What transport protocol does DNS primarily use?

The Domain Name System (DNS) primarily uses the User Datagram Protocol (UDP) for its operations. This is due to the nature of DNS queries, which are typically small, simple requests for resolving domain names to IP addresses. UDP is a connectionless protocol, which allows for faster performance as it does not require establishing a connection before sending data. This is particularly beneficial in the context of DNS, where users frequently make quick queries that do not require the overhead associated with a connection-oriented protocol.

Moreover, the standard DNS message size over UDP is limited to 512 bytes, which is generally sufficient for most standard DNS queries and responses. This lightweight nature and speed make UDP the preferred transport for DNS operations, facilitating rapid name resolution for applications and services over the internet.

In scenarios where the DNS response size exceeds the limits imposed by UDP (or if an error occurs), DNS can also use TCP as a fallback option, especially for zone transfers or larger queries. However, it’s important to note that the primary mode of operation for DNS remains UDP for its efficiency in handling the majority of name resolution requests.