Page 14 - EngineerIt January 2021
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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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