User Datagram Protocol (UDP)

UDP is a connectionless, lightweight transport‑layer protocol (Layer 4) that delivers datagrams with minimal overhead. It sacrifices reliability for speed and simplicity—there’s no handshake, no sequencing, and no built‑in retransmission.

Key Characteristics

Connectionless: Sends each packet (datagram) independently; no session setup or teardown.
Unreliable: No acknowledgments (ACKs), no guaranteed delivery, ordering, or duplicate suppression.
Low overhead: Minimal header (8 bytes), no congestion control, making it faster than TCP.
Port‑based multiplexing: Uses 16‑bit source & destination ports (1–65 535) to direct data to the correct application process.

When to Use UDP

Real‑time or streaming: VoIP, video conferencing, live broadcasts (e.g. RTP).
Simple query/response: DNS, DHCP, SNMP, TFTP.
Broadcast/multicast: One‑to‑many communications where speed is critical.
Applications tolerant of loss: Online gaming, some IoT telemetry.

Advantages & Disadvantages

Advantages	Disadvantages
Speed: No connection setup → lower latency.	No delivery guarantee: Packets may be lost or arrive out‑of‑order.
Low overhead: 8 byte header; minimal processing.	No congestion control: Can contribute to network congestion.
Application‑controlled reliability: Apps implement their own checks if needed.	No flow control: Receiver can be overwhelmed by sender.
Supports broadcast & multicast	No built‑in security: Data unauthenticated unless added above.

UDP Header Fields

Each UDP datagram carries an 8 byte header plus data: