Is the Internet ready for L4S?

Today, Catchpoint is pleased to be sharing the results of our Global Explicit Congestion Notification (ECN) Bleaching Rates measurement campaign, covering the state of ECN bleaching worldwide, according to Catchpoint’s perspective.  

ISPs, telecoms and streaming services, among others (this information should be of interest to anyone with ISP dependencies), will be able to draw on this information to determine if your network or an upstream network is experiencing ECN bleaching.  

Read the full data set.

ECN global bleaching rates, according to Catchpoint

The findings on ECN bleaching by country and ISP are based on running tests using Catchpoint’s enhanced traceroute, Pietrasanta Traceroute, through the Catchpoint IPM portal to collect data from over 500 nodes located in more than 80 countries around the world.  

By running traceroutes on Catchpoint’s industry-leading global node network, we are able to determine which ISPs, countries and/or specific cities are having issues when passing ECN marked traffic. The results demonstrate the view of ECN bleaching globally from Catchpoint’s unique (and as with any such research, partial) perspective. To our knowledge, this is one of the first measurement campaigns of its kind.  

L4S will speed up the Internet…

ECN plays a key role in ensuring networks are ready for Low Latency, Low Loss, and Scalable Throughput (L4S) technology.  

The new Internet standard, L4S, which was finalized and published in January 2023, sets out to speed up the Internet by making latency feedback shorter. When congestion starts, L4S allows your devices to find out about it almost instantly and start to resolve it. For ultra-low latency use cases like VR, multi-player gaming and streaming, L4S will have a major impact. Many major companies including Apple, Google, Comcast, Nokia, Deutsche Telekom, and others have shown interest in its implementation.

… if no one bleaches ECN

If ECN bleaching is found, this means that any methodology built on top of ECN such as L4S to detect congestion will not work.

Given the level of public interest in the new protocol, Catchpoint is now supporting the monitoring of ECN and its regular evaluation, through measurement campaigns such as this one.  

Latest findings

The team prepared these findings originally for a presentation shared at RIPE 88. Several people asked for further information and we hope the additional details presented here will be of interest to them, and the wider community.

For the set of measurements (May 2/3, 2024) prepared ahead of RIPE, we ran over 330,000 traceroutes globally and found 42,000 examples of ECN bleaching, demonstrating - at 12% of the total – that it’s a widespread issue. We are seeing ECN bleaching all over the world.

• The region with the highest rate of bleaching was Australia and Oceania at 31%, followed by Europe at 23%, then North America at 15%.
• The three countries with the highest bleaching rates, in the following order, are Estonia, Israel and New Zealand.
• ECN bleaching does not always happen when crossing a given ISP. This means that only some devices perform ECN bleaching, either on purpose or by accident.
• The ISPs introducing bleaching most of the time are Workonline in Africa, Arelion (Telia) in Asia, Europe, North America and South America, and Vocus in Oceania.

The location and number of our vantage points in a given region play a major role in the percentages we show. With a few probes, it is most likely that the traceroutes are going to cross the very same incumbent ISP that either show (100%) or not (0%) ECN bleaching. This is especially visible in Oceania and Europe, where the vast majority of ECN bleaching is caused by two incumbent ISPs: Vocus and Telia respectively.

A short FAQ on ECN & L4S

What is ECN?

Explicit Congestion Notification (ECN) is a longstanding mechanism in place on the IP stack to allow the network help endpoints "foresee" congestion between them. The concept is straightforward… If a close-to-be-congested piece of network equipment, such as a middle router, could tell its destination, "Hey, I'm almost congested! Can you two guys slow down your data transmission? Otherwise, I’m worried I will start to lose packets...", then the two endpoints can react in time to avoid the packet loss, paying only the price of a minor slow down.

What is ECN bleaching?

ECN bleaching occurs when a network device at any point between the source and the endpoint clears or “bleaches” the ECN flags. It only takes one instance of bleaching to remove the benefit of ECN since if any network device between the source and endpoint clears the ECN bits, the sender and receiver won’t find out about the impending congestion. Since you must arrive at your content via a transit provider or peering, it’s important to know if bleaching is occurring and to remove any instances of it.

Why is ECN important to L4S?

ECN and L4S need to be supported by the client and server but also every device within the network path. It only takes one instance of bleaching to remove the benefit of ECN since if any network device between the source and endpoint clears the ECN bits, the sender and receiver won’t find out about the impending congestion. Our measurements examine how often ECN bleaching occurs and where in the network it happens.

Why is ECN and L4S in the news all of a sudden?

ECN has been around for a while but with the increase in data and the requirement for high user experience particularly for streaming data, ECN is vital for L4S to succeed, and major investments are being made by large technology companies worldwide.  

L4S aims at reducing packet loss - hence latency caused by retransmissions - and at providing as responsive a set of services as possible. In addition to that, we have seen significant momentum from major companies lately - which always helps to push a new protocol to be deployed.

Working together to strengthen global networks

It’s our hope the data we are sharing is not used to specifically call out any one of us, but rather to provide specific insights to prompt collective action to strengthen global networks.

View the full data set.