DNS Flashcards
What is a top-level domain (TLD)?
TLDs tell users the general purpose of the service behind the domain name. Examples include .com, .org, .net
What are the 4 servers involved in loading a webpage?
- DNS recursor
- Root nameserver
- TLD nameserver
- Authoritative nameserver
What is the DNS recursor?
The recursor can be thought of as a librarian who is asked to go find a particular book somewhere in a library. The DNS recursor is a server designed to receive queries from client machines through applications such as web browsers. Typically the recursor is then responsible for making additional requests in order to satisfy the client’s DNS query.
What is the root nameserver?
The root server is the first step in translating (resolving) human readable host names into IP addresses. It can be thought of like an index in a library that points to different racks of books - typically it serves as a reference to other more specific locations.
What is a TLD nameserver?
The top level domain server (TLD) can be thought of as a specific rack of books in a library. This nameserver is the next step in the search for a specific IP address, and it hosts the last portion of a hostname (In example.com, the TLD server is “com”).
What is the authoritative nameserver?
The authoritative nameserver is the last stop in the nameserver query. If the authoritative name server has access to the requested record, it will return the IP address for the requested hostname back to the DNS Recursor (the librarian) that made the initial request.
What is the recursive DNS resolver?
The recursive resolver is the computer that responds to a recursive request from a client and takes the time to track down the DNS record. It does this by making a series of requests until it reaches the authoritative DNS nameserver for the requested record (or times out or returns an error if no record is found).
What are the 8 steps in the DNS lookup?
The 8 steps in a DNS lookup:
1. A user types ‘example.com’ into a web browser and the query travels into the Internet and is received by a DNS recursive resolver.
2.The resolver then queries a DNS root nameserver (.).
- The root server then responds to the resolver with the address of a Top Level Domain (TLD) DNS server (such as .com or .net), which stores the information for its domains. When searching for example.com, our request is pointed toward the .com TLD.
- The resolver then makes a request to the .com TLD.
- The TLD server then responds with the IP address of the domain’s nameserver, example.com.
- Lastly, the recursive resolver sends a query to the domain’s nameserver.
- The IP address for example.com is then returned to the resolver from the nameserver.
8.The DNS resolver then responds to the web browser with the IP address of the domain requested initially.
What is DNS resolver?
The DNS resolver is the first stop in the DNS lookup, and it is responsible for dealing with the client that made the initial request. The resolver starts the sequence of queries that ultimately leads to a URL being translated into the necessary IP address.
What are the types of DNS queries?
- recursive query
- iterative query
- non-recursive query
What happens in recursive query?
In a recursive query, a DNS client requires that a DNS server (typically a DNS recursive resolver) will respond to the client with either the requested resource record or an error message if the resolver can’t find the record.
What happens in iterative query?
in this situation the DNS client will allow a DNS server to return the best answer it can. If the queried DNS server does not have a match for the query name, it will return a referral to a DNS server authoritative for a lower level of the domain namespace. The DNS client will then make a query to the referral address. This process continues with additional DNS servers down the query chain until either an error or timeout occurs.
What happens in a non-recursive query?
Typically this will occur when a DNS resolver client queries a DNS server for a record that it has access to either because it’s authoritative for the record or the record exists inside of its cache.
