UDP (User Datagram Protocol) is a connectionless transport layer protocol that allows fast, minimal-overhead transmission of data. Unlike TCP, UDP does not guarantee reliable delivery, order, or error correction, making it ideal for applications requiring low latency.
Key Features:
- No connection setup – Data is sent without establishing a session.
- Minimal header overhead – Only 8 bytes, making it lightweight.
- No retransmissions – Lost packets are not resent.
- Supports broadcasting and multicasting.
Common Uses:
Streaming media (video/audio), online gaming, VoIP (Voice over IP), DNS queries.
Key Terms in UDP
- User Datagram Protocol (UDP) – A connectionless transport-layer protocol that enables fast, low-overhead data transmission.
- Datagram – A self-contained, independent packet of data sent without setup or acknowledgments.
- Connectionless – No persistent connection is required between sender and receiver.
- Checksum – An error-detection mechanism in the UDP header to detect corruption in data.
- Port Number – Identifies sending and receiving applications on the source and destination devices.
- Minimal Header Overhead – Only an 8-byte header (compared to TCP’s 20+ bytes), making it lightweight.
- Best-Effort Delivery – No guarantee of delivery, order, or duplicate prevention.
- Broadcast & Multicast – Supports one-to-many transmission, unlike TCP, which is strictly one-to-one.
- Low Latency – Suitable for real-time applications (gaming, voice calls, video streaming).
Breakdown of UDP Header Format
Unlike TCP, which is connection-oriented, UDP is a UDP is Stateless, connectionless (each packet is independent). The UDP header is much simpler compared to the TCP header.
1. Source Port (16 bits)
- Identifies the port number of the sender.
- Used to determine where the response should be sent (if needed).
2. Destination Port (16 bits)
- Identifies the port number of the receiver.
- Helps in directing the datagram to the correct application on the receiving device.
3. Length (16 bits)
- Specifies the total length of the UDP datagram, including both the header and the data.
- Minimum value is 8 bytes (header-only), and the maximum is 65,535 bytes.
4. Checksum (16 bits)
- Used for error detection.
- It covers the UDP header, data, and parts of the pseudo-header (from the IP layer).
- If not used, it may be set to 0.
5. Data (Variable length)
- Contains the actual message being transmitted.
- The size is determined by the Length field.
Summary
- UDP is lightweight, requiring only 8 bytes for its header.
- It lacks error correction, sequencing, and flow control, making it faster but less reliable than TCP.
- Common applications using UDP include DNS, VoIP, video streaming, and gaming.
Philosophy behind UDP Development:
- Simplicity and Speed: UDP is designed for applications that require quick data delivery without the need for error correction or retransmission.
- Minimalism: Unlike TCP, UDP does not establish a connection or provide delivery guarantees.
- Stateless Communication: It does not maintain session states between sender and receiver.
- Best-Effort Transmission: It sends data without confirming receipt, making it suitable for time-sensitive applications.
