Throughput below sync - congestion?

Hello everyone!

I've been lucky enough to purchase a flat in a FTTC area and have had sky fibre supplied. For about a week after install the speeds (on tests and downloads) were as I would expect - 35+Mb/s.

At some point in the last week or so throughput has slowed noticeably, yet my sync speed has remained unchanged. Since the problem is identical on wired and wireless connections, am I correct in saying this is the result of congestion on the network outside my control?

Speedtest:
http://www.thinkbroadband.com/speedtest/results.html...

Router stats:

Broadband Link Downstream Upstream
Connection Speed 39996 kbps 8972 kbps
Line Attenuation 22.5 dB 0.0 dB
Noise Margin 6.1 dB 6.6 dB

(upstream was nearer 10Mb/s when in master socket, but convenience of running on extension socket was worth some upload speed)

upstream was nearer 10Mb/s when in master socket, but convenience of running on extension socket was worth some upload speed

Might we see those same line stats from the router with it connected to test jack in the NTE ?

Yeah I'll do that this evening.

Do you think this could effect download speed even with the sync remaining at 40Mb?

The upload remains near enough the sync speed consistently.

It seems likely that you are suffering congestion somewhere; the FTTC connection (modem <-> cabinet) isn't likely to be the cause if your sync is staying at 40Mbps, and you aren't seeing any re-syncs.

There *is* a chance that you are suffering noise, errors, and packet loss over the link; and that this is having a knock-on impact to your throughput. However, DLM would normally notice such problems, and trigger some intervention, which would then be expected to fix the problem.

If DLM *had* intervened, then you'd certainly see some re-syncs. You'd almost certainly see an increase in latency. And you might see a decrease in speed (that would depend on how much spare capacity your line has over the 40Mbps limit set by Sky).

Line stats might help show if any of these have happened; seeing "before" figures will help identify any changes that have happened.

Just a thought, how are you checking your throughput speed?

If your using a online speed test you need to ensure your not running anything else in the background like Utorrentz, windows downloads, steam updates, etc that is potentially contending for the bandwidth of the test.

Hi, thanks for the reply.

I'm running speed tests from here and speedtest.net on a wired desktop, wired laptop and wireless laptop- all behave the same. I don't have anything using bandwidth in the background at the time (Win updates are set to notify only, steam/torrents etc closed and I live alone), but thanks for the reminder.

Yeah the consistant full speed sync was what was pointing me towards the congestion diagnosis. When the engineer installed the service his test showed zero errors on the line and an attainable rate of about 60Mb/s...so I think my line is good. I'll move the router back to the master socket tonight, post line stats and see if that improves the situation.

Hi all - thanks for the comments so far.

I've moved the router so it's directly connected to the test socket, the stats are now:
Broadband Link Downstream Upstream
Connection Speed 39994 kbps 9995 kbps
Line Attenuation 20.1 dB 0.0 dB
Noise Margin 12.6 dB 9.9 dB

Speed tests are still significantly slower than sync speed:
http://www.thinkbroadband.com/speedtest/button/13957...

I've also set up a quality monitor, which shows a disturbing long disconnect during the night while I slept:

My Broadband Ping

I came home late about 2 weeks ago and found the router unable to connect claiming it was physically unplugged, but it had sorted itself by morning...the plot thickens!

Can anyone help me make sense of this? I thought sky/bt were suffering congestion, but now it looks like I may have overnight disconnects to contend with too...

The odd wavy line for one of the tests suggests possible congestion somewhere

Thanks for the input. Does congestion constitute a fault or is it something that its up to BT/Sky to manage as they see fit?