In message <004201c2e82c$dea75af0$07120b0a(_at_)huaweizw6v4czf>, Zhang Bao Feng
writ
es:
Dear Eastlake,
You are absoutly right, but if considering about the end-to-end SIP call, this
lookup time will make some influence with the calling establish time, as Mich
ael mentioned, "The performance of lookups scales linearly (worst case) with
the number of zone cuts ".
So that's the reason why I want to know the real-data about the lookup time in
current DNS system. :-) It may be a problem for real-time applications.
I believe that the crucial factor is whether or not the relevant
NS records and their associated A records are cached. If they are,
lookups will go very quickly. Of course, the cache is populated by the
first such lookup, so that one might be somewhat slower.
--Steve Bellovin, http://www.research.att.com/~smb