DNSförfrågan

DNSförfrågan, or DNS query, is a request sent to a Domain Name System (DNS) server to resolve a domain name into an IP address. This process is fundamental to the functioning of the internet, as it translates human-readable domain names (like www.example.com) into numerical IP addresses (like 192.0.2.1) that computers use to identify each other on the network.

There are two main types of DNS queries: recursive and iterative. A recursive query is sent by a client to a DNS resolver, which then handles the entire resolution process, including querying other DNS servers if necessary. An iterative query, on the other hand, is sent by a DNS resolver to another DNS server, which responds with the best answer it has available, without performing further queries.

DNS queries can be performed using different protocols, with the most common being DNS over UDP (port 53) and DNS over TCP (also port 53). UDP is typically used for its speed and efficiency, while TCP is used for larger queries or when the response is too large to fit in a single UDP packet.

The structure of a DNS query includes several fields, such as the query ID, flags, question section, and additional sections. The query ID is a unique identifier for the query, while the flags indicate the type of query and other parameters. The question section contains the domain name being queried and the type of record being requested (e.g., A for IPv4 address, AAAA for IPv6 address, MX for mail exchange).

DNS queries can be subject to various security measures, such as DNSSEC (DNS Security Extensions), which adds a layer of cryptographic authentication to DNS responses, and DNS over HTTPS (DoH) or DNS over TLS (DoT), which encrypt DNS traffic to protect it from eavesdropping and tampering.