Date: Wed, 31 May 95 22:18:56 CDT From: lists@Seaman.Chenequa.WI.US (Richard Seaman, Jr) To: gwk@cray.com Cc: freebsd-questions@FreeBSD.org Subject: Re: ISDN support? Message-ID: <199506010319.WAA03734@gw.seaman.quaestus.com>
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On Wed, 31 May 95 21:37:11 +0200 you wrote:
>Hi there,
>
>the RELNOTES for 205 are not very clear about ISDN support. What
>hardware is supported, and what services? Does it behave just like a
>serial line or modem, so I can login somewhere and maybe bring up PPP?
>Can I bundle both B channels to achieve higher throughput? What about
>checking the originating telephone number if someone is dialing in, is
>it possible?
>
>Maybe there should be a FAQ. I would be willing to collect any
I agree about the FAQ. This gets asked often enough. As far as I know,
there are 4 categories of choice:
1) Async Terminal Adaptors (TA's). These act like, and look a lot like
modems. Even use AT commands, usually. There is no ISDN specfic support
needed or supplied for these. Just use SLIP or PPP as you would with
a modem. Some of these TA's will bond two B channels, some give you
only one. All that I have seen are limited to 115.2kbps async. I
have an Adtran ISU Express, and get ftp's of around 11k Bytes/sec using
2 B channels.
Drawbacks:
a) doesn't fully utilize the ISDN line (which can do 128kbps sync for
2 B channels). Also, no compression.
b) the remote end needs to be async and use compatible protocols too,
unless you have a TA that does some kind of conversion (some of the
async TA's claim to do async to sync PPP conversion).
c) the trend in TCP/IP over ISDN seems to clearly be towards sync PPP
or sync ML-PPP for 2 B channels.
Advantages:
Cheap and easy. No OS specific support needed.
2) Ethernet routers/bridges.
Some of these are either "single user" or "limited user", while
others will handle a full Class C or B network. Seems to me that
if you enable routing on your FreeBSD machine, you could get by
with the cheaper single user hardware and let FreeBSD do the
routing for you.
Advantages:
a) OS independent. No OS drivers needed.
b) easy ??? Setup on some of these is reputed to be a little hard.
But, from the standpoint of the FreeBSD machine, it should be
a piece of cake.
c) fast. Most (all?) do sync, and almost all do compression.
d) compatibility. Most of these are moving towards standard sync
PPP and sync ML-PPP per RFC's 1618 and RFC 1717
Disadvantages:
Cost. Though this is relative. Street price on async TA's is $400-550,
whereas single user ethernet router/bridges seem to be $750-1000 and
coming down.
3) PC Cards.
Here the problem is you need OS drivers for the card you want. Now,
as well as for future releases of the OS and for upgrades to the
cards (many of the cards have CPU's on them, with software either
downloaded to the cards at boot or in PROM somewhere). Cards can
give you the pricing of the async solution, with the performance and
(coming soon) interoperability of the ethernet routers/bridges.
So far none of the cards appears to do a simple emulation of an ethernet
card supported by FreeBSD, though the Combinet 10X0 series apparently
does a close emulation of an NE2000 adaptor. I understand a port
of the Linux NE2000 code to the Combinet adaptor is underway (or
maybe its released by now).
As to FreeBSD driver support, you'll have to ask someone else. But,
it was my impression that unless you're using one or two of the
Eurpean ISDN cards that are mentioned in FreeBSD-current, you're out
of luck.
4) Sync TA's. You can plug these into sync V35 or sync RS232 ports (depending
on the features of the specific TA). Again, no OS specific code is needed
for the ISDN TA, but obviously you need the sync adaptor and OS drivers
for it, unless you just plug it into a router with appropriate WAN ports.
Some of the async TA's will also do sync, for the same price.
A note of caution. ISDN interoperability does not appear anywhere close
to uniform. Whatever your ISP supports is what you'll almost certainly have
to conform to. Just because you buy "ISDN hardware" doesn't mean it will
work with anything on the far end of the ISDN line. In fact, chances are
very good it won't, unless you have gone to the specific trouble of trying
to ensure compatibility. And even then, unless the hardware on both ends
is from the same manufacturer, I'd say you're taking a risk.
Dick
Richard Seaman, Jr. Dick@Seaman.Chenequa.WI.US
5182 North Maple Lane voice: 414-367-5450
Chenequa, WI 53058 fax: 414-367-5852
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