Wdf222 cep ii

Subject Name Code Credit HoursWeb Design and Fundamentals

D.Balaganesh Lincoln University College

Web Design and FundamentalsWDF222

ByD.Balaganesh


Network

• Networkone computer connected to more then one computer is called Network



Advantages of networking

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




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



Type of Connection



Type of Connection• Point-to-point

– Dedicated link between two devices– The entire capacity of the channel is reserved– Ex) 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



Mesh Topology• Dedicated point-to-point link to

every other nodes • A mesh network with n nodes

has n(n-1)/2 links. A 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



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

topology• To share the advantages from various topologies



Categories of Networks



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



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



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


Network Vs Internet

Internet Network of network is called Internet



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

• VOIP - Voice over Internet Protocol

• Podcast - type of digital media consisting of an episodic series of audio, video, PDF

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



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



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.



Internet Connections

Various technologies available to connect a home computer to the Internet

Phone modem converts computer data into an analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data

Digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office

Cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth





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)



Data

• Analog data– Voice– Images

• Digital data– Text– Digitized voice or images



Modem



Analog Signaling

• represented by sine waves


time

(sec)

ampl

itude

(vol

ts) 1 cycle

frequency (hertz)= cycles per second

phase difference

Subject Name Code Credit HoursWeb Design and Fundamentals 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)

• Transmission– Analog: Works the same for analog or digital signals– Digital: Used only with digital signals




Modem

• Anlog• Digital• Modulation

– Digital to analog conversion

• Demodulation– Analog to Digital ConversionModulation and demodulation is called Modem


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



Faster Internet Connections• ISDN (Integrated Services Digital Network)– 64K or 128K– Always-on and expensive

• DSL (Digital Subscriber Line)– Up to 125 times faster than dialup

• DSS (Digital Satellite Service)– 500K

D.Balaganesh Lincoln University CollegeNeed proximity to a telephone switching station


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).



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



SERVICES OF INTERNET

• WWW• FTP• Telnet• E-mail



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.



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



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 willclick 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. D.Balaganesh Lincoln University College


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



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



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



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

senderspeaks into a telephone rather than typing, giving the name of the recipient

andthe message. That sender's voice signal is then digitalised and stored. The

systemcan then either deliver the message at a specified time in future or it can beretrieved from a database by the recipient.



E-CommerceElectronic commerce or e-commerce as it is popularly known refers to thepaperless exchange of business information using Electronic Data

Interchange,Electronic mail, Electronic Bulletin Boards, Electronic Fund Transfer and othernetwork based technologies. Electronic Commerce (EC) not only automatesmanual process and paper transactions, but it also helps organisations to

moveinto a fully electronic environment and change the way they usually operate.



Internet Important Terms

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



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



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.



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 Addresses

Hostname 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

Is there a correspondence between the parts of a hostname and an IP address?



Domain Name SystemHost numberThe part of the IP address that specifies a particular host (machine) on the network Yes, but what is it?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



Domain Name System

matisse.csc.villanova.edu


Computer

name

Domain name TLD


Domain Name System


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


Domain Name SystemOrganizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes


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

Do you email

someonein anothercountry?


Domain Name System

Domain name system (DNS) A distributed system for managing hostname resolutionDomain name serverA computer that attempts to translate a hostname into an IP address

Should the tables containing hostname/IP mappings be sorted or unsorted? Why?


Subject Name Code Credit HoursWeb Design and Fundamentals 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.


Subject Name Code Credit HoursWeb Design and Fundamentals 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



Structure of a Uniform Resource Locators


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



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



• What are 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; this savesyou having to “log in” to the web site each time you visit.



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



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



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

amessage more secure, so that only the intended recipient of the message willbe able to read the message. There are many means of enabling thisencryption, both via hardware and software. A famous encryption program iscalled PGP(Pretty Good Privacy)



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

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



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



Faster Internet Connections• ISDN (Integrated Services Digital Network)– 64K or 128K– Always-on and expensive

• DSL (Digital Subscriber Line)– Up to 125 times faster than dialup

• DSS (Digital Satellite Service)– 500K

D.Balaganesh Lincoln University CollegeNeed proximity to a telephone switching station


Network Layer




Layered Model: Sending a Letter



OSI Model(Open Systems Interconnection)• ISO is the organization. OSI is the model



Interaction between layers in the OSI model• Layer and interface



Physical Layer• The physical layer is responsible for movements of individual bits from

one hop (node) to the next• Mechanical and electrical specification, the procedures and functions



Physical Layer: Duties

• Physical characteristics of interfaces and media

• Representation of bits• Data rate• Synchronization of bits• Line configuration• Physical topology• Transmission mode



Data Link Layer• The data link layer is responsible for moving frames from

one hop (node) to the next• Transform the physical layer to a reliable (error-free) link



Data Link Layer: Duties

• Framing• Physical addressing• Flow control• Error control• Access control



Network Layer• The network layer is responsible for the delivery of

packets from the source host to the destination host



Network Layer: Duties• Logical addressing and routing



Transport Layer• The transport layer is responsible for delivery of a

message from one process to another



Transport Layer: Duties

• Service-point (port) addressing• Segmentation and reassembly• Connection control• Flow control• Error control



Reliable Process-to-Process Delivery of a Message



Session Layer• Session layer is responsible for dialog control and

synchronization



Presentation Layer• Presentation layer is responsible for translation,

compression, and encryption



Application Layer• Application layer is responsible for providing services to

the user



Application Layer: Services

• Network virtual terminal• Mail services• File transfer, access, and management• Directory services



Summary of Layers

Subject Name Code Credit HoursWeb Design and Fundamentals OSI layer vs TCP/IP Layer

TCP/IP PROTOCOL SUITE

To divide the services required to perform a task, the Internet has created a set of rules called protocols. These allow different local and wide area networks, using different technologies, to be connected together and carry a message from one point to another. The set, or suite, of protocols that controls the Internet today is referred to as the TCP/IP protocol suite. The abbreviations (TCP and IP) will become clear as we explain different protocols.


Subject Name Code Credit HoursWeb Design and Fundamentals The original TCP/IP protocol suite was defined as having four layers: host-to-network (or link), internet (network), transport and application.

The TCP/IP protocol suiteD.Balaganesh Lincoln University College



TCP/IP and OSI Model





TCP/IP Protocol Suite• Host-to-network : Physical and data link layer

– No specific protocol

• Network layer– IP(Internet Protocl), ARP(Address Resolution Protocol),

RARP(Reverse ARP), ICMP(Internet Control Message Protocol), IGMO(Internet Group Message Protocol)

• Transport layer– TCP(Transmission Control Protocol), UDP(User Datagram Protocl),

SCTP(Stream Control Transmission Protocol),

• Application Layer– Combined session, presentation, and application layers

Technology

Wdf222 cep ii