Comp 107 unit 7 and 8 (networking, internet and intranet) (1)

Subject Name Code Credit Hours

Copyright @ 2016 Lincoln University College

Unit 7 and 8Introduction to Networking, Internet and Intranet

ByLiang



Data Transfer

• Data transmission, digital transmission, or digital communications is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel.

http://en.wikipedia.org/wiki/Data

http://en.wikipedia.org/wiki/Digital_data

http://en.wikipedia.org/wiki/Bit_stream

http://en.wikipedia.org/wiki/Point-to-multipoint_communication



Examples

• Examples of such channels are copper wires, optical fibres, wireless communication channels, storage media and computer buses.

• The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal.

http://en.wikipedia.org/wiki/Copper_wire

http://en.wikipedia.org/wiki/Optical_fibre

http://en.wikipedia.org/wiki/Optical_fibre

http://en.wikipedia.org/wiki/Wireless

http://en.wikipedia.org/wiki/Storage_media

http://en.wikipedia.org/wiki/Bus_(computing)

http://en.wikipedia.org/wiki/Electromagnetic_field

http://en.wikipedia.org/wiki/Signal_(electronics)

http://en.wikipedia.org/wiki/Electrical_voltage

http://en.wikipedia.org/wiki/Radiowave

http://en.wikipedia.org/wiki/Microwave

http://en.wikipedia.org/wiki/Infrared



Network • Network

one computer connected to more then one computer is called Network

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Advantages of networking

• Connectivity and Communication• Data Sharing• Hardware Sharing• Internet Access• Internet Access Sharing• Data Security and Management• Performance Enhancement and Balancing• Entertainment

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Network• Network: A set of devices (nodes) connected by communication links• Node: Computer, printer, or any device capable of sending and/or

receiving data• To be considered effective and efficient, a network must meet a

number of criteria

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Copyright @ 2016 Lincoln University College05/01/2023 1-7

Type of Connection




Type of Connection• Point-to-point

– Dedicated link between two devices– The entire capacity of the channel is reserved– Eg. Microwave link, TV remote control

• Multipoint – More than two devices share a single link– Capacity of the channel is either

• Spatially shared: Devices can use the link simultaneously• Timeshare: Users take turns




Physical Topology

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Mesh Topology• Dedicated point-to-point link to

every other nodes • A mesh network with n nodes

has n(n-1)/2 links. Each node has n-1 I/O ports (links)

• Advantages: No traffic problems, robust, security, easy fault identification & isolation

• Disadvantages: Difficult installation/reconfiguration, space, cost




Star Topology• Dedicated point-to-point link only to a central controller, called a hub • Hub acts as an exchange: No direct traffic between devices• Advantages: Less expensive, robust • Disadvantages: dependency of the whole on one single point, the hub




Bus Topology• One long cable that links all nodes • tap, drop line, cable end• limit on the # of devices, distance between nodes • Advantages: Easy installation, cheap • Disadvantages: Difficult reconfiguration, no fault isolation, a fault or

break in the bus stops all transmission




Ring Topology• Dedicated point-to-point link only with the two nodes on each sides • One direction, repeater • Advantages: Easy reconfiguration, fault isolation• Disadvantage: Unidirectional traffic, a break in the ring cab disable the

entire network



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Hybrid Topology• Example: Main star topology with each branch connecting several stations in a bus

topology• To share the advantages from various topologies

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Categories of Networks

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Local Area Network (LAN)• Usually privately owned• A network for a single office, building, or campus a few Km • Common LAN topologies: bus, ring, star • An isolated LAN connecting 12 computers to a hub in a closet




Metropolitan Area Network (MAN)• Designed to extend to an entire city• Cable TV network, a company’s connected LANs• Owned by a private or a public company




Wide Area Network(WAN)• Long distance transmission, e.g., a country, a continent, the world • Enterprise network: A WAN that is owned and used by one company




Internetwork• Internetwork (internet) : two or more networks are

connected by internetworking devices • Internetworking devices: router, gateway, etc. • The Internet: a specific worldwide network




Internetwork Example• A heterogeneous network : four WANs and two LANs




Network Vs InternetInternet Network of network is called Internet

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Internet• Internet programming language• E-mail• SMS(short message service)• Social networking sites• Websites• Browser• Blog - Share your life's stories, videos and photos

• VOIP - Voice over Internet Protocol(Call from computer, telemarketer)


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Internet(con’t)

• Rss(Really simple Syndication) - TechNet provides RSS feeds for its security bulletins, advisories, magazine features, and other security-related alerts for IT professionals. Eg, short cut other

pages.

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The Internet

• Internet is a network of interconnected computers that is now global

• Internet born in 1969 - called ARPANET• 1969 ARPANET was connection of computers

at UCLA, Stanford, UCSB, Univ. of Utah


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The Advanced Research Projects Agency Network

• In 1969, the U.S. Defence Department funded a project to develop a network, which can withstand the bombing. Basically the idea was to develop a very secure network which can work even after a nuclear attack. This project was known as ARPANET.


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Internet Connections

Broadband A connection in which transfer speeds are faster than 768 kilobits per second

– DSL connections and cable modems are broadband connections

– The speed for downloads (getting data from the Internet to your home computer) may not be the same as uploads (sending data from your home computer to the Internet)


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Data

• Analog data– Voice– Images

• Digital data– Text– Digitized voice or images


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Modem


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Analog Signaling• represented by sine waves


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time

(sec)

ampl

itude

(vol

ts) 1 cycle

frequency (hertz)= cycles per second

phase difference



Three Components of Data Communication

• Data– Analog: Continuous value data (sound, light, temperature)– Digital: Discrete value (text, integers, symbols)

• Signal– Analog: Continuously varying electromagnetic wave– Digital: Series of voltage pulses (square wave)


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Modem

Process• Modulation

– Digital to analog conversion

• Demodulation– Analog to Digital Conversion




Modem Internet Connections• Dial-up connection via modem (56K)• Cable modems

– Network card and cable modem required– Always-on and 25 times faster than dial-up


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ISP (Internet Service Provider)

If you want to connect to the Internet, you need to subscribe via an Internet Service Provider. The ISP gives you a connection to the Internet either via your telephone line or via a special digital high speed line. An example of a popular ISP is AOL (America On-Line).


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Internet Service Provider (ISP)• Provides internet access to businesses,

organizations and individuals• Provides telecommunications equipment• User ID and password required• Connects you to backbone• E-mail account monthly fee• Should have local access telephone

numbers


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SERVICES OF INTERNET

• WWW• FTP• Telnet• E-mail


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What is the difference between the World Wide Web (WWW) and the Internet?

WWW is the acronym for the World Wide Web. It is also commonlyknown as ‘The Web’. The WWW is hypertext based information retrievaltool

• The World Wide Web (WWW) is just a small part of the Internet as a whole.

• The Internet, relates to all the hardware and software involved, and as well as including the WWW, also includes FTP (File Transfer Protocol – more about this later), email and newsgroups.

• The WWW is basically the text and pictures which you can view using your web browser, such as Microsoft Internet Explorer, or Netscape Navigator.


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World Wide Web Basics• Files interconnected via hypertext• Web pages make up a web site• Home Page• Links or hyperlinks• Web servers


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FTP (File Transfer Protocol)

File Transfer Protocol, is an Internet utility software used to uploadand download files. It gives access to directories or folders on remotecomputers and allows software, data and text files to be transferredbetween different kinds of computers.

• FTP is just a way of transferring data from one place to another over the Internet. If is often used for downloading large files from a web site. You do not really need to know anything about how it works, in most cases you will click on a link within a web page, and your web browser (such as Microsoft Internet Explorer) will take care of the FTP transfer for you, all you have to decide is where to store the file which you wish to download.




The basic objectives of FTP are

• to give flexibility and promote sharing of computer programs, files and data

• to transfer data reliably and more efficiently over network

• to encourage implicit or indirect use of remote computers using Internet

• to shield a user from variations in file storage systems among hosts


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Telnet (Remote Computing)

• Telnet (Remote Computing)Telnet or remote computing is telecommunication utility software,which uses available telecommunication facility and allows you tobecome a user on a remote computer. Once you gain access to theremote computer, you can use it for the intended purpose. TheTELNET works in a very step by step procedure. The commandstyped on the client computer are sent to the local Internet ServiceProvider (ISP), and then from the ISP to the remote computer thatyou have gained access. Most of the ISP provides facility to TELENETinto your own account from another city and check your e-mailwhile you are traveling or away on business


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E-Mail (Electronic Mail)E-mail or Electronic mail is a paperless method of sending messages,notes or letters from one person to another or even manypeople at the same time via Internet. E-mail is very fast compared tothe normal post. E-mail messages usually take only few seconds toarrive at their destination

Features of E-mail:• One-to-one or one-to-many communications• Instant communications• Physical presence of recipient is not required• Most inexpensive mail services, 24-hours a day and seven days a week• Encourages informal communications


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Voice Messaging

Voice MessagingIt is a new communication approach which is similar to electronic mail exceptthat it is audio message rather than text messages that are processed.

A sender speaks into a telephone rather than typing, giving the name of the recipient and the message. That sender's voice signal is then digitalised and stored.

The system can then either deliver the message at a specified time in future or it can be retrieved from a database by the recipient.


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Internet Important Terms

• HTTP• URL• Hyperlink• Browser• Cookies• Internet cache• SECURITY


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HTTP (Hypertext Transfer Protocol)

• HTTP stands for Hypertext Transfer Protocol. This is the language your web browser uses to request pages & graphics from the web server. You can see that your web browser is using the HTTP protocol when it is shown at the start of a web address such as http://www.yahoo.com


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URL (Uniform Resource Locator)

• The URL (Uniform Resource Locator) is just another name for a web address.

• The URL consists of the name of the protocol (usually HTTP or FTP) followed by the address of the computer you want to connect to, e.g. a URL of “ftp://ftp.cdrom.com” would instruct your web browser to use the FTP protocol to connect to the computer called ftp.cdrom.com.


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World Wide Web Basics• URL

– No spaces and Case sensitive– HTTP (Hypertext Transfer Protocol)

• HTML (Hypertext Markup Language)– .htm or .html file extension


Document nameand filename

extensionFoldername

Web servername

Web protocolstandard

http://www.cnn.com/showbiz/movies.htm



Network AddressesHostname A name made up of words separated by dots that uniquely identifies a computer on the InternetIP addressAn address made up of four one-byte numeric values separated by dots that uniquely identifies a computer on the Internet


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Domain Name SystemHost numberThe part of the IP address that specifies a particular host (machine) on the network Domain nameThe part of a hostname that specifies a specific organization or groupTop-level domain (TLD)The last section of a domain name that specifies the type of organization or its country of origin


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Domain Name System(cont’)


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Domain Name System (cont’)


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Figure 15.10 Top-level domains, including some relatively new ones



Domain Name System(cont’)Organizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes


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Figure 15.11Some of the top-level domain names based on country codes

Do you email

someonein anothercountry?



Domain Name Addressing

• Domain names can include any number of parts separated by periods, however most domain names currently in use have only three or four parts.

• Domain names follow hierarchical model that you can follow from top to bottom if you read the name from the right to the left.

• For example, the domain name gsb.uchicago.edu is the computer connected to the Internet at the Graduate School of Business (gsb), which is an academic unit of the University of Chicago (uchicago), which is an educational institution (edu).

• No other computer on the Internet has the same domain name.


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Uniform Resource Locators• The IP address and the domain name each identify a particular

computer on the Internet.• However, they do not indicate where a Web page’s HTML

document resides on that computer.• To identify a Web pages exact location, Web browsers rely on

Uniform Resource Locator (URL).• URL is a four-part addressing scheme that tells the Web

browser: What transfer protocol to use for transporting the file The domain name of the computer on which the file resides The pathname of the folder or directory on the computer on

which the file resides The name of the file


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Structure of a Uniform Resource Locators


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http://www.chicagosymphony.org/civicconcerts/index.htm

protocol

Domain name

pathname

filename

http => Hypertext Transfer Protocol



Hyperlink

A hyperlink is a piece of text (or a graphic) on a Web page, which when clicked on will automatically:

- Take you to a different part of the same page- Take you to a different page within the Web

site


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What is a web browser?

Web browsing applications include ‘Internet Explorer’ (from Microsoft) and ‘Netscape Navigator/Communicator’. In both cases there are many different versions, and you will find that the later versions offer much more versatility as well as a better range of built-in features. The web browser allows you to view web pages


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Cookies

• Some web sites can store hidden information about you on your hard diskusing cookies. • This information is stored in small text file. Cookies can beuseful, for instance, a site may store your preferences about a web site, sothat when you re-visit the site your preferences can be accessedautomatically. • Cookies are used by some web sites to identify you; thissaves you having to “log in” to the web site each time you visit.


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What is an Internet cache?

Each time you display a web site within your web browser, a copy of theinformation (both text and pictures) is saved on your hard disk. The reasonfor this is that the next time you want to re-visit the site, the information isquickly loaded from the copy on your hard disk, rather than slowly from theactual Internet site.• As pictures are stored in the cache, if you are visiting a site which has manyseparate web pages, with say a company logo on each page, then allsubsequent pages from that site will load a little faster as the logo graphicswill load from the cache, not via the Internet Eg. temp folder


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SECURITY CONSIDERATIONS• What is a digital certificate?• A digital certificate is used to encrypt information for secure transmissionacross the Internet. A digital certificate can be used to create a digitalsignature for an email, the signature guarantees the identity of sender, and italso ensures that the message cannot be tampered with in transit. A digitalcertificate can be purchased from a certificate authority such aswww.verisign.com who will verify your identity. Digital certificates are usedby Internet based shopping web sites to encrypt your credit card details sothey cannot be intercepted as they travel the Internet. You can view thedigital certificate for a secure web site by double clicking on the padlock inthe web browser status bar, e.g. https://www.paypal.com




SECURITY CONSIDERATIONS(Cont’)

What is encryption?• Encryption is a means of 'scrambling' an email message. It is used to make

a message more secure, so that only the intended recipient of the message will be able to read the message. There are many means of enabling this encryption, both via hardware and software.


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SECURITY CONSIDERATIONS(Cont’)

• What is a firewall?• A fire wall consists of software and hardware protection against invasion

via the Internet. In most larger companies any connection to the Internetautomatically goes through a firewall which would have been installed andcustomized by the companies technical IT team. In most cases you will beunaware of the firewall existence.


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Internet vs intranet

• Intranet is an internal private computer network or connection of one or more computer networks, whose use and access is restricted to an organization and its employees or members.. Such an intranet, mostly operates through a website, run by a local server, acting as a resource sharing medium. You could call it a scaled-down private Internet.

• Internet is a network of more than billion computers spread worldwide! It uses an ever improving set of Internet protocols (HTTP, FTP, SMTP, etc.) to transfer data. Unlike the intranet, the Internet and the information sharing service called the 'World Wide Web',


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The EndQuestions?

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