Nokia and Vodafone have conducted the world’s first trial of L4S technology over an end-to-end passive optical network (PON).

Pioneered by Nokia Bell Labs, L4S is an IETF internet standard that enables networks to maintain high throughput and low latency simultaneously.

Nokia’s research arm Nokia Bell Labs and Vodafone’s Fixed Access Center of Excellence performed the demonstration of L4S running over PON at Vodafone’s lab in Newbury, UK. The demonstration was performed on an end-to-end fixed access network built with Nokia technology.

It consisted of a broadband network gateway (BNG), a PON optical line terminal (OLT), multiple PON optical network terminals (ONTs) and wifi access points. The tests showed extremely low and consistent end-to-end latencies when travelling across every element of the network.

L4S stands for “Low Latency, Low Loss, and Scalable” throughput. It is an IETF standard technology that tackles a significant source of peak latency on the internet: queuing delays. Queuing delay happens when packets wait idly in buffers across the network, for instance in routers and modems, before being forwarded.

L4S networking technology (www.bell-labs.com/research-innovation/projects-and-initiatives/l4s) consistently achieves near-zero packet queuing delay, no matter how much load the network experiences. By eliminating queuing delays, L4S removes big variations in latency without compromising network speeds. In the lab tests, Vodafone (www.vodafone.com) and Nokia (www.nokia.com) measured consistent latencies of 1.05ms at local Ethernet ports running over a fully congested access network (BNG to ONT), and just 12.1ms when including a fully congested wifi link as the final connection.

While the tests were conducted using PONs, L4S can be implemented over any access technology, wireless or wireline, and applied to any latency-dependent application. In November, Nokia Bell Labs and Hololight, an innovator in enterprise XR, created a proof-of-concept demonstrating how L4S could support multiple simultaneous XR users over the same wireless connection without sacrificing performance.

“These highly encouraging results show L4S will unshackle any real-time application that would normally be constrained by high latency,” said Azimeh Sefidcon, head of network systems at Bell Labs for Nokia. “Videoconferencing, cloud-gaming, augmented reality and even the remote operations of drones would run flawlessly across the internet, without experiencing any significant queuing delays.”

L4S is a prime example of the network-application symbiosis that is a key component of Unext, an Nokia Bell Labs research initiative. Unext (www.bell-labs.com/research-innovation/projects-and-initiatives/unext) transforms the network into a self-managing, interactive operating system that breaks down barriers that have traditionally prevented network elements from interoperating.

“As a leading broadband provider, Vodafone aims to give customers a faster, more responsive, and reliable service unhindered by lag even during peak hours,” said Gavin Young, head of Vodafone’s Fixed Access Centre of Excellence. “L4S is an exciting technology with huge potential to achieve this goal, as well as deliver a more interactive and tactile internet experience for our customers.”