DNS Resolution

• Resolving addresses are performed with DNS Request messages.
• DNS requests may be iterative or recursive. At almost every step, the cache of the current system is checked before attempting another query to reduce the load on higher servers.
• Recursive requests allow the recipient of a DNS query to make it's own DNS query. That recipient can make it's own query if needed. This is the typical method.

• Iterative requests mean the host expects the DNS server to reply immediately, without asking any other DNS servers. The reply will either be from the cache, or a referral to another name server. Iterative requests may then be made by the initial host if needed.

• If at any point there is a known resolution, it is passed back down immediately. No need to bother anyone else in the chain. This answer will be cached as it goes back down.