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 <[email protected]>
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