Section II: Telecommunications Network Alternatives

Section II: Telecommunications Network Alternatives
TELECOMMUNICATIONS ALTERNATIVES
Telecommunications is a highly technical, rapidly changing field of information systems technology. Most end users do not need a detailed knowledge of its technical characteristics. However, they need a basic understanding and appreciation for some of the important characteristics of the basic components of telecommunications networks.
Analyzing Nielsen Media Research and Others
We can learn a lot about the business impact of wireless-based telecommunications alternatives from this case. Take a few minutes to read it, and we will discuss it (See Nielsen Media Research and Others in Section IX).
A TELECOMMUNICATIONS NETWORK MODEL - [Figure 4.10]
Generally, a communications network is any arrangement where a sender transmits a message to a receiver over a channel consisting of some type of medium. Figure 4.10 illustrates a simple conceptual model of a telecommunications network, which shows that it consists of five basic categories of components:
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Terminals
Terminals are any input/output devices that use telecommunications networks to transmit or receive data. They include:
1. Video Terminals
2. Microcomputers
3. Telephones
4. Office Equipment
5. Transaction Terminals
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Telecommunications Processors
Support data transmission and reception between terminals and computers. They include:
1. Modems
2. Switches
3. Routers
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Telecommunications Channels
Telecommunications channels are the part of a telecommunications network that connects the message source with the message receiver. They include the physical equipment used to connect one location to another for the purpose of transmitting and receiving information. Data are transmitted and received over channels, which use a variety of telecommunications media. Media include:
1. Copper Wires
2. Coaxial Cables
3. Fiber Optic Cables
4. Microwave Systems
5. Communications Satellites
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Computers
Telecommunications networks interconnect computers of all sizes and types. They include:
1. Host Computers (mainframes)
2. Front-End Processors (minicomputers)
3. Network Servers (microcomputers)
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Telecommunications Control Software
Consists of programs that control telecommunications activities and manage the functions of telecommunications networks. They include:
1. Telecommunications Monitors (mainframe host computers)
2. Network Operating Systems (microcomputer network servers)
3. Communications Packages (microcomputers)
TYPES OF TELECOMMUNICATIONS NETWORKS
There are many different types of telecommunications networks. However, from an end user point of view, there are only a few basic types, such as:
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Wide area networks
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Local area networks
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Virtual private networks
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Client/server networks
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Network Computing
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Peer-to-peer networks
Wide Area Network (WAN): [Figure 4.11]
Wide area networks are telecommunications networks that cover large geographic areas. These networks cover areas such as:
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Large city or metropolitan area
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Whole country
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Many countries and continents
Local Area Network (LAN): [Figure 4.12]
Local area networks are telecommunications networks that connect information-processing devices within a limited physical area. These networks cover areas such as:
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Offices
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Classrooms
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Buildings
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Manufacturing plant
Some of the characteristics of LANs include the following:
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LANs use a variety of telecommunications media, such as ordinary telephone wiring, coaxial cable, or wireless radio systems to interconnect microcomputer workstations and computer peripherals.
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To communicate over the network, a PC usually has a circuit board called a network interface card.
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Most LANs use a powerful microcomputer with a large disk capacity as a file server or network server that contains a network operating system program (e.g., Novell NetWare) that controls telecommunications and the use of network resources.
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LANs allow end users in a workgroup to communicate electronically; share hardware, software, and data resources; and pool their efforts when working on group projects.
Virtual Private Networks: [Figure 4.13]
Many organizations use virtual private networks (VPNs) to establish secure Intranets and extranets. A virtual private network is a secure network that uses the Internet as its main backbone network, but relies on the firewalls and other security features of the Internet and Intranet connections and those of participating organizations.
Client/Server Networks: [Figure 4.14]
Client/server networks have become the predominate information architecture of enterprise computing. Computing power has rapidly become distributed and interconnected throughout many organizations by networked computer systems that take the form of client/server networks.
Characteristics of a client/server network:
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End user PC or NC workstations are the clients.
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Clients are interconnected by local area networks and share application processing with network servers, which also manage the networks.
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LANs may be interconnected to other LANs and wide area networks of client workstations and servers.
Continuing Trend:
Downsizing of larger computer systems by replacing them with client/server networks. For example, a client/server network of several interconnected local area networks may replace a large mainframe-based network with many end user terminals. This typically involves a complex and costly effort to install new application software that replaces the software of older, traditional mainframe-based business information systems, now called legacy systems.
Client/server networks are seen as more economical and flexible than legacy systems in meeting end user, workgroup, and business unit needs, and more adaptable in adjusting to a diverse range of computing workloads.
Benefits of client/server computing include:
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Clients (end users) can perform some or most of the processing of their business applications.
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LAN servers can share application processing, manage work group collaboration, and control common hardware, software, and databases.
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Data can be completely processed locally, where most input and output must be handled.
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Provides access to the workstations and servers in other networks.
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Computer processing is more tailored to the needs of the end users.
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Increases information processing efficiency and effectiveness, as users are more responsible for their own application systems.
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Allows large central-site computers to handle the jobs they do best - such as high-volume transaction processing, communications network security and control, and maintenance and control of large corporate databases.
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Clients at local sites can access the corporate superservers to receive corporate wide management information or transmit summary transaction data reflecting local site activities.
Network Computing: [Figure 4.15]
The growing reliance on the computer hardware, software, and data resources of the Internet, Intranets, extranets, and other networks has emphasized that for many users “the network is the computer”. This network computing, or network-centric, concept views networks as the central computing resource of any computing environment. It appears to be the architecture that will take computing into the next century.
Features of network computing include:
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Network computers provide a browser-based user interface for processing small application programs called applets.
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Network computers are microcomputers without floppy or hard disk drives that are designed as low-cost networked computing devices.
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Servers provide the operating system, applets, databases, and database management software needed by the end users in the network.
Peer-to-Peer Networks: [Figure 4.16]
The emergence of peer-to-peer (P2P) networking technologies and applications is being hailed as a development that will revolutionize e-business and e-commerce and the Internet itself.
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In the Napster architecture, P2P file-sharing software connects your PC to a central server that contains a directory of all of the other users (peers) in the network. When you request a file, the software searches the directory for nay other users who have that file and are online at that moment. It then sends you a list of user names that are active links to all such users. Clicking on one of these user names prompts the software to connect your PC to their PC (making a peer-to-peer connection) and automatically transfers the file you want form their hard drive to yours.
Major Advantages and Limitations of Napster Architecture – it is reliant on a central directory and server. The directory server can be slowed or overwhelmed by too many users or technical problems. However, it provides the network with a platform that can better protect the integrity and security of the content and users of the network
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Gnutella architecture is a pure peer-to-peer network, since there is no central directory or server. First, the file-sharing software in a Gnutella-style P2P network connects your PC with one of the online users in the network. Then an active link to your user name is transmitted from peer to peer to all the online users in the network that the first user (and the other online users) encountered in previous sessions. In this way, active links to more and more peers spread throughout the network the more it is used. When you request a file, the software searches every online user and sends your list of active file names related to your request. Clicking on one of these automatically transfers the file from their hard drive to yours.
Major Advantages and Limitations of Gnutella P2P Architecture – Have been plagued by slow response times and bogus and corrupted files containing viruses, junk, static, and empty code.
TELECOMMUNICATIONS MEDIA
To get from here to there, data must move through something. A telephone line, a cable, or the atmospheres are all forms of transmission media, or channels.
Telecommunications channels (communication lines or links) are the means by which data and other forms of communications are transmitted between the sending and receiving devices in a telecommunications network.
Telecommunications media are the physical media used by telecommunications channels. They include:
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Twisted-pair Wire
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Coaxial Cable
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Fiber Optics
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Terrestrial Microwave
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Communications Satellites
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Cellular and PCS Systems
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Wireless LANs
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The Wireless Web
Twisted-Pair Wire:
Twisted-pair is ordinary telephone wire, consisting of copper wire twisted into pairs (twisted pair wire).
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Most widely used media for telecommunications.
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Used in established communications throughout the world.
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Used for both voice and data transmissions.
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Used extensively in home and office telephone systems and many LANs and WANs.
Disadvantages:
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Susceptible to a variety of types of electrical interference (noise), which limits the practical distances that data, can be transmitted without being garbled.
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Signals must be “refreshed” every one to two miles through the use of repeaters, which are very expensive.
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Does not offer security.
Coaxial Cable:
This telecommunications media consists of copper or aluminium wire wrapped with spacers to insulate and protect it. Insulation minimizes interference and distortion of the signals the cable carries.
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Can carry a large volume of data - about 100 million bits per second (1800 to 3600 voice calls at once). A 2" diameter coaxial cable can carry up to 5,500 channels.
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Coaxial cables can be bundled together into a much larger cable for ease of installation.
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Can be placed underground and laid on the floors of lakes and oceans.
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Allows for high-speed data transmission used in high-service metropolitan areas for cable TV systems, and for short-distance connection of computers and peripheral devices.
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Used extensively in office buildings and other work sites for local area networks.
Disadvantages:
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More expensive than twisted pair.
Fiber Optics:
This media consists of one or more hair-thin filaments of glass fiber wrapped in a protective jacket. Signals are converted to light form and fired by laser in bursts.
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Relatively low cost
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Offers high transmission volume. A 2" diameter fiber optic cable can carry up to 50,000 channels.
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Can carry digital signals, as well as analog thus increase communications and capability.
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Provides substantial size and weight reductions.
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Provides increased speed and greater carrying capacity than coaxial cable and twisted-pair lines. Is not affected by and does not generate electromagnetic radiation.
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Is not susceptible to electronic noise and so has much lower error rates than twisted-pair and coaxial cable.
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Speed of communications is 10,000 times faster than that of microwave and satellite systems.
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Message security of fiber optic communications is very resistant to illegal data theft; taps can be easily detected.
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Can be used undersea for transatlantic use.
Biggest disadvantages of using fiber optic cable are:
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Installation can be difficult, as splicing the cable to make connections is not easy; however, this disadvantage also offers an advantage, as the lines are more secure, making tapping them difficult.
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Costly to purchase.
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Specialized communications equipment is expensive.
WIRELESS TECHNOLOGIES
Terrestrial Microwave
Involves earthbound microwave systems, which transmit high-speed radio signals in a line-of-sight path between relay stations spaced approximately 30 miles apart.
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Uses the atmosphere as the medium through which to transmit signals.
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Used extensively for high-volume as well as long-distance communication of both data and voice in the form of electromagnetic waves
Disadvantages:
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Microwave signals cannot bend around the curvature of the earth; instead they must be relayed from point to point by microwave towers, or relay stations, placed approximately 30 miles apart. (The surface of the earth typically curves about 8 inches every mile).
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Saturation of the airwaves with microwave transmissions has reached its maximum.
Communications Satellites
Use the atmosphere as the medium through which to transmit signals. A satellite is some solar-powered electronic device that receives, amplifies, and retransmits signals; the satellite acts as a relay station between satellite transmission stations on the ground (earth stations). Three satellites placed in orbit can cover the entire surface of the earth, with some overlap.
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Used extensively for high-volume as well as long-distance communication of both data and voice.
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Cost-effective method for moving large quantities of data over long distances.
Disadvantages:
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Satellites are very expensive to develop and place in orbit.
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Signals weaken over long distances; weather conditions and solar activity can cause noise interference.
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A satellite is useful for only 7 - 10 years.
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Anyone can listen in on satellite signals, so sensitive data must be sent in a secret, or encrypted, form.
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Depending on the satellite’s transmission frequency, microwave stations on earth can “jam,” or prevent, transmission by operating at the same frequency.
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Signal transmission may be slow if the signals must travel over very long distances.
Cellular and PCS Systems:
Use several radio communications technologies that divide a geographic area into small areas or cells typically from one to several square miles. Each cell has its own low-power transmitter or radio relay antenna device to relay calls from one cell to another. This technology is used to support mobile phone service, and mobile voice and data communications.
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Important communications medium for mobile voice and data communications.
Disadvantages:
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Not secured lines
Wireless LANs:
Other buildings frequently do not have conduits for coaxial cables or additional twisted-pair wire, and the conduits in newer buildings may not have enough room to pull additional wring through. One solution to this problem is installing a wireless LAN, using one of several wireless technologies. These include:
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High-frequency radio technology similar to digital cellular
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Low-frequency radio technology called spread spectrum.
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Infrared technology which uses beams of infrared light.
Advantages:
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Eliminate the difficulty and costly task of wiring existing buildings.
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IEEE 802.11b (WI-FI) is faster and less expensive than Standard Ethernet and other common wire-based LAN technologies.
The Wireless Web:
Wireless access to the Internet, intranets, and extranets is growing as more Web-enabled information appliances proliferate.
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Smart telephones, pagers, PDSs, and other portable communications devices have become very thin clients in wireless networks.
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Agreement on a standard wireless application protocol (WAP) has encouraged the development of many wireless Web applications and services.
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Telecommunications industry continues to work on third generation (3G) wireless technologies whose goal is to raise wireless transmission speeds to enable streaming video and multimedia applications on mobile devices.
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WAP standard specifies how Web pages in HTML or XML are translated into a wireless markup language (WML) by filter software and pre-processed by proxy software to prepare the Web pages for wireless transmission from a Web server to a Web-enabled wireless device.
Disadvantages:
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Distance limitations
TELECOMMUNICATIONS PROCESSORS
Telecommunications processors such as modems, multiplexers, switches, and routers perform a variety of support functions between the computers and other devices in a telecommunications network. A telecommunications processor includes:
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Modems
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Multiplexers
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Internetworked Processors
Modems:
These devices are the most common type of communications processor, and are probably the most widely used data communications hardware in business. Functions of modems include:
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Convert digital computer signals to analog signals for transmission over telephone lines, then to receive these signals and convert them back to digital signals. This process is known as modulation and demodulation. The word "modem" is a contraction of modulate and demodulate.
Multiplexers
A multiplexer is a communications processor that allows a single communications channel to carry simultaneous data transmissions from many terminals. Typically, a multiplexer merges the transmissions of several terminals at one end of a communications channel, while a similar unit separates the individual transmissions at the receiving end.
Internetwork Processors:
Telecommunications networks are interconnected by special-purpose communications processors called internetwork processors such as switches, routers, hubs, and gateways.
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Switch - is a communications processor that makes connections between telecommunications circuits in a network so a telecommunications message can reach its intended destination.
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Router - is a communications processor that interconnects networks based on different rules or protocols, so a telecommunications message can be routed to its destination.
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Hub - is a post switching communications processor. This allows for the sharing of the network resources such as servers, LAN workstations, printers, etc.
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Gateway - is a communications processor that connects networks that use different communications architectures.
TELECOMMUNICATIONS SOFTWARE
Software is a vital component of all telecommunications networks. Telecommunications and network management software may reside in PCs, servers, mainframes, and communications processors like multiplexers and routers. Telecommunications software packages for mainframe-based WANs frequently use telecommunications monitors or teleprocessing monitors. Servers in LANs rely on network management software called network operating systems (E.g., Novell NetWare or Microsoft Windows NT Server). Corporate Intranets use network management software like Netscape’s Enterprise Server. Many times, telecommunications software known as middleware can help diverse networks communicate with each other.
Network Management:
Telecommunications software packages provide a variety of communications support services. For example, they work with a communications processor to connect and disconnect communications links and establish communications parameters such as transmission speed, mode, and direction.
Network management packages such as LAN network operating systems and WAN telecommunications monitors:
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Determine transmission priorities
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Route (switch) messages, polls, and terminals in the network
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Form waiting lines (queues) of transmission requests
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Detect and correct transmission errors
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Log statistics of network activity
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Protect network resources from unauthorized access
Examples of major network management functions include:
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