[39601] in North American Network Operators' Group
Re: PPPOE, MTU, and boom.
daemon@ATHENA.MIT.EDU (Alex Rubenstein)
Wed Jul 18 03:19:42 2001
Date: Wed, 18 Jul 2001 03:24:22 -0400 (Eastern Daylight Time)
From: Alex Rubenstein <alex@nac.net>
To: Chris Wedgwood <cw@f00f.org>
Cc: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <20010718190702.C16159@weta.f00f.org>
Message-ID: <Pine.WNT.4.33.0107180319210.932-100000@neon>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Errors-To: owner-nanog-outgoing@merit.edu
On Wed, 18 Jul 2001, Chris Wedgwood wrote:
> On Wed, Jul 18, 2001 at 07:57:23AM +0100, Stephen J. Wilcox wrote:
>
> Could it be Path MTU/fragmentation issues on account of the low
> MTU you have in combination with some ICMP issues where network
> admins have some screwy setup?
>
> That's exactly what it is... a large (1500 byte probably) TCP datagram
> with the DF bit set will be heading towards his edge device which are
> PPPoE connected.
Great domain, btw (f00f.org, brings back memories of division)...
Anyway, a great stride was just made in my lab^H^H^Hbasement. First off,
it appears a 'ip mtu 1492' on the Virtual-Template of the IOS Router
aggregating the PPPOE session is not strictly enforced, especially with
windows. Another words, I saw in the PPP debug that the MRU wasn't being
negotiated.
So, I found this really nifty utility, aptly named 'Mr. TCP':
http://www.dslreports.com/front/drtcp.html
It allows you to tinker with the Windows settings of TCP. I adjusted MTU
to 1400, wham-o, all the sites I listed started working; including, what I
didn't list before, the downloading of transactions via Quicken. Seems to
be a fixall.
-- Alex Rubenstein, AR97, K2AHR, alex@nac.net, latency, Al Reuben --
-- Net Access Corporation, 800-NET-ME-36, http://www.nac.net --
