TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are two core protocols of the Internet Protocol Suite. They serve distinct purposes and have different characteristics:

1. Connection Type

• TCP: Connection-oriented. Establishes a reliable connection between sender and receiver before data transfer starts (via a three-way handshake).
• UDP: Connectionless. Data is sent without establishing a connection, making it faster but less reliable.

2. Reliability

• TCP: Ensures data delivery. It provides error checking, retransmission of lost packets, and guarantees the order of data packets.
• UDP: Does not guarantee data delivery or order. If packets are lost or arrive out of sequence, it doesn’t handle retransmission.

3. Speed

• TCP: Slower due to overhead for establishing connections, error-checking, and retransmission.
• UDP: Faster because it doesn’t perform error-checking or manage packet delivery order.

4. Use Cases

• TCP: Used for applications requiring reliable communication, such as:
  • Web browsing (HTTP/HTTPS)
  • Email (SMTP, IMAP, POP3)
  • File transfers (FTP)
• UDP: Used for time-sensitive applications where speed is critical, such as:
  • Live video or audio streaming
  • Online gaming
  • DNS lookups

5. Header Size

• TCP: Larger header (20 bytes minimum), which adds more overhead.
• UDP: Smaller header (8 bytes), which is more lightweight.

6. Flow Control and Congestion Control

• TCP: Includes mechanisms to manage flow control and avoid network congestion.
• UDP: Lacks flow control and congestion control features.

Summary Table

Feature	TCP	UDP
Connection Type	Connection-oriented	Connectionless
Reliability	Reliable, ensures delivery	Unreliable, no guarantees
Speed	Slower (overhead)	Faster (no overhead)
Use Cases	Web, email, file transfer	Streaming, gaming, DNS
Header Size	Larger (20 bytes)	Smaller (8 bytes)
Flow/Congestion Control	Yes	No

Both protocols are vital and are used based on the requirements of the application or system being implemented.