[DNSOP] default value of draft-ietf-dnsop-avoid-fragmentation

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Dear DNSOP participants,

Thanks very much for good comments for draft-ietf-dnsop-avoid-fragmentation.

These are my proposal of Section 3.3.  Default Maximum DNS/UDP payload size.

I'm not sure what to do with "MAY, "SHOULD", or "MUST",
so please give us your opinion.

If it is acceptable, I will submit -05.

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3.3.  Default Maximum DNS/UDP payload size

   Default maximum DNS/UDP payload size depends on the connectivity of
   each node, it cannot be determined unconditinally.  However, there
   are good proposed values.

   Operators MAY select a good number from Table 1.

             +========================+==========+==========+
             |                 Source |     IPv4 | IPv6     |
             +========================+==========+==========+
             |      minimal: RFC 4035 |     1220 | 1220     |
             +------------------------+----------+----------+
             | Software developpers / |     1232 | 1232     |
             | DNSFlagDay2020 propose |          |          |
             +------------------------+----------+----------+
             | This document proposes |     1400 | 1400     |
             +------------------------+----------+----------+
             |  maximum: ethernet MTU |     1472 | 1452     |
             |                   1500 |          |          |
             +------------------------+----------+----------+
             |              calculate | MTU-20-8 | MTU-40-8 |
             +------------------------+----------+----------+

              Table 1: Default maximum DNS/UDP payload size

   However, operators of DNS servers SHOULD measure their path MTU to
   well-known locations on the Internet, such as [a-m].root-servers.net
   or [a-m].gtld-servers.net at setting up the servers.  The smallest
   value of path MTU is the server's path MTU to the Internet.  The
   server's maximum DNS/UDP payload size SHOULD be smaller than or equal
   to the reported path MTU minus IPv4/IPv6 header size (20/40) minus
   UDP header size (8).

   Details of default maximum DNS/UDP payload size is Appendix C.
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Kazunori Fujiwara, JPRS <[e-mail]>