[dns-wg] Re: FYI: IANA delegation procedure for the root zone and ipv6 glue

>>>>> "Roy" == Roy Arends <roy at dnss.ec> writes:

    Roy> Your wild guess is wrong, there are no queries possible that
    Roy> exceeds > 512 udp size. A QNAME has a maximum length of 255.

IIUC, there is nothing in the DNS protocol which limits the Question
Section to one QNAME/QTYPE/CLASS tuple. QDCOUNT can be > 1. Though I
suppose some could argue that a request which contained > 1 query was
unreasonable. [ISTR BIND will reject these with a FORMERR.] And if we
consider DDNS requests to be queries -- which in some sense they are
-- these can easily be bigger than 512 bytes. Just throw in a few
prerequisites and a handful of additions and deletions in the one DDNS
transaction.

Besides I think the original context of "unreasonable queries" was
really about queries which were unreasonable because of the responses
they'd provoke, not the size of the queries themselves. ie In the
absence of EDNS0 the server is forced to send truncated replies,
causing TCP retries. Come to think of it, a discussion of query size
is somewhat academic. If a query is going to be more than 512 bytes,
the client will have to either use TCP or EDNS0 to send it to the
server.