Re: [hylafax-users] race condition

[Aidan Van Dyk <aidan@xxxxxxxx>]

* Chris Weiss <cweiss@xxxxxxxxx> [080214 12:38]:
> On Thu, Feb 14, 2008 at 11:29 AM, Lee Howard <faxguy@xxxxxxxxxxxxxxxx> wrote:
> >  However, you may be able to work-around the issue by configuring
> >  Asterisk or the Diva server to allocate channels and/or modems in a
> >  "round-robin" fashion rather than always landing on the same
> >  channels/modems.
> 
> most defaults are to answer starting with the first free channel and
> do dial out starting with the last free channel.  main reason for this
> is the prevent picking up the phone to dial and accidentally answering
> a call, on a PRI you'd have to have 22 busy lines before that becomes
> possible where as a round-robin it's possible every time.  seems a
> pause is the best option, unless the PRI is only used for answering
> and not dialing

Sure, but with that you hit the problem Lee described.  So you have to
pick your pain when using an "AT" style interface to your PRI.

1) Always top-down/bottom-up
   You have the problem of the "RING/CALLID/RING/CALLID/RING" sequence
   when the 1st call disconnects quickly and a 2nd comes in quickly.
   There is no way for faxgetty to really know that that's 2 separate
   calls.  If you can't control the "timing" between calls, you're going
   to have these problems with this setup.

2) round-robin
   You have the problem of glare, where both sides pick the same channel
   to use at the same time.
   But if you can control your "busy" handling (like you can with both
   HylaFAX and Asterisk), you can pretty much make this problem a
   "non-issue" by making sure your jobs retry enough times for busy
   signals in your situation, and making asterisk roll over nicely on
   busy signals for incoming faxes.

-- 
Aidan Van Dyk                                             aidan@xxxxxxxx
Senior Software Developer                          +1 215 825-8700 x8103
iFAX Solutions, Inc.                                http://www.ifax.com/

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