Wireless
L4S in Wi-Fi: A Path to Seamless Interactive Experiences
Key Points
- Broadband service providers are beginning to implement L4S functionality in their networks. The technology enables applications to achieve low latency and high efficiency, ultimately helping deliver enhanced and more reliable user experiences.
- CableLabs worked with the Wireless Broadband Alliance to develop a set of guidelines for equipment suppliers to use when implementing L4S in their Wi-Fi products.
- Wi-Fi networks are frequently a point of congestion in end-to-end networks, creating a need for L4S support in those networks.
Modern networks deliver impressive speeds — often reaching gigabits per second — yet they still suffer from unpredictable delays that can disrupt interactive applications. Whether it’s video conferencing, cloud gaming or remote collaboration, these inconsistencies can lead to frustrating user experiences. As network operators strive to enhance reliability and responsiveness, a more effective solution is needed.
To address this need, the Internet Engineering Task Force (IETF) — an organization responsible for developing open internet standards — has specified the Low Latency, Low Loss, and Scalable (L4S) throughput architecture. L4S enables applications to implement a new mechanism to ensure that they are sending their data as fast as the network can support, but no faster. The result is efficient capacity usage with minimal queuing delay and low packet loss.
This shift to a more comprehensive quality of service (QoS) model is essential for delivering smooth and uninterrupted performance across a wide range of services, from gaming and video streaming to cloud computing and augmented reality.
What Is L4S?
The power of L4S stems from new congestion control algorithms that adapt to new fine-grain notifications of congestion at the IP layer across various network elements along an end-to-end (E2E) path. While L4S can be deployed on each element of the network, its most significant impact is at points of congestion, also referred to as network bottlenecks — where the rate of incoming packets can exceed the departure rate.
The cable industry already adopted support for L4S, as part of the Low Latency DOCSIS® 3.1 specifications (and it carries forward into DOCSIS 4.0 gear as well). Operators are beginning to enable this functionality in their networks, and more are expected to do so over the coming months. That said, the broadband access network segment is only one potential bottleneck. There are others on the E2E path.
The Need for L4S in Wi-Fi Networks
Wi-Fi networks, in particular, require L4S support as they are frequently a point of congestion in E2E networks. Indeed, although Wi-Fi networks often advertise their maximum capacity that is greater than the broadband access connection, actual performance is significantly influenced by factors such as the distance between clients and the access point (AP), as well as the number of APs and clients operating on the same channel. This need for L4S support is even more critical given that a substantial portion of internet traffic is transmitted over Wi-Fi.
WBA L4S Implementation Guidelines and NS3 Simulator
Wi-Fi presents unique challenges for L4S implementation compared to wired technologies such as DOCSIS® networks. While wired networks primarily see only buffering delays, Wi-Fi additionally introduces media access delays, which can be significant in congested environments. To tackle these challenges, CableLabs worked within the End-to-End QoS Working Group of the Wireless Broadband Alliance (WBA) to produce a set of guidelines to implement L4S in current Wi-Fi products.
The guidelines cover:
- An overview of L4S technology, explaining its mechanics and benefits.
- The importance of L4S support in Wi-Fi equipment for improving E2E application performance.
- Implementation strategies for Wi-Fi equipment suppliers to enable L4S functionality in their products.
- Simulation and test results demonstrating the advantages of L4S in real-world scenarios
The simulation results are based on a Wi-Fi NS3 model developed by CableLabs, designed to evaluate L4S performance in Wi-Fi networks. The model is open-source and available to industry and research players to support L4S deployment and assess its impact on various use cases. In addition, CableLabs provided field test data that were conducted with a Nokia AP.
The Future of L4S in Wi-Fi
Wi-Fi equipment suppliers today can leverage the L4S Implementation Guidelines to develop support on their existing platforms (e.g. Wi-Fi 7 devices). Several proposals from industry leaders, including CableLabs, aim to incorporate L4S support into the 802.11 Wi-Fi standard, ensuring native support for L4S across future Wi-Fi generations.
In addition, as the ecosystem matures, CableLabs will continue refining the NS3 model to expand its applicability to more scenarios and use cases. This ongoing effort is being advanced in collaboration with the WBA E2E QoS working group.
L4S is a critically important next step in the evolution of the internet that solves many of the issues that cause frustrations today, where it seems that bandwidth alone hasn’t fully enabled reliable and responsive interactive application experiences.
To fully take that step, the segments of the network that are the likely bottlenecks in residential deployments — the access network and the Wi-Fi segment — both need built-in support for L4S.