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Data & Information
• What is data?– Elements that can be represented by a finite set of
symbols, such as digits or alphabets
• What is information?– a tangible, measurable thing– a subjective construction
What Is Communication?
• Symbolic• Representational– “The map is not the territory.”– Communication is only as good as the
representation
• Examples– spoken language, gestures, actions, icons
Human Communication vs. Data Communication
• Human communication is richer, less predictable– Words vary in meaning with context– Many factors influence meaning and perception of
message
• Data communication is more precise– Exact replication of information– Computers do not interpret, they simply relay
Telecommunication
• Uses electricity to transmit messages• Speed of electricity dramatically extends
reach – Sound waves: ~670 mph– Electricity: ~186,000 (speed of light)
• Bandwidth= information-carrying capacity of a channel
Data Communication
• Adding storage overcomes time constraints• Store-and-forward communication– E-mail– voice mail– facsimile– file transfer– WWW
Information and Communication
• Companies depend on generation and movement of information
• Communications technology fundamental• Enables reshaping of corporations– Communication technology driving change– Allows geographical dispersal
• Becomes management nightmare
Information Communication
• Voice communications - telephone– PSTN and PBX
• Data communications - text and numbers• Image communications - fax and beyond• Video communications - videoconferencing
Data Communications, Data Networks, and the Internet
“The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point”
The Mathematical Theory of Communicationby Claude Shannon
Changes in Networking Technology
• Emergence of high-speed LANs– Centralized servers, distributed workgroups– High-speed local backbones
• Corporate WAN needsCorporate WAN needs– Data intensive applications spread across wide
geographical areas
• Digital electronics– Much higher bandwidth required for video/image
Three Layer Modelfor Enterprise Communication
• Applications– Seen by end users– Voice, email, IM, image, video, collaborations
• Enterprise services– Design, maintenance, and support of apps– Capacity management and QoS provisions
• Infrastructure– Communication links, LANs, WANs, Internet access
Convergence of Communication Facilities - Benefits
• Efficiency– Better use of existing resources– Centralized capacity planning, asset management,
and policy management
• Effectiveness– Flexibility, mobility, enhanced connectivity– Rapid standardized service deployment
• Transformation– Enterprise-wide adoption of global standards
Communication Tasks
Transmission system utilization Addressing
Interfacing Routing
Signal generation Recovery
Synchronization Message formatting
Exchange management Security
Error detection and correction Network management
Flow control
Transmission Lines
• The basic building block of any communications facility is the transmission line.
• The business manager is concerned with a The business manager is concerned with a facility providing the required capacity, with facility providing the required capacity, with acceptable reliability, at minimum cost.acceptable reliability, at minimum cost.
• However, the use of compression, multiplexing, However, the use of compression, multiplexing, load sharing, and other line features can load sharing, and other line features can significantly affect the end choicesignificantly affect the end choice
Transmission Media
• Convert electronic signal to transmit over some medium– Twisted-pair, coaxial cable, optical fiber cable,
terrestrial and satellite microwave (wireless)
Data Transmission
• Communication techniques– analog vs digital, synchronous vs asynchronous– modulation, flow control, interfaces– error detection and correction– Multiplexing and compression
Networks
• LAN - Local Area Network– single building or cluster of buildings– ethernet, token ring, star, wireless
• WAN - Wide Area Network– city-to-city, country-to-country– telephone, ISDN, ATM, etc.
• Wireless Network– radio, microwave, satellite
Internet
• Internet evolved from ARPANET• Developed to solve the dilemma of
communicating across arbitrary, multiple, packet-switched network
• TCP/IP provides the foundation