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Re: [RRG] Perplexing PMTUD and packet length observations
On 12 aug 2008, at 0:35, Templin, Fred L wrote:
Like I've been saying for a long time, reducing the user-visible MTU
of the internet is not an acceptable approach.
SEAL fixes that. What unacceptable is a mechanism that
requires reliable and secure delivery of ICMPs from
anonymous nodes on the Internet.
Well, nothing on the internet is reliable, and very few things are
secure.
That being said, ICMP too big messages are ESSENTIAL and MUST NOT be
filtered! Any other message from the IETF is unacceptable.
The first mistake was to invent the DF bit in the first place.
The second mistake is to suggest that the DF bit be set for ALL
packets to do PMTUD in RFC 1191.
[omitting a number of mistakes]
I'm not sure if implicitly making IPv6 packets unfragmentable was a
mistake, but relying on ICMP messages was.
In any event, all of these mistakes have been made and we aren't even
close to cleaning up the mess with stuff like RFC 4821, so now we have
to live with that, which means, among other things, taking very good
care of ICMP too big messages.
</rant>
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