L4S4

L4S4, or Low Latency, Low Loss Scalable Throughput, is a congestion control algorithm designed to improve the performance of data transmission over computer networks. It was developed by Google as an alternative to the traditional TCP congestion control mechanisms. L4S4 aims to provide better scalability and lower latency for high-bandwidth, low-latency applications, such as real-time video streaming and online gaming.

The core idea behind L4S4 is to differentiate between different types of traffic based on their sensitivity to latency and loss. It uses Explicit Congestion Notification (ECN) to mark packets when congestion is detected, allowing endpoints to adjust their sending rates accordingly. Unlike traditional TCP, which reduces its sending rate in response to packet loss, L4S4 allows endpoints to continue sending at a higher rate, provided they can handle the increased latency.

L4S4 operates in two modes: L4S and DCTCP. L4S is designed for high-bandwidth, low-latency applications and uses a more aggressive congestion control mechanism. DCTCP, on the other hand, is designed for traditional TCP traffic and uses a more conservative approach. The algorithm dynamically switches between these two modes based on the type of traffic being transmitted.

One of the key advantages of L4S4 is its ability to provide a more consistent user experience for high-bandwidth, low-latency applications. By reducing the impact of congestion on these types of traffic, L4S4 can help to improve the quality of real-time video streaming, online gaming, and other latency-sensitive applications. However, it is important to note that L4S4 is still a relatively new technology and may not be widely supported by all network devices and applications. As such, its adoption and effectiveness in real-world networks remain to be seen.