Key Features of UDP Protocol Explained

UDP (User Datagram Protocol)

1. Basic Definition

UDP is a connectionless, unreliable, datagram-oriented transport layer protocol in the TCP/IP protocol suite. It provides a simple way for applications to send datagrams without establishing a connection in advance, focusing on low latency rather than data integrity and order.

2. Core Characteristics

Connectionless: No three-way handshake is required before data transmission. The sender can directly send datagrams to the receiver, and the receiver does not need to confirm the connection status.
Unreliable Delivery: UDP does not guarantee that datagrams will reach the destination successfully, nor does it ensure the order of data arrival. There is no retransmission mechanism for lost packets, and no acknowledgment (ACK) is required for received packets.
Low Overhead: With fewer header fields and no connection maintenance overhead, UDP has faster transmission speed and lower latency compared to TCP.
Datagram Boundaries Preservation: Each UDP datagram is an independent transmission unit, and the receiver receives data in the same unit as the sender sends it.

3. UDP Header Structure

The UDP header is fixed at 8 bytes, consisting of 4 fields:

Field	Length (bytes)	Description
Source Port	2	Identifies the port number of the sending application
Destination Port	2	Identifies the port number of the receiving application
Length	2	Total length of the UDP header and data (minimum value is 8)
Checksum	2	Used to verify the integrity of the UDP header and data (optional in IPv4, mandatory in IPv6)

4. Typical Application Scenarios

UDP is widely used in scenarios where latency is more critical than reliability:

Real-time multimedia communication: Voice over IP (VoIP), video conferencing, live streaming
Online gaming: Ensures fast response of game data
IoT and sensor networks: Reduces transmission overhead for small data packets
Broadcast/multicast communication: Supports one-to-many data transmission (e.g., DHCP, DNS queries)

5. Comparison with TCP

Feature	UDP	TCP
Connection Type	Connectionless	Connection-oriented (three-way handshake)
Reliability	Unreliable (no retransmission/ACK)	Reliable (with retransmission, ACK, sequence number)
Overhead	Low	High
Order Preservation	Not guaranteed	Guaranteed
Use Case	Real-time services	File transfer, web browsing (services requiring data integrity)