Re: ISDN preference

[Damion Yates <nospam [at] rd.bbc.co.uk>]

On Mon, 24 Jan 2000, French, Alastair wrote:

> I need to connect a small private network (with a linux box currently acting
> as a firewall and performing masqerading) via ISDN.
>
> As far as I can see I have three options
>
> ISDN router, connected via a secondary network card on the linux box

I think this is the most expensive option, you won't be able to use Linux's
masqerading support, but often routers come with their own NAT, it's possibly
easier to setup as it's all they are supposed to sit their doing, so the
instructions will be specific and correct, you'll probably lack support for
some protocols, like realmedia, irc's DCC and more as they come. Linux's
masqerading support is good and constantly worked on. This would be a solid
state system you won't hear if left on all the time.

> External ISDN TA, via serial port on Linux box

I've done this, I had a crap old 486 and had to get an extra isa serial card
to be able to do 115200 baud to the isdn box. It was just like a modem to
the OS, AT caused OK to come back, AT [at] MENU gave a fancy menu (if you like
that) this meant setting up pppd was trivial (no change from normal modem
only faster), it was _really_ fast, faster than I thought 64kpbs could give,
which made me wonder about 56k modems vs 64k ISDN, I'd pretty much say ISDN
is worth the difference in cost after seeing it in action.

It did take about 7 seconds before I had reliable tcp/ip to anywhere (dial on
demand using kerneld's /sbin/request-route system), but as this was much
faster than a modem I didn't mind the pause.

> Internal ISDN TA in linux box

This is much more low level, could be more difficult to get working, My dad's
done this (with some coaching by phone from me, as he's still learning
Linux), you use a different pppd for synchronous ppp (ipppd).

You're much closer to the ISDN layers and so have more cool abilities, should
you want to play with them (you're own ISDN to another owned ISDN in a
company for example), this is less use for just connecting to an ISP, but you
could do fancy stuff with CLIP (Caller ID) and suchlike, it's up to you.
Once setup this is gonna be the same as an external TA, but probably cheaper
and from what I've heard the connection time can be much faster. If I was
gonna do ISDN gateways again, I'd use this myself, much more fun and fiddly,
more control, MUCH cheaper.

> What a peoples views on these, which is best, easier to setup, relibility
> etc.

You'll need your masqerading Linux box on all the time for the later two,
that is about the only advantage of using an ISDN router.

> Something I also need to know is how to do channel bonding (bundling) the
> router would handle this automatically I would have thought, but what about
> the others

You'd need to see which ISP's will support this, all three should work with
BONDing though.

Damion

--
Damion Yates - Senior Internet Operations Engineer - Internet Services
email: Damion.Yates [at] bbc.co.uk - phone: +44 1737 839510

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