Broken PMTUD for . + TLD servers, was: Re: Smallest Transit MTU

Iljitsch van Beijnum iljitsch at
Sun Jan 9 23:39:54 UTC 2005

On 10-jan-05, at 0:08, Mark Andrews wrote:

> 	Well DNS (not EDNS) is limited to 512 octets so you unless there
> 	are real links (not ones artificially constrained to demonstrate
> 	a issue) this should not be a issue in practice.

No, fortunately not. But it's still VERY wrong and it must be fixed.

> 	Note for IPv6 one sets IPV6_USE_MIN_MTU on the UDP socket so this
> 	should be a non-issue there.

In IPv6 PMTUD is handled at the IP layer so the second packet that's 
too large will be fragmented at the source, so there is no issue.

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