Accessing the internet Chapter Notes | IGCSE Cambridge Computing for Year 6 - Class 6 PDF Download

Transmission characteristics

Wi-Fi:

• Wired/Wireless: Wireless
• Bandwidth: Capable of transmitting data at speeds up to 1.6 Gbps.
• Transmission Distance: Approximately 30 meters indoors, though this can be reduced by interference.
• Security: Security can be a concern. Wi-Fi networks are visible to anyone within range and require a password for access. Passwords can be vulnerable to brute-force attacks.
• Interference: Wi-Fi signals can be disrupted by physical barriers like walls and electronic devices such as microwaves and TVs.

Bluetooth:

• Wired/Wireless: Wireless
• Bandwidth: Bluetooth 5 can transmit data at lower rates compared to Wi-Fi.
• Transmission Distance: Up to 40 meters indoors, subject to interference.
• Security: Security is considered weak. Devices are discoverable within range, and there are known security vulnerabilities that can allow unauthorized connections.
• Interference: Best performance is achieved with a clear line of sight. Interference can come from Wi-Fi networks, physical obstructions, and other electronic devices.

Cellular Data (4G and 5G):

• Bandwidth:
  • 4G: Average speeds between 8 and 10 Mbps.
  • 5G: Average speeds around 100 Mbps.
• Transmission Distance:
  • 4G: Up to 16 kilometers.
  • 5G: Approximately 500 meters.
• Security: Both 4G and 5G have robust security features provided by cellular networks.
• Interference: Similar to Wi-Fi and Bluetooth, cellular signals can be affected by physical barriers and the environment, including buildings, landscape, and weather conditions.

Each wireless method has its own set of advantages and limitations, and the choice between them depends on factors like required data speeds, range, security needs, and the specific use case. For instance, Wi-Fi is commonly used for high-speed internet access within buildings, Bluetooth for short-range device connections, and cellular data for mobile internet access over wide areas.

Accessing web pages: IP addresses

Accessing web pages involves interacting with servers that store the content you wish to view or use. Here’s a simplified explanation of how IP addresses play a role in this process:

Servers and Content:

1. Servers are specialized computers that store and serve content like web pages, videos, audio, and messages.
2. They are often housed in server farms, which can contain many servers in one location.

Web Servers:

1. Web servers specifically store web pages and are set up to handle requests from users who want to access these pages.

Publishing Files:

1. To make files available on the internet, administrators upload them to a server’s hard drive.
2. Users can access these files by entering a URL into their web browser.

IP Addresses:

1. Every device on a network, including servers, is assigned a unique IP address.
2. An IP address is a numerical label that allows devices to communicate over a network.
3. It typically consists of four numbers separated by periods, with each number ranging from 0 to 255 (e.g., 192.124.2.213).

Home Network Example:

1. On a home network, each device is given a unique IP address, such as 192.168.1.42 for a Wi-Fi robot vacuum cleaner.
2. Devices use these IP addresses to send messages to each other, rather than using the device’s name.

Common IP Address Patterns:

1. It’s common for home network IP addresses to start with 192.168.1., followed by a unique number for each device.

By understanding IP addresses, you can grasp how devices on both home networks and the internet are identified and communicate with each other. This system ensures that data is sent to and received from the correct locations, enabling the functionality of the internet as we know it.

URLs

URLs, or Uniform Resource Locators, are the addresses we use to access content on the internet because they are much easier to remember than numerical IP addresses. Here’s a breakdown of how URLs work and their structure:

Purpose of URLs:

1. URLs locate files on a web server, allowing us to access web pages, stream videos, or use messaging services.

Structure of a URL:

1. A URL is composed of several parts, each directing us to the correct server. The domain name is the part that varies based on the web server you want to visit.

Domain Levels:

1. The top-level domain (TLD) is at the end of the domain name, such as .com, .net, or .org.
2. There are over 1000 TLDs available, but .com is the most common for commercial purposes.

Examples of TLDs:

1. .com: Commercial
2. .net: Network
3. .in: India
4. .au: Australia
5. .ng: Nigeria
6. .ph: Philippines
7. .eg: Egypt
8. .ae: United Arab Emirates
9. .id: Indonesia

Each TLD has a specific use or association with a country or type of organization. When you type a URL into your web browser, it translates the domain name into the server’s IP address to retrieve the content you requested.

Accessing web pages: DNS

The Domain Name System (DNS) is a critical component of the internet’s infrastructure, acting as the directory that links domain names to IP addresses. Here’s a step-by-step explanation of how DNS works when you access a web page:

URL Entry:

1. You enter a URL (like http://www.africanews.com) into your web browser.

DNS Lookup:

1. The browser sends a request to a DNS server to find the corresponding IP address for the domain name (africanews.com).

IP Address Retrieval:

1. The DNS server responds with the IP address of the web server where the website’s files are stored (e.g., 81.92.228.150 for africanews.com).

Error Handling:

1. If the DNS server can’t find the IP address, it asks a higher-level DNS server.
2. If no DNS server can find the IP address, a 404 error is returned, indicating the page was not found.

Web Page Request:

1. Once the IP address is known, the browser sends a request to that address.
2. The web server then sends back the web page to be displayed in the browser.

DNS makes it possible for us to use memorable domain names instead of having to remember numerical IP addresses for every website we want to visit. It’s like a phonebook for the internet, translating human-friendly names into the numerical addresses that computers use to communicate with each other.

Padlocks and HTTPS

Understanding the security of web pages is essential when browsing the internet. Here’s a breakdown of key points regarding web browsers, SSL certificates, and HTTPS:

Web Browsers:

1. Web browsers are application software used to access and display content on the World Wide Web.
2. They feature navigation buttons and an address bar for user interaction.

Web Page Security:

1. Not all web pages require the same level of security. Pages that handle sensitive information, like payment details, need higher security.
2. SSL (Secure Sockets Layer) certificates are used to secure data transmitted between a web server and a browser.

Identifying Secure Websites:

1. A padlock icon in the address bar indicates that the web page has an SSL certificate, signifying a secure connection.
2. The URL beginning with https (Hypertext Transfer Protocol Secure) means that the data is sent securely.

SSL Certificates:

1. An SSL certificate encrypts data sent from the user to the web server, protecting it from being intercepted by hackers.
2. Encryption scrambles the data into an unreadable format that can only be decrypted by the intended recipient.

HTTPS Protocol:

1. HTTPS is the secure version of HTTP, ensuring that all communication between your web browser and the website is encrypted.

By looking for the padlock icon and checking for ‘https’ in the URL, you can verify that the website you are visiting is taking measures to protect your data. Always ensure that websites where you enter personal or financial information are secured with HTTPS.

Insecure websites

Risks of Non-Secure Websites:

1. Avoid entering sensitive information, such as passwords or credit card numbers, on websites that are not secure.
2. Even if a website appears secure, your computer could be compromised by malware that misleads the browser about the security of a website.

Verifying Certificate Authenticity:

1. You can view the certificate by clicking on the padlock icon in the address bar.
2. The certificate will show who issued it (e.g., R3 for micropython.org) and confirm the website’s authenticity.

Checking Domain Ownership:

1. To ensure that the company actually owns the website, you can use services like https://who.is to find the domain owner’s details.
2. This service typically provides the address and contact information for the domain owner.

Remember: While SSL and HTTPS add a layer of security, they do not guarantee complete safety. Always verify the certificate and domain ownership, especially before sharing personal information or conducting transactions online. Keep your computer’s security software updated to protect against viruses and malware that could compromise your data.

Keeping it all secure

Security in data transmission is a critical aspect of modern communication, especially over networks where the risk of interception is high. Here’s a breakdown of the key points about keeping data secure:

Importance of Encryption:

1. Encryption is the process of encoding messages or information in such a way that only authorized parties can access it.
2. Without encryption, any data sent over a network, known as plaintext, can be intercepted and read by unauthorized individuals.

How Encryption Works:

1. Encrypted data is scrambled into an unreadable format that can only be understood if decrypted with the correct key.
2. For example, a bank would never send login details in plaintext due to the risk of interception. Instead, they would use encryption to secure the message.

Encryption Algorithms:

1. Algorithms are used to encrypt and decrypt data. The sender and receiver must agree on the algorithm and the key used.
2. The Caesar Cipher is a basic encryption technique where each letter in the plaintext is shifted a certain number of places down the alphabet.
3. A Simple Substitution Cipher is another method where letters are replaced with other letters or symbols based on a specific system.

SSL (Secure Sockets Layer):

1. SSL is a powerful form of encryption used to secure data transmitted over the internet.
2. It ensures that even if data is intercepted, it cannot be decoded without the unique encryption key.

Sending messages

In network communication, data is often transmitted in binary form between devices, each identified by a unique IP address. However, this data can be subject to errors due to various factors:

• Power Surges: Sudden increases in voltage can disrupt the normal flow of data.
• Damaged Cables: Physical damage to cables can lead to loss or corruption of data.
• Electrical Interference: Other electronic devices can cause electromagnetic interference, altering the binary signals.
• Hacking: Malicious attacks can intentionally corrupt data or alter the binary bits.

These issues can cause the binary bits (1s and 0s) to change state, leading to errors in the transmitted data. To mitigate these errors, various error detection and correction methods are employed, such as parity checks, checksums, and more sophisticated algorithms like cyclic redundancy checks (CRC). These methods help ensure that the data received is the same as the data sent, maintaining the integrity of communication over networks.

Intelligent search engines

Search engines are powerful tools that help users navigate the vast amount of information available on the internet. Here’s a detailed look at how they work and their evolving capabilities:

1. Database of Websites:

   • Search engines maintain extensive databases of websites and their content, allowing users to query and retrieve relevant web pages.

2. Keyword-Based Searches:

   • Users can type in keywords or phrases, and the search engine will return a list of web pages that match those terms.
   • Most searches are concise, often consisting of one to three words.

3. Machine Learning and AI:

   • Search engines are increasingly using machine learning and artificial intelligence to refine search results and make them more relevant to the user’s intent.
   • They track which pages users select for a given search term and adjust rankings to help future users find those pages more easily.

4. Location-Based Results:

   • Many search engines use the user’s location to provide geographically relevant results.
   • For instance, a search for “bicycle repair shops” in Cairo will return local results from that area.

5. Search Engine Optimization (SEO):

   • With the vast number of web pages indexed, there is significant competition to appear at the top of search results.
   • SEO is a field dedicated to improving the visibility of websites within search engine rankings.

6. Security and Privacy:

   • As search engines collect data on user behavior, concerns about privacy and data security have become more prominent.
   • Users are encouraged to be mindful of their privacy settings and the information they share online.

Search engines are continually evolving, becoming more sophisticated in understanding user queries and providing the most relevant results. They are an integral part of the digital experience, shaping how we find and interact with information on the internet.

Al and reverse image searches

Search Engines and Keyword Queries:

• Traditionally, search engines have relied on keywords to determine the relevance of web pages to a user’s query.
• Keywords are extracted from the user’s input, and non-essential words are disregarded to focus the search results.

Innovations in Search: Image-Based Queries:

• Advancements in AI have enabled search engines to offer image-based searching, also known as reverse image search.
• This technology utilizes image-recognition to analyze an uploaded image and find related content or similar images online.

How Reverse Image Search Operates:

• Users can initiate a search by selecting the ‘search by image’ option in their web browser.
• Upon uploading an image, the search engine compares it against a vast database, looking for distinctive features such as points, colors, lines, and textures.
• The results showcase similar images and direct users to pertinent web pages.

Case Study: Identifying a Helicopter:

• An example is provided where a reverse image search successfully identifies a helicopter, pinpointing its make and model as a ‘Bell 206’.
• This demonstrates the search engine’s capability to not only recognize the object but also provide detailed information about it.

The Role of AI in Search Accuracy:

• With billions of searches conducted daily, search engines like Google have a wealth of data to refine their AI algorithms.
• Over time, these algorithms become more precise, learning from each search to deliver increasingly accurate results.

Interactive AI Tools:

• Search engines are incorporating machine learning to enhance user interaction, such as matching user-drawn images with similar ones in the database.
• An interactive example involves a user drawing a giraffe, with the AI comparing it to previous drawings to identify the subject.

The Future of Search:

• Image recognition is not only improving the accuracy of search results but also expanding the ways users can search, moving beyond traditional text queries.