International Speed - August 2016

International Download Speeds - Special Experiment with Analysis

TrueNet tests File Download Speeds from our overseas servers to measure performance from our international neighbours.

We ensure the download file is not held in New Zealand (cached), so that the test truly measures international performance. 

High Speed Fibre and Cable Time of Day

We measure the speed of a file downloaded from our Sydney and Dallas Servers.  Our tests have been based on 1MB files, assuming correctly that most connections are able to reach the maximum speed their line will allow within the time taken to download a 1MB file.  

However, we have identified that Ramp-up, the time taken to reach the fastest speed possible on a line, varies by ISP and technology.  Ramp-up only affects small file downloads where the maximum speed cannot be reached, this is common for websites, and mostly explains why lines with speeds greater than about 20Mb/s (See Charts 1, 3 and 4 above for Fibre, Cable and the best VDSL) do not improve website downloads.   

Fibre lines on 100Mb/s or more take almost exactly 1MB to reach 100Mb/s on the best ISP lines, we measure the speed of each quarter of a file as it is downloaded, so our tests show only the last quarter measured as the best possible speed.  Therefore, while past results are published based on a 1MB file download, since Spetember 2016 our test results are published using the fastest speed reached in a 2MB file download.  We also check these against a less frequent 5MB file download.

Chart 10: Australian download speeds for High Speed Connections (Speed Limited to that reached within a 1MB file)

Note Chart 10 shows the maximum speed reached during a 1MB file download, the speed may go on to higher levels with more data ( i.e. using a bigger file size).  

Our opinion is that downloading large files from overseas is rare, most large files are stored as copies in NZ, so the main files are going to be website files with pictures in the range 200kB to 1MB.  We plan to do further research into file sizes in websites.  Meanwhile, we have decided to increase our international file size to 2MB.  

This section reviews our research to develop a fair and reliable test.

What is the speed of download?  Is it the speed a file eventually gets to in a 100MB download for example, or is it a speed that is reached in a specified time?  This is a difficult question that is often decided as being the fastest file download speed achieved when downloading a massive file, which is often not in common use.  We normally use a 1MB file, and that has been sufficient until faster connections became more prevalent.  

Downloading a file starts slowly, and as more of the file is downloaded it increases speed until the maximum speed is detected by the equipment at each end, this process is called Ramp-up.   Ramp-up tends to take longer the further the distance the file travels, however Australia is only about twice the distance from Auckland as Dunedin, an important consideration for those ISPs with services based from Auckland only.

We were approached by Spark, concerned that our measurement of Australian downloads was using a file that is too small (1MB) for Ramp-up.  We checked our results, and found that slower service speeds of 50Mb/s and below are fine.  However, Spark lines definitely do not reach full speed by the time our current test finishes for service speeds of 100Mb/s or more.   Almost all copper lines do not exceed 50Mb/s so are reporting accurately.  

In order to research what file is best to use we compared the Ramp-up on three different sizes -1, 2 and 5MB files.   We found results depend on the ISP, some ISPs reach the peak speed during smaller file size downloads and some do not.  Below are the comparison of four key ISPs download averages over a large sample of files with the three different file sizes tested.  As a result of our testing  we are choosing to use the 2MB file for future downloads because that will ensure the best testing on the limited data caps that our volunteers are prepared to provide.

Chart 11, Our previous standard 1MB file Ramp-up

It is evident from Chart 11 that during the last quarter of the 1MB file download, the best quartile speed is short of 100Mb/s, and it may still be increasing in speed.  Vodafone are able to Rampup quicker than other ISPs, and achieve 80Mb/s average over that last quarter, while Spark is trailing behind at 50Mb/s.   The last quarter is the average speed of the whole of the last quarter, so if the file does reach 100Mb/s before finishing it may not be measured if some of that final quarter was slower. 

Chart 12: We doubled the file size, to see if speeds reach the capacity of the line and found that they do for Vodafone, but maybe not for the other three ISPs, with Spark only just reaching 50% of line speed.

For the 2MB file, the chart once again shows Vodafone's faster Rampup with 100Mb/s panelists averaging almost 90Mb/s from Sydney in the last quartile.   Although the other ISPs are still increasing in speed they fail to reach the 100Mb/s before the file has completed downloading.

Chart 12, A new 2MB test file Ramp-up

Chart 13: We tried a 5MB file, ie five times our standard file size.  While Ramp-up is still occuring on 2Degrees and Spark, it clearly finishes on Orcon and Vodafone, well before the first 2MB is downloaded.

With this much larger 5MB file, we can see that Vodafone download average reaches close to 100Mb/s, and maybe 2Degress may get there.  Orcon appears to have reached a cap of a bit over 80Mb/s.  2Degrees & Spark may still be increasing in speed.  Note 2MB is 40% of a 5MB file.

Chart 13, A new 5MB test file Ramp-up

Normal International speed will be re-appearing next month


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