[bind10-dev] NSAS Using Authority/Additional Information?

[Jerry Scharf]

dumb question that may be at the root here:

Does the selection of the closest enclosing zone get made from data in 
the rrset cache or from a separate data store? In all the systems I have 
seen, the decision is made by looking into the cache directly. If so, 
then you really don't need to keep hardly anything but the IP -> ttl 
mapping for the selection code in the resolver. Just extract the IP list 
by tracing the cache. It just seems to be easier from my simple minded 
view to keep any piece of data in one place. The cache has to have all 
the TTL management code in it already, why reproduce or partially 
reproduce it?

If there is the desire to hook an lookaside of zone->IPs to make the 
process faster, it should IMO be as simple as possible and maintain the 
minimum of state. Keep all the real data in the cache and come up with 
some kind of simple mechanism and/or timer for revalidating the 
lookaside. If you use a timer, add some fuzz so you don't get surges of 
validations on high qps systems.  Resource limits on the IP/ttl data and 
the lookaside should be a simple LRU.

jerry