[dns-operations] Does anyone pay attention to the EDNS0 UDP payload size in responses?

P Vixie paul at redbarn.org
Sat Oct 8 21:23:29 UTC 2016

The responder's advertised buffer size can be used to constrain the size of subsequent update messages.

On October 8, 2016 11:54:46 PM GMT+03:00, Paul Hoffman <phoffman at proper.com> wrote:
>Greetings. As I was doing a bit of unrelated research, I found that 
>Google DNS always returns 512 for the UDP payload size in EDNS0 
>responses, even when the response itself is bigger. For instance, "dig 
>@ dns-oarc.org dnskey +dnssec" sends back a message of 1597 
>bytes, but
>    ; EDNS: version: 0, flags: do; udp: 512
>Reading RFC 6891, I see nothing that indicates that the MTU in a 
>response is actually relevant to anything. Section 6.2.4 talks about
>size probably being constant over short periods of time, but not about 
>it actually being relevant.
>Is there client software out there that looks at the MTU in the
>and does something with that value if it seems "small"? If so, what?
>--Paul Hoffman
>dns-operations mailing list
>dns-operations at lists.dns-oarc.net
>dns-operations mailing list

Sent from my Android device with K-9 Mail. Please excuse my brevity.
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