Broadband Speed Test results

Sorry if this is the wrong place but I could not spot a forum specifically for the broadband speed test.

My question relates to the Speed Test Analysis display. I believe this shows three separate graphs, one for idle time, one for when download is predominant and one for when upload is predominant. The colours separate the graphs rather than indicate quality (for me, up is red but the letter score is better than down which is green). I also assume that the different bars within a graph represent the percentage of latencies within a range of latencies - though without a scale, I cannot be sure of whether the scales are similar or different. So my first question is "Do I understand the display correctly?"

Second question, my download latency is scored as E while my upload is B. Does the good upload latency mean that the buffering I control is reasonable while my ISP is not doing very well with their buffers - or does it tell me that download is poor because I am not responding quickly enough to confirm receipt whereas upload is good because the ISP responds quickly - or maybe something else entirely?

Colour just groups the latency tests, each bar is one latency test, so yellow is when the speed test was doing nothing else, i.e. idle, green is a test during the download phase and red during the upload phase.

Hover over each of the bars to see the value.

You want particularly during the idle phase for all the latency tests to be similar or same value, during download and upload you get more variation, and the size of the difference between idle and download/upload phases lets you determine something called buffer bloat, i.e. if you connection is very busy in one direction how delayed are small packets or in real world use if doing a massive download and your latency shoots up to 800ms for example then ACKs and other packets linked to opening a web page will be slow to travel back and forth.

Thanks for the explanation - the display makes good sense now.

So I get between 40 and 80 ms during idle, 250ms or thereabouts during download (except for one measurement of 312ms and one of 792ms being the first and second measurements taken and then mostly 90ms to 100ms for upload with a few at 150ms.

My ISP is Plusnet. Is it Plusnet who are not well set up and causing the odd 792ms value, or is it my end that is in some way not acknowledging the arrival of the data rapidly enough?

If the former, then I cannot do much about it, if the latter then I can work at it to improve things.

Incidentally, the Broadband Quality Monitor shows an idle latency of something in the 15/16ms region (green band) with the blue band being so small on top of that to be within the same range. Why is the BQM result less than a third of the size of the speed test result?

BQM is an ICMP ping of just 28 bytes, latency test is a larger packet over HTTP and TCP so will be higher figures, but the consistency is the important bit.

One odd high value during download is nothing to worry about, even if it was 792ms for all of them during download for most people that is no problem, as I said only an issue if you want to upload a lot at the same time as downloading a lot