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[tcpm] PLPMTUD for all protocols

Mikael Abrahamsson <swmike@swm.pp.se> Wed, 28 March 2018 08:43 UTC

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Date: Wed, 28 Mar 2018 10:43:40 +0200
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: tcpm@ietf.org
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Subject: [tcpm] PLPMTUD for all protocols
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Hi,

In trying to advocate for all protocols implementing PLPMTUD (RFC4821) and 
shipping with it default on, I received pushback when I suggested/asked 
why modern TCP stacks don't come with PMTU blackhole detect turned on.

Relevant reading is draft-bonica-intarea-frag-fragile-01, where PMTU 
blackhole is one part of this problem space.

I tried turning on PMTU blackhole in Linux quickly in a case I had, and it 
worked around the PMTU blackhole we had for a certain deployment scenario 
(which couldn't be fixed unless the NMS could reconfigure the device in 
question, which it couldn't because PMTU blackhole existed).

People suggested to me that the current TCP stack implementations are 
broken when it comes to PMTU blackhole detection and workaround, so that's 
why it's not on.

What's wrong with it, and how do we fix it?

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

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