Date: Thu, 14 Mar 96 9:06:28 MET From: Greg Lehey <lehey.pad@sni.de> To: cmlambertus@ucdavis.edu (Chris Lambertus) Cc: hackers@freebsd.org (Hackers; FreeBSD), jkrause.padg@sni.de Subject: Re: Microsoft "Get ISDN"? Message-ID: <199603140810.JAA25804@nixpbe.pdb.sni.de> In-Reply-To: <199603132328.PAA02191@cygnus.ucdavis.edu>; from "Chris Lambertus" at Mar 13, 96 3:27 pm
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> >> Now, the idea of configuring the ISDN for a "Windows-based PC" sounds like >> typical Microsoft-speak, but is the provisioning process as difficult as MS >> makes it out to be if I don't go through them? > > No. It is very simple to get an ISDN line. You have what boils down > to two options. One BRI (64Kbit) or two bonded BRI's (128Kbit). You > call the phone company, and they will come in and install the line and > give you the SPID numbers your ISDN modem needs to connect properly. In fact, a Basic Rate Interface (BRI) comprises two B channels (64 kb/s), used for data transfer, and one D channel (16 kb/s), used for signalling. You *can* bond the B channels (though not in the current FreeBSD implementations), but normally they're used for two independent connections. Some telcos offer single B channels, but they're castrated BRIs. >> Also, I just checked FreeBSD's ISDN support as of -current, and it only >> supports two "Dr. Neuheus" brand internal ISDN adapters! Does this mean >> that, given a choice, I should ask for an external ISDN modem? If so, >> which brands are recommended for use with FreeBSD? Also, am I correct to >> assume that an external ISDN modem is treated just like a regular >> Hayes-compatible modem, or does it require special kernel support? -current still only supports the Dr. Neuhaus boards, but software is available for other boards. Juergen Krause (one of the original authors) and I are talking about it, and others are doing things, but Juergen wants to tidy up the software before including it in the tree. Probably the boards of choice are the Teles/Creatix S0 boards (S0 is a German term for BRI), which over here cost in the order of $100 and handle both B channels, so you have a potential of 16 kbyte/s transfer rate. I don't like "ISDN modem"s for a number of reasons: 1. They're more expensive 2. In my experience, they're *much* less reliable. 3. They require to be connected by an async line. Considering that 128 kb/s ISDN translates to 160 kb/s async, it's evident that you can't keep up the same speed. In addition, conventional "El Cheapo" serial interfaces lose data at this speed. 4. You can't run raw IP over them, mainly because of (3). 5. You can't use them for connect on demand. The board solution can allow the system to disconnect after a certain idle time, and then reconnect when another packet arrives (from either side). 6. I'm not sure about this, but I believe call setup is slower. On a direct connect board, call setup is round 2 seconds. This is particularly important for point (5). > The simplest way to configure an ISDN device is by using an ISDN->Ethernet > bridge. This is a box that plugs into your ISDN line on one end, and into > your Ethernet on the other end. This is true. This is what I currently do while trying to iron out the wrinklies on the FreeBSD solution. It's definitely not the cheapest, though. For the record, I use the same Creatix board in this configuration: it's a diskless 286 with public domain software, runs various protocols (including raw IP) to multiple destinations, and does just about everything except snmp. > You can also get ISDN modems that plug into your serial port which > are then used as point to point links (ppp, slip). As the Germans say, you can also put rivets in your ears, hang slices of sausage on them, and claim you're a dachshund. > I would stay away from internal ISDN cards. The support for them on > anything other than 'doze is minimal at best. With an external box, > you can also be assured that it'll move with your hardware should you > change platforms. Internal cards definitely offer more problems in the short term. Jordan's still waiting for a pair, and then he's promised to try out the FreeBSD software, which was developed in Germany. I'm personally expecting a few problems because of differences in the ISDN signalling implementation. If anybody else is interested, please contact me. Greg
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