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Obj:Obj: 1.2, to understand networks 1.2, to understand networksHW:HW: Review sheet Review sheet

Quiz next class Sections 1.0 – 1.2Quiz next class Sections 1.0 – 1.2

Do Now:Do Now:

p.47 #1.4 and 1.5p.47 #1.4 and 1.5

C1 D3C1 D3

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NetworksNetworks

A A networknetwork is two or more computers that is two or more computers that are connected so that data and resources are connected so that data and resources can be sharedcan be shared

Most computers are connected to some Most computers are connected to some kind of networkkind of network

Each computer has its own Each computer has its own network network addressaddress, which uniquely identifies it among , which uniquely identifies it among the othersthe others

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A A file serverfile server is a network computer is a network computer dedicated to storing programs and data dedicated to storing programs and data that are shared among network usersthat are shared among network users

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Network ConnectionsNetwork Connections Each computer in a network could be directly connected to Each computer in a network could be directly connected to

every other computer in the networkevery other computer in the network

These are calledThese are called point-to-point point-to-point connectionsconnections

This technique is not practical formore than a few close machines

Adding a computer requiresa new communication linefor each computer alreadyin the network

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Network ConnectionsNetwork Connections Most networks share a single communication lineMost networks share a single communication line

Adding a new computer to the network is relatively Adding a new computer to the network is relatively easyeasy

Network traffic must taketurns using the line, whichintroduces delays

Often information is brokendown in parts, called packets,which are sent to the receivingmachine and then reassembled

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Local-Area NetworksLocal-Area Networks

LAN

A Local-Area Network(LAN) covers a smalldistance and a smallnumber of computers

A LAN often connects the machinesin a single room or building

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Wide-Area NetworksWide-Area Networks

LAN

A Wide-Area Network (WAN)connects two or more LANs,often over long distances

A LAN usually is ownedby one organization, buta WAN often connectsgroups in different countries

LAN

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The InternetThe Internet The The InternetInternet is a WAN which spans the entire planet is a WAN which spans the entire planet

The word Internet comes from the term The word Internet comes from the term internetworkinginternetworking, which implies communication among , which implies communication among networksnetworks

It started as a United States government project, It started as a United States government project, sponsored by the Advanced Research Projects Agency sponsored by the Advanced Research Projects Agency (ARPA) - originally it was called the ARPANET(ARPA) - originally it was called the ARPANET

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The Internet grew quickly throughout the The Internet grew quickly throughout the 1980s and 90s1980s and 90s

Less than 600 computers were connected Less than 600 computers were connected to the Internet in 1983; by the year 2000 to the Internet in 1983; by the year 2000 there were over 10 millionthere were over 10 million

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TCP/IPTCP/IP

A protocol is a set of rules that determine how A protocol is a set of rules that determine how things communicate with each otherthings communicate with each other

The software which manages Internet The software which manages Internet communication follows a suite of protocols communication follows a suite of protocols called called TCP/IPTCP/IP

The The Internet ProtocolInternet Protocol (IP) determines the (IP) determines the format of the information as it is transferredformat of the information as it is transferred

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The The Transmission Control ProtocolTransmission Control Protocol (TCP) (TCP) dictates how messages are reassembled dictates how messages are reassembled and handles lost informationand handles lost information

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IP and Internet AddressesIP and Internet Addresses

Each computer on the Internet has a unique Each computer on the Internet has a unique IP addressIP address, such as: , such as:

204.192.116.2204.192.116.2

Most computers also have a unique Internet Most computers also have a unique Internet name, which also is referred to as an name, which also is referred to as an Internet Internet addressaddress::

spencer.villanova.eduspencer.villanova.edu

kant.gestalt-llc.comkant.gestalt-llc.com

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The first part indicates a particular The first part indicates a particular computer (computer (spencerspencer))

The rest is the The rest is the domain namedomain name, indicating , indicating the organization (the organization (villanova.eduvillanova.edu))

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Domain NamesDomain Names The last part of each domain name, called a The last part of each domain name, called a top-level top-level

domain domain (TLD) indicates the type of organization:(TLD) indicates the type of organization:

educomorgnet

- educational institution- commercial entity- non-profit organization- network-based organization

Sometimes the suffixindicates the country: New TLDs have

recently been added:

biz, info, tv, name

ukaucase

- United Kingdom- Australia- Canada- Sweden

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Domain NamesDomain Names A domain name can have several partsA domain name can have several parts

Unique domain names mean that multiple sites can Unique domain names mean that multiple sites can have individual computers with the same local namehave individual computers with the same local name

When used, an Internet address is translated to an IP When used, an Internet address is translated to an IP address by software called the address by software called the Domain Name Domain Name SystemSystem (DNS) (DNS)

There is There is nono one-to-one correspondence between the one-to-one correspondence between the sections of an IP address and the sections of an sections of an IP address and the sections of an Internet addressInternet address

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The World Wide WebThe World Wide Web

The The World Wide WebWorld Wide Web allows many allows many different types of information to be different types of information to be accessed using a common interfaceaccessed using a common interface

A A browserbrowser is a program which accesses is a program which accesses and presents informationand presents information

text, graphics, video, sound, audio, text, graphics, video, sound, audio, executable programsexecutable programs

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A Web document usually contains A Web document usually contains linkslinks to to other Web documents, creating a other Web documents, creating a hypermediahypermedia environment environment

The term Web comes from the fact that The term Web comes from the fact that information is not organized in a linear information is not organized in a linear fashionfashion

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The World Wide WebThe World Wide Web Web documents are often defined using the Web documents are often defined using the

HyperText Markup LanguageHyperText Markup Language (HTML) (HTML)

Information on the Web is found using a Information on the Web is found using a Uniform Uniform Resource LocatorResource Locator (URL): (URL):

http://www.lycos.comhttp://www.lycos.com

http://www.villanova.edu/webinfo/domains.htmlhttp://www.villanova.edu/webinfo/domains.html

ftp://java.sun.com/applets/animation.zip

A URL indicates a protocol (http), a domain, and A URL indicates a protocol (http), a domain, and possibly specific documentspossibly specific documents

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QuestionsQuestions How many computers must be connected to How many computers must be connected to

be called a be called a networknetwork?? (2)(2) What is the difference between a LAN and a What is the difference between a LAN and a

WAN?WAN? (LAN: small distance, less computers; WAN: (LAN: small distance, less computers; WAN:

connects two or more LANs)connects two or more LANs) Is the internet at LAN or a WAN?Is the internet at LAN or a WAN? (WAN)(WAN)

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More QuestionsMore Questions

What does TCP stand for?What does TCP stand for? (Transmission Control Protocol)(Transmission Control Protocol) What does TCP do?What does TCP do? (determines formal of info as it’s transferred)(determines formal of info as it’s transferred) What does IP stand for?What does IP stand for? (Internet Protocol)(Internet Protocol) What does it do?What does it do? (dictates how messages are reassembled and (dictates how messages are reassembled and

handles lost info)handles lost info)

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More QuestionsMore Questions

In “cread.marsd.org” , which part is the In “cread.marsd.org” , which part is the domain name?domain name?

(marsd.org)(marsd.org) Name one of the new TLDs (top level Name one of the new TLDs (top level

domains).domains). (biz, info, tv, name)(biz, info, tv, name)