & Bandwidth

[Derek Conniffe]

Hi all,

I'm using VOIPJET to make international calls with an IAX2 connection
between my local asterisk server and their server(s).

At times I seem to have a problem if 5 or more international calls are made
at once - I'm on a 1024kbps download and 256kbps upload DSL line (only the
asterisk server uses this DSL line).  Today I switched the codec from ulaw
to ilbc in an attempt to lower the bandwidth requirements.

I have read many times that IAX2 has a signaling overhead (30 or 40kbps?)
and then every channel uses the codec bandwidth.

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.

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)

I'd be very keen to hear from anyone who has knowledge on using IAX2 to
route multiple outgoing calls.

Thanks very much,

Derek Conniffe

PS I notice that if three international calls are being made and I run "iax2
show channels" at the CLI prompt I can see three IAX2 channels being shown:

Channel               Peer             Username    ID (Lo/Rem)  Seq (Tx/Rx)
Lag      Jitter  JitBuf  Format
IAX2/voipjet/1        216.118.117.46   xx         00001/00004  00148/00150
00120ms  0016ms  0064ms  ilbc
IAX2/voipjet/2        216.118.117.46   xx         00002/00081  00130/00126
00150ms  0054ms  0065ms  ilbc
IAX2/voipjet/3        216.118.117.46   xx         00003/00071  00230/00232
00120ms  0015ms  0065ms  ilbc

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