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Wan internet

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Transcript

  • 1. WWW Journey through the InternetInfrastructure The journey begins in a browser, where a URL is typed into the address bar. In this example, the journey is to the RA Online website. http://www.rothesayacademy.org.uk/
  • 2. WWW Journey through the InternetInfrastructure A browser is a piece of software which interprets HTML and other scripting languages to produce a web page. A URL is a Uniform Resource Locator (a “web address”).
  • 3. WWW Journey through the InternetInfrastructure After typing the URL the browser sends an instruction to the computer’s modem to dial the user’s ISP. This is called Dial-Up Networking (or DUN). The modem converts the digital signal to analogue for communication down the telephone line (PSTN)
  • 4. WWW Journey through the InternetInfrastructure An ISP is an Internet Service Provider – a company which specialises in providing Internet access. In this example, the modem is dialling Virgin Net. A modem is not the only way of getting on the Internet – ISDN, DSL, Satellite and many other services are available and much faster!
  • 5. WWW Journey through the InternetInfrastructure In order for the computer to be able to connect and communicate with the ISP server, the computer that is dialling must have the TCP/IP Protocols installed.
  • 6. WWW Journey through the InternetInfrastructure TCP/IP stands for Transport Control Protocol / Internet Protocol. You can see whether this is installed on your machine by looking in the ‘Networks’ section of the ‘Control Panel’.
  • 7. WWW Journey through the InternetInfrastructure When the computer connects to the ISP server, it sends username and password information via TCP/IP to verify that this is a legitimate connection. The server tells the computer what it is doing and this is shown in the connection window.
  • 8. WWW Journey through the InternetInfrastructure If the server recognises the username and password from its database, it agrees to the connection. The computer then sends the URL that was originally typed into the browser’s address bar to the ISP server.
  • 9. WWW Journey through the InternetInfrastructure The URL is sent to the DNS at the ISP. The DNS is the Domain Name Server. This converts the URL into an IP Address which is then sent to the ISP where the domain is hosted for collection, via the Internet Backbone.
  • 10. WWW Journey through the InternetInfrastructure The Internet backbone is maintained by a NSP (Network Service Provider). When you dial-up, you do not connect to the backbone: your ISP does this for you.
  • 11. WWW Journey through the InternetInfrastructureDomain Names and IP Addresses:Fully Qualified Domain Names (FQDNs) - such aswww.rothesayacademy.org.uk are used to help Internet users.This is because the Internet uses IP Addresses, not domainnames to find web sites and IP Addresses are strings ofnumbers, which are difficult to understand.The DNS (Domain Name Server) knows the IP Addresses of allregistered web sites. It converts the domain names into IPAddresses and uses this to request a web page from that IPAddress.
  • 12. WWW Journey through the InternetInfrastructureHow a Domain Name is structured: This specifies the PROTOCOL that should be used to fetch the information. HTTP is ‘Hypertext Transfer Protocol’ which means ‘rules for moving web pages from one computer to another’.http://www.rothesayacademy.org.uk/Curric/ICT/index.html
  • 13. WWW Journey through the InternetInfrastructureHow a Domain Name is structured:http://www.rothesayacademy.org.uk/Curric/ICT/index.html WWW stands for ‘World Wide Web’. This part of a domain name instructs the ISP to look on this part of the Internet for the information. It also forms part of the web server name.
  • 14. WWW Journey through the InternetInfrastructureHow a Domain Name is structured: This part is the FQDN (Domain Name). Also known as the Root Domain.http://www.rothesayacademy.org.uk/Curric/ICT/index.html The ‘.uk’ part of the root domain is a TOP LEVEL DOMAIN. There are many of these, including .com and .edu.
  • 15. WWW Journey through the Internet InfrastructureHow a Domain Name is structured:http://www.rothesayacademy.org.uk/Curric/ICT/index.htmlThese specify the folder names on the web server. Called the path. In thisinstance, the folder for the ICT Online website is inside the ‘Curric’ folder. Itis important to remember that web addresses are CASE SENSITIVE.
  • 16. WWW Journey through the Internet InfrastructureHow a Domain Name is structured:The final part of the web address specifies the name of the web page.These will normally end in ‘.html’ or ‘.htm’.http://www.rothesayacademy.org.uk/Curric/ICT/index.html
  • 17. WWW Journey through the InternetInfrastructureConversion to an IP Address:http://www.rothesayacademy.org.uk/Curric/ICT/index.html http://212.44.57.62, etc.
  • 18. WWW Journey through the InternetInfrastructure The request is made to the server at argyll-bute.sch.uk to send a copy of the first page of the RA Online website to ISP server. It transfers the web page via HTTP – Hypertext Transfer Protocol.
  • 19. WWW Journey through the InternetInfrastructure The ISP then transfers the web page to the requesting browser, again by HTTP and TCP/IP.
  • 20. WWW Journey through the InternetInfrastructure The browser interprets the web page code and displays the web page. The journey is now complete, and has only taken a few seconds.