Modified for 2005Chapter 2: Introduction to the web and internet 1 Introduction to the Web and...

Modified for 2005Chapter 2: Introduction to the web and internet 1 Introduction to the Web and Internet Questions Answered in this Chapter: What is the internet ? What are the characteristics of the internet that make it work? What are the content types on the web? How are websites created? What is behind the growth of the web and Internet?

Modified for 2005Chapter 2: Introduction to the web and internet 2

Modified for 2005Chapter 2: Introduction to the web and internet 3 The Original WWW Like the internet, radio began as a communication medium Early market medium known as wireless telegraphy or telephony; radios point-to-point wireless messaging Demand for radio broadcasting surged in 1922 when it shifted from a point-to-point communication tool to a broadcast medium During the 1920s, all 48 states in the US had at least one radio station By 1925, 27 of the original 48 stations were out of business Revenue sources such as programming subsides from radio-set sales, radio taxes, generalized goodwill for corporate sponsors and advertising emerged as new revenue generation models The pay for service revenue model allowed radio to compete with telegraph and cut the price of telegraph by 30%

Modified for 2005Chapter 2: Introduction to the web and internet 5 Early networks Internets beginnings can be traced back to memos written in 1962 by MITs Joseph Carl Robnett Licklider outlining the galactic networking concept Great advances were made in network technology in 1960s To connect computers and permit transfer of information locally, many organizations installed Local Area Networks LAN technology was limited by geographical distance To allow computer and networks separated by larger geographical distance to communicate ARPA (Advanced Research Projects Agency) developed a Wide Area Network (WAN) called the ARPANET

Modified for 2005Chapter 2: Introduction to the web and internet 6 APPLICATION APPLICATION EXAMPLE EXAMPLE REQUIREMENT REQUIREMENT ONLINE DATA ENTRY INVENTORY CONTROL DIRECT RESPONSE REQUIRED ON-LINE TEXT RETRIEVAL HOSPITAL INFO SYSTEM HIGH VOLUME REAL TIME RESPONSE LIBRARY SYSTEMS INQUIRY / RESPONSE POINT-OF SALES RESPONSE WITHIN SECONDS AIRLINE RESERVATIONS CREDIT CHECKING ADMINISTRATIVE MESSAGES ELECTRONIC MAIL SHORT RESPONSE / DELIVERY TIMES PROCESS CONTROL COMPUTER AIDED MANUFACTURING : NUMERIC MACHINE CONTROL CONTINUOUS INPUT / ONLINE RESPONSES INTERCOMPUTER DATA EXCHANGE ELECTRONIC FUNDS TRANSFER BURST TRANSFER OF LARGE DATA BLOCKS ON-LINE IMMEDIATE RESPONSE 9.5 Business Tasks Requiring Networks

Modified for 2005Chapter 2: Introduction to the web and internet 7 CONTINUOUS WAVEFORM PASSES THRU SYSTEM VOICE COMMUNICATIONS * 9.8 Analog Signal

Modified for 2005Chapter 2: Introduction to the web and internet 8 DISCRETE WAVEFORM TWO DISCRETE STATES: 1-BIT & 0-BIT ON / OFF PULSE DATA COMMUNICATION * 9.9 Digital Signal

Modified for 2005Chapter 2: Introduction to the web and internet 9 MEANS BY WHICH DATA ARE TRANSMITTED: TWISTED PAIR (Copper Wires) COAXIAL CABLE: (Insulated Copper Wires) FIBER-OPTIC CABLE WIRELESS (including radio signals) * 9.10 Ways to Transmit Signals

Modified for 2005Chapter 2: Introduction to the web and internet 10 10 5 - 10 8 : AM Radio; Short Wave; FM; VHF-TV 10 8 - 10 10 : UHF-TV, Cellular Phones, RAM Mobile, Data, Cordless Phone, Paging, Narrow Band PCS, Industrial 10 10 - 10 12 : Radar, Microwave 10 13 - 10 14 : Infra Red, Remote Control, Wireless * 9.12 Wireless Spectrum (in Megahertz)

Modified for 2005Chapter 2: Introduction to the web and internet 11 10 15 - 10 16 : Visible Light; Fiber Optics 10 18 - 10 22 : X-Ray, Gamma, Cosmic, Personal Communication Services (PCS) * 9.13 Wireless Spectrum (in megahertz)

Modified for 2005Chapter 2: Introduction to the web and internet 12 MEDIUM MEDIUM SPEED SPEED TWISTED PAIR TWISTED PAIR 300 BPS - 10 MBPS 300 BPS - 10 MBPS MICROWAVE MICROWAVE 256 KBPS - 100 MBPS 256 KBPS - 100 MBPS SATELLITE SATELLITE 256 KBPS - 100 MBPS 256 KBPS - 100 MBPS COAXIAL CABLE COAXIAL CABLE 56 KBPS - 200 MBPS 56 KBPS - 200 MBPS FIBER OPTICS FIBER OPTICS 56 KBPS - 10 GBPS 56 KBPS - 10 GBPS BPS: BITS PER SECOND BPS: BITS PER SECOND KBPS: KILOBITS PER SECOND KBPS: KILOBITS PER SECOND MBPS: MEGABITS PER SECOND MBPS: MEGABITS PER SECOND GBPS: GIGABITS PER SECOND GBPS: GIGABITS PER SECOND 9.18 Speed of Media

Modified for 2005Chapter 2: Introduction to the web and internet 14 LANS: Multiple Access Methods Fixed assignment Partition channel so each node gets a slice of the bandwidth Essentially circuit switching thus inefficient Examples: TDMA, FDMA, CDMA (all used in wireless/cellular environments) Contention-based Nodes contends equally for bandwidth and recover from collisions Examples: Aloha, Ethernet Token-based or reservation-based Take turns using the channel Examples: Token ring

Modified for 2005Chapter 2: Introduction to the web and internet 15 Ethernet History Developed by Bob Metcalfe and others at Xerox PARC in mid-1970s Roots in Aloha packet-radio network Standardized by Xerox, DEC, and Intel in 1978 LAN standards define MAC and physical layer connectivity IEEE 802.3 (CSMA/CD - Ethernet) standard originally 2Mbps IEEE 802.3u standard for 100Mbps Ethernet IEEE 802.3z standard for 1,000Mbps Ethernet IEEE 802.11..n Wireless LAN (1999) IEEE 802.15 (wireless personal area net, ~2002,Bluetooth) CSMA/CD: Ethernets Media Access Control (MAC) policy

Modified for 2005Chapter 2: Introduction to the web and internet 16 Ethernet Overview (contd.) Ethernet by definition is a broadcast protocol - Most popular packet-switched LAN technology Bandwidths: 10Mbps, 100Mbps, 1Gbps signal can be received by all hosts Switching enables individual hosts to communicate Network layer packets are transmitted over an Ethernet by encapsulating Frame Format Dest addr 644832 CRCPreamble Src addr TypeBody 1648

Modified for 2005Chapter 2: Introduction to the web and internet 17 Internetworking Software is used to go between discrete networks The two most well-known pieces of internetworking software are the TCP and IP IP software set rules of data transfer over the network TCP software ensures the safe and reliable transfer of data With open system nature of TCP/IP development, software development and computer companies could more easily build TCP/IP compliant software and hardware TCP/IP standard network protocol laid the groundwork that enabled the deep internetworking that made internet possible

Modified for 2005Chapter 2: Introduction to the web and internet 18 http://www.ibiblio.org/pioneers/baran.html Paul Baran -Worked for RAND from 1959. -Must design a network to survive nuclear attacks. -Vulnerabilities were in the topology -1964 three topology types -suggests Packet Switching - Military and AT&T reject the idea. 1

Modified for 2005Chapter 2: Introduction to the web and internet 19 J.C.R. Licklider -He worked for several years at ARPA where he set the stage for the creation of the ARPANET. -He also worked at Bolt Beranek and Newman (BBN) from 1957 to 1968, where he acquired 2 computers for BBN, that would be developed into the first computers connected on the ARPANET. -From 1950 at MIT he had worked on a Cold War project called SAGE designed to create computer-based air defense systems against Soviet bombers. Computing was batch processing and took a lot of time. In 1960, Licklider published his groundbreaking work "Man Computer Symbiosis.", andMan Computer Symbiosis. much of his work has lead to the developments in Interactive processing.

Modified for 2005Chapter 2: Introduction to the web and internet 20 Early History of the ARPANET 1958Eisenhower forms the ARPA (Advance Research Projects Agency) in response to the USSR's launch of the Sputnik. 1966 December: ARPA Computer Network (ARPANET) project begins. 1967 April: Suggested that the ARPANET utilize a separate computer between the host and the network. This computer would perform the packet switching/routing. This separate computer dubbed the Interface Message Processor or IMP. 1968 December: Contract to build the IMPs is won by Bolt Beranek and Newman Inc. (BBN) 1969 April: First specification for Host to IMP communication (BBN report 1822) is released. The discussion of the Host to Host Protocol begins with RFC 1. The Network Working Group (NWG) forms to deal with the task of Host- Host layer communication protocols. September: The first IMP is delivered and connected to a Sigma 7 computer at UCLA. This IMP constitutes the first node of the ARPANET. October: The second node of the ARPANET is installed at Stanford Research Institute (SRI). The IMP is connected to an SDS 940 Computer. The first message is sent across the network and received. November: The third node of the ARPANET is installed at UCSB. December: The fourth node of the ARPANET is installed at The University of Utah.

Modified for 2005Chapter 2: Introduction to the web and internet 21 What is the Internet? The internet is a collection of wires, protocols and hardware that allows the electronic transmission of data over TCP/IP Any data can be transferred over the net, e.g., email, faxes,video,voice & web pages Technically www (web) and the net are not the same.The web is an application for the net

Modified for 2005Chapter 2: Introduction to the web and internet 22 BBN Bolt, Beranek and Newman (now called BBN Technologies) is a technology company that provides research and development services. BBN is based in Cambridge, Massachusetts. It is also a defense contractor.defense contractor Founded in 1947 by Leo Beranek and Richard Bolt, both professors at MIT, with Bolt's former student Robert Newman, Bolt, Beranek and Newman started life as an acoustical consulting company. Their first contract was consultation for the design of the acoustics of the United Nations Assembly Hall in New York.Leo BeranekRichard BoltMITRobert NewmanacousticalUnited Nations Work in acoustics then required substantial calculations which led to an interest and later business opportunities in computing. Although BBN still has a substantial interest in acoustics, it is now better known for its activities in computing. Some of BBN's developments of note are the implementation and operation of the ARPANET, the first person-to-person network email sent, the invention of the @ sign in an email address, the first router and the development of the TCP protocol.ARPANET@emailrouterTCP BBN creates large multi-processor systems for warfare simulation for the U.S. Navy. U.S. Navy http://www.bbn.com

Modified for 2005Chapter 2: Introduction to the web and internet 23 How the internet works Characteristics that allow shared access of data in a network : 1.Unique identification of each computer on the network Internet is a network of millions of computers and thousands of networks intertwined together. Thus it was important that each computer can be uniquely identified by assigning a specific Internet Protocol(IP) address. (16 bit in V4. 128 bit in V6.) e.g.,198.108.95.145 2.Human-friendly addressing Domain Name System(DNS) gave each computer on the network an address comprising an easily recognizable letters and words instead of an IP address. e.g., www.philanthropy.com

Modified for 2005Chapter 2: Introduction to the web and internet 26 How the internet works(contd) 3.Packet Switching To remedy delays associated with unequally sized data transfers, instead of transferring files in their entirety, whole files are broken up into data packets before being transferred over the network. 4.Routing Routers are dedicated, special-purpose computers which serve as an intermediary between networks. They route packets efficiently through networks. Routers are building blocks of the internet.

Modified for 2005Chapter 2: Introduction to the web and internet 28 Switching Networks

Modified for 2005Chapter 2: Introduction to the web and internet 29 Circuit Switching Basics Dedicated communication path between two stations Three phases Circuit establishment Data transfer Circuit disconnect Developed for voice traffic (phone) Once connected, transfer is transparent Inefficient Channel capacity dedicated for duration of connection If no data, capacity wasted Set up (connection) takes time

Modified for 2005Chapter 2: Introduction to the web and internet 30 Circuit Switching Routing Requirements: Efficiency Resilience Static routing uses the same approach all the time Dynamic routing allows for changes in routing depending on traffic Alternate routing allows different sets of routes may be used at different times

Modified for 2005Chapter 2: Introduction to the web and internet 31 Circuit Switching Alternate Routing Example

Modified for 2005Chapter 2: Introduction to the web and internet 33 Packet-Switching Basics Longer messages split into packets, data transmitted in small packets. In each switching node, packets are received, stored briefly, and passed on to the next node. Advantages: Line efficiency, no busy conditions, priorities,...

Modified for 2005Chapter 2: Introduction to the web and internet 34 Packet Switching Datagram Each packet treated independently Packets can take any practical route Packets may arrive out of order Packets may go missing Up to receiver to re-order packets and recover from missing packets

Modified for 2005Chapter 2: Introduction to the web and internet 35 Packet Switching Virtual Circuit Preplanned route established before any packets sent Call request and call accept packets establish connection (handshake) Each packet contains a virtual circuit identifier instead of destination address No routing decisions required for each packet Clear request to drop circuit Not a dedicated path

Modified for 2005Chapter 2: Introduction to the web and internet 36 Packet Switching Virtual Circuit v Datagram Virtual circuit Network can provide sequencing and error control Packets are forwarded more quickly No routing decisions to make Less reliable Loss of a node looses all circuits through that node Datagram No call setup phase Better if few packets More flexible Routing can be used to avoid congested parts of the network

Modified for 2005Chapter 2: Introduction to the web and internet 37 Routing Requirements Correctness Simplicity Robustness Stability Fairness Optimality Efficiency

Modified for 2005Chapter 2: Introduction to the web and internet 39 How the internet works (contd) 5.Reliability and Transmission control Protocol IP software handles packet deliveries and TCP handles safe delivery of packages. 6.Standardization Without the TCP/IP standardization, there would have been many negative tradeoffs, such as inflexibility and increased functional and switching costs.

Modified for 2005Chapter 2: Introduction to the web and internet 40 TCP Standardization Networking technologies are not inherently compatible. Before the development of internetworking technology an organization with networks had two options: One Alternative- allow groups to have network technology best suited to them, which was not flexible Other alternative have a standard

Modified for 2005Chapter 2: Introduction to the web and internet 41 Functions of TCP/IP Prevents loss of data Checks packets Eliminates duplicate packets Sends confirmation when the packet is received If confirmation is not received, then the packet is retransmitted Enables reliable and error-free communication over the net

Modified for 2005Chapter 2: Introduction to the web and internet 42 What Web pages are made of The entire Web is built upon three concepts: web pages (documents seen on the browser), links (connecting one web page to another), and servers (storing and transmitting the information to the browsers for display) No special software is required to create a web page Majority of pages are created using Hyper Text MarkUp Language(HTML). There is a growing use of XHTML and XML.

Modified for 2005Chapter 2: Introduction to the web and internet 44 Contents of the web Links Internal Anchor Links: Internal anchors are used to connect with other locations within the same document. Page Links: Page links allow users to link to other web pages. Mail-to Links: Mail links are used to let users send feedback and questions directly to them. Forms Forms are basically web pages where the user can enter information on the fields provided on the page.Forms are useful in getting highly structured feedback.

Modified for 2005Chapter 2: Introduction to the web and internet 45 Contents of the web(contd) Images The most supported image formats on the Web are Graphic Image Format (GIF) and Joint Picture Encoding Group(JPEG). Multimedia Web supports multimedia file type such as images, audio and video. Capturing contents and compressing data Printed images can be captured with low cost scanners and photos can be downloaded with digital video cameras. Audio Sounds can be captured, compressed and stored for use on the web. Video (Streaming Technologies) Video capture cards allow users to capture the analog video output of camcorders, VCRs and DVD players.

Modified for 2005Chapter 2: Introduction to the web and internet 46 How are Web Sites Created? 1.A Web page can be made by adding text-based codes called Hyper Text Markup Language (HTML) to a text file.Text editor allows to create WebPages and gives more flexibility and control over design and layout. 2.Document conversion tools enable existing documents and new documents to be created and posted with minimal investment in learning markup language. 3.Several web authoring tools are available; e.g., Microsoft FrontPage lets users add multimedia objects such as sound and animation to their web pages. 4.High-end Web authoring tools such as Dreamweaver and Adobe GoLive offer more powerful site creation and management features, and allow expanded features such as database integration to be built in a web site.

Modified for 2005Chapter 2: Introduction to the web and internet 48 Behind the Scenes Browsers make the retrieval process transparent Uniform Resource Locator tells the browser several things about how to access the desired content: 1.The transmission protocol to access the content. e.g., Hyper Text Transfer Protocol for Web Pages, File Transfer Protocol (FTP) for transmission of files and the extended S-HTTP for a higher degree of security. 2.The name of the computer where the content can be found 3.The directory on the computer where content is stored and the name of the file containing the content.

Modified for 2005Chapter 2: Introduction to the web and internet 51 INTERNET ADDRESS [email protected] INDIVIDUAL OR ORGANIZATION NAME HOST COMPUTER LOCATION DOMAIN 10.11

Modified for 2005Chapter 2: Introduction to the web and internet 52 WWW ADDRESS http//www.datamation.com GO TO WEB WEB SITE NAME TYPE OF ORGANIZATION 10.18

Modified for 2005Chapter 2: Introduction to the web and internet 53 Factors behind the growth of the net Ease of content consumption Browser versatility and convenience Speed Easy to download Platform independence Ease of content creation Standards

Modified for 2005Chapter 2: Introduction to the web and internet 1 Introduction to the Web and...

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