netbsd-help: Why is SLIP so slow on a dial up, but fast on a direct connect?

Subject: Why is SLIP so slow on a dial up, but fast on a direct connect?
To: 'netbsd-help' <netbsd-help@NetBSD.ORG>
From: John Maier <JohnAM@datastorm.com>
List: netbsd-help
Date: 09/29/1995 09:07:00

I've a external Supera 28.8 off of my server (486DX2-66, 8megs, 16550 
UART) with the port set to 38400. I am connecting to the server with 
another Supera 28.8.
I have noticed a strange thing, if I directly connect to the server with 
a serial line, I can get outstanding transfer rates. When I replace the 
line with the modem and dial up (from a PC running Trumpet, or anything 
else), the rates are terrible (lots of pauses from the server).
I tried turning off compression, and error corrections, but this didn't 
really help.
Some the things I notice are, if the link is left idle for a moment and 
then a FTP xfer is started, initially the rate is fairly quick (2800 
bytes/sec) and begins quickly to drop to 400 bytes/sec. Telnet exhibits 
the same problems.
What's up? Has anyone else seen this. BTW this is the second machine 
I've setup that exhibits these problems.
jam
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