How to measure real latency, as experienced by your customers?

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Latency has become a hot topic with the introduction of 5G. When advocating 5G services, the industry talks about gigabit download speeds and about 1ms latency in 5G (but forgets to mention that this is the radio link latency, not to the content, but more about that later).

A low latency is truly beneficial for some daily mobile applications, like VoIP calls and real-time multiplayer gaming. If the visions of self-driving cars running over 5G becomes reality, a low latency surely is important there, too.

So, what is the latency that your customers are truly experiencing in their daily usage of the mobile network?

It is fundamental to note that “latency” can be used to describe different metrics. It can be either the one-way latency between two points, or the two-way latency or Round Trip Time (RTT).

The one-way latency is challenging to calculate accurately as it requires the clocks to be synchronized between the measuring nodes. One could also simply measure the RTT and divide it by two to get a rough estimate of the one-way latency. Yet, in asymmetric networks, which mobile networks are, this would be inaccurate. The RTT (or what people often refer to as “ping”) is much easier to measure, as the sending and receiving timestamps are taken from the same physical clock.

Components of the latency that affect the consumers’ apps is the sum of many factors:

1. Radio link

2. Access network

3. Core network

4. Content server

The radio link (1) and access network (2) are the key components that eventually define most of the latency. The radio link, in particular, is the part that often becomes congested, increasing the latency of the mobile applications data flow.

Core networks (3) do not easily get congested, unless some hardware or cables do break. The RTT introduced by a fiber core is roughly 1ms/1000km but the hardware used increases this further, to a range of 1.5-3ms/1000km.

Content servers (4), residing in a data center, can be a bottleneck if the service is run on inadequate hardware not up to the task of serving the current user base. The hardware can introduce latency in the server nodes themselves, the internal data center network or the external internet connection.

How should you measure latency?

If we focus on crowdsourced measurement methodologies, we notice that most players have a look-up system that seeks to allocate the nearest measurement node for the test. The more nodes you have, the better the chances are that the end point is physically close to the measuring device and the lower reported latency.

Often with latency, one can measure the jitter, a notion of how stable the latency is and a way to show how much fluctuation there is. The closer the content is to the end user, the lower the jitter is, too.

Yet, as most players measure latency before a synthetic speed measurement, the reported latency and jitter present optimal results in an unloaded network.

Our daily apps do not operate in empty environments. Our apps send and receive data all the time, some more, and some less, and depending on the other users in the network, the capacity available changes. As the available capacity of the radio network drops, the user data starts to get buffered before transmission and latency grows.

Netradar measures latency inside the ongoing users’ data transfers. We use sophisticated AI (artificial intelligence) algorithms to decide when and how to measure the latency.

Our analytics can therefore present the real latencies experienced by the end users, while using their daily mobile apps.

Furthermore, at the heart of Netradar is our algorithms that can identify network congestion and show user data transfers that were limited by the mobile network. By combining our latency measurements with the congestion detection algorithms, and the detailed contextual data, Netradar can provide a very detailed picture of the performance of a mobile network, from a country to city level, down to individual routing areas, base stations and even antenna sectors.

What does Netradar analytics show ?

Our analytics, in relation to latency, show the familiar metrics that most crowdsourced systems or dedicated measurement hardware can show and a lot more. As we know when the network is running perfectly, and when there is a shortage of capacity, we can analyze the configurations of different parts of the network and help optimize the performance and the behavior.

The Netradar analytics show, in terms of latency:

1. Average latency as consumers and their apps experience the mobile network in their daily journey, regardless of the network capacity;

2. Minimum latency, the optimal case, when everything works perfectly (similar to the typical latencies reported by speed tests);

3. Maximum latency, the worst case, when the network is seriously overloaded;

4. Latency when there is ample capacity to server the users;

5. Latency in a congested network;

6. Latencies caused by handovers between base stations or radio technologies;

7. All of the above can be applied to radio technologies: 3G, 4G and 5G (SA and NSA), as well as

8. To any number of reference points that enable a very extensive view of data connectivity, even international network peering.

In Netradar, latency is not a simple single value, rather a multi-dimensional metric that can be used to study in detail your own network, and the ones of your competitors.

To deploy Netradar

Netradar is a solution for collecting private network performance analytics. As such, our customers have the ability to deploy measurement points anywhere on the planet. We can rotate the location to test latency between different national hot-spots, data centers or even access network hubs. We can also measure around the world, to see latency to different countries, or to major cloud providers like Amazon, Google and Microsoft.

Our latency measurement servers are designed to be extremely lightweight, yet powerful. A single server running in a virtual machine can serve tens of thousands of customers. This is yet another benefit from our architecture and methodology: you do not need to deploy heavy servers for testing top speeds, only lightweight “ping” servers.

An example from Germany

To illustrate what Netradar shows, we pulled data from the past couple of months from the three major players in Germany. Here are some examples of what we can notice immediately:

• One of the providers has a lower minimum latency than the other two providers: a very significant difference- if I were a gamer, the choice of provider would be clear to me.

• One provider has much more latencies from congested data transfers that indicates a much higher load in the network and not enough capacity to serve the customers. I would potentially avoid this operator.

• One provider has a higher average latency, which indicates potential configuration sub optimality or even network issues.

• One provider has a very high average of the minimum latencies, calculated per data transfers - not a perfect partner for running delay sensitive applications.

• The difference between optimal latency and latency in a congested network can become as high as 200ms for one provider, which will impact substantially mobile apps.

• Looking at individual regions, Brandenburg has very high latencies from two network providers The same can be noticed in Saxony-Anhalt where two providers have high latencies without significant network load. The worst regional latency is found in Mecklenburg-Vorpommern where one provider offers up to 100% higher latencies than the two other providers. Avery significant impact on customer experience.

• Looking at individual regions, Brandenburg has very high latencies from two network providers. The same can be noticed in Saxony-Anhalt where two providers have high latencies without significant network load. The worst regional latency is found in Mecklenburg-Vorpommern where one provider offers up to 100% higher latencies than the two other providers. Avery significant impact on customer experience.

• Looking at 5G, there is no difference in latency to 4G. This is due to the Non-Standalone Access (NSA) mode of deploying 5G, where the access network is the same for both 4G and 5G. In some cases, the 5G latency is even higher than 4G as people make use of the full bit rates and data transfer capabilities of the technology and load the network with traffic. Hopefully Standalone Access (SA) will change this, for both unloaded and congested networks.

Conclusions

In summary, with the wide range of apps and services, and the emerging 5G networks, latency must be seen as an important metric besides bit rate. Measuring the real latency experienced by customers is critical as it sheds light on how the network is configured and how it performs with the daily apps and the data transfers. Finding these misconfigurations and network segments with a limited capacity will make a difference between an average network service and a great one.

Only Netradar can provide a full picture of the network performance as experienced by the end users. Book an introduction session and solution's demo by contacting tomi.paatsila@netradar.com

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