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 resourcesUsually found on a user’s desktopOften 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