What Are Domain Name System (DNS) Resolvers and How Do They Work?

DNS resolvers play a key role in converting Web links to IP addresses, acting as a link between your computer and the Internet's DNS infrastructure. A DNS resolver is a local server that stores a central database of DNS nameservers and manages DNS requests for all the clients on your network. With DNS resolvers, your computer does not need to store addresses for multiple online nameservers, a process which is difficult to manage effectively.

How DNS Works

DNS systems allow network clients to convert Universal Resource Locators, or URLs, into IP addresses. This is a key part of network operation, as computers and other devices generally need to know each other's IP address in order to communicate over a network. When you provide your computer with a Web link, the computer issues a DNS request asking for the IP address that corresponds to that address. The DNS then responds with the corresponding address, allowing the computer to communicate with the server that hosts that site.

Role of Resolvers

A DNS resolver is a server that acts as a “first port of call” in the DNS process. When a network client contacts a resolver, that resolver contacts multiple authoritative nameservers -- the servers that actually hold the IP address information -- in order to get the necessary IP address. DNS requests may involve nameservers all over the world.

Increased Efficiency

DNS resolvers increase the efficiency of a DNS system. Without resolvers, every computer on a network would need to be provided with the addresses of several authoritative nameservers in order to resolve addresses. In addition, each computer's server list would need to be kept up to date individually. Using resolvers means that all the clients on a network have access to a central list of authoritative nameservers, reducing the management time needed to keep the system current.

Performance Benefits

Some DNS resolvers cache the results they send to clients. This means that if another client requests the same IP address at a later time, the resolver can provide that IP address directly without having to contact any external nameservers. Storing results locally improves DNS response time and helps to reduce network load, because certain DNS results do not need to leave the local network in order to be fulfilled.