Comparing CUBIC, BBR, and Reno Congestion Control Algorithms

Choosing the best congestion control algorithm for your network can significantly impact performance, especially in varying network conditions. Here’s a comparison of three popular algorithms: CUBIC, BBR, and Reno.

CUBIC

• Default in Linux: CUBIC is the default congestion control algorithm in many Linux distributions, including Debian.
• Stability: It has been extensively tested and is known for its stability in various environments.
• Performance: Optimized for high-speed, long-distance networks, CUBIC performs well under typical network conditions.

BBR (Bottleneck Bandwidth and Round-trip propagation time)

• Developed by Google: BBR is designed to optimize bandwidth and minimize latency.
• Performance: It excels in networks with high latency and packet loss, such as mobile networks or long-distance connections.
• Adoption: BBR is gaining popularity due to its ability to achieve higher throughput and lower latency compared to traditional algorithms like CUBIC.

Reno

• Classic Algorithm: Reno is one of the older congestion control algorithms and was widely used before the introduction of more advanced algorithms like CUBIC and BBR.
• Simplicity: It uses a simpler congestion control mechanism based on additive increase/multiplicative decrease (AIMD).
• Performance: While not as efficient as CUBIC or BBR in high-speed or high-latency networks, Reno is still effective in stable, low-latency environments.

Which One to Choose?

• General Use: If your network conditions are stable and you don’t experience significant latency or packet loss, CUBIC is a reliable choice.
• High Latency/Packet Loss: For environments with high latency or frequent packet loss, BBR might offer better performance.
• Stable, Low-Latency Networks: If you operate in a stable, low-latency environment and prefer a simpler algorithm, Reno can be a good option.

Testing and Implementation

To determine the best algorithm for your specific situation, you can test each one under your typical network conditions. Here’s how you can switch between them on a Debian system:

1. Check Current Algorithm: sysctl net.ipv4.tcp_congestion_control
2. List Available Algorithms: sysctl net.ipv4.tcp_available_congestion_control
3. Switch to a Different Algorithm:
   • For CUBIC:sudo sysctl -w net.ipv4.tcp_congestion_control=cubic
   • For BBR:sudo sysctl -w net.ipv4.tcp_congestion_control=bbr
   • For Reno:sudo sysctl -w net.ipv4.tcp_congestion_control=reno
4. Make the Change Permanent:
   • Add the following line to your /etc/sysctl.conf file:net.ipv4.tcp_congestion_control=<algorithm>
   • Replace <algorithm> with cubic, bbr, or reno.

By testing these algorithms, you can identify which one provides the best performance for your network conditions.