Date: Thu, 15 Jun 2000 18:00:29 +0200 From: Gerhard Sittig <Gerhard.Sittig@gmx.net> To: freebsd-isdn@FreeBSD.ORG Subject: Re: reject Message-ID: <20000615180028.M9883@speedy.gsinet> In-Reply-To: <200006142105.XAA38649@peedub.muc.de>; from garyj@peedub.muc.de on Wed, Jun 14, 2000 at 11:05:48PM %2B0200 References: <200006142049.WAA00914@cat.turbocat.de> <200006142105.XAA38649@peedub.muc.de>
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On Wed, Jun 14, 2000 at 23:05 +0200, Gary Jennejohn wrote:
> David Wetzel writes:
> >> From: Gary Jennejohn <garyj@peedub.muc.de>
> >
> >> Wait a second. If you have 2 devices on an S0 bus responding
> >> to the same number then I would expect a race condition to
> >> result. It doesn't seem reasonable to me to expect isdnd to
> >> reject calls for other devices on the bus. In fact, I would
> >> suspect that it would violate some standard. IMHO that's a
> >> function which a PBX should carry out.
> >
> >No. i4b/the anwering machine should answer the call and hang
> >up.
Accepting the call with an AM and immediately hanging up is one
solution. But regarding immediate _rejection_ this *is* possible
(and we've been through that a few years ago in another project).
AFAICT (I'm not an communications expert and might use the wrong
terms, but you surely get the idea) an incoming call is just
signalled to the internal bus(ses). *Every* device has the
opportunity to
- ignore the call ("not mine, I don't care")
- accept the call ("I _could_ handle this" in the meaning of "I
apply for getting this job"!)
- reject the call ("not for me _and_for_nobody_else_ I can think
of")
There's a chance for multiple devices to accept the signalled
call (not to get them, that's something the PBX will handle due
to the packets' serialisation on the bus). And I consider this
to be a feature. Think of signalling a voice call on many phones
and have the user decide where to pick up the receiver. Or have
a few remote control computers sit there and have them choose
whether it's their working hour and whom they respond to. That's
where they can share a MSN quite well.
To summarize: There is a rejection message a device can emit
speaking for *everyone* on the bus. It's just rarely used and
might not be available at a userland command level. And it's
very rare cases where this message is appropriate.
> Oh, the _answering machine_ handles it. Now I understand. But I
> had the impression from his mail that he wanted isdnd to reject
> calls for other devices on the S0 bus, which can't work AFAICT.
See above. We really suffered from this and it took quite some
time to find out there's even such a feature and it's used in the
software. Actually this tough rejection completely prevented the
neighbour machines from getting any call (although they *saw*
them). But this sounds like it absolutely is what's wanted here.
(Mis)using the AM will accept the connection for a moment and
lead to cost and a blocked B channel (i.e. data channel in
contrast to the rejection completely handled in D channel
messages). This should be considered -- unless one wants to
"punish" the to be banned caller.
virtually yours 82D1 9B9C 01DC 4FB4 D7B4 61BE 3F49 4F77 72DE DA76
Gerhard Sittig true | mail -s "get gpg key" Gerhard.Sittig@gmx.net
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