Unusual start to Downloads

[psyber]

hey i have noticed on a lot of my speed tests it always begins to download at an insane speed for 1 second then pans out

   i have only has fibre for 1 day so would this be an effect of the 10 day testing thing (iv heard it only applies to adsl tho)

    i have sky fibre unlimited 38mbps  (FTTC)

    estimated line speed of 20.4 - 30.8mbps

    1.7km from exchange

    350-400m from street box thing

Broadband Link	Downstream	Upstream
Connection Speed	25678 kbps	5185 kbps
Line Attenuation	24.1 dB	0.0 dB
Noise Margin	6.6 dB	6.6 dB

here are my recent download tests

 

 

Edited December 14, 2016 by psyber
my memory is corrupt

[psyber]

How am i able to achieve 58mbps on a 38mbps plan? Even though its only for 1 second, does this mean that those speeds are achievable?

Sky also do a 70ish mbps plan but they said it would be pointless opting for that as my estimated line speed is only 20-30mbps

if those speeds are possible is my isp fobbing me off by limiting my speed so i dont get the full 38mbps?

 

 

[Sean]

The spike at the start can sometimes be caused by the Internet Security (virus checker) or the browser itself.

 

For example, many Internet Security products start analysing the data of each connection before passing the data stream to the browser.  In the split second this happens, the data coming in is queued.  Once the Internet security product is satisfied this is not a threat, it passes this chunk along with any queued data to the browser.  To the speed test, this burst of data appears as the spike at the start of the graph.

 

I often see this happen with the Firefox web browser, which also seems to hold up the data stream near the start of the test.  For example, occasionally when I start a speed test, Firefox stutters and then seems to skip ahead 10% where the speed test script sees this chunk as a speed spike.  The following shows an example of the spike where I did a test on Firefox for Android, in this case over the Meteor LTE (4G) network.

 

[psyber]

thank you for your reply, that seems to make more sense than my isp pulling a fast one on me