Subject: Debug bug #170628: further info request

From: Darren Tucker <[email-masked]>
Date: Mon, 07 Apr 2003 23:34:51 +1000

Hi.
	I'm helping out with some outstanding Debian OpenSSH bugs.

	Regarding bug 170628, are there any packet filters, firewalls or NAT
devices between the client and server?  The problem described is
characteristic of a MTU/fragmentation issue where an intermediate device
drops IP fragments.  These tend to show up when interactive activity
generates enough traffic to send full-size packet(s).

	From the bug report:
> Typical "freezing points":
> - paste a few paragraphs of text
Sends the whole buffer at once.

> - ls on directory with many files
Generates many screenfuls of data.

> - running program which generates plenty of output (e.g. latex) on
>   the remote computer 
Ditto.

> - listing backwards through e-mails in pine
Most terminal emulators can scroll down, however scrolling up requires
redrawing the entire screen.

Other common triggers:
* cat'ing a large file.
* starting an X11 app.

	You can try setting the MTU of one end to be 576 (the minimum
permitted) with by executing "ifconfig ethX mtu 576".  You only need
change one end, TCP will negotiate a maximum segment size (MSS) based on
the smaller of the two MTUs.  This is not optimal but may work.

	If your problem goes away then you can experiment to find the optimal
settings.  For futher info, please see
http://marc.theaimsgroup.com/?l=openssh-unix-dev&m=102413585608801 .

		-Daz.

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.