Date: Thu, 3 Sep 1998 20:52:05 +0200 (CEST) From: torstenb@vmunix.org (Torsten Blum) To: leo@wau.mis.ah.nl Cc: freebsd-isdn@FreeBSD.ORG Subject: Re: called-back, rejects and auto hangup Message-ID: <m0zEeUH-00069xC@onizuka.vmunix.org> References: <19980902220352.22500@wau.mis.ah.nl> <19980903162118.27170@wau.mis.ah.nl>
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In freebsd-isdn you write:
>> I think Gary said it already: the remote calls back almost immediately; long
>> before the local call to the remote is disconnected - this can be seen
>> from the traces you sent me in private mail.
>Can you tell me why you think this is the case?
There are point-to-point and point-to-multipoint isdn lines.
(the German Telekom calls them "Anlagenanschluss" and "Mehrgeraeteanschluss")
The first one only supports one ISDN terminal equipment (phone, router, TA,
isdn card etc) while a point-to-multipoint line supports up to 8 TE's.
When a incomming call is arrives on a isdn point-to-multipoint line, all
connected ISDN TE's are informed about the call. When an TE rejects the
call ("call rejected", "user busy" etc) it's still possible for other TE's
to accept the call. So the isdn switch has to wait till all remaining
TE's signalled the switch wether they want to accept the call or not. If there's
no response from the other TE's, the call will be rejected.
Imagine the case where two ISDN phones are connected to an ISDN line. The first
one is in use, the other one is free. When an incomming call arrives, the
first ISDN phone will reject the call with "user busy", but the second one
can still accept the call.
On a point-to-point line you don't have this problem - since there is only
one ISDN equipment and a reject will take affect immediately.
Well, this applies to euro isdn. Dunno about ISDN in the US, but that's not
what we're talking about. It's too different compared to what we have here
in europe ;-)
>> The only help for this situation is, to delay the callback from the remote
>> for a time it takes to disconnect the local to the remote.
No, this is not the only help, it's not even acceptable - IMHO.
ISDN equipment that supports "ISDN callback" has to life with those call
collisions.
More than 5 years ago we already used ISDN-callback here in germany - with
different "router packages" for DOS (KA9Q with ISDN drivers and other,
custom made, software) for example.
It's quite interesting to see that esp. ISDN-routers from the US
(Ascend Pipeline/Max) can't handle this. There are other ISDN routers
(Bintec for example) which do not have any problem with call collisions
during isdn-callback.
I work this this equipment every day and have some equipment at home and
access to even more equipment at work. If anyone (Helmuth ?) want's to test
isdn callback (or anything else), I'm more than happy to provide access to
the equipment.
-tb
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