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Date:      Sun, 12 May 1996 03:20:28 +0200 (MET DST)
From:      Daniel Eriksson <daniel@icon.pp.se>
To:        freebsd-questions@freebsd.org
Subject:   Setting MTU on tun0
Message-ID:  <199605120120.DAA03958@icon.pp.se>

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I'm using user-mode PPP (iijpp) to connect to my provider over a
28k8-modem (USR Courier) connected to the computer via a 16550A
on an ISA-card. I'v tried both 2.1-STABLE and 2.2-CURRENT (latest
SNAP) and the symptoms are the same.

The problem is poor performance when sending data. It's close to
impossible to get any kind of data out from the computer. Downloading
data work good though (3k/sec FTP). I'm no expert, but AFAIK I've got
2 major sources to look at for the error:

* Computer<->modem (RTS/CTS)
* MTU-size

I asked a similar question a couple of months back and was told that
I only needed to recompile /sys/net/if_tun.h with a different
setting for TUNMTU. However, whatever I do I still end up with a
MTU of 1500 (as reported by netstat -i). How do I force iijpp to
use an MTU of 552? I've tried changing every occourance of 1500
in /sys/net/ without success. :-(

Do I need to do anything special in order to get RTS/CTS to work?
Must I edit rc.serial, or are they enabled by default?

--
Daniel Eriksson, daniel@icon.pp.se



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