Understand network protocols (TCP/IP, HTTP, FTP)

📡 Communications Technology: Network Protocols

TCP/IP – The Internet’s Road Map

Think of the Internet as a huge city. TCP/IP is the set of rules that tells cars (data packets) how to get from one address to another.

TCP (Transmission Control Protocol) is like a reliable postal service: it guarantees that every letter arrives, in the right order, and without errors.
IP (Internet Protocol) is the address system – it tells the postal service where to deliver each letter.

Example: When you send a photo to a friend, TCP breaks it into packets, adds a header with the destination IP, and sends them across the network. The packets may take different routes, but TCP reassembles them at the destination.

Key points for the exam:

  • Explain the purpose of TCP and IP separately.
  • Describe how TCP ensures reliable delivery (handshake, sequence numbers, acknowledgements).
  • Give an example of how IP addresses are written (e.g., $192.168.0.1$).

HTTP – The Web’s Letter System

HTTP (HyperText Transfer Protocol) is the language that browsers and web servers use to talk. It’s like sending a letter that says, “Give me this webpage.”

Request–Response Cycle:

  1. User types https://example.com → Browser sends an HTTP GET request.
  2. Server receives the request, processes it, and sends back an HTTP 200 OK response with the HTML, CSS, and images.
  3. Browser renders the page for the user.

HTTPS adds a 🔒 layer of encryption (SSL/TLS) so that no one can read or tamper with the data.

Exam tip:
  • Define HTTP and its main methods (GET, POST, PUT, DELETE).
  • Explain the role of status codes (e.g., 200, 404, 500).
  • Describe why HTTPS is important for security.

FTP – File Delivery Service

FTP (File Transfer Protocol) is like a courier service that moves large parcels (files) between computers. It’s used when you need to upload or download files from a server.

How it works:

  1. Client connects to the server’s FTP port (usually 21).
  2. Client authenticates with a username and password.
  3. Client issues commands (e.g., RETR file.txt to download, STOR image.png to upload).
  4. Server responds with status messages and transfers the file.

Security note: Traditional FTP sends credentials in plain text. Secure alternatives include SFTP (SSH File Transfer Protocol) and FTPS (FTP over TLS).

Exam tip:
  • Explain the FTP command flow.
  • Discuss the difference between FTP, SFTP, and FTPS.
  • Provide an example of a typical FTP session.

Protocol Comparison Table

Protocol Purpose Key Features
TCP/IP Transport & addressing across networks Reliable, ordered delivery; IP routing; port numbers
HTTP Web content transfer Stateless, request/response, status codes, caching
FTP File transfer between hosts Separate control & data channels, authentication, command set

Exam Preparation Checklist

1️⃣ Understand the core concepts: Know what each protocol does and why it matters.
2️⃣ Use diagrams: Sketch the TCP handshake, HTTP request/response, and FTP session flow.
3️⃣ Relate to real life: Compare protocols to postal services, email, and file delivery to make explanations memorable.
4️⃣ Practice questions: Write short answers for “Explain the difference between HTTP and HTTPS” or “Describe the steps in an FTP session.”
5️⃣ Review key terms: Handshake, sequence number, status code, port, authentication, encryption.
6️⃣ Time yourself: During the exam, allocate ~5 minutes per protocol to cover all points.

Revision

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