Date: Thu, 6 Jul 1995 12:14:25 -0500 (CDT) From: Joe Greco <jgreco@brasil.moneng.mei.com> To: msmith@atrad.adelaide.edu.au (Michael Smith) Cc: hackers@freebsd.org Subject: Re: current SOTA in ISDN support? Message-ID: <199507061714.MAA11598@brasil.moneng.mei.com> In-Reply-To: <199507060157.LAA18633@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Jul 6, 95 11:27:07 am
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> Greetings all, > A quick question for the ISDN-enabled out there. I'm > currently helping a BBS owner add a BSD box to provide ISPish services > for his users. He wants to go ISDN, and obviously needs to know > which way to turn when it comes to buying an interface. > > I'm curious to know what people are using - I know Amancio has the Ascend > box, and appears to be very happy with it; I seem to recall someone I don't recall exactly what Amancio has. I suspect it may be an Ethernet bridge. > saying something about a Motorola card at some stage, but I've > no idea who or when. (This is for use in Canada). Probably me, Motorola terminal adapter, not a card, just an external box. > A search of the mailing list archives (that's a neat toy, by the way!) > shows lots of people asking for support, but not much in the way > of hard answers. > > Unfortunately, I'm not in a position to write a driver either 8( When in doubt, avoid the need-a-driver problem. 8-) Combinet and other manufacturers have Ethernet bridge products. These devices speak a propietary protocol over one or two B channels and make an Ethernet device look like it's on a remote network: ----------- ------------ ------------ | | FreeBSD |-------| Combinet |----/ /PSTN/ /----| Combinet |------+ ----------- ------------ ------------ | You :-) Ether ISDN Ma Bell ISDN Remote Netwk (ISP, work, etc) Combinet has a PRI interface so you can have a "central hub" supporting many sessions simultaneously rather than having a rats nest of BRI combinets on the remote network side; we use this here at MEI extensively. Downside: Propietary protocol. You can only speak to other Combinets - in particular other Combinets that are willing to talk to you. Downside: Requires an Ethernet card in the FreeBSD box. Downside: Lower cost units only support a single device on the remote side (although you could route over IP if you had a second Ethernet at your home - but no other devices on the network segment between your PC and Combinet). Upside: Works with any Ethernet appliance. This is a MAJOR PLUS and probably counteracts most of the downsides. ;-) Upside: Can transparently do 2 B-channels. Can dial-on-demand and kill idle links transparently. Downside: Relatively expensive. Upside: I'm fairly certain they do compression. Combinet is only one provider of these devices; they're the ones I'm really familiar with. Ascend and others make similar offerings. Look for "Network bridges". Next solution: ISDN terminal adapters via standard async serial. I won't draw a picture. We all know how modems work. A terminal adapter is basically an ISDN "modem" - but it's all "digital" - no modulator/demodulator. You connect to the TA via a serial port (16550 absolutely mandatory!!!) and the TA can connect to remote ISDN TA's. Upside: Standard protocols. Interoperability between vendors. Can be used like a modem (not forced to use as a network connection). I can connect to the TA's at the local BBS and download files with rzsz. Upside: Configures just like a standard modem dial-up connection. You can drop in place of your current V.34 solution. Downside: You start stressing the IRQ's on your FreeBSD box (on a 386DX/40 it's not toooo bad). Downside: No compression (at least on the units I'm aware of). Notes: Motorola has a number of solutions. The UTA-220(?) is capable of doing sync or async serial - and can do 128Kbps with a bonded connection, IF you are running sync. They have been promising to provide a 115,200Kbps bonded solution for async, but have failed to deliver as of this writing (promised availability: this last spring). It is a damn good unit - has two serial ports so you can use each B-channel separately, and would be a perfect TA *if* it could do bonded async. It can't, though, at least not right now. There are also several options available that incorporate V.34 (etc) modem technology into a TA or provide an analog phone jack on the TA. This may or may not be good for your application. The TA/modem units I have considered generally only are able to use one B channel. Since an ISDN line has two B channels, this would be wasteful in an ISP environment - ideally what I would REALLY like to see is something like the UTA-220 which had added functionality - two V.34 modems and the ability to use any mix of V.34 and V.120 on either channel, or the ability to use both channels bonded together. This would provide great flexibility for an ISP and I'm suprised nobody's done it. ;-) ODS has been running a pair of UTA-220's, and aside from some minor problems with the TA software which should be fixed "RSN" (along with an async bonding implementation), these have been great performers. NONE of these solutions are difficult to implement without ANY special ISDN support within FreeBSD. The next solution: get a sync serial card and an ISDN TA. With a unit capable of bonding like the UTA-220, you can do 128Kbps. If you get a GOOD sync card, you're also all set to go with a pair of CSU/DSU's and go T1. This is perhaps more expensive than async serial (the sync cards are $$$$$$), but may be less expensive than a Combinet style solution. This of course requires sync card support. Emerging Technologies(?) has done all that for you, if you buy their product :-) (I'm looking at doing so, but need more details...). That's an "already implemented but mild amount of work" solution. Then there's the ISDN PC cards. I don't have too many details. Everybody has one: Digiboard, IBM, etc. They're all propietary, AFAIK, and probably all have various tradeoffs. They are certainly the most likely to be a "cheap" solution - except you'll find yourself ripping hair when you run into a bug of some sort while trying to write your driver. :-( I think that FreeBSD *MUST* have support for these eventually - I do not mean to discourage anyone who has the hardware and will to write a driver - but the lack of standards is truly disheartening.... it's like Ethernet cards but worse. My hat's off to anyone who braves these waters. ;-) ... Joe ------------------------------------------------------------------------------- Joe Greco - Systems Administrator jgreco@ns.sol.net Solaria Public Access UNIX - Milwaukee, WI 414/342-4847
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