Date: Thu, 3 Sep 1998 23:23:29 +0200 (CEST) From: torstenb@vmunix.org (Torsten Blum) To: leo@wau.mis.ah.nl (Leo Weppelman) Cc: freebsd-isdn@FreeBSD.ORG Subject: Re: called-back, rejects and auto hangup Message-ID: <m0zEgqn-00069xC@onizuka.vmunix.org> In-Reply-To: <19980903224845.15992@wau.mis.ah.nl> from Leo Weppelman at "Sep 3, 98 10:48:45 pm"
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Leo Weppelman wrote: > >From what I know, the machine at work is directly connected to a dutch telecom > (PTT) connection. We have one main-number & 4 MSN's. Is this multi-point? Sounds like point to multipoint. > The makes me think multipoint is most common. At home I have an A/B adapter > connected to the NT1 (modem & cheapo phone) and my Atari with Teles... It's common for single BRI's - in case of PBX and other equipment that uses >1 BRI it's often point-to-point > But shouldn't at least one channel be free for such a collision to happen? yes - usually. (call-waiting makes it more complicated, but let's ignore that here) In the point-to-multipoint case you should have a free 2nd B-channel on the BRI line that receives the call-back. Let's call the machines "A" and "B". A calls B, B sees the SETUP message in the D-Channel and rejects the call. The B-Channel is not yet established but "reserved" (it's a bit more complicated, but that way it's easier to explain ;-). When B rejects the call and calls back. But as I wrote earlier it takes some time till A receives that call-reject message from the switch. At that time, B already called A. Since one B-Channel is still reserved and can not be used (the reject has not yet been received by A) yet, another B-Channel is needed. if the 2nd B-Channel is not free, the callback fails. (call-waiting complicates things here too, but let's just ignore that for now). In this case, B should just wait a few secs and try again - otherwise callback won't work if you already use one b-channel. -tb To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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