5.1 The internet and the world wide web-1.pdf

The Internet and the WWW Objectives: Understand the difference between the internet and the world wide web. Understand what is meant by a uniform resource locator (URL). Describe the purpose and operation of hypertext transfer protocol (HTTP) and hypertext transfer protocol secure (HTTPS)....

The Internet and the WWW Objectives: Understand the difference between the internet and the world wide web. Understand what is meant by a uniform resource locator (URL). Describe the purpose and operation of hypertext transfer protocol (HTTP) and hypertext transfer protocol secure (HTTPS). Explain the purpose and functions of a web browser. Describe how web pages are located, retrieved and displayed of on a device when a user enters a URL. Explain what is meant by cookies and how they are used, including session cookies and persistent cookies. Textbook reference: Page 180 – 184 Difference between the internet and the world wide web Internet (Interconnected Network) A big network of networks (physical infrastructure: hardware) uses TCP/IP (transmission control protocol/internet protocol) WWW (World Wide Web) collection of multimedia web pages and other documents which are stored on websites (information) accessed by web browsers(e.g., Google Chrome, Microsoft Edge, Mozilla Firefox) websites and webpages are stored on web servers uses HTTP (hypertext transfer protocol) Note: WWW uses the internet to access information from servers and other computers  Uniform resource locator (URL) IP addresses are also assigned for servers. IP address of web servers remain unchanged. An IP address may be used instead of typing a URL. Web Browsers: Are used to access web pages interpret HTML pages use URL instead of IP addresses URL Are text addresses used to access websites URL format URL format: protocol://website address/path/filename https://www.cambridgeinternational.org/about-us/what-we-do.html Protocol: mostly http or https Website address: domain host (www) domain name (name of website) domain type (.com,.org,.net,.gov, and so on); it may also be a country code (.mu, uk, and so on). Path is the web page (if this is omitted then it is the root directory of the website) Filename/webpage name is the item from the web page Hypertext transfer protocol (HTTP) and hypertext transfer protocol secure (HTTPS) Data packets are sent around the Internet using different protocols (rules) HTTP: Protocol for data transfer of web pages Some web pages contain private and sensitive information HTTPS: Ensures secure data connection between the server and computer exchanging information Data is encrypted at sender’s end and decrypted at receiver’s end Use of SSL (Secure Socket Layer)/ TLS (Transport Layer Security) Note: observe the padlock next to the URL in web browsers accessing HTTPS websites Purpose and functions of a web browser Web browsers are software that allow users to access and display web pages on their computer screens. Web browsers interpret (translate) the HTML(HyperText Markup Language) from websites and show the result of the translation Some features of web browsers are: storing bookmarks and favourites recording user history using multiple tabs storing cookies providing navigation tools and an address bar Web pages All webpages are: written in HTML Hosted on a web server (each web server has a unique IP address) A browser needs to know the IP address of the web server to access a webpage The user needs to know the IP address An easier way is to replace the IP address by a URL URL is in a more human readable form URL is easier to remember than an IP address DNS (Domain Name Service) DNS Standard technology for managing public names of websites and other Internet domains Domain names eliminate the need for a user to memorise IP addresses DNS servers contain a database of URLs with the matching IP address Role of a DNS in converting a URL to IP DNS process involves converting a host name (such as www.google.com) into an IP address the computer can understand (such as 8.8.8.8) DNS servers contain a database of URLs with the matching IP addresses 1. The user opens their web browser and types in the URL (www.google.com) and the web browser asks the DNS server for the IP address of the website. 2. The DNS server can’t find the URL in its database or its cache and sends out a request to another DNS server. 3. The second DNS server finds the URL and can map it to 8.8.8.8; the IP address is sent back to the first DNS server which now puts the IP address and associated URL into its cache/database. 4. This IP address is then sent back to the user’s computer. 5. The computer now sets up a communication with the website server and the required pages are downloaded. The web browser interprets the HTML and displays the information on the user’s screen. Cookies Cookies are small files or code stored on a user’s computer. They are sent by a web server to a browser on a user’s computer. Some uses of cookies: Save user’s preferences tracking user preferences (used to customize the webpage of each user) Store login details Store items in an online shopping cart Session and persistent cookies 2 types of cookies: Session cookie Persistent cookie Session cookie Temporary (deleted when browser is closed) Persistent cookie Have expiration dates (saved on computer’s hard drive) They remain even when the browser is closed Used to make websites “remember” users on next visit E.g., user login details  Exercise 2210/11/M/J/18 No10  Exercise 2210/12/M/J/19 No6  Exercise 2210/13/O/N/22 No10  Exercise 2210/11/M/J/22 No9