In reply to a post by jchamier:

The interleave I believe was applied to my line on day 2 and has never been lifted. Judging from the fact my lowest ping to a bbc site (on Windows 7) is 18ms and other people report 8ms. :-/

18ms I remember those days

In reply to a post by HiPing:

Thank you very much for the in-depth reply, filled in a fair few gaps in my knowledge there.
So swapping to another provider, along with all the hassle this causes, chances are, I would'nt see any change anyway.
Ah well, no real option but to hang on and hope for the best then.

Any chance you could perform a tracert to the BBC? It would inform us of where the latency has its highest jump.

Aside from Interleaving, it could be an increase on Sky's backhaul/core network.

In reply to a post by HiPing:

In regards to crosstalk, can that actually be blamed for such a sudden increase in latency, it wasnt a gradual increase it happened immediately.

A large number of lab experiments on crosstalk have been going on for VDSL2, especially as the boffins develop the vectoring concept that will (hopefully) eradicate the effects.

Those experiments tend to show that each line might suffer from umpteen disturbers, but the effect is not equal - and a few of the disturbers have a much more pronounced effect.

So crosstalk might have been gradually being added to the line, or it might just have been a single "heavy" disturber that got turned on. Perhaps they just happen to have the cable next to yours in the run back to the cabinet.

Either way, once sufficient crosstalk is in place, that causes sufficient errors on the line, DLM intervenes to set one of a number of profiles, which set a speed limit and/or a level of interleaving (which reduces speed too).

So yes: gradual increases in crosstalk eventually lead to a step change in latency.

But not usually that large. We had a line problem, and latency went from 13ms to 20ms (then back again a month after the problem was fixed).

I have 2 nodes available to me when connecting to BT.

I believe one is peterborough which gives me 13ms to bbc.co.uk but has spikes every 4 to 5 packets up to 16-17ms. The other which I am using which I believe goes via birmingham is 17ms to the bbc but is much more stable on the jitter.

Here is a tracert on the latter. This is on a fastpath connection.

Tracing route to bbc.co.uk [212.58.241.131]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms unknown [192.168.1.253]
2 5 ms 5 ms 5 ms 217.32.144.166
3 6 ms 6 ms 6 ms 217.32.144.206
4 8 ms 8 ms 8 ms 213.120.181.206
5 8 ms 7 ms 7 ms 217.41.169.221
6 7 ms 7 ms 7 ms 217.41.169.109
7 20 ms 7 ms 7 ms acc2-10GigE-9-3-0.sf.21cn-ipp.bt.net [109.159.25
1.223]
8 15 ms 15 ms 15 ms core1-te0-2-4-0.ilford.ukcore.bt.net [109.159.25
1.141]
9 13 ms 13 ms 13 ms peer2-xe11-0-0.telehouse.ukcore.bt.net [109.159.
254.130]
10 14 ms 14 ms 14 ms 194.74.65.42
11 * * * Request timed out.
12 16 ms 16 ms 35 ms ae1.er01.rbsov.bbc.co.uk [132.185.254.46]
13 17 ms 17 ms 19 ms 132.185.255.60
14 17 ms 17 ms 17 ms 212.58.241.131

Cheers for that, I will post one tonight when I get in from work.

My cab is the ECI 128 , which has more space than we have houses in our part of the village (other cabs further down the village). It turned out when BT installed fibre for me I was the first one in the village to get it (21 Oct 12). Must have been a mad rush for fibre after I joined, i should have kept my mouth shut.

Yeah. On first installation, my modem reported a maximum attainable speed of 83Mbps. Now (a year later) it says 78Mbps.

Luckily, we haven't resynced for the last month, so it is still running at 80/20. It won't next time though...

In reply to a post by Chrysalis:

I have 2 nodes available to me when connecting to BT.

That's a good point... Most MSANs are (or should be) dual-parented, so there are 2 different routes back to the core network. And for some the difference is significant.

IIRC each PPP session ends up routed one way or the other, so a disconnect/connect at *router* level could cause a change.

In reply to a post by WWWombat:

Yeah. On first installation, my modem reported a maximum attainable speed of 83Mbps. Now (a year later) it says 78Mbps.

Luckily, we haven't resynced for the last month, so it is still running at 80/20. It won't next time though...

Count yourself lucky ... mine has dropped about 15Mbps over 20 months and an extra drop due to Christmas!

mine dropped 20 very quickly. given the potential 40% or so drop expected from crosstalk I would say a 83 to 78 drop over that period of time is pretty good.

Edited by Chrysalis (Tue 18-Dec-12 18:23:52)