IP Address...or Who Am I?

For computers to talk on a network, they need a unique address. The most common type of address is an Internet Protocol, or IP, address. The address consists of a network portion and a device (computer) portion. I use the term "device" only because it could be something other than a computer, like a printer, tablet or smartphone. It isn’t critical to understanding IP Addresses that there is a separate network portion and a separate device portion, but it does become important when you to want to understand how data moves across your personal network and across the internet.

Currently, the most common format of IP address is Internet Protocol version 4 (IPv4). It consists of four groupings of 8 bits (each grouping is called an octet) separated by periods. While it is four groupings of bits, it is more commonly represented as four numbers between 0 and 255 separated by periods. Since I have a permanent IP Address on the internet, my address is 72.1.133.246. Since you’re reading this on my website, you may know it more commonly as www.tbruce.com (the name associated with the IP Address, and viewable as http://www.tbruce.com in your web browser’s window).

There are two types of IP Addresses: Static IP addresses and Dynamic IP Addresses. Static IP Addresses are permanently assigned to you by your Internet Service Provider (ISP). The only reason you need a static IP Address is if you want to provide a service (like email or manage a web server) on the Internet. This ensures people can always find you since your IP Address will always be the same. Most people, however, have a dynamic IP Address given to them when the turn on their computer, router or dial into their Internet Service Provider. The ISP keeps track of a list of addresses and gives it out to users (devices) when they connect to the internet.

Many users who have a broad-band connection (through a cable modem, DSL, or FIOS/Fiber Optic Service) think they have a static IP address because it’s the same every time they connect. However, it’s just a coincidence and they could get a different IP address at any time.

I’d like to add one last comment about IP Addresses before I explain the significance of the bits. There are two different types of IP Addresses: routable (addresses that are directly accessible on the internet) and non-routable (or what I’m going to call “private”) IP Addresses. (NOTE: This is not the same as a Virtual Private Network or VPN, which is a separate topic). Most homes and businesses have private IP addresses assigned to their employee’s or home computers. Then there is a device called a router that translates the “private” IP Address to a public IP Address and allows users to do things like browse the web and send email, among other activities. These devices are called “routers” because they route, or move traffic, between the two networks (the public and private or between two private networks). These devices may also be described as wireless routers or firewall-routers and are sold by companies like Cisco (Linksys), Netgear, and Buffalo, to name just a few manufacturers.

These private IP Addresses usually start with 10.x.x.x, 172.16.x.x (to 172.31.x.x), or 192.168.x.x (where “x” is some value between 0 and 255). These addresses fall into a range of defined IP addresses for a private (or a non-routable) network. (NOTE: I do NOT use the term secure. The use of a “private” network does not in any way mean your communications are secure from unauthorized users!) This allows communications between your devices (on your private network) and limits the data that “leaks” onto the Internet. In effect, it reduces the amount of “unnecessary” data on the Internet. (NOTE: This does not prevent viruses or other bad software from sending unauthorized data off your computer or network!) If you want more information on network addressing, please see http://www.ietf.org/rfc/rfc1918.txt

This document explains how Internet Protocol (IP) Addresses are unique on a particular network and allows computer or devices to talk to on another. It also provides a basic explanation of how private networks reduce the data traffic on the internet and connect local devices together.

Originally written: May 15, 2008, Finished Editing: October 28, 2008