Networking 101 Guide

  The Basics

What is Networking Technology?

Networking technology consists of the hardware devices and software programs that transfer information between computers. Most networks in use today are interoperable with other networks because of the standards that exist for communication between network systems. 

How Computers View Information
People use computers to create, manipulate, and store many kinds of information, such as numbers, words, pictures, sound, and video. Information is stored on a computer in digital form. Regardless of the format in which the information is presented to a human being, the data is all pretty much the same from the perspective of the computer: collections of ones and zeros. These individual ones and zeros are referred to as "bits" of binary data.

Computers can transfer and manipulate this information in multiple ways: sometimes as a continuous "stream" of bits, as in the case of a live audio or video broadcast, and sometimes as blocks, which have a known number of bits. Streams or blocks of data, like files, email, and web pages all appear to a computer as collections of ones and zeros.

Speed and Units of Measurement
In the same way that you can measure the speed of cars or airplanes, you can measure the speed at which a particular piece of technology can transfer information.

The basic units of measurement for computer networking speed are:

Bit: A bit is the smallest and simplest piece of information that a computer can manipulate. A bit is either 0 or 1, with 0 meaning off and 1 meaning on. The term binary means a choice between two possible options-0 and 1. Computers combine collections of bits into more complex forms in order to represent data.

Byte (A byte is 8 bits): A byte usually represents a single character, such as a digit or a letter of the alphabet.

Bps (Bits per second): The number of bits transferred per second.

Kbps (Kilobits per second): Thousands of bits transferred per second. A typical modem can transfer 53,333 bits per second. The "56K" transmission is not possible due to limitations imposed by the FCC on the upper speed limit of modems.

Mbps (Megabits per second): Millions of bits transferred per second. An Ethernet card can transfer up to 10Mbps, or 10 million bits per second. A Fast Ethernet card can transfer up to 100Mbps, or 100 million bits per second.

Gbps (Gigabits per second): Billions of bits transferred per second. Large companies, telephone companies, and Internet companies measure traffic in gigabits per second, since their systems combine hundreds or even thousands of transmissions using the same connection.

Calculating Transmission Times
Suppose you have a document that contains 100,000 words, and you want to know how long it will take to transfer over a phone line using a 33.6Kbps modem.

• 100,000 words, at an average of 5 characters per word, totals 500,000 --characters.

• Each character takes one byte, so the document represents 500,000 --bytes.

• Each byte is represented by 8 bits, so 500,000 x 8=4,000,000 bits.

• 4,000,000 bits divided by 33,600=119 seconds, or about 2 minutes to --transfer a 100,000 word document.

Protocols
Computers can convert information into different forms, so that it can be transferred over different kinds of wiring systems. To ensure that systems created by different manufacturers can communicate with each other, engineering standards called protocols are observed. There are two basic types of protocols: physical and logical. Physical protocols control how information is sent over physical media like copper wire or fiber optic cabling. Logical protocols control how information is packaged and addressed for use by applications. Physical and logical protocols are usually used in conjunction with each other. Ethernet is a physical protocol. TCP/IP, which stands for Transmission Control Protocol/Internet Protocol, is an example of a logical protocol.

Defining Ethernet Technology

Ethernet cards transfer computer data more quickly than telephone modems. Instead of trying to carry data over a connection that was intended to carry the human voice, an Ethernet connection is designed to make the most efficient possible use of the wiring and system to carry computer data.

Ethernet (10BaseT)
The term Ethernet refers to computer communications devices that operate according to the guidelines contained in IEEE802.3, an industry standard that ensures that equipment from different manufacturers can interoperate. Information can be exchanged between Ethernet devices at up to 10Mbps. The kind of wire used to transfer Ethernet information is similar to but not identical to ordinary copper telephone cabling. Ethernet is also referred to as 10BaseT.

Fast Ethernet (100BaseTX)
The term Fast Ethernet refers to computer communications equipment that operates according to the guidelines contained in IEEE802.3u, an industry standard that ensures that equipment from different manufacturers can interoperate. Information can be exchanged between Fast Ethernet devices at up to 100Mbps. Fast Ethernet is also referred to as 100BaseTX (over copper wire), and 100BaseFX (over fiber optic cable).

Ethernet versus Fast Ethernet
As you can tell by the name, a Fast Ethernet connection is faster than regular Ethernet– to be precise, it's 10 times faster. Many companies are installing Fast Ethernet in their corporate networks, either as the standard speed for all workstations or as high-speed links between multiple Ethernet workgroups.

You can combine Ethernet and Fast Ethernet connections within the same network. This is generally accomplished by making connections of different types to the same switch. A device which interconnects different speeds of connection is called a "bridge," although that does not have to be the only function of the device.

Other Ways to Connect Computers Together

Ethernet and Fast Ethernet are not the only technologies you need to know about in order to connect your company's computers to the world.

Analog Modems
An analog modem allows you to send digital information (like computer data) over an analog link (a system designed to carry the sound of the human voice, rather than numbers).

Modulation uses sound waves rather than electrical signals in order to represent digital data. When a modem creates sounds on a telephone line, it is modulating the sound tones to send a representation of bits to the other computer, and demodulating, or interpreting, the sounds it hears from the other computer back to the digital format in which it existed on the other computer.

ISDN
ISDN stands for Integrated Services Digital Network. ISDN is a way of sending digital data over regular copper wiring. Although ISDN requires a special kind of telephone line from your telephone company, ISDN service is available in most urban areas. The speed and reliability of ISDN makes it an ideal choice for connecting a group of computers to the Internet.

The most common category of ISDN service used to connect a company to the Internet is called BRI, or Basic Rate Interface. A BRI ISDN connection consists of 2 "B" channels, each of which can transfer data at 64Kbps in either direction, as well as a "D" channel which is used by the phone company computer for "signaling," which means opening and closing connections.

You don't have to buy both B channels: many telephone companies will let you purchase the use of just one 64Kbps B channel, allowing you to add the second B channel later when you need 128Kbps of data-carrying capacity. ISDN B channels can also be used to carry voice telephone conversations, just like a regular telephone line.

Many small and medium-sized offices use an Internet gateway and an ISDN modem to connect their corporate networks to the Internet.

T1
A T1 line is a high-capacity data link supplied by a telephone company. A T1 line can carry up to 1.544Mbps of data in either direction. T1 lines are used to connect large companies and Internet Service Providers to the Internet.

Cabling

There are two common types of cabling used to connect Ethernet and Fast Ethernet devices: copper media and fiber optic media.

Copper Media
Most copper media that is used in offices is unshielded, which means that it comes in a relatively lightweight casing. It is called Unshielded Twisted Pair, or UTP, because of the way wires are twisted inside the casing. The two most common types of wire are UTP Category 3 wiring, which is suitable for 10BaseT Ethernet connections, and UTP Category 5, which is suitable for 10BaseT and 100BaseTX Ethernet connections.

Fiber Optic Media
Although this section commonly refers to carrying Ethernet signals over copper wiring, you can also purchase devices which use fiber optic media to carry network conversations. Fiber optic media has two major advantages over copper wiring:

• It can carry signals further – A fiber optic connection can carry a signal for --up to 1.25 miles (2 KM) without amplification or repetition. Compare that --to 100 yards (approximately 100 meters) for a signal carried over
--copper wire.

• It is not vulnerable to electromagnetic radiation – Since fiber optic media --carries network traffic as flashes of light instead of as electrical signals, it --does not suffer signal interference. For example, if you are trying to string --network cabling through a factory, and find that interference from
--machinery or fluorescent lighting is interfering with communications --on your network, you can install fiber optic cable as an -interference-free alternative.