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User Datagram Protocol

What is UDP ?

User Datagram Protocol (UDP) is a lightweight, connectionless transport protocol that provides minimal services. Unlike TCP, UDP does not require handshaking before communication begins. It is commonly used in applications where low latency and efficiency are more critical than reliability.

UDP Packet Creation and Transmission

  • UDP does not require a handshake before communication begins, unlike TCP.
  • When an application sends data, UDP creates a packet called a datagram.
  • This datagram includes a fixed 8-byte header and the data payload.
  • The header contains essential information such as the source and destination port numbers.
  • UDP sends this datagram directly to the destination IP address without any confirmation from the receiver.

Unreliable and Connectionless Nature

  • Datagrams are independent units and may arrive out of order, or not at all.
  • UDP does not have built-in error recovery. If a packet is lost or corrupted, it is not retransmitted.
  • This lack of guaranteed delivery and retransmission is why UDP is considered an unreliable protocol.
  • UDP communication is connectionless, meaning it doesn't establish or maintain a connection. This reduces overhead and delay, which is ideal for time-sensitive applications.
  • If reliability is a requirement, the application must handle packet loss and retransmission on its own.

Key Characteristics:

  • Unreliable data transfer: UDP does not guarantee delivery of data.
  • No ordering of messages: Packets may arrive out of order.
  • No error recovery: If a packet is lost or corrupted, it is not retransmitted.
  • Connectionless communication: No need to establish or maintain a connection.
  • Low overhead: Smaller header size compared to TCP (TCP header ranges from 20-60 bytes as compared to UDP header has fixed size of 8 bytes).

Use Cases of UDP

UDP is useful for applications that prioritize speed over reliability:

  • Finer application-level control: Allows applications to manage packet loss, retransmission, and congestion control.
  • No connection establishment: Reduces delay, making it suitable for time-sensitive applications.
  • No connection state: Ideal for handling large numbers of clients efficiently.
  • Small packet header overhead: More efficient for simple data transmission.

Common Applications:

  1. Streaming Media (Audio/Video)
  2. DNS (Domain Name System)
  3. Online Gaming
  4. IoT (Internet of Things) Devices