ip addresses: Just as in real life if want to communicate with someone, we need a phone, it could be landline/mobile. In addition we also need one number, which should be unique. Then only we will be able to communicate. Same way if we want 2 or more than 2 systems to communicate, we need unique numbers for the systems, that numbers are called ip addresses. The ip addresses are 32 bit (ipv4), although new ipv6 is 128 bit. But here our focus will be on 32 bit ipv4.