<html><head></head><body>The responder's advertised buffer size can be used to constrain the size of subsequent update messages.<br><br><div class="gmail_quote">On October 8, 2016 11:54:46 PM GMT+03:00, Paul Hoffman <phoffman@proper.com> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Greetings. As I was doing a bit of unrelated research, I found that <br />Google DNS always returns 512 for the UDP payload size in EDNS0 <br />responses, even when the response itself is bigger. For instance, "dig <br />@8.8.8.8 <a href="http://dns-oarc.org">dns-oarc.org</a> dnskey +dnssec" sends back a message of 1597 <br />bytes, but<br /> ;; OPT PSEUDOSECTION:<br /> ; EDNS: version: 0, flags: do; udp: 512<br /><br />Reading RFC 6891, I see nothing that indicates that the MTU in a <br />response is actually relevant to anything. Section 6.2.4 talks about the <br />size probably being constant over short periods of time, but not about <br />it actually being relevant.<br /><br />Is there client software out there that looks at the MTU in the response <br />and does something with that value if it seems "small"? If so, what?<br /><br />--Paul Hoffman<br /><hr /><br />dns-operations mailing list<br />dns-operations@lists.dns-oarc.net<br /><a
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