Download Lesson 1

What is a Network?
Living Online Lesson 1
Mrs. Elzey
Objectives
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Describe a network.
Explain the benefits of a network.
List and describe the types of networks.
List and describe communications media.
Describe communications hardware.
Describe communications software.
Describe the different network topologies.
Describe network architecture.
Describe network protocols.
Introducing Networks
2 or more computers linked together
 LAN
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 Local Area
Network
 Confined to a limited area
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WAN
 Wide Area
Network
 Covers a large area
Data communication
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Transferring data from one location to another
Components needed:
 A sending
device; usually a computer
 A communication device; usually a modem which
converts the data signal into signals supported by the
channel (wiring)
 A communication channel or path; telephone wire or
cables; device used to carry the signal
 A receiving device; usually a computer
 Communications software
Communication components
Networks and the Benefits
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Most have at least 1 server
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Many clients
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Manages network resources
Relies on the server for the resources
Benefits
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Information sharing – authorized users can use other computers
on the network to access and share information and data.
Hardware sharing – one device connected to a network can
serve the needs of many users.
Software sharing – all users on the network can access a
program from one central location.
Collaborative environment – enables users to work together on
group projects
Communication Media
(wiring or wireless)
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Used to transfer the data from 1
computer to another
Commonly known as the communication
channel
Physical media
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Twisted pair
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Least expensive
Same type used for telephone systems
2 Copper wires twisted around one
another
One carries the signal the other is
grounded to absorb interference
Coaxial
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Primary type used by cable television
now widely used for networks
More expensive than twisted pair
Wiring or Wireless
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Fiber optic
 Glass tubing
 Carries more data
 Lighter
 Less susceptible to
interference
 Very fragile and expensive
Radio
 Must be sent in a straight
line
Microwaves
 Must be sent in a straight
line
Satellites
Network Hardware
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Modem – acronym for
Modulate-Demodulate
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Means to convert analog
signals to digital and viseversa
 Allows data to be sent over
telephone lines
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Cable modem
Network Interface Card (NIC) –
controls the sending and
receiving of data between PCs
and LANs
Hub – a junction where data
arrives from 1 or more
directions and forwarded out in
1 or more directions
Network Hardware (cont’d)
Bridge – a computer that connects 1 LAN
to another LAN
 Gateway – software and hardware that
links 2 different types of networks that use
different protocols
 Router – directs the path to send data
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LAN
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Confined to a limited geographical
area
2 types:
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Client/Server:
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1 or more computers on the network
acts as a server
The server manages network resources
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Printer: manages the printing
Database: manages the database files
High speed computer with lots of
storage space
Network O/S and applications are
stored on the server
All other computers connected are
clients. They share the resources on the
server.
Peer-to-Peer
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All computers are equal
People determine which files they want
to share on their computer with others.
Easy to setup and manage
Client/Server
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Client/Server:
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1 or more computers on the
network acts as a server
The server manages network
resources
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Printer: manages the
printing
Database: manages the
database files
High speed computer with
lots of storage space
Network O/S and applications
are stored on the server
All other computers
connected are clients. They
share the resources on the
server.
Peer to Peer
 Peer-to-Peer
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All computers are equal
People determine which
files they want to share
on their computer with
others.
Easy to setup and
manage
WAN
Usually consists of 2 or more LANs and
are connected by routers.
 Largest WAN known is the Internet.
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Network Topologies
Network Topologies:Linear Bus
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All devices are connected to and share a master
cable
 There
is no host computer
 Data is transmitted in both directions
 Easy to install and inexpensive
Network Topologies:Ring
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Devices are connected in
a circle.
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Each computer is
connected to an adjoining
device on either side
Data travels around the
ring from device to device.
More difficult to install and
manage and more
expensive.
Provides faster
transmission speeds and
can span large distances.
Network Topologies: Tree
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A tree topology combines
characteristics of linear bus
and star topologies.
It consists of groups of starconfigured workstations
connected to a linear bus
backbone cable
Tree topologies allow for the
expansion of an existing
network, and enable schools to
configure a network to meet
their needs.
Network Topologies: Star
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All devices are connected
to a central hub or
computer.
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All data from a computer
goes to the hub then back
out.
Easy to install and manage
Can cause bottleneck
because data must pass
through the hub
Requires more cabling
Communication
Protocols
A protocol is…
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An agreed-on set of rules and procedures
 Example:
Procedure for coming into class
 Procedure for leaving class
 Rules for driving
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Staying on the right-hand side of the road
 Stopping at a red light
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Communication protocol
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An agreed-on set of rules and procedures
for transmitting data between 2 or more
devices.
 How
the sending device indicates it has
finished sending the message
 How the receiving device indicates it has
received the message
 The type of error checking to be used
Communication Protocol
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Many have been developed, but with
networking and LANs, the 2 most popular
are:
 Ethernet
 Token
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Ring
Internet Protocol
 TCP/IP
Communication Protocols
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Ethernet: 1st approved industry standard
 Most
popular
 Based on the bus topology
 Can work with star
 Supports data transfer rates of up to 10 megabytes
per second (Mbps)
 2 versions
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Fast Ethernet
Gigabit Ethernet
Communication Protocols
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Token ring: 2nd most widely used
 Computers
are arranged in a circle
 A special signal travels around the ring
 A computer on the ring catches the “token” to
send a message
 Attaches a message to it and then lets it travel
around the network
Communication Protocol
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TCP/IP: acronym for Transmission Control
Protocol/Internet Protocol
 Used
by LANs and WANs
 Adopted as a standard to connect hosts
(servers or computers) on the Internet.
LAN Topologies Summary
Physical
Topology
Common Cable
Common
Protocol
Linear Bus
Twisted Pair
Coaxial
Fiber
Ethernet (PC)
LocalTalk(Apple)
Star
Twisted Pair
Fiber
Ethernet
LocalTalk
Star-Wired Ring
Twisted Pair
Token Ring
Ring
Twisted Pair
Coaxial
Fiber
Ethernet
Network Operating Systems
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2 types are needed
 Desktop
Windows
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 Mac OS
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 Network
Windows
 Unix
 Novell
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