Connectivity of computers has become more important over the past few years
Communication systems are the electronic systems that transmit data over communications lines
End users need to understand the following:
Basics of communication channels
Connection devices
Data transmission
Networks
Network architectures
Network types
Ask students to give examples of communication devices that they use daily
Connectivity is a concept related to using computer networks to link people and resources
Microcomputers. Minicomputers, and mainframes can all be connected
Wireless revolution
Use of mobile or wireless devices
The revolution is the support of more than just the wireless telephone
Many devices can and will connect to one another with out any physical connection
Electronic systems that transmit data from one location to another
Communication systems can be wired or wireless
Basic elements
Sending and receiving devices - computer or a specialized device
Communication channel –carries the message
Connection devices – act as an interface between sending and receiving devices
Data transmission specifications – rules and procedures that coordinate the sending and receiving devices
Channels are essential to a communication system
They carry data
Types of channels
Telephone lines
Coaxial cables
Fiver-optic cable
Infrared
Broadcast radio
Microwave
Satellite
Twisted pair – slowest; being phased out by more advanced and reliable media
Coaxial cable – single solid copper ore; 80 times transmission of twisted pair; television and computer networks
Fiber optic – 26,000 times capacity of twisted pair; more secure and reliable; best over limited distances; lighter and less expensive than coax
Wireless connections do not use a solid substance to connect ; uses the air itself
Types of wireless connections are:
Infrared
Light waves used over short distances
Sometimes called line of sight communications
Sending and receiving devices must be in clear view of one another
Broadcast radio – uses towers called transceivers
Web-enabled devices follow a standard known as Wi-FI (wireless fidelity)
Microwave – uses high frequency radio waves
Also line of sight
Used for short distances
Bluetooth used for distances up to 33 feet (not line of sight)
Satellite – uses satellite orbiting 22,000 miles above the earth as microwave relay stations
Uplink is sending information
Downlink refers to receiving
These are becoming popular in automobiles to provide navigation
Signals sent either analog – telephone signals – or digital – computer signals
Modem – modulator/demodulator; most are built into the system unit already
Wireless modem may be external, internal, or a PC Card
Does not use cables
Signals are sent through the air
Standard telephone lines and conventional modems use a dial-up service
Slow
Still popular, but many are using other types of connections
Several technical matters affect data communications
One is bandwidth – bits-per-second (bps) transmission capability of a channel
Three types:
Voiceband – low bandwidth; standard phone line; too slow for many types of transmissions – especially high-quality video
Medium band – with special leased lines for larger computer systems; not typically used by individuals
Broadband – used for high-capacity transmissions (DSL, cable, satellite connections); specialized high-speed devices; effectively transmits high-quality video and other communication needs; typically 1.5 mbps; higher speeds possible
Rules for exchanging data between computers
Essential features of protocol
Id sending and receiving devices (IP address); Internet unique number address
Reformatting – allows message to be broken into packets so easier to transmit over Internet through various interconnected networks; allows message to be reassembled at destination
A computer network is a communication system that connects two or more computers sot that they can exchange information and share resources
Node - any device connected to a network
Client - a node that requests and uses resources available from other nodes
Server - a node that shares resources with other nodes
Hub – the center or central node for other nodes
Network operating system (NOS) - software to control and coordinate activities between computers on a network
Distributed processing - computing power located and shared at different locations
Host computer - large centralized computer
Network manager – a computer specialist; network administrator
Communications networks differ in geographical size. Three important types are:
LANs
Computers and devices linked in close proximity to each other
Linked by cable
Typically use a bus form of organization
With gateways, LAN’s can be connected to other LAN’s or any other type of network
MANs
Network linking nodes and resources within the geographical bounds of a city
Cellular phones can extend the reach of a MAN
WANs
Country-wide and world-wide networks
Use microwave relays and satellites to reach users
Internet widest WAN
Home networking
Radio frequency
Telephone lines
Electric wiring
Cables
NIC/adapter cards
Networks are connections of two or more computers that work together to exchange information and share resources
The network architecture describes how the network is arranged and how the resources are coordinated and shared
Network architecture also describes how a computer network is configured and what strategies are used
Topology – network arrangement or configuration
Host computer - large centralized computer, usually a mainframe
Star - nodes are connected to a single computer called a host
All communications pass through this host
Can be used as a time sharing system
Bus network - each device handles its own communications control
No host computer
Common connecting cable called a bus
Not as efficient as star, but it is low cost and widely used
Ring network
Each device connected to two others forming a ring
No central files server or computer
Messages passed around ring until reach correct destination
Often used to link mainframes – especially over wide geographical areas
Useful in decentralized organization
Makes possible distributed data processing system
Computers can perform processing tasks on own
Can also share programs, data, and other resources
Sometime called hybrid network
Consists of several computers linked to central host computer
All computers can server as hosts to other computers (unlike star network)
Host at top could be mainframe; computers below could be minis; then “down” to micros
Useful in centralized organization
Strategy: ways of coordinating the sharing of information and resources in a network
Terminal network system
Centralized host, usually a mainframe
Nodes are usually terminals with little or no processing capabilities
Reservation systems
Peer-to-peer network system - nodes act as both servers and clients
A node could obtain files from another node, and provide files to another node
Bus topology best example Client/server network systems
Powerful computer coordinates services
This server provides access to centralized resources
Enterprise computing describes the trend toward integrating or connecting all of company’s computer resources together
Intranets are private networks within an organization
Extranets are private networks connecting organizations
Organizational firewalls typically use proxy servers to provide security
Ask students to give examples of each
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