TCP/IP Basics

TCP/IP, or IP for short, is probably the most important “language” on Earth now, connecting everything together in this technologically dependent world, yet most people don’t understand it.

Everyday devices like computers, telephones, printers, TVs, phones, ATMs, cash registers, gas pumps, to name a few, all communicate with each other on TCP/IP.

I will attempt to explain TCP/IP in the context of everyday life, avoiding the unnecessary complication of the really high-tech stuff that overcomplicates it for the layman. Admittedly, this oversimplifies it and won’t stand up to the scrutiny of computer Geeks, but it communicates the basics as they pertain to the general user/public.

IP version 4 (IPv4), which is what most devices on Earth are still using, is a numbering system that gives every device a unique address, much like license plates on cars. This is made of four sets or “octets” of numbers separated by periods, eg: (that happens to be

The numbers can only go up to 254 each for any single device, so there’s a hard limit of just over 4 billion addresses, which is certainly not enough for all of the devices on Earth.

This IPv4 address exhaustion came to a head on January 3, 2011, when every routable IP address was used. Since then, a new IP version 6 has been implemented, which is used between the high-level Internet Service Providers (ISP) and the Worldwide Web’s infrastructure, however IPV4 devices, which we are all still using, have to be supported.

In anticipation of address exhaustion, a solution was created in 1996 to allow homes and small businesses to use private ranges of addresses which would not cause havoc through the Internet, called “non-routable IPs”. These non-routable IP ranges depend on Routers to work.

The non-routable IP ranges that were reserved are 10.x.y.z, 172.16.y.z through 176.31.y.z, and 192.168.y.z (octet ranges of 0-254 are denoted by the letters x, y or z)

“Non-Routable” means that the IP address can’t be seen through a Router. For example, anything starting with a 192.168 can’t be seen by any device outside of a Router.

The function of the Router is to act as a spokesperson for your network to the Internet. The Router takes any communications request from the non-routable IP device and passes it to the outside world with your single and unique WAN IP address assigned to your home or business Internet service.

If we program all of the devices on a LAN with non-routable IP addresses, we can have hundreds of devices in our home or business using the same addresses as other homes and businesses with no conflict, because they all look like a single and unique WAN IP address to the rest of the world.

The most popular non-routable IP ranges start with 192.168.x.y. Most out-of-the-box Routers will have a factory programmed IP address of or or

For a device to see another device on your network, the first three fields, or octets, of the IP address have to be the same. This generally limits any network to using addresses for every device which start with the same first three octets and unique numbers for the fourth octet. These first three octets are referred to as your “network number” or “Subnet”. A typical home or office may have a network number or Subnet of 192.168.1.x and every device has only got a different fourth octet.

LAN IP addresses come in two flavours; Static or Dynamic.

Static IP addresses are un-changing IPs which are programmed to a device in order for it to always be exactly where you expect it, for example a security DVR, printer or scanner.

Dynamic IPs are temporary automatically granted addresses that may change any time the device is off for extended times. These are usually suitable for devices that need web access but you don’t need access to them from another device, for example a smart phone or TV.

These fundamentals are some of the basic requirements of a healthy IP communication. Not conforming to these practices may allow some functionality, but would most certainly affect stability.

We’ll talk more about the difference between Local Area Networks (LANs) and Wide Area Networks (WANs) in our next segment.

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