FTTC - Slowdown over time

I was connected with Plusnet last September/October. I had a line fault to start with that caused some problems, but after that was sorted out I was able to get speeds of around 73/18 consistently.

According to the speedtest.net logs it started slowing down in November. I stopped doing regular speed tests after a while and just checked my sync speed to make sure it was still in the 70's, which it always was. Of the speed tests I did do though, it was stuck in the high 50's since December with a peak of 66Mb/s downstream at the end of June, with upstream still over 18Mb/s. I kept a closer eye on it since then and all July it's been between 48 and 52 down, and 16 up. In fact the upstream is pretty much exactly 16 no matter what server I test with and what time of day, almost as if I'm being capped at that.

I have raised a ticket with Plusnet and we are awaiting feedback from OR now. After reading some other threads, I'm wondering if this is just crosstalk? I've read that speeds can drop by 20Mb/s due to crosstalk. I did suggest this to Plusnet but they think it's too much of a drop. Their own test shows that there are no faults, and Interleaving is off.

Why does the sync speed show 71.6Mb/s if I cannot go above 52Mb/s? I know there is a delay before that number changes but it's been showing in the 70's since last year. The latency on the speed tests always shows an amazing 5ms if I pick the right server to test on.

Any thoughts appreciated please.

[edit] The BT Wholesale test today shows max achievable downstream speed as 54.19Mb/s, max up as 20Mb/s. I guess that is going to be more current than the 71.6Mb/s that Plusnet show. Still, it's changed a lot since it was installed and a couple of months after.[/edit]

Edited by Zackary (Sat 20-Jul-13 10:27:58)

You seem to be assuming that the figure that shows on the Plusnet portal is the sync speed - it isn't and can effectively be ignored. It is supposed to be Plusnet's copy of the IP profile, but in your case it clearly hasn't updated, since your IP profile is 54.19Mb/s. As the Plusnet figure is higher than this, it is having no effect on your speed so you can ignore it. From your IP profile, your sync speed is 55980 or thereabouts.

Edit: My Plusnet profile shows 72.4Mb/s and has done for ages. My sync speed has been 71606 for the past few months and my IP profile 69.31Mb/s. As the Plusnet figure is higher than either I am perfectly happy with it.

Edited by kasg (Sat 20-Jul-13 12:19:56)

I'm not assuming it - I'm reading what Plusnet say, which is that it is my sync speed. Like I said before though, I know there is a delay in that updating, although I agree it does seem to be stuck. I'm surprised the tech guy I spoke to didn't update it.

That aside, my speed has still dropped a fair bit but the more I read other people's experiences, the more I think it's down to crosstalk.

It was never a copy of the sync speed, but the IP profile, which is a bit lower. If I were you I wouldn't want it updated as it would be of no benefit. You could be right about crosstalk but it does sound excessive and should, I think, be investigated.

Ok I appreciate your thoughts on this Kasg, thank you.

Update...

Openreach have visited and are at a loss to explain my problem. He did several tests and was very thorough and cannot find anything wrong with my line.

From 73/18Mbps I am now on 52/16Mbps. It is not down to the DLM and according to the engineer, not crosstalk either. I am simply running at the maximum speed my line is capable of.

I am awaiting a call from my provider about it, but would appreciate some help with where to go next before I speak to them.

In reply to a post by Zackary:

I am awaiting a call from my provider about it, but would appreciate some help with where to go next before I speak to them.

Do you have a TBBQM graph? Or some other way to measure jitter?

IT could be just increased usage of FTTC on your exchange and cabinet but the drop seems on the high side for that

In reply to a post by Andrue:

Do you have a TBBQM graph? Or some other way to measure jitter?

I haven't been provided with such a graph by my provider. The pingtest.net site does a test for jitter and shows that I have no measurable jitter. That is only a test over a few seconds of course so I'm not sure how valid that is. I just did that test again and it shows 4ms, which it reckons is still excellent.

In reply to a post by Bob_s2:

IT could be just increased usage of FTTC on your exchange and cabinet but the drop seems on the high side for that

I thought the same. The engineer said that all new connections in the cabinet won't interfere with mine anyway as they work from the bottom up with new connections, whereas my connection, being the first, was made at the top. Well I'm not convinced by that to be honest but that's what he said.