IP : Every computer connected to the Internet is assigned a unique number known as an Internet Protocol (IP) address. IP addresses consist of four numbers separated by periods (also called a “dotted-quad”) and look something like 127.0.0.1. Since these numbers are usually assigned to internet service providers within country-based blocks, an IP address can often be used to identify the country from which a computer is connecting to the Internet. Subnet Mask : In IPv4 networks, the routing prefix is traditionally expressed as a subnet mask, which is the prefix bit mask expressed in quad-dotted decimal representation. For example, 255.255.255.0 is the subnet mask for the 192.168.1.0/24 prefix. Subnetting breaks a network into smaller realms that may use existing address space more efficiently, and, when physically separated, may prevent excessive rates of Ethernet packet collision in a larger network. A subnet mask allows IP networks to be subdivided for security and performance purposes