Address Resolution in DNS (Domain Name System)

DNS (Domain Name System) is an essential component of the internet infrastructure that translates human-readable domain names into computer-readable numbers called IP addresses. When you type in a website address in your web browser, then DNS translates into an IP address such as 126.32.0.36 (Assume) this IP address is used by computers for identification and then, they communicate with each other.

The process of converting domain names into IP addresses is called address resolution. Address resolution plays a critical role in the functioning of the Internet as it enables users to access websites using easy-to-remember domain names instead of complex IP addresses.

Address Resolution Process

This process involves several steps starting from the end user’s computer and lastly at the authoritative DNS server for the requested domain. Let’s understand each of these in steps.

1. Local DNS Lookup

The first step in the address resolution process is a local DNS lookup. When a user types a domain name in his web browser, their computer first checks its local DNS cache to see if it already has the corresponding IP address. If the IP address is found, the browser can immediately establish a connection to the website. However, if the IP address is not found, the computer proceeds to the next step.

2. Recursive DNS Query

The user's computer sends a recursive query to the resolver DNS server if the IP address is not located in the local cache memory. Resolver is typically provided by the user’s ISP (internet service provider) or a public DNS provider such as Google DNS or OpenDNS.

Once the resolver DNS server obtains the IP address associated with the domain, it stores this information in the cache memory for future reference. If multiple users are accessing the same domain name, the resolver DNS server may also provide this information to other users to speed up the process of accessing the domain name.

3. Looking up TLD (Top Level Domain DNS Servers)

The IP address of the TLD DNS server in charge of the requested domain’s TLD is returned by the root DNS server in response to the recursive inquiry. Once the recursive resolver receives the IP address of the TLD DNS responsible for the requested domain, it sends a query to that server to request the IP address of the authoritative DNS server for the domain.

4. Authoritative DNS Server Lookup

The IP address of the authoritative DNS Server for the desired domain is then returned to the resolver server by the TLD Server. The DNS server that can provide the domain name’s IP address and has the most recent information about it is the official DNS server.

It is important to note that if the authoritative DNS doesn’t have the most recent information about the domain name, it will forward the query to other DNS servers until the most up-to-date information is found. This ensures that users are always undirected to the correct IP address for the domain name they are trying to access.

5. IP Address Response

The authoritative DNS server for the requested domain receives a query from the resolver server and replies with the domain name‘s IP address. The user can now access the website using the IP address after the resolver caches it and transmits it back to the user’s computer.

After receiving the IP address from the authoritative DNS server, the resolver caches this information in its memory for future use. This helps to speed up the DNS lookup process. For the upcoming queries for the same domain name. It is worth noting that the process of DNS resolution is typically transparent to the user. Who only needs to enter the domain name in their web browser to access the desired website.

6. TTL (Time to Live)

Along with the IP address response, the resolver server also returns a TTL (Time to Live) number. The TTL indicates how long the resolver and other DNS servers can store the IP address before it expires. The resolver must run a new DNS query to get the most recent IP address when the TTL ends.

Conclusion

Users can reach websites using simple-to-remember domain names thanks to the address resolution, an essential DNS function. There are several stages in the address resolution procedure, such as recursive queries, caching, and TTL (Time to live) with millions of DNS servers located all over the globe, the DNS infrastructure is widely dispersed and essential to the operation of the internet. Without DNS, it would be extremely inconvenient and impractical for users to reach websites because they would have to memorize and use complicated IP addresses. To guarantee that users can quickly and dependably access the websites they need to, the address resolution process.