C/IL 102 Computer and Information Literacy
CHAPTER 6
COMMUNICATIONS AND NETWORKS
WHAT IS COMMUNICATIONS?
Transmission of data and information between two or more computers
EXAMPLES OF HOW COMMUNICATIONS IS USED
Electronic mail (e-mail)
Voice mail
Facsimile (fax)
Telecommuting
Videoconferencing
Groupware
Electronic data interchange (EDI)
Global positioning systems (GPSs)
Bulletin board systems (BBSs)
Online services
The Internet
A COMMUNICATIONS SYSTEM MODEL
A computer or a terminal
Communications equipment that sends data
Communications channel
Communications equipment that receives data
Another computer
Communications software
TRANSMISSION MEDIA
Twisted-pair cable
Shielded twisted-pair (STP)
Unshielded twisted-pair (UTP) or 10baseT
Coaxial cable (coax)
Cable TV
Thinnet - 10base2
Fiber-optic cable
Low weight
High speed
Microwave transmission
Terrestrial microwave
Communications satellites
Uplink
Downlink
Geosynchronous orbit
Wireless transmission: radio and light waves
Infrared light
Portable radio data terminal
Cellular telephone
Communications Channels
LINE CONFIGURATIONS
Point-to-point lines
Switched line -- Handshake
Dedicated line (leased or private line)
Multidrop (multipoint) lines
Spring 1998
C/IL 102 Computer and Information Literacy
Multiple devices (terminals) along a single line
CHARACTERISTICS OF COMMUNICATIONS CHANNELS
Types of signals: digital and analog
Digital signals are electrical pulses – T1(1.5Mbps), T3(45Mbps)
Analog signals are continuous wave -- voice
ISDN
Transmission modes: asynchronous and synchronous
Asynchronous - irregular intervals
Synchronous - regular intervals
Direction of transmission: simplex, half-duplex, and full-duplex
Simplex - one direction only
Half-duplex - either direction, but only one direction at a time
Full-duplex - both directions at the same time
Transmission rate
Bandwidth
Measured in bits per second (bps)
COMMUNICATIONS SOFTWARE
Dialing
File transfer
Terminal emulation
Internet access
COMMUNICATIONS EQUIPMENT
Modems: External & internal modem
Multiplexers (MUX): combines multiple data streams into one
Front-end processors: dedicated to handling the communications
Network interface cards (NIC)
Wiring hubs (concentrator or multistation access unit (MAU))
Gateways: Connect different types of networks
Bridges: Connect similar types of networks
Routers: Connect several networks together
COMMUNICATIONS NETWORKS
Local area networks (LANs)
LAN Applications
HW, SW, and information resource sharing
File-server and client-server networks
Peer-to-peer networks
Network operating systems
Wide area networks (WANs)
Metropolitan area network (MAN)
Common carriers
Value-added carriers
Value-added networks
Packet-switching
NETWORK CONFIGURATIONS
Star network
Bus network
Ring network
COMMUNICATIONS PROTOCOLS
A set of rules and procedures for exchanging information between computers
Ethernet
Spring 1998
C/IL 102 Computer and Information Literacy
Most widely used (10Mbps)
Fast-Ethernet (100Mbps)
Token ring
Second most widely used
Token
Spring 1998
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