Internet Protocol: Street Addresses of the Internet

The TCP/IP model defines the four communication functions that protocols perform. TCP/IP is an open standard, which means that one company does not control it.

– Network Fundamentals, CCNA Exploration Companion © 2008 Cisco Systems Inc.

TCP/IP: Transport Control Protocol/Internet Protocol

This quote from a Cisco CCNA textbook gives the industry definition for TCP/IP, but it does little to help us understand how the protocol actually delivers electrons of data across that etheric gulf woven of links known as the World Wide Web to our eyes and ears in the comfort of our own home or business.

To help understand the following section of this article think of the Internet Protocol addresses as street addresses identifying each and every resource networked.

The country designation in the address is a large network which can be divided up into subnets which are then represented by the state designator of your address. The resulting subnet is then divided up into smaller subnets to represent the city and divided into what we can consider our “street” subnet. It is in this subnet that our Public IP address which would represent our house’s or place of business’s address number.

Public and Private IP Addresses

A Public IP address is defined in RFC 3330 (text) and a Private IP address is defined in RFC 1918 (text).

In essence a Public IP address is the Public Facing IP address which is identified with you on the World Wide Web. An example of a Public IP address in the North West is This IP represents a location in the USA, the state of Washington, in the Seattle area.

Your Public IP address can be discovered simply by using What Is My IP website’s services. Additional information is given such as the Internet Service Provider, whether or not a proxy server is being used, etc.

A Private IP address is exactly that, private. Unless your system is directly connected to the Internet, which some severs may be, you will be converting your Public IP address into a Private IP address through Network Address Translation in a router that is connected to the modem which gets you online to the Web. After your router has translated your Public IP into a Private IP address your personal networked resources are then somewhat hidden from the Internet at large.

With the proper equipment businesses as well as home users can then subnet the private IP address into subnets for local groupings of networked resources or logical groups of individuals such as the different departments in a company.

This is essentially TCP/IP in a nutshell. For more information on how the magic happens to get the data into a format for traveling across the Wild Web of ether and gossamer strands I cover the TCP/IP Layered Model in Protocol Data Unit: A Suitcase for Electrons.

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