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From: vjs@calcite.UUCP (Vernon Schryver)
Newsgroups: comp.unix.i386
Subject: Re: ISC 2.2 SL/IP throughput?
Message-ID: <94@calcite.UUCP>
Date: 1 Sep 90 18:06:19 GMT
References: <25@astph.UUCP> <3694@wb3ffv.ampr.org> <26@astph.UUCP> <1990Aug28.140547.14767@nstar.uucp>
Organization: Rhyolite Software, Mountain View, CA
Lines: 24

> SlIP requires the use of duplex modems for best throughput, and the HST
> is limited by the baud rate of the "back channel"

It has been widely reported that you can get some less than 960 Bytes/sec
through FTP over SLIP over a v.32 line (e.g. any of several v.32 modems or
a Telebit T2500), and somewhat more than 1,100 Bytes/sec through FTP over
SLIP over Telebit PEP (e.g. Telebit T2500 or TB+).  Among other places, I
have heard these reports in the BARRNet community from developers running
386 clones.

9600 b/s V.32 is prefered for most SLIP uses, because the 40 byte TCP/IP
headers are painful on half-duplex modem protocols like PEP (there is no
reverse channel in PEP).  You can (since I have) compress and predict the
TCP/IP headers to less than a PEP micro packet to make SLIP not
significantly more painful over PEP than cu.

In sum, if you are transfering files, use PEP.   If you are typing to
rlogin, use v.32.  (This may not apply if you have 14.4 bps V.32.)

Van Jacobson header compression code has been published in an RFC.  I'm
told it is also in 4.3BSD Reno.


Vernon Schryver,   vjs@calcite.uucp