Strange

Been having some fun changing my wiring, up to today my router was upstairs on an extension. I have now put a switch in its place and moved the router downstairs to the master socket. In this process I have lost half a meg sync since moving to the master socket.

Any ideas why?

More noise sources nearby?

How long before since you last sync'ed, and at what time of day. It's easy to lose 500kbps between mid-day and "dark time" sync's.

In reply to a post by MrSaffron:

More noise sources nearby?

Possibly although upstairs is a studio so lots of PSUs and other equipment. Downstairs just a PC and a few power blocks. Will check DSL cable routing.

In reply to a post by RobertoS:

How long before since you last sync'ed, and at what time of day. It's easy to lose 500kbps between mid-day and "dark time" sync's.

Re-sync was about 1630 so just turning dark, will check in daylight hours.

There's another thing I have PhyR and SRA enabled on my router, does BT equipment support these?

SRA, to my knowledge definitely not. It'll drop the connection and resync at a new speed if it needs too, not seamlessly, it'll drop entirely.

PhyR - not sure what it is off the top of my head and too tired to google it right now.

Re-sync during daylight hours gained about 300 kbos, Checked dsl wire routing, not near any power blocks, getting about 17837 now. Used to get well over 18 meg and 19 on LLU, Strange,

In reply to a post by Banger:

There's another thing I have PhyR and SRA enabled on my router, does BT equipment support these?

The only provider I ever found that supported SRA was the now defunct UK Online. It was very useful on my line at the time which had a long section on poles so saw a fairly high day/night noise difference despite the ringwire being isolated. Not that many routers supported it then and I had to hunt around for one that did - a Billion of some sort iirc.

Have you tried the TEST socket to see what your connection speed is?

This will show you the best speed you can expect - so if things slow down using normal wiring/setup then it shows something's causing a problem.

EDIT: I take it your Default/Target SNRM hasn't changed while your been playing with things?

Edited by b4dger (Sun 18-Jan-15 17:23:30)

Is the old extension still connected to the unfiltered line? If so, it will act as a "bridged tap" and that (especially on VDSL) can lose some speed at the master. Note that it doesn't matter if the extension is not used. The solution is either to disconnect the extension completely or connect it via the filtered output on an Interstitial adapter or a VDSL faceplate. (Of course this is true for any other extensions too).

If you sync via the test socket (removing the faceplate) and find that your sull sync rate returns (or better), that will almost certainly be the issue.

Tried the test socket and gained very little about 100kbps. I was tweaking SNR to 1.5db but since interleaving kicked in I have had to use 2.0db as it just wouldn't hold sync.

Looks like I'll have to live with it.

Tweaking increases sync speed (which is what you intend), which increases error rates. That, plus any losses of connection, could be the cause of the interleaving in the first place.

In other words, it's quite possible you have over-tweaked and ended up being counter-productive. It was fine on O2/Be and think Sky, where the DLM was basically deactivated after the first three days, (ceased to be dynamic in fact), but on a BT Wholesale service it really is on all the time.

That's why for many years the default sync-time margin was 6dB. These days the BTW DLM will drop it to 3dB when appropriate, in fact sometimes when it isn't. We have had people having to get their ISP to get it fixed at 6dB because of 3dB being unstable.

It's worth keeping an eye on the FEC and ES/SES rates. Huge amounts of FECs can kill the router CPU and really slow down the throughput.

100kbps change on a re-sync is basically "no change". More than that much fluctuation is normal.

Interleaving kicked in after a phone fault Im pondering getting it switched off at ISP.

In reply to a post by RobertoS:

Huge amounts of FECs can kill the router CPU and really slow down the throughput.

Do you have some guidelines as to how huge is 'huge' (per unit time)?

Do you have some guidelines as to how huge is 'huge' (per unit time)?

My adsl drops (sometimes) when I get spikes >50 to 70 thousand per min, these normally happen when lightning is in the vicinity.

My average 24 hr total is about 100,000, with a few few spikes of about 2500/min

Ian

In my case I was very aware of it at several thousand per millisecond . Where it becomes critical I have no idea, but a million or so a day doesn't seem to bother a 5Mbps ADSL2+ line.

It will of course depend a lot on the modem CPU rating.

And, of course, OP will only see FECs if on Interleaved, not Fast Path.

Here's what routerstats says I presume Reed Solomon is FEC?

Noise Margin: 2.3 dB
Line Attenuation: 27.5 dB

SuperFrames: 3333127
SF (CRC) Errors: 124
Reed Solomon: 773285688
RS Corrected: 11330899
RS Un-Corrected: 7036
HEC: 119
Errored Seconds: 115
Severe ES: 0

Interleave Depth: 96
Bitswaps: 69

Total Uptimes (From SF counts):
WAN: 0 days, 15:01:30

Edited by Banger (Mon 19-Jan-15 00:43:12)

Reed Solomon is the error correction methodology, and I think that counter is the number of packets received,

RSCorrected is the FECs and RSUn-Corrected the ones it couldn't. Both are packet counts. The uncorrected ones require a "stutter" while they are retransmitted.

You are running at around 800,000 FECs per hour. That is why the DLM has put you on interleaved. No doubt about it. You need to sync untweaked and see what happens to the error rate.

Note that even when you are not using the connection there are packets passing continuously all the time. Just with no data in them. Like a stream of empty addressed envelopes coming through you letterbox. The transmission or not of data makes no significant difference to the error rates.

sometimes i had the same problems as you and i just let it go.

What are the consequences of forcing Interleaving off, eg fast path. More sync I presume but will the line become less stable?

If a line suffers from some noise then Interleaving can help with correcting the errors. But, if errors are low then fastpath would give you higher performance and lower latency. In the end it all depends on the characteristics of the line - the shorter the line the more benefit to fastpath.

I'd agree with that. In my old house I had a line with 35dB attenuation that just managed to achieve maximum sync on ADSL. When I went to an LLU provider and ADSL2+ it was ~ 9Mbps iirc. I had them try turning off interleave which was on by default and the throughput and stability suffered so I had to get them to put interleave back on. To my mind anything less that a pretty good line needs interleave although gamers will put up with the problems using fastpath on such a line will bring.