A) Is there consensus that it's better to set TC bit than to return
only some RRsets of critical additional data?
This is an issue that ought to be raised on namedroppers as the protocol rules cover the setting of the TC bit.
B) Is it better to omit all the courtesy addional data, rather than
omit some RRsets?
There's a tradeoff. If the sender omits information, it'll get hit with another query. If it sends more information, it may mislead the client.
The ingredients to this question also involve EDNS0.
I'd assume this, but it's not necessarily what I'd recommend now -
If the query arrives without EDNS0 (no OPT RR), then the client is older, hence is probably not fully functional on IPv6. In this case, the choice would be to send nothing or just the A record, whatever fits in the 512 byte message.
If the query arrives with EDNS0, it'll probably advertise a much larger acceptable return size, rendering this a non-issue. But in the odd event that the advertised larger size isn't enough for both, then I'd assume AAAA is preferred because this is a newer DNS client.
I wouldn't bet much on that assumption though.
C) (This is relevant if you answered "no" to B) Is it better to set
TC bit rather than return only some RRsets with courtesy
additional data?
It's best to stick with the current specifications on this. ;) The TC bit only means that some "important" data was left behind.
Opinions? Discussion? Etc.?
As for my personal preference: A) probably yes (not sure). B) yes, omit everything. C) possibly yes, not sure. (Doesn't matter if "yes" to B)
-- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Edward Lewis +1-703-227-9854 ARIN Research Engineer
If time travel were ever to be realized, public key crypto is toast. . dnsop resources:_____________________________________________________ web user interface: http://darkwing.uoregon.edu/~llynch/dnsop.html mhonarc archive: http://darkwing.uoregon.edu/~llynch/dnsop/index.html
