Flashcards in DNS Deck (3)
What is a iterative query?
-A client asks the DNS server for an answer, and the server returns the best answer.
-Usually stored in server's cache.
-If the server doesn’t know the answer, it may direct the client to another server through a referral.
What is a recursive query?
-The client sends a query to a name server, asking it to respond the requested answer or with an error message.
The server can’t come up with the right answer.
The domain name doesn’t exist.
Here’s what happens to resolve the request:
1. The resolver sends a recursive DNS query to its local DNS server asking for the IP address of www.whitehouse.gov. The local name server is responsible for resolving the name, and it cannot refer the resolver to another name server.
2. The local name server checks its zones, and it finds no zones corresponding to the requested domain name.
3. The root name server has authority for the root domain and will reply with the IP address of a name server for the .gov top-level domain.
4. The local name server sends an iterative query for www.whitehouse.gov to the Gov name server.
5. The Gov name server replies with the IP address of the name server servicing the domain www.whitehouse.gov
6. The local name server sends an iterative query forwww.whitehouse.gov to the whitehouse.gov name server.
7. The whitehouse.gov name server replies with the IP address corresponding to www.whitehouse.gov.
8. The local name server sends the IP address of www.whitehouse.gov back to the original resolver.