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Re: [v6ops] Quick measurement: MTUs on the general Internet

Iljitsch van Beijnum <iljitsch@muada.com> Thu, 18 December 2014 14:57 UTC

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Subject: Re: [v6ops] Quick measurement: MTUs on the general Internet
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I left the tcpdumps running for almost a week and did a more thorough analysis of the results, see:

Maximum packet sizes on the internet 
http://www.bgpexpert.com/article.php?article=151

Internet packet sizes part 2: IPv4 path MTU discovery is dead
http://www.bgpexpert.com/article.php?article=152

Quick summary: all IPv6 hosts and 99.7% of IPv4 hosts advertise they can handle at least 1280 bytes in their TCP MSS and about 65% can handle 1500.

In almost a week, I didn't get a single IPv4 too big, so it seems that in practice, IPv4 PMTUD is no longer used. (Please confirm with a larger dataset before taking any actions based on this!) However, depending on PMTUD doesn't lead to obvious problems with IPv6.

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