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Lecture 02 fundamental concepts of internet and www khalid khan

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  • BITNET: Because It’s Time Network, City University of New York.CSNET: Computer Science Network, Purdue University, University of Delaware, University of Wisconsin, RAND Corporation, Bolt, Beranek, and Newman.
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    • 1. Fundamentals ofInternet and World Wide Web Lecture 02 By: Khalid Khan Department of Computer Science University of Peshawar 1
    • 2.  A Brief Introduction to  Web Servers ◦ Web Server Operation Internet ◦ General Server Characteristics ◦ Origins ◦ Apache, IIS etc. ◦ What Internet is?  Uniform Resource ◦ IP Addresses Locators ◦ Domain Names ◦ URL Formats ◦ URL paths) The World Wide Web  HTTP ◦ Origins ◦ Request Phase ◦ Web or Internet? ◦ Response Phase Web Browsers  FTP  Searching on the Internet 2
    • 3.  1958 – USSR launches Sputnik, first artificial earth satellite. 1960s – the US Department of Defence (DoD) gave the concept of a large scale computer network. 1969-Software called Network Control Protocol (NCP) provided communication between the hosts. The US DoD’s Advanced Research Project Agency (ARPA) funded the construction of such network – called ARPAnet. ◦ ARPA Net was text based. ◦ Communicate through email. ◦ Technique (packet switching) ◦ Protocol (TCP) ◦ ARPA reach to the development of IP (Internetworking protocol) creating a network of networks. ◦ Combined set is called TCP/IP 3
    • 4.  1970s and early 1980s – other networks such as BITNET and CSNET were also created but never became dominant networks. 1986 – NSFnet, sponsored by National Science Foundation(NSF) – initially connected five universities, but after establishment it became available to other institutions and laboratories too. 1990 – NSFnet replaced ARPAnet 1992– NSFnet connected more than 1 million computers around the world. 1995 – a small part of NSFnet returned to being a research network, and the rest became known as INTERNET 4
    • 5. A Brief Introduction to Internet 1985 1993 NSFNET founded Web Browser 1969 1983 by The National “Mosaic” invented ARPANET DOD Mandated Science by Mark AndreesenR&D Project Adoption of TCP/IP Foundation ARPANET INTERNET 1974 1983 Vinton Cerf ARPANET Split 1991and Robert Kahn into ARPANET and World Wide WebInitiated TCP/IP MILNET Released by Tim-Berners Lee
    • 6.  The Internet is a huge collection of computers connected in a communications network. ◦ The computers are of every manageable size, configuration, and manufacturer. ◦ Some of the devices connected are not computers at all e.g. plotter and printers etc. All of these diverse devices to communicate with each other using a protocol, TCP/IP. Each computer on a network is assign a unique ID called IP address, just like people home or street address. 6
    • 7.  For people, Internet nodes are identified by names, for computers, they are identified by numeric addresses. ◦ If one wants to send data to the computer on same network, he needs the physical address of the computer to which data is intended to be sent. ◦ But if the receiving computer lies on another network, or Internet for example, then IP address of the recipient is required to address it. The Internet Protocol(IP) address of a machine is a unique 32-bit number (IPv4), written in the form of numbers separated by dots(.).e.g. 191.57.126.0. New IP standard, approved in 1998, is IPv6 in which the address space was expanded to 128bits. ◦ This change is essential to face the rapid growth of computers. 7
    • 8.  A domain name represents a group of hosts on the Internet. A full domain name is a sequence of labels separated by dots It combines a host name and a TLD to form a fully qualified host name which provides a user friendly way to uniquely identify a site on the Internet. The DNS translates fully –qualified names into IP addresses. For example a yahoo website can be reached by typing http://www.yahoo.com or alternatively you can type the IP address of the yahoo server (e.g. like 207.168.92.4) in to browser. 8
    • 9.  We would go crazy if we would have to remember the IP addresses of all the web sites that we wanted to visit The Domain Name System translates between domain names and IP addresses of devices connected to the Internet ◦ A domain name (a part of the URL) is a unique alphanumeric name such as upesh.edu ◦ The top level domain name is edu and the secondary level domain name is upesh in the above example (there could be up to 127 levels, but more than 4 is rare)
    • 10.  The fully qualified host name of a computer on Internet has three major parts: The host name: The hostname is the name of the particular host on the internet. The domain name: A domain name is usually the name of the company that owns the site or a word or phrase that otherwise describes the site. Domain encapsulate host names The TLD: It usually refers to the type of organization that owns the domain name e.g. com, org, edu, gov, pk etc . www.university.peshawar.net 10
    • 11. 11
    • 12. Domain Name and Host IP ADDRESSES DOMAIN NAMESEvery device connectedhas a unique 32-bit Human DNS Readableaddress cnn.com Every device Translation connected has an Machine Readable alphanumeric Between e.g. 151.196.19.22 address domain Names and IP Addresses
    • 13.  Domain Names. Generic top level domains .com .biz .info .edu .mil .net, etc. Country codes or Country Domain .pk, .jp, .cn, .us, etc.
    • 14. 1945 – Vannevar Bush 1945 – Invent Memex ? 14
    • 15.  1965 – Ted Nelson◦ Coined the term “hypertext”◦ Project: “Xanadu”:◦ “A File Structure for the Complex, the Changing, and theIndeterminate.” 20th National Conference, NewYork, Association for Computing Machinery, 1965. In 1989, Tim Berners-Lee at CETN (European Laboratory for Particle Physics) proposed a new protocol for the internet as well as a system of document access to use it. This new system was called World Wide Web (WWW) which allow scientists around the world to use the Internet to exchange document to describe their work. 15
    • 16.  The release of the first graphical interface, Mosaic, in February 1993. 1995 – 2001 ◦ “Dot coms” like AOL, Yahoo, Netscape, ◦ Google ◦ Internet Explorer” 16
    • 17.  The Internet and the Web are not the same thing. Internet is a collection of computers and other devices connected by equipment that allows them to communicate with each other. The web is a collection of distributed documents referred to as “pages” located on computers (servers) all over the world. Servers store hypertext markup language(HTML) files and respond to requests. The Internet was quite useful before the Web was developed, and is still useful without it. However, most users use Internet through the use of Web. 17
    • 18. The web is based on a three-part architecture. HTML HTTP GUI Databases TCP/IP-based network GUI ContentWeb clients Web Servers Software applications
    • 19. The Web operates in a client/server configuration: Client: A client computer is one which requests for services to a server. Client uses a software called Web Browser for this purpose. Server: A computer that send responds to a client request, using a software called Web Server. HTTP is the most common protocol used for the communication between browsers and servers.Examples of browsers are Microsoft Internet Explorer, NetscapeNavigator, Opera, Chrome, Mozilla Firefox etc. 19
    • 20.  Web servers are programs that provide documents to the requesting browsers. Servers are slave programs: ◦ A web server stores web pages and delivers those pages upon client request. A web server software is installed on the web server. ◦ They act only when requests are made to them by browsers running on other computers on the Internet. Examples of Web Servers are:  Microsoft Internet Information Server(IIS)  Apache  SunONE etc. 20
    • 21.  URLs are used to identify documents (resources) on the Internet. Different types of resources identified by different forms of URLs, but with same general format: Scheme: object-address 21
    • 22.  Each page of information on the web has a unique address called the URL at which it can be found.http://faculty.uscupstate.edu/atzacheva/lecture1.html The documentcan be obtained Host Name - Path to the Web File Name Denotes that the File using the The Name of Page is Written in HTML Hypertext Web Server HyperText MarkupTransfer Protocol Language (HTTP) 2 1 3 Host Name Protocol File Name
    • 23.  Scheme: object-address Scheme: a communications protocol Common schemes include http, ftp, gopher, telnet, file, mailto, and news. Most important is HTTP, which supports the Web, and used to request and send eXtensible Hypertext Markup Language (XHTML) documents. In case of using HTTP, the form of the object address of a URL is: http://fully-qualified-domain-name/path-to-document.html 23
    • 24.  All Web communications transactions use the same protocol, the HTTP. The current version of HTTP is 1.1, defined by World Wide Web Consortium (W3C) in June 2011, as HTTP consists of two phases: Request phase Response phase Each HTTP communication (request or response) between a browser and a Web server consists of two parts: Header – contains information about communication Body – contains the data of the communication, if there is any. 24
    • 25. i. The Request Phase ii. The Response Phase 25
    • 26.  FTP works on the client/server principle. A client program enables the user to interact with a server in order to access information and services on the server computer. Files that can be transferred are stored on computers called FTP servers. To access these files, an FTP client program is used. This is an interface that allows the user to locate the file(s) to be transferred and initiate the transfer process There are two modes of transfer in FTP: ASCII is used only for files saved in ASCII format (this includes Postscript files) Binary is used for files that are formatted and saved using a word processing software like WordPerfect (.txt), spreadsheets (.xls), images (.jpg, .gif), and many executable programs (.exe) and videos (.avi). 26
    • 27.  Searching the Web The two most basic and commonly used Web-based search tools are: Directories A directory enables you to search for information by selecting categories of subject matter. The directory separates subjects into general categories, which are broken into increasingly specific designers. http://www.lookmart.com Search Engines A search engine lets you search for information by typing one or more words. The engine then displays a list of Web pages that contain information related to your words. http://www.google.com.pk/ 27
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