Common operational misconceptions

Masataka Ohta mohta at
Tue Feb 21 04:01:59 UTC 2012

Steven Bellovin wrote:

>> I'm not sure what, do you think, is the problem, because the
>> paragraph of RFC2923 you quote has nothing to do with TCP
>> MSS.
> Sure it does.  That's in 2.1; the start of it discusses PMTUD
> failing for various reasons including firewalls.


Though I have never assumed existence of firewalls, if you are
saying IPv6 will be even less operational because of firewalls,
I have no counter argument.

> The text I quoted says, in so many words, "send smaller packets".
> I don't know how it's possible to be more explicit than that.

No disagreement.

I have been keep saying that IPv6 can't depend on PMTUD and
must send packets of 1280B or less.

It's George Bonser, not me, who said there were other ways.

> Please cite in context.  The text I quoted says that one option
> is to try turning off DF; the next paragraph notes that you can't
> do that on v6.

I thought the context is whether IPv6 is operational or not.

Or, is it whether PMTUDv4 operational or not?

Or, is your problem completely different from the above two?

Your clarification is helpful

					Masataka Ohta

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