1.4 DNS

At this point, we mentioned MAC address and IP address. A MAC address is a 48-bit number, while an IP address (according to IPv4) is a 32-bit number. It is difficult for people to remember web site addresses as numbers.

Consequently, DNS was invented so that we can associate IP addresses with symbolic names that we can easily remember. The analogy of a world without DNS is that your cell phone has no address book. You have to remember exact phone numbers to reach others. A world with DNS, on the other hand, is a world with caller ID and phone-books. You just say ``Johnny'', and your cell phone automatically looks up the actual phone number.

DNS also provides one level of abstraction. A web site can change the actual IP address. As long as the ``phone book'' is updated accordingly, everyone can still locate the web site.