Subject: Re: pppoe problem
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Christopher Vance <>
List: tech-net
Date: 12/14/2001 19:49:40
On Fri, Dec 14, 2001 at 03:24:53AM -0500, der Mouse wrote:
: Though I suppose this depends on cvsup: does it always die at exactly
: the same place, and is that place always the first time it wants to
: send a "large" (roughly, >1500 bytes) amount of data without flushing
: and blocking for a reply from the other end?

I have no reason to believe it's always the same place.  If you're
reasonably current in what you're updating, cvsup tends to send lots
of stuff to the server before you see much in the way of files coming
back, since most of what you have is discovered to be still current.

: If not, it probably isn't PMTU-D.
: This does sound remarkably like a problem I've had for a logn time,
: wherein a connection will come up and start transferring data fast, but
: gradually slow down and stall, and eventually time out.  It doesn't
: always time out at the same place, and I've not investigated far enough
: to say much more - but these symptoms "smell" more like that than like
: PMTU-D blackhole trouble.
: > Without MSS clamping you won't be able to fix this.
: The right fix is - if it really is a PMTU-D blackhole - to get the
: broken router/host fixed.  MSS clamping is at best papering over the

It's out in the real world, and didn't cause me any problem when my
pppoe was done using iijppp/FreeBSD.

: real problem, and it depends on a number of shaky assumptions (which,
: to be fair, it looks to me as though you'd get away with; it may be
: good enough for an interim patch for your case).

I'll try rp-pppoe as an alternative on NetBSD before I try OpenBSD or
reinstall FreeBSD on the box.  I was trying to have multiple IP
filtering software in use, hence the variety of OS.  Now that my box
count is down by one, I've lost on that one.  :-(

Christopher Vance