TCP (Transmission Control Protocol) vs UDP (User Datagram Protocol)

Blog / TCP (Transmission Control Protocol) vs UDP (User Datagram Protocol)
TL;DR Summary
  • TCP is reliable connection-oriented protocol that sends packets in order with retransmission on failure. Think web browsing.
  • UDP is an unreliable, connectionless protocol and sends datagrams without guarantee of delivery. Think video streaming.

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TCP (Transmission Control Protocol)
TCP diagram
What it is
  • TCP is a connection-oriented transport layer protocol that ensures the reliable, ordered, and error-checked delivery of a stream of data between applications.
How it works
  • Establishes a connection using process known as a three-way handshake.
  • Segments data into packets, numbers them for ordering.
  • Receiver acknowledges received packets.
  • If packets are lost, TCP will retransmit them.
Use Cases
  • TCP is used where data integrity and accuracy are more critical than speed. It is ideal for:
    • Web browsing (HTTP/HTTPS)
    • File transfers (FTP)
    • Email (SMTP, POP3, IMAP)
Advantages
  • Reliable: Guarantees the delivery of packets in the correct order without duplication.
  • Flow Control: Manages data packet flow to prevent network congestion.
  • Error Checking: Checks packets for errors and ensures error-free data communication.
Disadvantages
  • Higher Latency: The process of establishing connections and acknowledging data can introduce delays.
  • Overhead: More protocol overhead due to acknowledgments, retransmissions, and status checks, leading to reduced efficiency.
  • Less efficient for real-time applications: Not ideal for applications needing real-time data transmission like live streaming or online gaming due to variability in transmission times.
UDP (User Datagram Protocol)
UDP diagram
What it is
  • UDP is a connectionless, lightweight transport layer protocol that allows packets of data to be sent without establishing a connection between the sender and receiver by providing a simple, unreliable communication method between applications.
How it works
  • Sends data packets (datagrams) without establishing a connection.
  • No handshaking, sequencing, or acknowledgment of received packets.
  • Packets can arrive out of order, be duplicated, or not arrive at all.
Use Cases
  • UDP is used in situations where speed is crucial and a certain amount of data loss is acceptable. Common applications include live video or audio streaming (e.g., VoIP, online gaming)
Advantages
  • Low latency: No need to establish a connection before sending data.
  • Efficient: Minimal protocol overhead, making it faster than TCP and more suited for real-time applications.
Disadvantages
  • Unreliable: Packets may be lost or arrive out of order. No inherent error-checking or recovery mechanisms.
  • No congestion control: Can contribute to network congestion, leading to higher packet loss.