telecommunications & networks chapter 6. is for management2 communication model message is...
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Telecommunications & Networks
Chapter 6
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Communication Model
Message is communicated via a signal Transmission medium (communication channel)
“carries” the signal
Feedback
Encode Decode
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Telecommunications
Electronic transmission of signals, e.g., telephone, radio, television
Telecommunication medium: Anything that carries an electronic signal & interfaces between a sending device & a receiving device
Data Communications: A subset of telecommunications referring to the sending, transmission, & receiving of data -- typically between computer systems
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Communications & TelecommunicationsIn human speech, signals are transmitted through the
air; in telecommunications, signals are transmitted through various media
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Elements of Telecommunications
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Types of telecommunication Media (1)
Twisted Pair Insulated copper wire Electrical signals
Coaxial Cable Inner wire core surrounded by shielding Electrical signals Higher transmission speeds than twisted
pair Fiber-optic Cable
Extremely thin strands of glass bound together
Light pulse signals Very high transmission speeds
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Types of Telecommunication Media (2)
Microwave Satellite
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Types of Telecommunication Media (3)
Cellular transmission signals are transmitted to receivers & integrated into the regular network.
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Modems
Translate digital signals to analog for transmission over the Public Switched Telephone Network (PSTN)
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Carriers & Services (1)
Common Carriers: Long distance telephone companies (AT&T, Sprint)
Value-Added Carriers: Private telecom systems offering enhanced services for a fee
Switched Lines: Circuits that use switching equipment to allow one device to connect to other devices (typical phone lines)
Dedicated Lines: Point-to-point circuits with no switching or dialing
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Carriers & Services (2)
Private Branch Exchange (PBX)Telecommunications switching equipment that allows
users within an organization to share outside linesCapable of handling both voice & data traffic
Integrated Services Digital Network (ISDN)Uses existing telecommunications infrastructure to
simultaneously transmit digital voice, data, & videoBeing phased out in North America (cable & ADSL are
replacing this service) T1 Circuits
High speed dedicated lines (1.54 Mbps) Equivalent to 24 regular voice lines
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Types of Network Configurations
Ring Bus
Star
Hierarchical
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LANs & WANs
Local Area Network (LAN): Connects computer systems & devices in the same geographic area (can be ring, bus, hierarchical, star, hybrid)
Wide Area Network (WAN): Ties together large geographic regions using microwave & satellite transmission or telephone lines
International Network (Global Area Network: GAN): Links systems between countries
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Types of Computing Connectivity (1)
Terminal-to-Host Applications & databases
reside on host mainframe computer
User accesses applications via a “dumb” terminal
File ServerFile server transfers data &
programs to PCs on the network where the PCs perform most processing.
“Dumb”terminal
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Types of Computing Connectivity (2)
Client/ServerApplications & databases reside on specialized host
computers (servers)Processing is shared between the host server & the
clientClient & server may be different types of computers
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Advantages & Disadvantages of Client/Server Computing
AdvantagesReduced costs Improved performance Increased security
Disadvantages Increased costsLoss of controlComplex multi-vendor
environment
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Communication Software
Communications Software: Provides error checking, message formatting, communication logs, data security/privacy, & translation capabilities for networks
Network Operating System (NOS): Systems software that controls the devices on a network & allows them to communicate with each other
Network Management Software: Monitors the use of network resources, scans for viruses, & ensures compliance with software licenses
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Communication Protocols
Protocol: Rules that ensure communications among different types of computers from multiple manufacturersOpen Systems Interconnection (OSI): Leading protocol
“model”; comprised of 7 layersTransmission Control Protocol/Internet Protocol
(TCP/IP): Two communication protocols of the Internet that work together (rapidly overtaking OSI)
Systems Network Architecture (SNA): IBM’s proprietary communication protocol
Ethernet: Protocol standard developed for LANs using a bus topology
X.400 & X.500: Standards for message handling & network directories
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Bridges, Routers, Gateways, & Switches
Bridge: Connects two or more networks that use the same protocol at the media control sublayer of the data link layer
Router: Operates at the network level of the OSI model with more sophisticated addressing software than bridges; can determine preferred paths
Gateway : Operates at or above the OSI transport layer & links LANs or networks that employ different architectures & use dissimilar protocols
Switch: Switches data to its destination by a point-to-point (rather than shared) connection
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Telecommunications Applications (1)
Linking computers & data terminals: Download & upload information
Voice Mail: Enables users to send, receive, & save verbal messages, including sending the same message to a “group”
E-mail: Enables users to send, receive, & save text messages & attached documents
Telecommuting: Enables employees to work away from the office using PCs & networks to communicate electronically
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Telecommunications Applications (2)
VideoconferencingAllows participants to
conduct long-distance meetings “face to face” while eliminating travel
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Telecommunications Applications (3)
Electronic Data Interchange (EDI)
Uses networks to allow output from one organization’s system to be processed directly as input to another organization’s systems, without human
intervention; follows standards & procedures
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Case: Nav Canada, pages 284-285
Next Class: Chapter 7