NETWORKING

Computer networks consist of multiple computers and other electrical devices linked together. Networks are classified as local area networks (LANs) or wide area networks (WANs). The difference between LANs and WANs is usually determined by the length of the network. Generally, a LAN's distance includes only several hundred yards. LANs reside mostly in offices, work areas, classrooms, one building, or within several buildings. WANs exist over many miles, across several cities, and even around the world. WANs are multifaceted and complex networks. They require many devices that connect different computers using diverse communication services. WAN communication speed, reliability, and connectivity are more challenging to manage than those of a LAN.

HISTORICAL ACHIEVEMENTS IN COMMUNICATION AND TRANSPORTATION

Networks were developed as a communication method between computers at remote sites. They trace their roots back to nineteenth-century communication and transportation historical achievements. In America, people have always strived for faster travel and communication systems, particularly between the East and West Coasts. These systems included technology and experiments of varying complexity. For example, the Pony Express operated between 1860 and 1861. It provided seven-day mail service between St. Joseph, Missouri, and Sacramento, California.

In 1861 the Western Union Telegraph Company replaced the Pony Express and provided a faster, more reliable communication service. Furthermore, the transcontinental railroad was completed at Promontory, Utah, in 1869. These events improved the telegraph industry. The telephone was invented in 1876, and the first transcontinental telephone line was joined at Wendover, Utah, in 1915. This national telephone network provided a foundation for the wide area computer networks that evolved later in the twentieth century.

NETWORK CHARACTERISTICS

Ownership

LANs consist of computers, scanners, printers, and cables, which are privately owned. WANs connect computers, scanners, printers, and other devices that sometimes may be leased or rented from public and private telephone companies or data communication companies. These networks place high demands on security and reliability.

In addition, the communication line or medium that a company uses for its network is either cable or a wireless technology. When a business creates a WAN, it might not manage all the lines. Sometimes a business leases lines from a communication company. These companies are data and voice carriers such as MCI, Sprint, Verizon, Williams Communications, and AT&T. In these cases, the WAN is not entirely owned by the initial business. The business owns the line up to the point where the handoff with the data carrier occurs. Then, the carrier company handles the transfer of data and hands it back to the business's private LAN network at a location many miles away.

LAN size

The size of a LAN is set by the type of LAN configuration and specifications. For example, a LAN in a building might use an Ethernet technology such as 10Base2, also known as Thin Ethernet. This network technology can have one segment 656 feet (200 meters) in length or five linked segments up to 3,281 feet (1,000 meters) in length. A segment is the length of cable between two computers. For 10Base2, the 10 stands for 10 megabits per second, Base means baseband, and 2 equals 200 meters. Another technology is fiber distributed data interface (FDDI). FDDI networks can be up to 124 miles (200 kilometers) in length; these, however, are mostly used as backbone cables that link several LANs.

WAN size

Because WANs cover large areas, they consist of network technology that extends farther distances than LANs. They incorporate technologies such as FDDI, DSL (digital subscriber line), satellite, and microwave communications. Also, they require routers, switches, and hubs that amplify and direct signals to other routers, switches, and hubs. They can increase their distances nationally and globally.

Speed

Another characteristic of a computer network is speed. Network speeds are measured in bits per second. For example, a byte consists of 8 bits, and one alphabetic character or numeric digit consists of 1 byte. If an average word length is five characters and an average double-spaced page is about 200 words, then a page (counting words and spaces) would consist of about 9,600 bits—((200 words×5 characters)+199 spaces)×8 bits. If a network speed is 9,600 bits per second (bps), then a normal double-spaced page is transmitted every second. If a network speed is 56,000 bits per second (56Kbps), about six pages of information per second would be transmitted.

LANs and WANs, however, are typically faster than 9,600 and 56,000 bps. Many networks are 10, 16, or 100 megabits per second (Mbps). A 100 Mbps network can send 100,000,000 bits in one second—or 10,416 pages per second. Some networks can transmit 2 billion to 8 billion bits per second (gigabits, or Gbps). At 2 Gbps (2,000,000,000/9600), 208,000 pages flash by every second—more than most people read in a lifetime. Network speeds are even reaching terabits per second. One Gbps equals a thousand gigabits—almost unthinkable!

Signal carriers

The medium used to carry signals on a network can be conducted or radiated. Electric signals over wire are conducted. Fiber optic, microwave, infrared, and radio waves are examples of radiated media.

Wire can be shielded (STP) or unshielded (UTP) twisted pair or coaxial cable. UTP is cheaper to install than STP or coaxial cable; therefore, it is a popular network choice. STP or coaxial cable, however, should be used if there is electromagnetic interference on the network. Other networks overcome electromagnetic interference using fiber optic lines and wireless media. They are more expensive, however, than UTP wiring.

Twisted pair wires are rated by the American Wire Gauge (AWG) standard. Smaller numbers mean thicker wires. Regular telephone wire is rated a 28—too thin for most LANs. LANs use AWG ratings between 22 and 26. Another characteristic of twisted pair wires are the number of twists per foot. More twists may reduce cross talk and interference. Cross talk is when one line picks up noise or voices from another line during a conversation or data transmission. Usually 2 twists per foot are a minimum, while 4 are preferred.

Furthermore, the Electronic Industries Association (EIA) has another standard for rating wires. The EIA classifies LAN wires for different uses. For example, Category 3 (Cat 3) must contain 3 twists per foot and is commonly used in creating 10 Mbps LANs. Cat 5 is good for 100 Mbps and has sustained speeds up to 2 Gbps. Cat 7 reliably supports speeds up to 600 Mbps.

Baseband versus Broadband

Currently, most LANs use baseband transmission. Baseband means that there is one signal transmission per line. This means the channel or line is full when one device is sending data. It is easier for baseband LANs than for broadband LANs to have high speeds, behave reliably, and operate with low error rates. Also, baseband LANs are easily monitored by network administrators.

Broadband, on the other hand, means that the line can handle several transmission signals at one time. This is accomplished using different frequencies that act as separate channels. This is called frequency division multiplexing. Broadband networks have the capacity to handle more channels than baseband networks, but they are more expensive and intricate. A single cable that transmits many television channels is an example of broadband technology.

Because of the high interest in obtaining Internet services, broadband technology is becoming more affordable and widespread. For example, some cities are implementing a technology called broadband over power lines (PBL). PBL is a computer network providing Internet data service using broadband transmissions over public power lines. These networks operate at speeds of 90 Mbps.

NETWORK SECURITY

Networks are diverse connections of components that are susceptible to interference, such as unauthorized breaches by attackers. Because of these vulnerabilities, network administrators have ongoing challenges keeping networks secure. Some of the vulnerabilities include eavesdropping, viruses, denial of service (DoS), spoofing, and e-mail bombs. These potential hazards can disrupt and curtail the goals of effective networks. Government networks, financial institutions, educational institutions, and specialty businesses are highly susceptible to attackers. Some of the methods to assure better security are established network firewalls, computer user policies, filter rules, incoming packet inspection mechanisms, and server isolation. While these can be successful, they are not foolproof. Network security planning and implementation is ongoing and constantly improving.

Wireless networks

Wireless LANs are becoming more useful in homes, businesses, and schools. They are also known as Wi-Fi networks. Most of these networks use radio waves for their transmission medium, but some use infrared light waves. Radio waves travel free at the speed of 186,000 miles per second. Unlike light waves, radio waves can travel long distances and can penetrate through nonmetallic objects. Radio waves spread out over vast areas. Because of these advantages, wireless LAN and WAN networks are expanding rapidly.

Interoperability

A concern on wireless networks, interoperability results when vendors produce wireless components that do not work together. Efforts to prevent this from happening have been implemented. One example is the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. Most wireless vendors have agreed to follow this standard when producing wireless components. Also, the Wireless Ethernet Compatibility Alliance began certifying vendors who produce components that adhere to 802.11 provisions.

Security on Wi-Fi networks is also a major concern. Security protocols for wireless networks are provided in the 802.11i IEEE data communication standard. This standard defines security protocols that prevent the major security issues such as eavesdropping, spoofing, DoS, and others.

SUMMARY

Networks have become an operational necessity for just about every business, government entity, school, and household. Burgeoning information demands make it necessary to link computers for efficient data sharing, storage, and communication. E-mail services are becoming a communication staple among computer owners. Additionally, enhanced services such as electronic commerce, graphics, and videoconferencing are causing networks to grow and expand. Properly managed networks increase productivity and assist managers and administrators with communication demands. Consequently, networks are an essential component of the information system plan of every business. Networks provide a crucial advantage for end users.

see also Information Systems ; Videoconferencing

Dennis J. LaBonty