[bind10-dev] Resolver - address database requirements

[Stephen Morris]

A couple of questions:

An entry in the database (now renamed "Nameserver Address Store") is created when the resolver receives a referral for a parent zone.  For example, in looking up www.example.com, the referral information from the com nameserver will contain the list of nameservers for example.com plus possible glue records.  The resolver will pass this information to NAS, which will use it to seed the nameserver information for the zone.  However, the information in the parent zone is just a hint - it is the zone itself that is authoritative for that information.

There appear to be three options:

a) Do nothing, just use the information as given.

b) Use the information given in the initial referral as a guide and have the NAS explicitly query for nameservers from the zone (and follow it up with queries for the addresses of the nameservers).  While this is taking place pass the referral data back; when it is complete, use the authoritative data.

c) The resolver has to report round-trip times back to the NAS for the latter to update the metrics used to select a nameserver address.  It could also pass back the Authority and Additional sections from the query and the NAS use that to update the information with authoritative data.

What does BIND-9 do, and should the behaviour be changed for BIND-10?

Related to option (c) is the question of expiration times.  If the resolver is updating the NAS with Authority and Additional information, it should be possible for the NAS to update the expiration time for entries in the NAS (for the NS information and the addresses of the in-zone nameservers).  This will incur additional overhead - is it worth the effort?

Stephen