What Are the Two Types of DNS Server Requests?
When it comes to the Domain Name System (DNS), there are two types of server requests that play a crucial role in translating domain names into IP addresses. These requests are known as recursive and iterative.
Recursive DNS Server Requests
A recursive DNS query is the most common type of request made by client devices, such as computers, smartphones, or tablets. When a user enters a URL into their web browser, their device sends a recursive DNS query to the local DNS resolver. The resolver then performs all the necessary steps to find the IP address associated with the domain name.
The recursive process involves multiple steps:
- The local resolver checks its cache to see if it has previously resolved the domain name. If it has, it returns the corresponding IP address immediately.
- If the cache does not contain the requested information, the local resolver contacts one of the root servers in the DNS hierarchy. These root servers provide information about top-level domains (TLDs) like .com, .org, or .net.
- The root server responds to the resolver’s query with a referral to a TLD server responsible for handling requests for that specific TLD.
- The resolver then contacts the TLD server and receives another referral to one of the authoritative name servers responsible for storing information about that particular domain.
- The final step involves querying one of these authoritative name servers for the IP address associated with the domain name and returning it back to the client device.
Iterative DNS Server Requests
An iterative DNS query is the type of request made by DNS resolvers when they need to resolve a domain name that is not cached. Unlike recursive queries, iterative queries do not require the resolver to find the IP address on behalf of the client.
During an iterative query:
- The resolver sends a request to one of the root servers, asking for information about the TLD server responsible for the requested domain name’s TLD.
- The root server provides a referral to the resolver, pointing it to the appropriate TLD server.
- The resolver then contacts the TLD server and receives another referral, this time pointing it to one of the authoritative name servers responsible for that specific domain.
- Finally, the resolver sends a query directly to one of these authoritative name servers and receives a response containing the IP address associated with the requested domain name.
It’s important to note that iterative queries place more responsibility on DNS resolvers as they need to handle multiple requests and keep track of referrals. On the other hand, recursive queries simplify things for client devices, as they only need to send a single request and await a response.
Recursive and iterative DNS server requests are two fundamental types of queries used in translating domain names into IP addresses. Understanding how these requests work can provide valuable insights into how DNS functions in resolving domain names and ensuring smooth internet connectivity.