This is the first in a series of articles intended to help business users, cast into the role of security manager or administrator, understand how the technology that underlies the small and medium size business network works. In this installment, we begin with a series overview followed by an introduction to how a computer, and the network to which it's attached, see information.
It's not my intent to make you a network expert. The purpose of this series is to introduce basic concepts of networking. This mile-high understanding of how information flows around your organization is necessary before you can attempt to protect that information.
First, we'll look at how data is formatted. Next, we'll define a network at the most basic level. We'll then gradually expand the network with the introduction of additional network components and concepts. At the end of this series, you'll:
- Understand how data is formatted
- Understand network fundamentals
- Understand how information is transmitted over a network
- Understand how hubs, switches, firewalls, and routers are used and when each is the right answer for connecting network resources
- Be able to discuss LAN's, WAN's, and the Internet
- Understand how wireless networks work
In this article, we explore a few basic computing concepts we need to cover before launching into the world of networking. We also take a look at the format data takes as it travels between devices and how network addressing works. Throughout this book, we use the Ethernet standard to explain network principles.
Bits and bytes All information in a computer is composed of bits (binary digits). A bit is a 1 or a 0, represented in a computer's circuits as the presence (1) or lack (0) of voltage. A collection of eight bits, known as a byte, represents a value in Base 2 (see Base 2 Number System). In order for one device on a network to properly interpret the bytes sent from another device, they must share a common coding format that defines the meaning of each byte value. The most common of these formats is ASCII (American Standard Code for Information Interchange). Windows-based systems typically use this format. Table 1 is a partial list of ASCII codes and the symbols, letters, and numbers they represent. To a computer, the word HELLO would look like the collection of bits shown in Figure 1.