From: jasonp@sunbabe.Prime.COM (Jason Pascucci)
Subject: Re: Obtaining ISDN
Organization: ComputerVision Services
Distribution: usa
Date: Tue, 17 Nov 1992 03:41:29 GMT

In article <1992Nov16.235427.11813@advtech.uswest.com>, huntting@advtech.uswest.com (Brad Huntting) writes:
|> In article <1992Nov13.154757.28389@bmerh85.bnr.ca> coghlan@bnr.ca (Patrick Coghlan) writes:
|> >[With ISDN at home] you would have:
|> 
|> >- a 64 k/bit data line which does not interfere with your use of the 
|> >  telephone
|> 
|> As opposed to a 14.4Kb/s real throughput on a single POTS line.  For us
|> realistic folks it's really more like ~35Kb/s when you include V.42bis
|> compression.  Of course now I'll be flamed by the half of the group for
|> comparring apples and oranges again, but in the real world it's
|> perfectly reasonable to compare these because you cant buy ISDN with
|> compression.  (Or did I miss something?)

Realistic? Excuse me?

For pure data (text) throuput on a V32/V42/MNP, I've seen about 20kb/s with 
zero line noise, with compressed binaries going down to 14.4 with a tail 
wind.( which is what you can expect when people FTP)

This all drops down to uselessness when there's line noise. Now, add 
SLIP onto that, and you go down to about 10kb/s throughput, with about 
300-400ms ping time, possibly due to funny buffering somewhere. It turns 
out compression doesn't do very well under SLIP, but I haven't quite figured 
out why. 

Putting tcp/ip over X25, in my experience, has about a 5-10% overhead
(approx.). The ISDN line is supposed to be as reliable as one T1 line,
so insignificant noise problems. Therefore, you can get a 60kb/s
sustained throughput, with, as I understand it, fairly fast
ping times. This is faster then my 56kb leased line now. When I was in school
(another 56kb link),and running xrn here xdisplayed to my workstation 
at  school, it was useable. I have found that it's just
too much data to pump through a 14.4 modem running SLIP. I've
tried running xterm over slip@14.4, but it's still too painful, 
being reliable at a throughput of about 300(110?) baud. I get 9600-like
response running a telnet session without difficulty.

About billing, I was under the impression that you were billed
for connect time, not for distance. I thought, like the internet,
they'd just pass the data around, making it much more useful
(read inexpensive) for WAN technology.

And, the outragously high priced customer equipment is because
of rarity. There isn't much more significant electronics inside
than inside a good highspeed modem...or, more closely, a good
ethernet controller, that are now selling for $300-400 dollars. When 
the technology becomes more solid, and there are more people 
competing, the prices will drop. It's the way of the world...

The truth is, I'd envision stopping off at the airport, and
plugging in my PC to a jack in the wall, and giving it
a dime every 10kbits, or so. :) You get the picture...

|> brad

This, of course, isn't saying I wouldn't rather have fiber to
my doorstep...in 5 years, ethernet speeds will be wimpy
and we'll need more, and fiber should be able to keep us
going for a while...

--
Jason R. Pascucci
jasonp@primerd.prime.com
Disclaimer: I don't speak for my company on this matter.