Each device that's connected to the web has a specific identifier known as IP (Internet Protocol) address. This includes PCs, web servers, smartphones, switches, and so on. The pool of IP addresses, which was introduced initially, has been distributed, hence the so-called IPv4 IP addresses are steadily being replaced with IPv6 addresses. Every domain which opens an internet site has an IP record, that is the address of the server where it's hosted. When using the IPv4 system, the record is called A and it consists of four sets of numbers from 1 to 255 divided by a dot, while within the IPv6 system it's called AAAA and it is made up of 8 sets of hexadecimal numbers i.e. this kind of records use numbers from 0 to 9 and letters from A to F. An example of an AAAA record is 2010:0c48:43d3:2142:1012:8c3a:2475:2435 and this format works with a substantially larger number of IPs compared with the IPv4 format.