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

[P Vixie]

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 
>@8.8.8.8 dns-oarc.org dnskey +dnssec" sends back a message of 1597 
>bytes, but
>    ;; OPT PSEUDOSECTION:
>    ; 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
>the 
>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
>response 
>and does something with that value if it seems "small"? If so, what?
>
>--Paul Hoffman
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-- 
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