Newsgroups: comp.dcom.modems
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Are Trailblazers good for SLIP 9600 Baud? What then?
Message-ID: <1989Jul2.000435.29496@utzoo.uucp>
Organization: U of Toronto Zoology
References: <219@csis.oz>
Date: Sun, 2 Jul 89 00:04:35 GMT

In article <219@csis.oz> scott@csis.oz (Scott Milton) writes:
>Do Trailblazers work well with SLIP?
>What modems should I use for 9600 Baud SLIP?
>
>I have been told that because TCP sends acknowledgments for every packet,
>that Trailblazers don't work well, as they are designed for large traffic
>flows in a single direction for longer periods. With SLIP they spend alot of
>the time working out that they have to change direction...

Trailblazers in PEP mode are not great for SLIP.  With header compression
and other tweaks they can be passable; the terminal room at the San Diego
Usenix had its Internet connection done that way.  It wasn't great, but
it did work okay when I tried it -- although people who used it at busier
times were less happy, I gather.  (Unfortunately the compression code, from
Van Jacobson, is not widely available yet.)

At present, you're better off with a V.32 modem for 9600-baud SLIP.  The
Baltimore Usenix terminal room used a Telebit T2500 in V.32 mode, and was
a noticeable improvement on San Diego.  Other V.32 modems should also be
okay, but make sure you get real V.32 (there is at least one half-duplex
modem using a protocol related to V.32).  Don't expect miracles; try before
you buy.  There are things that can be done to optimize TCP/IP for slow 
lines, but your system almost certainly doesn't do them.
-- 
$10 million equals 18 PM       |     Henry Spencer at U of Toronto Zoology
(Pentagon-Minutes). -Tom Neff  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu