Re: ECN: Clearing the air (fwd)

David S. Miller
2001-01-29T07:38:20Z

James Sutherland writes:
> Except you can detect and deal with these "PMTU black holes". Just as you
> should detect and deal with ECN black holes. Maybe an ideal Internet
> wouldn't have them, but this one does. If you can find an ideal Internet,
> go code for it: until then, stick with the real one. It's all we've got.

Guess what, Linux works not around PMTU black holes either for the
same exact reason we will not work around ECN.

I'm getting a bit tired of you, and I suppose others are as
well. You are being nothing but a pompous ass.

Anyways, let me quote a comment from the Linux source code where
we would have done PMTU black hole detection:

/* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu black
hole detection. :-(

It is place to make it. It is not made. I do not want
to make it. It is disguisting. It does not work in any
case. Let me to cite the same draft, which requires for
us to implement this:

"The one security concern raised by this memo is that ICMP black holes
are often caused by over-zealous security administrators who block
all ICMP messages. It is vitally important that those who design and
deploy security systems understand the impact of strict filtering on
upper-layer protocols. The safest web site in the world is worthless
if most TCP implementations cannot transfer data from it. It would
be far nicer to have all of the black holes fixed rather than fixing
all of the TCP implementations."

Golden words :-).
*/

Later,
David S. Miller
davem@redhat.com