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Understanding Networks
Computer Technology
What is a Network?
 Two or more computers connected
to each other so they can—
 Exchange Information
 E-mail messages
 Documents
 Share Resources
 Disk storage
 Printers
 Share Applications
 First computer network invented
when ancient mathematicians
connected their abacuses together
with string so they could instantly
share their answers
Types of Network Connections
Electrical cables carry information in the
form of electrical signals
Fiber-optic cables enable computers to
communicate at extremely high speeds by
using impulses of light
Wireless networks enable computers to
communicate by using radio signals
Terminology
Network Terms
File Server
A computer connected to a network that
distributes resources to other users.
Contains the software to manage and process
files for other network users.
Host Computer
Refers to any computer that provides services
to network users.
Used more commonly with the Internet.
Network Terms (continued)
Workstation
Refers to a personal computer connected to a
network.
Example: Each computer in the classroom.
Client
Refers to the software on a computer that
allows the user to access the server.
Example: Novell Netware
Network Connection Devices
 Modem
 A device that sends and receives data to and from computers
over telephone lines.
 Hubs
 A device that connects several components of a network.
 Routers
 A device that connects at least two networks.
 Gateway
 A device that serves as an entrance to another network.
 All of these can be used alone or combination.
Network Components
Client Computers
Used to access network resources
Usually found on a user’s desktop
Often called workstations
Server Computers
Provide
 Shared resources
 Disk storage
 Printers
 Network services
 E-mail
 Internet access
Run a specialized network operating system
 Windows 2000
 Netware
 Linux
Network Interface Cards (NICS)
 Small circuit board that converts the
digital signals from a computer into
signals that can travel over a network.
 Enables the computer to communicate
over a network.
 Most NICS use a networking standard
called Ethernet.
 Every client and every server must
have a NIC.
 Desktop Computers have the NIC
inside the case with a jack on the
outside for the network cable.
 Notebook or Laptop Computers have
a special card that fits into a slot or
opening in the case.
Cables
Physically connect
computers together to
form a network
Types
 Twisted pair (10BaseT)
 Coaxial (10Base2)
 Fiber-optic (high-speed
connections)
Hubs and Switches
 Hub
 Common connection point for devices in a
network
 Doesn’t know anything about the computers
connected to its ports, so it sends packets to
every computer
 Switch
 Used to network multiple computers together.
 Two Types
 Low-end switches are typically small, flat
boxes with 4 to 8 Ethernet ports.
 High-end switches can have more than 50
ports and often are rack mounted.
 Knows which computer is connected to each
of its ports, so it only sends packet to the
correct port
Wireless Network
Enables computers to communicate
through radio signals
Radio transmitters and receivers take the
place of cables
Advantages: More flexibility than cabled
network
Disadvantages: Less secure than cabled
network
Network Types
Local Area Network (LAN)
 Network located within a limited geographical area, such
as a school or small business
 Each computer or printer on the network is called a
“node”
 Geographic distance, not number of computers indicates
it is a LAN
Wide Area Network (WAN)
 Network that spans a large geographic territory
 Connect two or more LANs that are relatively far apart
 Geographic distance, not number of computers indicates
it is a WAN
Network Topology
Shape of how the computers and other network
components connect to each other
Terms
 Node
 Device that is connected to the network
 Same as a computer
 Packet
 Message sent over the network from one node to another
node
 Includes the address of the node that sent the packet,
address of the node the packet is going to, and the data.
Network Topology Types
Bus Topology
Nodes are strung together in a line
Commonly used for LANs
Network Topology Types
Star Topology
 Each network node connects
to a central device called a
hub or a switch
 Commonly used for LANs
 If the hub fails, all computers
on the network are
disconnected
Network Topology Types
Ring Topology
 Each network computer and
device are connected to each
other to form a large circle
 Each packet is sent around
the circle from computer to
computer until it reaches its
destination
Network Topology Types
Mesh Topology
 Multiple connections between
each of the nodes on the
network
 Network can use an
alternative route to deliver a
packet if one cable breaks
IP Address
A unique identifying number assigned to
each computer connected to the internet.
Example – 204.127.102.001
Each computer on a network should have
its own separate IP Address or conflicts
will occur when there are duplicate
addresses.
Internet
What is the Internet?
Global network connecting millions of computers
Each internet computer, called a host, is
independent
Not synonymous with World Wide Web (www)
Requires
 Internet Service Provider (ISP) or Online Service
Provider (OSP)
 Browser
 Search Engine
Internet Terms
 Internet Service Provider (ISP)
 Company that provides access to the Internet so you can
 Browse the web
 Send and receive e-mail
 Requires you to
 Pay a monthly fee, in exchange for
• Software package
• Username
• Password
 Have a modem
 Browser
 Software application used to locate and display web pages
 Search Engine
 Searches documents for specified keywords
 Returns a list of the documents that contain the keywords
Internet Terms
HTTP (Hypertext Transfer Protocol)
 Language used to transfer data within the World Wide
Web
URL (Uniform Resource Locator)
 Method used to identify locations on the Internet
 Format: http://server-name.path
 Example: http://www.microsoft.com
 Domain
 Last part of the URL
 Identifies the server type
•
•
•
•
.com indicates a commercial company
.edu indicates educational
.gov indicates government
.mil indicates military
Internet Terms
 Freeware
 Copyrighted software the author usually gives away for free
 Author retains the copyright, which means
 You cannot do anything with it that the author hasn’t authorized
 You can use the software, but not sell it
 Shareware
 Software distributed on the basis of an honor system
 Usually free, but in most cases, the author asks you to pay a
small fee if you like it and use it on a regular basis
 You can copy shareware and give it to your friends and
colleagues, but they need to pay a fee if they use the product
Internet Terms
Public Domain
Refers to any program that is not copyrighted
Software that is free and can be used without
restrictions
Spam
Electronic junk mail or junk newsgroup postings
Internet Terms
 Boolean Operator
 Used to narrow or broaden you search
 Helps eliminate unrelated documents
 Most common terms
 AND
• Narrows a search by combining terms
• Retrieves documents that use both the terms you specify
 Example: Portland AND Oregon
 OR
• Broadens a search to include results that contain either of the words
you enter
 Example: Liberal OR Democrat
 NOT
• Narrows a search by excluding search terms
• Retrieves documents that contain one, not both terms
 Example: Oregon NOT Travel
Internet Terms
Trolling
To deliberately post derogatory or inflammatory
comments to a community forum, chat room,
newsgroup, or blog in order to bait other users
into responding.
To surf the Internet