Re: A router bug?

Alan Cox (alan@lxorguk.ukuu.org.uk)
Mon, 1 Feb 1999 20:28:07 +0000 (GMT)


> in the "Fragmentation Needed" message, and IP will use it.
> If the gateway does not provide next hop information, then IP
> will reduce the MTU to the next lower value taken from a table
> of "popular" media MTUs.

Thats what we do

> o An ICMP "Echo Request" of full MTU size is generated and
> sent out with the "Don't Fragment" bit on.

and bounces off every firewall which is correctly configured. A good 50%
or more of major sites block icmp echo, 90% of them get it right. Also it
isnt required for an end host to support frames >576 bytes except by
prior agreement (hence TCP MSS option).

> it. [0,2] Default: Strategy 2

ie nasty hack. Unclean unclean 8)

Alan

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