Re: Microsoft.com PMTUD black hole?

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Microsoft.com PMTUD black hole?
\ Nathan Anderson/FSR (6 May 2008)
. \ Brandon Butterworth (6 May 2008)
. . \ Iljitsch van Beijnum (6 May 2008)
. . . \ Nathan Anderson/FSR (6 May 2008)
. . . . \ Nathan Anderson/FSR (6 May 2008)
. . . . \ Iljitsch van Beijnum (7 May 2008)
. . . . . \ Nathan Anderson/FSR (7 May 2008)
. . . \ Bjørn Mork (7 May 2008)
. . \ Nathan Anderson/FSR (6 May 2008)
. \ Robert Bonomi (6 May 2008)
. . \ Tomas L. Byrnes (7 May 2008)
. . . \ Marshall Eubanks (7 May 2008)
. . . \ Nathan Anderson/FSR (7 May 2008)
. . \ Nathan Anderson/FSR (7 May 2008)
. . . \ Randy Bush (7 May 2008)
. . . \ Glen Turner (7 May 2008)
. . . . \ Mark Newton (7 May 2008)
. . . . \ Patrick Giagnocavo (7 May 2008)
. . . \ Rich Kulawiec (7 May 2008)
. . . . \ Nathan Anderson/FSR (7 May 2008)
. . . . . \ Michael Sinatra (7 May 2008)
. . . . . . \ Iljitsch van Beijnum (7 May 2008)
. . . . . . . \ Tomas L. Byrnes (7 May 2008)
. . . . . . . . \ Nathan Anderson/FSR (7 May 2008)
. . . . . . . . . \ Iljitsch van Beijnum (7 May 2008)
. . . . . . . . . . \ Nathan Anderson/FSR (7 May 2008)
. . . . . . . . . \ Tomas L. Byrnes (7 May 2008)
. . . . . . . . . . \ Iljitsch van Beijnum (7 May 2008)
. . . . . . . . . . . \ Tomas L. Byrnes (7 May 2008)
. . . . . . . . . . \ Nathan Anderson/FSR (7 May 2008)
. . . . . . . \ Tomas L. Byrnes (7 May 2008)
. . . . . . . . \ Nathan Anderson/FSR (7 May 2008)
. . . . . . . \ Bjørn Mork (8 May 2008)
. . . . . . . . \ Joel Jaeggli (8 May 2008)
. . . . . . . . . \ Iljitsch van Beijnum (8 May 2008)
. . . . . . . . . . \ Smith, Donald (8 May 2008)
. . . . . . \ Hank Nussbacher (8 May 2008)
. . . . . \ Deepak Jain (7 May 2008)
. . . . . . \ SML (7 May 2008)
. . . . . . \ Tony Finch (8 May 2008)
. . . . . . . \ Blaine Christian (8 May 2008)
. . \ Stephen Sprunk (7 May 2008)
. \ Iljitsch van Beijnum (7 May 2008)
. \ Nathan Anderson/FSR (7 May 2008)
. . \ Tomas L. Byrnes (7 May 2008)
. . . \ Nathan Anderson/FSR (7 May 2008)
. . . \ Matthew Petach (12 May 2008)
. \ Michael Sinatra (7 May 2008)
. \ Scott Weeks (8 May 2008)
. \ Janet Sullivan (8 May 2008)
. . \ Niels Bakker (8 May 2008)

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Subject:	Re: Microsoft.com PMTUD black hole?
Group:	Nanog
From:	Iljitsch van Beijnum
Date:	7 May 2008

On 7 mei 2008, at 21:46, Michael Sinatra wrote:

>> MS does in fact block _all_ ICMP
>> at the edge of their network, that they are aware that this will in
>> fact
>> break PMTUD, and that they have no current plans to change this
>> practice
>> which they have implemented in the interest of security.

> Perhaps
> they should also block _all_ TCP and UDP as well, and then we can
> move on.

> I agree with Iljitsch that it happens frequently, but I think I am
> justified in expecting more than that from Microsoft. Anything less
> would be unprofessional.

Right.

Now Microsoft is also the company that built the OS that could be
crashed by a maliciously crafted fragmented IP packet, so maybe
there's something to this security policy. (One hopes that this bug
and others like it are now fixed.)

However, in that case the only workable course of action would be TO
DISABLE PATH MTU DISCOVERY!

You can't have your cake and eat it too.

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