Chapter 1. Basic Concepts

In this chapter...

• Analog and Digital

• Bauds, Bits, Bytes and Codes—Getting Down to Basics

• Bandwidth—Measuring Capacity

• Compression and Multiplexing

• Protocols and Architectures

• LANs, MANs and WANs

Advanced telecommunications technologies have dramatically changed the way businesses operate, spawning new services and creating an interconnected worldwide community. It's difficult to imagine doing business without the ability to electronically exchange email, PowerPoint®, spreadsheet and PDF documents. The whole pace of innovation and the ability to make informed decisions would be notably slower without this capability. New developments in computer technology have had a major impact on telecommunications. Faster processors have increased the speed and power of routers and made speech recognition viable for applications such as Internet access, access to flight information and directory information.

A grasp of fundamental concepts such as digital, analog, bandwidth, compression, protocols, codes and bits provides a basis for comprehending the myriad concepts used to describe futuristic networks. Understanding cellular services, fiber optics and the Internet all depend on understanding basic terminology.

Protocols are an important ingredient in enabling computers to communicate. A protocol impacts speed, efficiency and the user interface to services. Protocols may be likened to etiquette. Just as etiquette spells out who shakes hands first and how people greet each other, protocols spell out the order in which computers transmit and how long computers should wait before they terminate a transmission. Protocols provide a common way to handle functions such as error detection and error correction. Protocols have an important role in the ease of developing applications. In cellular networks, protocols are used for the important function of defining security standards to make eavesdropping difficult.

Computers from different vendors exchange files, electronic mail and attachments across networks. Architectures and protocol suites make communications between computers and peripherals from different manufacturers possible. Layers within architectures contain protocols that define functions such as routing, error checking and addressing. The architecture or protocol suite is the umbrella under which devices communicate with each other. A protocol suite, Transmission Control Protocol/Internet Protocol (TCP/IP) is the foundation for the Internet.

Computers in homes and offices are connected together by local area networks (LANs), located within a building or in a campus environment. LANs link computers, printers, scanners and shared devices such as modems, videoconferencing units and facsimile machines to each other and to the Internet. LANs are connected to other LANs over metropolitan area networks (MANs) within cities, and wide area networks (WANs) across countries. Large attachments and Internet downloads have added congestion to internal data networks. Network congestion results in delays in transmission of, for example, email and database lookups. High-speed routers, switches, multiplexers and compression lessen congestion.

Multiplexers and compression make networks more efficient. Compression squeezes large amounts of data into smaller “pipes,” something like putting data into a corset. Physicians can access x-ray images over networks because improvements in compression make the images small enough to transmit efficiently. Compression has had a major impact on the nature of the Internet, particularly its use in streaming media. Compression in combination with more powerful computers and faster modems is making it possible to hear reasonably good quality music and radio over the Internet. It is changing the way consumers buy and listen to music.

Multiplexing adds efficiency by providing the means for multiple devices to share one transmission path. In the 1960s, T-1 had a significant impact on public network capacity, costs and reliability by allowing 24 communications paths to be carried digitally on one high-speed link. Today, dense wavelength division multiplexing schemes are common with one fiber optic link capable of transmitting 129,024 voice calls at optical carrier (OC) 192 rates of 10 gigabits per second. It is not a surprise, given this capacity, that experts are predicting a glut in backbone carrier networks. Backbones, also called the core, carry traffic on high-capacity lines between on and off ramps to networks.

The most common points of congestion in networks are where data enters and leaves the backbone. These on and off ramps, the network edges, are being upgraded. Routers responsible for carrying traffic to carriers' core networks are being developed to keep up with the speed of fiber optic backbone networks. New high-speed routers and wider availability of fiber optic cabling are bringing capacity closer to end-user commercial locations.