A friend of mine recently tried to visit research.microsoft.com, he was unable to. He spent some time on it, and came up with the following scenario:

• linux router with pmtu clamping
  • linux client does not work
  • windows client works

• linux router with conditional pmtu clamping (if the mss is within 1400:1536)
  • linux client works
  • windows client works

I could reproduce this myself, for my setup research.microsoft.com did not work too, but I felt I would not loose too much anyway.

After some time he provided some pcap dumps for all possible combinations and scenarios, so I felt guilty and finally gave it a shot.

So what is wrong with research.microsoft.com?

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