Page 14 - EngineerIt January 2021

IoT

Not so fast... this is what you

should know about internet

speed tests

By Keith Laaks, Executive Head of Technology at Vox

What is the difference between capacity and throughput and
are speed-testing services as reliable as we’d like to think?

ack when you had ADSL and tested your speed by downloading files, you often
got very close to the speed of your line, be it 4Mpbs, 10Mpbs or 20Mpbs. You
Bunderstood that the ‘missing Mbps’ was due to the internet protocol overhead
that you need to account for. You were happy with your overall experience.
Now, a fibre infrastructure provider rolls out in your area and you decide to upgrade
to a 100Mbps line. You eagerly run the same test again, and based on your past
experience, you expect to see a download speed around the 95Mbps mark. But you are
horrified to find that the download performance on that file is only around 35Mbps - no
matter how many times you redo your test.
You then turn to some of the speed-testing services available on the internet and Choosing the right server and
the results there too don’t look right to you. Internet speed testing platforms are latency
notoriously inaccurate and unreliable, yet too many people rely on them to test their Some speed testing services geo-
online speeds, not really understanding the multitude of factors that can impact locate users by their IP address and
internet performance, only to be left disgruntled with their internet service provider then automatically select the ‘closest’
(ISP). What is going on here? server when running a test.
Some of the misunderstanding can perhaps be traced back to the days of ADSL, Unfortunately, their logic is somewhat
when the line was the bottleneck and internet users became accustomed to upgrading broken. Instead of constraining their
the pipe to get better performance – typically going from a 1Mbps line to a 4Mbps to a server selection to ensure it's
10Mbps line and so on. However, in the fibre era, where we are seeing pipes of 50 to connected to the users’ ISP network,
100Mbps, or even 1Gbps, the line is no longer the bottleneck. they just choose any server,
Many speed testing platforms have their limitations and either use the incorrect regardless of the ISP network it's
methodology, or overlook important aspects that impact on the quality and performance connected to. You then end up with
of your connection to the internet. situations where a user in George
(for example), whose fibre access
Understanding capacity and throughput circuit first touches his ISP’s network
Firstly, it is important to understand the difference between capacity and throughput. in Cape Town, runs his speed test to
Capacity - popularly known as bandwidth - is what ISPs sell, and it is a measure of the a small WISP’s server in George with
amount of data per second (Mbps) that a communication link can transport. Throughput, only a 50Mbps internet connection.
on the other hand, is the actual amount of data that is successfully sent or received over In this example, the customer will
the communication link. need to manually override the auto-
Speed tests measure throughput and not capacity, and there are a number of selection and choose to instead run
constraints in the system that prevent throughput from ever reaching capacity levels. the test to a server in Cape Town, in
For instance, the architecture of some laptops – even if not connected to the internet order to get a more realistic result.
via Wi-Fi, but to the router via a cable – is simply not designed to get to 1Gbps. In Yet, the bigger issue is that of
addition, the way it is set up, the CPU, the operating system, browsers and antivirus latency, which is determined by the
software all impact throughput speeds. overall path (routers and
Another basic mistake that people make is performing a speed test over Wi-Fi, interconnecting links) that IP packets
forgetting that the further they are from their access point, the lower the link capacity. and signals traverse, and is a huge
Consequently, as you move further away from your access point, Wi-Fi throughput also factor in TCP/IP performance. TCP,
drops rapidly and becomes your overall limiting factor, especially on faster line speeds. part of the TCP/IP communications

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