Date: Mon, 27 May 1996 14:53:50 +0900 (JST) From: Michael Hancock <michaelh@cet.co.jp> To: "Louis A. Mamakos" <louie@TransSys.COM> Cc: FreeBSD hackers list <FreeBSD-hackers@freebsd.ORG> Subject: Re: all this talk about routers and all... Message-ID: <Pine.SV4.3.93.960527141028.24993A-100000@parkplace.cet.co.jp> In-Reply-To: <199605270438.AAA11508@whizzo.transsys.com>
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On Mon, 27 May 1996, Louis A. Mamakos wrote: > > Having said that, I don't want people to get the impression that this is a > > FreeBSD vs. Ascend religious war. This about making an ISDN solution with > > FreeBSD. > > > > Ascend just naturally comes up as a benchmark but I don't think > > its necessary for the advocates of Ascend to defend it unless there is > > blatant misinformation posted in this mailing list. > > The major point not really discussed if you're making a comparison is > the fact that you can install V.34 digital modems in an Ascend > solution, and use the same ISDN PRI facility to service both callers > with V.32/V.32bis/V.34 modems, as well as callers with ISDN TAs or > doing synchronous PPP on an 64 kb/s B channel. This would require specialized hardware to do with a PC so I don't think it should be a primary focus. Any software work that is done should probably have some hooks to do this in the future if such hardware were to become available. > > I'm interested in seeing something work with FreeBSD because Net/3 is > > world class code, the radix trie stuff makes routing very efficient. > > Maybe some of van Jacobson's post Net/3 research on large contiguous > > buffers will find it's way into BSD when the cost of RAM becomes less of > > an issue. > > I think the real software issue isn't really the IP forwarding > function which is done pretty well well in FreeBSD. It's likely not > "complicated" routing, as you can cobble stuff together using gated. > This code is pretty mature in the FreeBSD environment. The > difficultly faced is building a ISDN signalling stack to run on the D > channel and talk to the switch. This is where a bunch of emperical > knowledge and experence has made an Ascend platform a good choice in > many environments. I meant to say that the IP forwarding is a non-issue because we have something very good already. I agree that the ISDN knowhow is the biggest value-add that Ascend has and they rightly deserve to profit from it. I think there are a significant amount of people that would like to see a FreeBSD box plus ISDN card solution. > You'll need a Q.920/Q.921 LAPD level-2 protocol to run on the 64kb/s D > channel to carry frame back and forth between the ISDN terminal and > the switch. Certainly the HDLC implementation would be done in the > hardware interface, but there are also some higher-level X.25-like > transport stuff going on in here, too. > > Then you'll need a Q.930/Q.931 level-3 protocol stack for actually > communicating call processing events between the switch and the ISDN > terminal. I believe this is where you'll find a variety of different, > switch-specific implementation differences to deal with. Not to advocate monopolies, but in Japan there is only one (NTT). In the states we have ATT, Northern Telecom, and others. I'm not sure what they have in Europe. I imported a DigiBoard BRI card a while back and it had an NTT configuration built in. I don't know how much work this is. > I think this is where the real challange is. Once you've managed to > get the ISDN call running, you can hack it into your existing PPP > stack without huge differences and away you go. That why I was > interested in what sort of software development kits might be > available, and the status of the drivers. My past experience has been > that there are no real freely available ISDN signalling stacks > available, so either you roll your own from scratch or license it from > someone else. I think the Ascend gurus were ex-hayes people and have been working with digital technologies for a long time before they started Ascend so it would probably be difficult to find people that can match their experience. Greg and a group of guys in Germany have been working with other ISDN cards so it would probably be a good idea to look at what they've done so far. -mike hancock
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