Transcript Class 1 - Sept. 7

Data Communication Systems
and Networks
CSCI 465
Martin van Bommel
Lecture 1
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 Communication
by Claude Shannon
Changes in Networking Technology
• Emergence of high-speed LANs
– Centralized servers, distributed workgroups
– High-speed local backbones
• Corporate WAN needs
– Data intensive applications spread across wide
geographical areas
• Digital electronics
– Much higher bandwidth required for video/image
Three Layer Model
for 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
Communications Model
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
Data Communications Model
Transmission Lines
• The basic building block of any
communications facility is the transmission
line.
• The business manager is concerned with a
facility providing the required capacity, with
acceptable reliability, at minimum cost.
• However, the use of compression,
multiplexing, load sharing, and other line
features can significantly affect the end
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
Internet – Key Elements
Internet Architecture
Network Configuration