[Asterisk-Users] IAX2 Channels & Bandwidth

[Michael Graves]

On Sat, 15 Jan 2005 19:58:15 -0000, Derek Conniffe wrote:

>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.

It makes perfect sense that you have such troubles. Using G.711 each
call will use 64k on each leg, thats 64k inbound and outboard. With
overheads I've seens this often averages up to 80k per leg. 

64k x 5 = 320k outbound
80k x 5 = 400k outbound

You don't have enough bandwidth. Your switch ti iLBC should take care
of this, although that cost of some call quality.

I too use VoipJet. I've been very happy with their service. I upgraded
my DSL to 768k upload in order to get around just the bandwidth issue
that you have seen.

Michael

>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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--
Michael Graves                           mgraves at pixelpower.com
Sr. Product Specialist                          www.pixelpower.com
Pixel Power Inc.                                 mgraves at mstvp.com

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