2025-04-30

When building network applications, choosing the right protocol can significantly impact performance. Two of the most common transport protocols, TCP and UDP, offer different trade-offs in reliability, speed, and overhead.

In this post, I compared TCP and UDP round-trip times on a local machine.

What are TCP and UDP?

• TCP (Transmission Control Protocol) is connection-oriented, ensuring reliable, ordered delivery of packets. It’s widely used for web traffic, email, and file transfers.
• UDP (User Datagram Protocol) is connectionless, with minimal overhead, making it suitable for real-time applications, such as video streaming and online games.

But how much faster is UDP in practice?

Benchmark Setup

• Language: Go
• Envoironment: macOS, localhost
• Messages: 10,000 round-trip messages
• Message size: minimal (small ping–pong messages)

Each message’s round-trip time (RTT) was measured using Go’s time package. Both protocols were implemented using native Go net packages.

Result Summary

Code TCP:

Average round-trip time: 11.275957ms
Dropped messages: 0
Errors: 0

UDP:

Average round-trip time: 11.22507mss
Dropped messages: 0
Errors: 0

Interpretation

In this test with a simulated 10ms network delay, the results show TCP and UDP performing nearly identically in average round-trip time. This may seem surprising given UDP’s lightweight reputation, but the closeness of results can be attributed to several factors:

• Artificial delay dominates: The added sleep of 10ms in both servers overshadows protocol differences.

  // Simulate network by pausing the server for 10 milliseconds after receiving data
  time.Sleep(time.Millisecond * 10)
  

• Reliable loopback interface: On localhost, with no packet loss or congestion, the benefits of UDP’s minimalism are reduced.
• Efficient TCP implementation: TCP benefits from connection reuse and system-level optimisations.

The result reinforces the idea that real-world conditions are key to revealing true protocol behaviour differences.

Key Takeaways

• Real-world UDP gains may not appear in local tests. The difference becomes clearer on real networks with latency, jitter, and potential packet loss.
• Use the right tool. TCP is great when reliability matters.

<Home>