Domain Name System (DNS)

All devices on a network have a unique IP address, which allows communication among themselves. However, some networks may be very large, such as the internet, with a lot of devices. Since each device has an IP address, it would eventually become a bit difficult to remember each device's IP address. Let's imagine you want to visit www.facebook.com; this address is known as a host name, and we humans would open our web browser and simply enter www.facebook.com into the address bar within our web browser, and within a few seconds Facebook's website is presented to us. However, in the background, your computer will resolve the host name, www.facebook.com, to the various IP addresses which belongs to Facebook such as, 31.13.71.38:

The protocol that is responsible for resolving hostnames to IP addresses is known as DNS. The DNS protocol operates on UDP port 53. However, TCP port 53 is used to exchange DNS entries between one DNS server and another; this process is known as DNS zone transfer.