On Fri, Sep 23, 2016 at 05:03:00PM +0100, RW wrote: > I've been wondering whether recursive is actually the correct term. > > As I understand it there are two types of DNS lookup: > > 1. Iterative - where results are found by working down through > multiple servers from the root servers. > > 2. Recursive - where a request is made to a single nameserver which > handles the whole look-up on behalf of a client. > > What this turns on is whether a forwarding server is a distinct > class of of nameserver or a type of recursive server. I think the > latter is most logical, since both provide a recursive interface. > Definitions of the term "recursive server" that I've seen contrast it > only with "authoritative server". > > One thing is certain, what you want is a name server that does > *iterative* lookups.
A forwarding server is a recursive server. The two are more or less synonymous. Both iterative and recursive servers may or may not cache their results to speed up future queries for the same information. Authoritative servers are the original source of the record data for one or more sections of the DNS hierarchy. If they receive a request for a record they hold authority over, they return it directly. If they receive a request for a record they _don't_ hold authority, then it depends on how the server is configured. It could recurse, it could iterate, or it could reject the query. Most internet-facing authoriative servers reject queries for parts of the domain hierarchy they don't hold authority over. --Sean
