11 / 12 Application Layer & Protocols

Eight One Eight Zero

A resolver receives a DNS message over UDP port 53. Only its first 33 bytes are shown, the fixed header followed by the question section; whatever follows has been cut from the dump.

0000  8f 3a 81 80 00 01 00 03  00 00 00 00 03 77 77 77
0010  07 65 78 61 6d 70 6c 65  03 63 6f 6d 00 00 01 00
0020  01

Which single statement about it is true?

A

TC is set, so the resolver must repeat the query over TCP.

B

It is a successful response holding 3 answer records for www.example.com type A, from a server that is not authoritative for the zone.

C

It is a query, since RD is set and only queries ask for recursion.

D

AA is set, so this came straight from the authoritative name server for example.com.