Transcript Part I
ULI101 – XHTML Basics (Part I) Internet / Web Concepts Brief History TCP/IP Web Servers / Web Browsers URL HTTP / HTML Internet - History Computers were not always set-up to form networks Critical Periods: 1957 – USSR launches Sputnik I & II launches (starting the “space-race” between USSR & USA) 1958 – U.S. government developed 2 agencies to keep up with technologies: NASA (National Aeronautics and Space Administration) ARPA (Advanced Research Projects Agency) This agency’s purpose was to allow U.S. technology to “keepup” with the USSR. Internet - History ARPAnet (Late 60s) Network of computers to keep computer networks operational in case of Nuclear war. Also allow communication among defense research scientists. Allows for “packet-switching” Known as the ancestor to the “Internet” ARPAnet lead to a development of many other key technologies such as: Telnet (1970). FTP (1972) E-mail standard (using “@” symbol after username - 1973) TCP/IP (1977) Internet - History TCP/IP (Transmission Control Protocol / Internet Protocol) Considered to be the basic communication language of the Internet. TCP/IP is a two-layer Program: Higher Layer: TCP Lower Layer: IP Manages the assembling or file into packets that are transmitted over the Internet and received by a TCP layer that resembles the packets into the original message. Handles the address portion of each package so that it gets to the right destination. Each gateway computer on the network check this address to see where to forward message Internet - History National Science Foundation (NSF) In the mid 1980s, the National Science Foundation (NSF) funded the purchase of 5 supercomputers, to be located in different parts of the United States. The NSFnet was formed to link these supercomputers and allow institutions in other parts of the country to access and share the costly machines. This was to be the first backbone of the Internet. Network Access Points (NAPs) In the mid 90s, as commercial interest in the Internet increased, the NSFnet was replaced by a backbone of commercial networks, connected by Network Access Points (NAPs). World Wide Web - History Critical Periods: 80s – Networks in widespread use, but although hyperlinks existed, they were not consistently applied. Tim Berners-Lee (considered to be the father of the World Wide Web) developed method to allow fellow CERN employees to communicate and share ideas via hyperlinks. This lead to the development of: HTTP Server / FTP Server Hypertext Transfer Protocol (HTTP) Hypertext Markup Language (HTML) Uniform Resource Locator (URL) Line-mode browser The World Wide Web (www) is a subset of the Internet. The www amounts to text documents that are stored on computers. The www are all the resources on the Internet that use HTTP. World Wide Web - History Critical Periods: 90s – Tim Berners-Lee made these key technologies available to the public via download. Allowed CERN to release code and technology to the public domain. 1993 – First graphical web browser called Mosaic created by Marc Andreesen while working for NCSA. Mosaic was originally created for the X-window platform. Release of Mosiac browser triggered interest in the World Wide Web. 1994 – Marc Andreesen left NCSA to form Netscape Communication Corporation with Jim Clark. Web Concepts The Internet The Internet is a global communications network consisting of thousands of networks typically interconnected by fiber optic cabling. The World Wide Web (WWW) The World Wide Web The Web is a conglomeration of what amounts to text documents, stored on computers on the Internet, and available for examination by users of the Internet, anywhere in the world. The World Wide Web is all the resources and users on the Internet that are using what is known as the Hypertext Transfer Protocol (HTTP). According to Tim Berners-Lee: “The World Wide Web is the universe of network-accessible information, an embodiment of human knowledge." Web Concepts Web Browser A Web browser is a program (Netscape or Microsoft Internet Explorer) that allows you to view information on the World Wide Web in a graphical format. The standard for Web browsers is that they interpret HTML (Hypertext Markup Language) documents, at the very least. Web Concepts Web Server A web server program uses a client/server model that makes use of the World Wide Web’s Hypertext Transfer Protocol (HTTP) to serve files that form Web pages to Web users. Web server hosts the pages, scripts, programs, and multimedia files via HTTP Server-Side Client-Side Web Server Web Pages Internet Web Browser Note: The two leading Web Servers are: • Apache (Unix, Linux, Windows) most widely used • MS Internet Information Server (MS-Windows) Web Concepts HTML Considered basically as a document language – mainly to design and display data (e.g. text, links, images) in a browser. HTML was one of the first simple-to-use languages derived from a more complex and harderto-learn language developed earlier called SGML (Standardized General Markup Language). Appearance (in web browser) code <html> <head> <title>Sample Title Name</title> </head> <body> Information to be displayed </body> </html> Tags can be used to enhance the display of text on the web browser. Links can be created to connect to other web pages. Web Concepts Domain Name Server (DNS) Static IP addresses are shown in groups of numbers separated by periods (eg. 123.123.23.2) Since static IP addresses are hard to remember, a Domain Name can be associated with a static IP address www.tucows.com Last element indicates type of website. Indicates the protocol – in this case, the world wide web. Middle element indicates name of server. Note: A domain name always goes from general information on the right to specific information on the left Web Concepts Domain Name Server (DNS) The last element in the DNS can relate to many things such as commercial site, organization, government (even country). A present, there are over 200 recognized country domains. Below is a chart of commonly recognized domain names Domain .com .edu .gov .mil .net .org Description Commercial Educational institute Government Military ISP Non-profit organization Domain .ae .am .ar .br .ca .uk .us Description United Arab Emirates Armenia Argentina Brazil Canada United Kingdom United States Web Concepts Universal Resource Locator (URL) Considered to be the website address. Also referred to as URI (Uniform Resource Indicator) Various formats for a URL/URI include: Protocol://domainname (e.g. Webpage) Protocol://domainname:port (e.g. Streaming audio) Protocol://domainname:port/uri (e.g. .Net applications) Web Concepts Web Developer Tools There are many tools that a web developer can use to create web pages: Graphical Web Authoring Applications (e.g. Dreamweaver) Graphical Editing Applications (e.g. Paintshop Pro, GIMP, etc) Other tools (SSH, FTP, etc…) In this course, you will be required to use only a text editor (like vi, nled, pico, etc…) to create or edit your web pages. (i.e. graphical authoring applications are not allowed). You will have an account on a server called Matrix to practice and work on web page assignments.