3 History of Internet Started 1960s - Packet Switching Research project by U.S. Department of DefenseARPAnet (Advanced Research Projects Agency)Really took off in 1993
4 History of the World Wide Web CERN (Tim Berners-Lee) developed authoring language and distribution system for creating and sharing multimedia-enabled, integrated electronic documents over the InternetWorld Wide Web and HTML was bornAllows relationships between documents and elementsNCSA developed Mosaic to view these documents
5 Overview The Internet The WWW How does it all work? Hardware Software NetworkingProtocols
6 Internet and World Wide Web What’s the difference between the two terms?
7 The Internet and the WWW The Internet (late 60s): “It’s a worldwide collection of computer networks – a network of networks – sharing digital information via a common set of networking and software protocols.”HTML & XHTML – The Definitive GuideThe World Wide Web (early 90s): the monster application that runs on the Internet infrastructure (over 2 billion pages).With the invention of GUI -> color, voice and video were added to the Internet.
8 History of the Internet Started 1960s - Packet SwitchingResearch project by U.S. Department of DefenseARPAnet (Advanced Research Projects Agency)Really took off in 1993, why?URL
9 History of the World Wide Web CERN (Tim Berners-Lee) developed authoring language and distribution system for creating and sharing multimedia-enabled, integrated electronic documents over the InternetWorld Wide Web and HTML was born.Allows relationships between documents and elements.NCSA developed Mosaic to view these docs.URL
10 Overview The Internet The WWW How does it all work? Hardware Software NetworkingProtocols
11 HardwareThe difference between hardware and software is you can touch hardware.The hardware you need to be connected to the Internet isA computerA networking device, e.g. a modem or network cardA connection, e.g.At home, an Internet Service ProviderAt school, a LAN connection
12 Most modems today have a maximum speed of 56 Kbps. Telephone (Dial-Up) Modem: Low Speed but Inexpensive & Widely AvailableModem - device that sends and receives data over telephone lines to and from computersMost modems today have a maximum speed of 56 Kbps.Using a modem and phone line to establish a connection to the Internet is called making a dial-up connection.FACTOID: Just 20 years ago, most modems operated at a speed of only 300 bps. What a difference!
13 Internet Service Provider (ISP) ISP - a company that connects you through your communications line to its servers, or central computer, which connect you to the Internet via another company’s network access pointsWell-known ISPs:AOL (America Online)EarthlinkMicrosoft Network (MSN)AT&T WorldNetProdigyPOP (Point of Presence) - your ISP’s local access number for your area.Log on - make connection to the remote computer of your ISP.
14 SoftwareSoftware is a term used to describe programs that allow the hardware to do things for you.You need a few pieces of software to connect to the InternetAn operating system, e.g. Windows XPA browser, e.g. Internet Explorer, Firefox, OperaIf you want to develop web sites or pages, you need a few moreAuthoring tool, e.g. Notepad, Dreamweaver or FrontpageFTP program, to transfer files from your client machine (in front of you) to the server (your students account), e.g. SSH
15 ProtocolsBecause networks use a wide variety of hardware and software, protocols are needed to coordinate communication and data transmission.A protocol is a set of rules for the exchange of data across communication lines.Protocols make the whole thing work!
16 Standards Organizations World Wide Web Consortium (W3C)Internet Engineering Task Force (IETF)URL
17 What protocols doIdentify the different devices in the communication path.Establish the speed and method for transmission of data.Alert the receiving device to the incoming data.Determine the method of error checking and correction.
18 HyperText Transfer Protocol HTTP is the protocol responsible for transferring and displaying web pages.HTTP uses the client/server model of computing.The client is the user’s web browser: a software program that retrieves the page and displays it. (I.E, Netscape).A Web browser can either be text-based, or graphical.A Web page is stored on a Web server, which makes the page available to users of the Web.The server is the web server where the page resides. (Ex:
19 TCP/IP protocol TCP – Transmission Control Processing IP – Internet ProtocolTCP: Rules to control on how messages are broken down into packets, and then reassembled at the final destination.IP: Rules to label packets for delivery and to control the packet’s path from sender to recipient.TCP/IP software processes data transmission through the Internet.
20 Internet protocolsSimple Mail Transfer Protocol (SMTP): transferring messages from one machine to anotherFile Transfer Protocol (FTP): transferring files between local and remote machines.Telnet: a terminal emulation protocol used to remote login.Others?TCP/IPHTTPPOP
21 IP addresses: dotted quads Each node in the IP world is identified by a unique 32-bit number called an IP address.IP addresses appear as a series of four 8-bit numbers separated by dots (dotted quads). Each number ranges from 0 to 255.students.cs.depaul.eduIP addresses are usually assigned human-readable names (domain names).
25 Domain Name Amazon. COM yahoo.com microsoft.com depaul.edu chicago.com news.comcnn.com
26 Domain Name ServerA Domain Name Server is responsible for the mapping between domain names and IP addresses.bach.cs.depaul.eduOrg. type (top level domain)Organization nameHost name.com.org.gov.mil.net.fr.museum.bizHow to convert a domain name into an IP address or IP address into domain name : Use MS/DOS command prompt on WINDOWS:Type: nslookup <domain name> or <IP address>depaul.edu is domain name, i.e. depaul is a subdomain of .educs.depaul.edu is considered a subdomain of depaul.edua root server looking for an ip address for cs.depaul.edu would probably query the depaul.edu domain for an ip addressIP address:
27 A Typical HTTP Exchange Client: Please open a connectionto ‘ and send methe default file. I am located atIP AddressNetscape’s URLWindowNY TimesWeb ServerServer: Let me check…. Okay, the default file at this site is of type HTML. It is 1749 bytes in size. Thedate is Tue, May 2nd at 15:33:33.NY Times Web Page
28 Web Pages and Web Browsers A Web page is stored on a Web server, which makes the page available to users of the Web.To view a Web page, the user runs a Web browser, a software program that retrieves the page and displays it.A Web browser can either be text-based, or graphical.
29 URL: Uniform Resource Locator People on the Web use a naming conventioncalled the uniform resource locator (URL).A URL consists of at least two and as many as four parts.A simple two part URL contains the protocol used to access the resource followed by the location of the resource.Example:A more complex URL may have a file name and a path where the file can be found.
30 A Web URL deconstructed The user is a directory in the systemThe protocol usedpath that indicatesthe location of thedocument in thehost’s file systemdomaindocumentname