Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Define URL, DNS, and IP address and explain their roles.
• Describe the structure of a URL and its components.
• Explain how DNS translates domain names into IP addresses.
• Identify the basic elements of HTML structure.
• Create a simple, structured HTML document.

Lesson summary

This week, we delve deeper into the foundation of the internet and the technologies that make the World Wide Web function. Understanding these concepts is crucial because the internet has become an integral part of South African life, impacting communication, education, commerce, and even social interactions. From accessing educational resources online to participating in e-commerce and connecting with family and friends across the country or globally, a solid grasp of internet technologies and web concepts is essential for active participation in the digital age.

Lesson notes

2.1 Understanding URLs (Uniform Resource Locators) A URL, or Uniform Resource Locator, is essentially a web address. It's the address you type into your browser to find a specific web page or resource on the internet. The URL provides a standardized way to locate resources, ensuring you can access what you're looking for. The structure of a URL typically includes the following components: Protocol: This specifies how your browser should communicate with the web server. Common protocols include `http://` (Hypertext Transfer Protocol) and `https://` (Hypertext Transfer Protocol Secure). `https://` indicates that the connection is encrypted, ensuring secure data transfer.

Domain Name: This is the human-readable name of the website, such as `www.example.com`. It's easier to remember than the server's numerical IP address.

Path: This specifies the location of the particular resource (web page, image, document, etc.) on the web server. For example, `/images/logo.png` might point to an image file named `logo.png` within the `images` directory.

Query Parameters (Optional): These are used to pass information to the web server. They typically start with a question mark (?) and consist of key-value pairs separated by ampersands (&). For example, `?search=IT+Grade+10&sort=relevance` would pass the search term "IT Grade 10" and specify that the results should be sorted by relevance.

Fragment Identifier (Optional): This specifies a specific section within a webpage. It begins with a hash symbol (#). For example, `#introduction` might take you directly to the "introduction" section of the page.

Example: `https://www.sabcnews.com/sabcnews/national/2024/07/28/loadshedding-causes-more-problems-for-businesses` Protocol: `https://` (secure HTTP)

Domain Name: `www.sabcnews.com` Path: `/sabcnews/national/2024/07/28/loadshedding-causes-more-problems-for-businesses` Query Parameters: None Fragment Identifier: None 2.2 Domain Name System (DNS) The Domain Name System (DNS) acts as the internet's phonebook. When you type a domain name (like `www.uct.ac.za`) into your browser, the DNS translates that name into the corresponding IP address, which is the numerical address of the server hosting the website. Computers communicate using IP addresses, not domain names. Without DNS, we would have to remember long strings of numbers to access websites.

How DNS Works: Your computer sends a DNS query to a DNS server (usually provided by your internet service provider - ISP). The DNS server checks its records. If it has the IP address for the domain name in its cache, it returns the IP address to your computer. If the DNS server doesn't have the IP address, it contacts other DNS servers, starting with root servers, to find the authoritative DNS server for the domain name. The authoritative DNS server contains the correct IP address and returns it to the ISP's DNS server, which then returns it to your computer. Your computer uses the IP address to connect to the web server hosting the website. This process happens automatically and very quickly, making it seamless for users. Imagine trying to remember the IP address of every website you visit! 2.3 IP Addresses (Internet Protocol Addresses) An IP address is a unique numerical identifier assigned to each device connected to a network (including the internet). It's like a physical address for your computer on the internet, allowing data to be routed to the correct destination. There are two main versions of IP addresses: IPv4 and IPv

6. IPv4: Uses a 32-bit address, typically represented as four numbers separated by dots (e.g., `192.168.1.1`). IPv4 addresses are becoming scarce due to the rapid growth of the internet.

IPv6: Uses a 128-bit address, represented as eight groups of hexadecimal numbers separated by colons (e.g., `2001:0db8:85a3:0000:0000:8a2e:0370:7334`). IPv6 provides a vastly larger address space to accommodate the increasing number of internet-connected devices. When you visit a website, your computer uses the website's IP address to establish a connection and exchange data. Your own IP address is used to ensure the website knows where to send the requested information.

Example (South African context): Let's say a student in Soweto wants to access the website of the University of Johannesburg (`www.uj.ac.za`). The student types `www.uj.ac.za` into their browser. Their computer sends a DNS query to their ISP's DNS server (e.g., Afrihost, Telkom). The DNS server finds the IP address of `www.uj.ac.za` (e.g., `196.43.160.20`) and returns it to the student's computer. The student's computer uses the IP address to connect to the web server at the University of Johannesburg and request the website. The UJ web server sends the website data back to the student's computer, using the student's IP address as the destination. 2.4 Basic HTML Structure HTML (HyperText Markup Language) is the foundation of most web pages. It provides the structure and content of a webpage.