Introduction to Information Technology Turban, Rainer and Potter John Wiley & Sons, Inc. Copyright 2005
Network and Telecommunications Basics
Chapter Outline The telecommunications system Network services Network protocols Network processing Types of computer networks TG 4 3
Learning Objectives Describe the component of a telecommunications system Describe the eight basic types of communications media, including their advantages and disadvantages. Describe the major types of network services. Describe the Ethernet and TCP/IP protocols. Differentiate between client/server computing and peer-to-peer computing Describe the two major types of networks. TG 4 4
TG4.1The telecommunications system Telecommunications system: Combination of hardware and software that transmits information (text, data, graphics, and voice) from one location to another. Analog signal: Continuous waves that transmit information by altering the amplitude and frequency of the waves. Digital signal: A discrete pulse, either on or off, that conveys information in a binary form. TG 4 5
The major components of a telecommunications system: Hardware Communications media Communications networks Communications software Data communications providers Communications protocols Communication applications TG 4 6
Communications processors Hardware devices that support data transmission and reception across a telecommunications system. Modem: Device that converts signals from analog to digital and vice versa. TG 4 7
Multiplexer: Electronic device that allows a single communications channel to carry data transmission simultaneously from many sources. Front-end processor: A small secondary computer, dedicated solely to communication, that manages all routing communications with peripheral devices. TG 4 8
Communication media and channels Communication channel. Pathway for communicating data form one location to another. TG 4 9
Cable media: Communications channels that use physical wires or cables to transmit data and information. Broadcast ( wireless) media: Communication channels that use electromagnetic media (the airwaves ) to transmit data. Twisted-pairs wire: copper wire twisted together in pairs used for most business telephone wiring. TG 4 10
Coaxial cable. Insulated copper wire; used to carry high-speed data traffic and television signals. Fibber- optic cable. Thousand of very thin filaments of glass fibers, surround by cladding, that transmit information via light pulses generated by lasers. Microwave transmission. Communication channel that uses towers to send wireless signals; used for highvolume, long-distance, point-to-point communication. TG 4 11
Satellite transmission. Communications channel that uses orbiting satellites to send digital transmission point-to-point. Propagation delay. Brief pause between the sending and receipt of a satellite transmission. Global positioning system (GPS). A wireless system that uses satellites to enable users to determine their position anywhere on the earth. TG 4 12
Radio transmission. Communications channel that uses radio wave frequencies to send data directly between transmitters and receivers over short distances. Satellite radio (digital radio). Form of radio transmission that offers uninterrupted, near CDquality music beamed to your radio from space. Cellular radio technology. Use of radio transmission between cells in geographic service areas and a mobile telephone switching office, enabling wireless phone service. TG 4 13
Personal communication services (PCS) technology. Wireless communication technology that uses lowerpower, higher-frequency radio waves than cellular radio technology, making PCS devices effective in places where cellular devices are not. Infrared. Red light not commonly visible to human eyes; can be modulated or pulsed for conveying information. Bandwidth. The range of frequencies available in a communications channel stated in bits per second. TG 4 14
TG4.2 Network services Computer network. A system connecting communications media, hardware, and software needed of two or more computer systems and/ or devices. Switched lined. Telephone lines through which data transmissions can be routed or switched to their destination. Dedicated lines (leased lines). telephone line that provide a constant connection between two devices and require no switching or dialing. TG 4 15
Integrated services digital network (ISDN). A high-speed technology that allows users to transfer voice, video, image, and data simultaneously, over existing telephone lines. Digital subscriber line (DSL). A high-speed, digital data-transmission technology using existing analog telephone lines. TG 4 16
Cable modem. A modem that operates over coaxial cable and offers high-speed access to the Internet or corporate intranets. Packet switching. Data transmission technology that breaks up blocks of text into small, fixed bundles of data (packets) that are sent independently through the network. Frame relay. A data transmission technology that is faster and less expensive than packet switching. TG 4 17
Fibber distributed data inference (FDDI). Data transmission standard based on high-speed, high-capacity capabilities of fiber optics. Asynchronous transfer mode (ATM). Data transmission technology that uses packet switching and allows for almost unlimited bandwidth on demand. TG 4 18
Switched-hub technology. Data transmission technology that boots local area networks by adding an ATM-like packet-switching capability. Synchronous optical network (SONET). An interface standard for transporting digital signals over fiber-optic lines; allows the integration of transmissions from multiple vendors. T-carrier System. A digital transmission system that defines circuits that operate at different rates, all of which are multiples of the basic 64 kbps used to transport a signal voice call. TG 4 19
TG4.3 Network protocols Protocol. The set of rules and procedures governing transmission across a network Ethernet. The most common network protocol. TG 4 20
Gigabit Ethernet. The most common network protocol in large corporations, which provides data transmission speeds of one billion bits per second. Transmission control protocol / internet protocol (TCP/IP). A file transfer protocol that can send large files of information across sometimesunreliable networks with assurance that the data will arrive uncorrupted. TG 4 21
The International Standards Organization open systems interconnection protocol (ISO-OSI) The ISO-OSI model defines how software on different system communicates at different layers. The model has seven layers, each having its own well-defined function. Layer 1: physical layer: define the mechanism for communicating with the transmission media and interface hardware. Layer 2: data link layer: validates the integrity of the flow of data. Layer 3. network layer: defines the protocols for data routing to ensure that information arrives at the correct destination TG 4 22
The International Standards Organization open systems interconnection protocol (ISO-OSI) cont Layer 4: transport layer: defines the protocols for structuring messages. Layer 5: session layer : coordinates communications and maintains the session for as long as needed including security and log-on functions. Layer 6: presentation layer; defines the way data is formatted, converted and encoded Layer7: application layer. Defines the way that applications programs such as e-mail interact with the network TG 4 23
TG4.4 Network processing strategies Distributed processing. Network architecture that divides processing work between two or more computers, linked together in a network. Client/ server computing. Form of distributed processing in which some machines (servers) perform computing functions for end user PCs (clients). Peer- to peer processing. A type of client/ server distributed processing that allows two or more computers to pool their resources, making each computer both a client and a server TG 4 24
TG4.5 Types of computer networks Local area network (LAN). Network that connects communications devices in a limited geographical region (e.g., a building ), so that every user device on the network can communicate with every other device. Topology. The physical layout and connectivity of a network TG 4 25
LAN technology File server. A repository of various software and data files for the network, which determines who gets access to what and in what sequence Network interface card. Hardware that specifics the data transmission rate, the size of message units, the addressing information attached to each message and network topology. Gateway. A communications processor that connects dissimilar networks by translating from one set of protocols to another Bridge. A communications processor that connects two networks of the same type. Router. A communications processor that routes message through several connected LANs or to a wide area network. TG 4 26
Wireless local area networks (WLANs) WLANs: Technologies (e.g., Bluetooth and wifi) that provide LAN connectivity over short distance, typically limited to less than 150 meters. Bluetooth. A wireless technology that enables temporary, short-range connection between wireless devices and enables these devices to communicate with each other via low-power radio frequencies. TG 4 27
Wireless local area networks (WLANs) Wi-Fi (Wireless Fidelity). A wireless technology that can transmit information at a range up to 300 feet; another name for the 802.11b standard on which most WLANs run. Private branch exchange (PBX). a type of LAN that controls telephone switching at a company site. TG 4 28
Wide area networks (WAN) A network, generally are provided by a common telecommunications carrier, that covers a wide geographic area. Value-added network (VAN). A private, dataonly network that is managed by an outside third party and used by multiple organizations to obtain economies in the cost of network service and network management. TG 4 29
Wide area networks (WAN) cont Virtual private network (VPN). A WAN operated by a common carrier; provides a gateway between a corporate LAN and the Internet. Tunnelling. The process of sending data over the Internet in encrypted form. TG 4 30
Enterprise Networking Interconnected multiple LANs and WANs. TG 4 31
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