Subject: Re: TCP MSS option value

From: der Mouse <[email-masked]>
Date: Fri, 28 Jan 2000 13:13:34 -0500 (EST)

> Try surfing the web from behind a path with a bottleneck IP MTU of
> 1480 some time..  if you advertise an MSS greater than 1440, you'll
> never see a full page from many servers..

I'm behind a link with an MTU of either 1024 or 1400, depending on
which address I use, and I've found a couple of websites I never see
anything back from.  Snooping on the far side of the choke point shows
too-large packets coming in with DF set and need-frag ICMPs going back,
with no sign the ICMPs are being listened to.

I sent mail to the owners of one of the websites; no response, and last
time I checked no fix.

I'm seriously considering having the low-MTU link effectively ignore
DF, broken as that would be.  Anyone have any hint of a working
clue-by-four to thwack such bozos with?

					der Mouse

			       [email-masked]
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From: Rick Jones <[email-masked]>
Date: Fri, 28 Jan 2000 14:44:49 -0800

> with no sign the ICMPs are being listened to.

ah, the joys of someone, somewhere in the middle of the path, or even at
one end or the other deciding to block ICMP traffic. an example of what
happens when a mechanism is designed based on being able to believe in
the goodness of ones fellow participants meets a network that "evolves"
to include nefarious types.

> clue-by-four to thwack such bozos with?

I forget, do any of the Host requirements RFC's say that a host must try
a smaller PTMU as part of their retransmission strategies?

rick jones
-- 
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