Date: Sun, 28 Nov 1999 03:23:56 +0100 (CET) From: Bert Driehuis <bert_driehuis@nl.compuware.com> To: Andrew Gordon <arg@arg1.demon.co.uk> Cc: Roger Hardiman <roger@cs.strath.ac.uk>, isdn@FreeBSD.ORG Subject: Re: Help - I need a login shell over my ISDN line Message-ID: <Pine.BSI.4.10.9911280255540.24425-100000@c1111.nl.compuware.com> In-Reply-To: <Pine.BSF.4.21.9911280048590.5545-100000@server.arg.sj.co.uk>
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On Sun, 28 Nov 1999, Andrew Gordon wrote: > From an I4B point of view, the hard part is not implementing the protocols > themselves, but the infrastructure to support them: Rec. V.120 itself is > only 36 pages, and the code to do HDLC over the B channel already exists > for other other purposes in I4B. The major stuff to write is the tty > handling, call set-up control etc. Errr... I tried doing just that, and found that that something is very different between the B-channel data used for e.g. PPP and for V.120 (that, or all of the V.120 implementations I used for reference don't produce a packet that is formed like the V.120 spec suggests). The data I see when I do a packet dump for an incoming call from a V.120 device doesn't even look like the data format described in recommendation V.120. Maybe I'm overlooking the obvious, though. I tried the rbch driver in one of the attempts (writing a userland driver to access it is, as you say, pretty straightforward). That said, the V.120 protocol is not complicated, so it seems quite appropriate to put it into the kernel and just be another kind of tty, which would make running, say, a getty on the thing trivial. The terminal interface stuff already is in i4b, so all we need is the V.120 glue. > In BISDN, there was a skeleton of this, doing all the work in the > kernel. However, it occurs to me that you might be able to save a lot of > work by doing it as a daemon: you can get all the tty stuff by sitting on > the back end of a pty, and you can probably get most of the ISDN interface > out of the RBCH stuff that /usr/sbin/ppp has recently started using: it > needs to do much the same work (exchanging HDLC frames over the B channel, > dialling calls etc.). I don't recall anything even resembling V.120 in bisdn. There was a terminal thing over the B channel, but that was not V.120 to my recollection. > One thing I am not sure of is whether /usr/sbin/ppp is able to accept > incoming ISDN calls (I haven't been following that work too closely). If > it does, then all the interfaces you need are there to drop in a V.120 > daemon. Well, I hope to be corrected, but I've been staring at packet dumps and the V.120 specs for weeks and sort of found it needs some specific support at the HDLC level. I've been tearing out my hair by the handful over this thing... Cheers, -- Bert Bert Driehuis, MIS -- bert_driehuis@nl.compuware.com -- +31-20-3116119 Hi! I'm a signature virus! Copy me to your .signature and help me spread! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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