DNS stands for "Domain Name System," and it is used to manage and operate domain names on the internet. To communicate over the internet (IP networks), it is necessary to specify the IP address of the destination. However, IP addresses are numerical sequences, which are not suitable for humans to remember. For this reason, domain names such as "f5.com" are typically used for access. The role of DNS is to associate these domain names with their corresponding IP addresses. The process of finding an IP address from a domain name is called "forward lookup," whereas the process of finding a domain name from an IP address is called "reverse lookup." Together, these processes are referred to as "name resolution."
DNS is made up of numerous DNS servers that exist worldwide. No single DNS server holds all domain information; instead, a system called "delegation" is used to divide the management of domains. This allows the information required for name resolution to be managed in a decentralized manner. A domain that is managed in this way is called a "zone," and the DNS server managing a specific zone is referred to as the "DNS content server" or "authoritative DNS server" for that zone. On the other hand, a server that receives queries from users, makes requests to other DNS servers, and returns the results to users is called a "DNS caching server."
DNS servers are indispensable for operating the modern internet, but DNS servers with vulnerabilities can become targets for malicious attacks. Examples of such attacks include "delegation/transfer notification injection attacks" and "DNS flooding attacks." To protect against these kinds of attacks, the use of DNS proxies is effective. F5 provides the "F5 BIG-IP," which is equipped with DNS proxy functionalities.
