RE: large organization nameservers sending icmp packets to dns servers.

The point is, if you are the authority, you know how big the packet is. If you know it ain't over 512, then you don't need TCP.

Or are you saying you do? Wouldn't it be 'incredibly stupid' for recursive servers to -require- TCP, even for < 512 byte packets?

A TCP query is just as valid as a UDP query. If you claim to provide DNS for a zone but fail to respond to valid queries, you are breaking your promise. It's not whether or not you need TCP. It's that if you promise to provide a service, you should in fact provide that service. DS