L4S: Low Latency, Low Loss, and Scalable Throughput (RFC 9330)

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Imagine streaming your favorite 4K movie or playing high-speed online games with virtually no lag. That’s the promise of L4S:

The need for speed and reliability in internet services is paramount. Enter RFC 9330, a groundbreaking document from the IETF that’s set to revolutionize how we experience the internet. This Low Latency, Low Loss, and Scalable Throughput (L4S) Internet Service Architecture is a solution designed to drastically reduce internet queuing delays and congestion losses.

βš™οΈ Applications and Use Cases: The L4S architecture significantly enhances various applications, particularly those requiring low latency.

These include cloud-based gaming, VoIP, video conferencing, web browsing, adaptive video streaming, and instant messaging.

L4S’s low latency enables advanced cloud applications like interactive video and virtual/augmented reality, even on overloaded networks. It’s particularly beneficial for applications sensitive to latency, such as interactive remote presence and remote control of machinery.

L4S is applicable across diverse network types, including DSL, mobile, and satellite, and supports a range of transport controls like TCP/SCTP and RTP/RMCAT.

It’s not just about speed; it’s about consistency and reliability. The L4S architecture targets the root causes of network delays, integrating advanced congestion control mechanisms.

πŸ’‘ This means smoother video calls, faster file transfers, and a more responsive internet experience overall.

What sets RFC 9330 apart is its focus on scalable throughput.

Netdev 0x13 - Implementing the 'TCP Prague' Requirements for L4S

It’s not just for the tech giants; this architecture benefits everyone from small startups to large ISPs, ensuring that the internet can keep up with our ever-growing data demands.

With its innovative approach to tackling internet congestion, RFC 9330 is poised to be a game-changer for tech enthusiasts and everyday users alike.

It delves into the intricacies of capacity-seeking congestion controllers and a modified ECN system, offering insights into the future of internet architecture.

The L4S architecture is a complex system for improving internet performance, consisting of three main components:

  1. Scalable Congestion Control on Sending Hosts: This part involves sophisticated methods for sending data over the internet. It adjusts the data flow to avoid congestion, ensuring faster and more reliable transmissions.
  2. Active Queue Management (AQM) at Network Bottlenecks: This component is deployed in network routers and switches. It intelligently manages data packets in busy network areas to reduce delays and prevent data loss.
  3. Protocol Linking Senders and Network: This establishes a communication protocol between the sending hosts and the network. It ensures that the new methods of sending data are compatible with the network’s way of managing traffic.

How Is This Different Than TCP Congestion Control?

L4S differs from traditional TCP congestion control in its approach to handling network congestion.

TCP typically detects congestion through packet loss, leading to a series of adjustments like exponential backoff and retransmission of lost packets.

This often necessitates large router buffers, which can introduce additional latency.

In contrast, L4S enhances the communication between routers and end devices.

It utilizes an additional bit in IP packets, allowing routers to explicitly indicate congestion before packet loss occurs. This direct signaling enables more efficient congestion management without relying on exponential backoff or large buffers.

Consequently, L4S can reduce both the need for retransmissions and the latency associated with large buffers, offering a more efficient and responsive network experience.


Whether you’re a network engineer, a tech enthusiast, or just someone who loves a seamless online experience, RFC 9330 is a treasure trove.