In message <004201c2e82c$dea75af0$07120b0a@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