Data Communication Systems and Networks

CSCI 465Martin 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 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

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 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

Internet – Key Elements

Internet Architecture

Network Configuration