🌐 TCP, UDP, and FTP — Computer Networks (Simple Notes)

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⚙️ What Are Network Protocols?

Network protocols are rules that define how data is sent and received between devices in a network.
They ensure that all systems communicate properly and data reaches safely and accurately.

Three common protocols are:

• TCP (Transmission Control Protocol)
• UDP (User Datagram Protocol)
• FTP (File Transfer Protocol)

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🔹 TCP (Transmission Control Protocol)

🧠 What is TCP?

TCP is a connection-oriented protocol that ensures reliable data transfer between devices.
It means a connection is first established before data is sent, and every packet is checked to ensure it arrives correctly.

⚙️ Main Features

• Reliable: Guarantees data delivery without loss or duplication.
• Connection-Oriented: A handshake (connection setup) happens before data transfer.
• Error Checking: Ensures data integrity using acknowledgment (ACK).
• Ordered Delivery: Data packets arrive in the correct order.
• Flow Control: Manages data speed to prevent congestion.

🧩 Process

1. Connection Establishment: Using 3-way handshake (SYN, SYN-ACK, ACK).
2. Data Transfer: Data is divided into segments and sent.
3. Connection Termination: Connection ends after successful delivery.

💡 Example

Used for:

• Web browsing (HTTP/HTTPS)
• Email (SMTP, IMAP, POP3)
• File transfers (FTP)

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🔹 UDP (User Datagram Protocol)

🧠 What is UDP?

UDP is a connectionless protocol used for fast and simple data transfer where reliability is not a major concern.
It does not check if data is received or not — this makes it faster but less reliable.

⚙️ Main Features

• Unreliable but Fast: No acknowledgment, so no delays.
• Connectionless: No setup before sending data.
• No Flow Control or Error Recovery: If data is lost, it’s not resent.
• Low Overhead: Ideal for real-time communication.

💡 Example

Used for:

• Video streaming
• Online gaming
• Voice calls (VoIP)
• DNS queries

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🔹 FTP (File Transfer Protocol)

🧠 What is FTP?

FTP is a standard protocol for transferring files between computers over a network.
It uses TCP to provide reliable communication between a client and a server.

⚙️ How It Works

• Users connect to an FTP server using a username and password.
• Once connected, they can upload, download, delete, or rename files.
• Uses two TCP connections:
  • Control Connection (Port 21): For sending commands.
  • Data Connection (Port 20): For transferring files.

💡 Example

Used for:

• Uploading websites to a server.
• Downloading software or large files.
• Backing up data on remote servers.

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🔗 Difference Between TCP and UDP

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📘 Summary

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✅ In short:

• TCP ensures accurate and ordered delivery.
• UDP sends data quickly without checking reliability.
• FTP helps transfer files using TCP for secure communication.

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