Anycast DNS is a further development of traditional DNS (unicast DNS), in which several nodes worldwide share the same IP address. In contrast to unicast, where requests are sent to a single server, anycast sends requests to the geologically closest available node. This enables an optimized distribution of data traffic, reduces latency and offers protection against DDoS attacks (DNS flood).
Every device or server that has a connection to the Internet has a unique IP address. With unicast, communication follows a 1:1 pattern, i.e. all communication from a specific device is sent to a specific target device. Anycast is different. With anycast, communication takes place according to the 1:n pattern. This means that a specific device can communicate with several servers that all use the same IP address or IP pool.
You can think of an IP address like a postal address. It is always tied to a specific location to which a message is sent. With Anycast, however, it is as if the recipient has several residences around the world. The letter is then always delivered to the nearest residence, depending on where the sender sends the letter from.
DNS (Domain Name System) acts as a kind of "phone book" of the Internet by converting human-friendly domain names into machine-readable IP addresses. The conversion of a host name into alphanumeric IP addresses is known as resolving. This is done via so-called DNS resolvers. When a user wants to visit a website, the client, e.g. PC, cell phone, smartphone, etc., requests the IP address of the website from a DNS resolver.
With Anycast, this request is sent to a network of DNS resolvers instead of to a specific resolver. This speeds up the resolution of the request considerably, as it is always routed to the nearest and best available resolver. Furthermore, a network of DNS resolvers has the advantage that the availability of DNS resolution services is greatly increased. If a DNS resolver is not available, the request can be processed by another resolver in the network.
In the conventional unicast DNS system, a single IP address is used for a DNS server. This means that all requests from Internet users are sent to this specific IP address. This central point of contact is responsible for resolving domain names into IP addresses.
This has the disadvantage that unicast DNS servers can become overloaded during heavy traffic, especially in regions with a high number of internet users. Concentrating all requests on a single IP address can lead to delays and affect overall performance. Furthermore, using a single IP address also carries the risk of failure. If the central DNS server fails or is unavailable, all associated services can be affected. This single-point-of-failure scenario is a vulnerability that can be addressed by an improved DNS infrastructure, as is the case with Anycast DNS.
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