Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!bywater!acheron!archet!larouch!jparnas
From: jparnas@larouch.UUCP (Jacob Parnas)
Newsgroups: comp.dcom.modems
Subject: Re: Are Trailblazers good for SLIP 9600 Baud? What then?
Keywords: trailblazers slip modems tcp
Message-ID: <337@larouch.UUCP>
Date: 3 Jul 89 05:30:14 GMT
References: <219@csis.oz> <37389@sgi.SGI.COM> <12036@s.ms.uky.edu>
Reply-To: jparnas@larouch.UUCP (Jacob Parnas)
Organization: Larouch Headquarters, Hopewell Junction, NY
Lines: 33

In article <12036@s.ms.uky.edu> david@ms.uky.edu (David Herron -- One of the vertebrae) writes:
>...
>SLIP, depending on what you're doing, isn't necessarily one-direction.
>Generally speaking it's equal in each direction.
>...

SLIP is usually going full speed in one direction and without header
compression sending several ~ 40 byte packets per second in the other
direction.  The trailblazer (PEP protocol) does well for with
applications that mind high latentcy (like ftp, which gets about
1.1Kbytes/second vs. about .9Kbytes/second using V.32 modems.) but does
very poorly on interactive applications like rlogin, telnet, ping, etc
without header compression.  For instance, ping takes about 1200-1600
ms. in PEP mode vs. about 270ms.  with V.32 modems.  In a telnet or
rlogin, PEP gets 20 characters behind (what you are typing) sometimes,
while V.32 gets at most 1 or 2 characters behind).

The Telebit T2500 has both PEP and V.32.  I get mail and news in PEP mode
and use V.32 for SLIP.  V.32 wins big over PEP if you are running two
applications that want full bandwidth in both directions.  For instance,
once I got .8 Kilobytes/second on simultaneous ftps in opposite directions
in V.32 mode!  This has useful benefits.  For instance, it is reasonable
to rdist from your work machine to your home machine at the same time
as you are running rlogin from your work machine to your home machine in
V.32 mode, but I think performance would be much worse in PEP mode.

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