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14 Communications technology (3)

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1.

Question 2

Describe the role of HTTP in web communication. Explain the difference between HTTP GET and POST requests, and provide an example of when each would be used.

HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the World Wide Web. It defines how messages are formatted and transmitted between web browsers and web servers. HTTP operates on a request-response model. A client (e.g., a web browser) sends a request to a server, and the server responds with the requested data (e.g., an HTML document, image, or other resource).

HTTP GET requests are used to retrieve data from a server. The data is typically appended to the URL as query parameters. GET requests are generally idempotent (making the same request multiple times has the same effect as making it once) and are suitable for read-only operations.

Example of GET: A user clicks a link to view a product page on an e-commerce website. The browser sends a GET request to the server for the product page, and the server responds with the HTML code for that page.

HTTP POST requests are used to send data to a server to create or update a resource. The data is included in the request body. POST requests are not idempotent and are commonly used for operations that modify data, such as submitting a form, uploading a file, or creating a new user account.

Example of POST: A user submits a form on a website (e.g., a registration form). The browser sends a POST request to the server with the form data in the request body. The server processes the data and creates a new user account.

2.

Explain the purpose of a web server and describe the key components involved in delivering web content to a client. Include a discussion of the role of HTTP.

A web server is a server that delivers web content (e.g., HTML documents, images, videos) to clients (e.g., web browsers) over the internet. Its primary purpose is to respond to client requests for web resources.

The key components involved in delivering web content are:

Web Server Software: Software like Apache, Nginx, or IIS handles incoming HTTP requests and serves the appropriate content.

HTTP (Hypertext Transfer Protocol): This is the protocol used for communication between web browsers and web servers. It defines how requests and responses are formatted and transmitted. HTTP requests specify the resource requested (e.g., a specific web page), and the server responds with the requested data.

HTML, CSS, JavaScript: These are the languages used to create web pages. The web server delivers these files to the client's browser.

Images, Videos, Other Media: The web server also serves multimedia content.

Database Server (often): Many web applications rely on databases to store and retrieve data. The web server interacts with the database server to fetch and display dynamic content.

HTTP plays a critical role. It uses a request-response model. A client sends an HTTP request to the server, specifying the desired resource. The server then processes the request and sends back an HTTP response, which includes the requested data and a status code indicating the success or failure of the request. HTTP methods (e.g., GET, POST) define the type of action to be performed.

3.

Question 3

Explain the purpose of FTP and how it works. Describe the difference between active and passive FTP modes, and explain when each mode would be preferred.

FTP (File Transfer Protocol) is a standard network protocol used for transferring files between a client and a server on a computer network. It allows users to upload, download, delete, rename, and create directories on a remote server.

FTP operates using two connections: one control connection (for commands) and one data connection (for file transfer). The control connection is typically port 21, and the data connection can use port 20 (active mode) or a dynamically assigned port (passive mode).

Active FTP Mode: In active mode, the client initiates a connection to the server on port 21. The server then initiates a connection back to the client on a port chosen by the server. This can be problematic if the client is behind a firewall, as the firewall may block incoming connections from the server.

Passive FTP Mode: In passive mode, the client initiates a connection to the server on port 21. The client then requests the server to assign a port for the data connection. The client then connects to the server on the assigned port. This mode is generally preferred because it allows clients behind firewalls to connect to the server without firewall issues.

When to use Active vs. Passive:

Active FTP: Suitable when the client is not behind a firewall and the server is directly accessible. However, avoid if the client is behind a firewall.

Passive FTP: Preferred when the client is behind a firewall or NAT (Network Address Translation). It provides better compatibility with firewalls and networks with NAT.