From: picone@csc000.csc.ti.com (Joe Picone)
Subject: Terminal Adapters Continued...[lstowell@pyrnova.pyramid.com.pyramid.com (Lon Stowell)]
Originator: picone@csc000
Organization: Tsukuba Research and Development Center
Date: Wed, 30 Dec 1992 01:41:40 GMT

> In article <PICONE.92Dec28142448@csc000.csc.ti.com> picone@csc000.csc.ti.com (Joe Picone) writes:
> >I would like to replace some analog modems with "ISDN terminal adapters"
> >if possible. Here is my current configuration:
> >
> >	(57.6K)    (14.4K)			  (14.4K)  (38.4K)
> >X terminal -> analog -> analog phone line -> analog -> annex -> ethernet
> >	      modem			     modem
> >
> >(2) The modems operate at v.32 in an UNCOMPRESSED mode.
> >
>       How slooooooooooooooow.

My application is a home terminal app: I dialup to computers at work
and run X windows over the telephone line. We use Graphon terminals
and Telebit Worldblazer modems.  The current system is the best setup
I have had - pretty fast over local telephone lines.

Modem compression on top of Graphon's proprietary compression only slows
interactive response, and isn't very effective.  Just my personal
opinion (based on an evaluation): non-Graphon X terminals, such as
NCDs, are hopeless (SLIP, Xemote, etc. are all too slow).

> >Questions:
> >
> >Can I replace the analog portion (modems/phone lines) with an ISDN
> >terminal adapter and ISDN telephone line?
> >
>     You'd be much better off stepping back and looking at the big
>     picture.
> 
>     Why not replace the entire kludge with the Combinet ISDN "smart"
>     bridges?    
> 
>     X-term || Enet <--> Combinet--ISDN======ISDN--Combinet <--> || Host
> 	   |
>     X-term |     
> 
> Its really an Ethernet "smart" compression bridge.   
> 
> This unit uses an ISDN BRI.  It has dynamic compression/decompression
> of data for increased thruput.  It can use a single B channel or
> inverse mux both together for 128 Kb thruput.   You can select an 
> inactivity timer for the ISDN connection.....if no packets 
> are sent, it will disconnect.  As soon as a packet is seen NOT
> destined for the local E'net, it reconnects the ISDN circuit.   
> 
> Combinet still makes E'net bridges which use leased 56K + circuits,
> this new ISDN unit is merely a new flavor of same...except that it
> is smart enough to drop the ISDN ckt when it is idle.
> 
>    Combinet
>    333 W. El Camino Real Suite 310
>    Sunnyvale CA 94087
>    408-522-9020

I don't care what you use, as long as it is cheap. The current
terminal/analog modem equipment costs about $1500 per user. We already
own an Annex III. I only need a 1 terminal capacity at each home, so
it seems running local ethernets at home is rather wasteful.  Also,
since the Graphon terminal uses a host-based communications program,
having local smarts at the home isn't useful (all traffic comes from
the host).

Now, if I were to start buying workstations for the home, it might be
a different story.  However, for many reasons (software environments,
lack of disk space, difficulty in maintaining parallel software
environments) the X terminal approach described above is a real
winner.

I think a 57.6K link will make a noticeable improvement in the
interactive response. If you have never used a Graphon X terminal, and
do not want to do intensive graphics at home (I do software
development, emacs, netnews, x-y graphs, etc. at home), you really
should check them out. I think an X terminal in the home is a great
application for ISDN in its current form - provided we can find some
good TAs.

I will post the feedback from my previous message in a few days -
there seem to be some good candidate TAs.
Newsgroups: comp.dcom.isdn