What controls Sync speed

Started by Poverty, Jul 13, 2009, 10:24:18

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Poverty

Hallo everybody, I'm new to this forum and this is my first post.

I've been on <8M for three years now and until about a month ago my sync speed had been around 6500 K with a DS margin of 10 to 12 dB and DS line attenuation of 38 dB.  As far as I know I never had a drop-out.  I turn my router off each night between about 10pm and 9am.

About a month ago one morning I found that my router had connected at a speed of around 5300 K with an increased DS margin of 16 to 18 dB and still with an attenuation of 38 dB.  It's been consistently like that ever since.

Due to the BT BRAS profile equipment, by DS traffic speed has dropped from around 5600 K to around 3900 K.

I always thought that sync speed was a function of line quality, but the above figures seem to suggest that my line has not deteriorated, so I am wondering if BT can limit the sync speed as well as having the BRAS traffic speed control.

Does anybody know if this is the case?

Simon

:welc:  :karma:

Do you know if your line is, or soon to be, WBC enabled?
Simon.
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This post reflects my own views, opinions and experience, not those of IDNet.

Rik

Hi and welcome to the forum. :welc: :karma:

Sync speed is a function of two things, line length and the more intangible line quality. For the latter, the chief issue is susceptibility to noise pickup.

The fact you appear to have had a target noise margin of 12db says that your line does pick up noise and that BT's dynamic line management software has increased the target margin to stabilise it, and, in the process, almost certainly turned interleaving on. From the look of things, the line has deteriorated further and the target NM has increased to 15db, which costs you some more sync speed. You should be on a profile of 4.5M if you are connecting at 5300 though, so I wonder if there is still some instability.

Could you do a BT speed test and paste the results of that, plus your downstream line stats please, ie sync speed, noise margin and attenuation.
Rik
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This post reflects my own views, opinions and experience, not those of IDNet.

Poverty

Thanks for the replies.

My exchange (Coverdale) is not yet on the WBC timetable.

I cannot yet do a BT speed sheck - I have tried three times, but each time after pressing "go", I an told there is a server error.  I will try again later.

My current router stats are:
DS Margin 16dB
Sync speed 5600 K (best for some time)
DS Attenuation 38dB
Interleaved (I have always been interleaved).

I am one kilometre from the exchange as the cable is routed.

I will get back later when I can do a BT speed test.

Thanks.

Rik

The cable length looks closer to 3k than 1, on that attenuation. I'm guessing your profile is lagging after a low sync speed. :(
Rik
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This post reflects my own views, opinions and experience, not those of IDNet.

Poverty

Yes, I dare say you are right about the delayed profile effect, but it is the sudden and continuing drop in sync speed that puzzles me.

Rik

Do you have any earlier stats? Has anything changed in your home, eg new phone sockets or attached devices, new electrical devices?
Rik
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This post reflects my own views, opinions and experience, not those of IDNet.

Steve

 :welc:

I am sure Rik et al will get you sorted ,however whilst your trying to evaluate the problem with the use of the test socket if you've got one etc its best to leave your router on continuously 24 hours a day . BT are quite happy to raise your margin and reduce your sync rate after a short period of instability which may now well have passed. In order to get back to where you are any reduction in margin via the automated BT system (if it works) takes 15 days of continuous connection.
Steve
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This post reflects my own views, opinions and experience, not those of IDNet.

Ray

Ray
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This post reflects my own views, opinions and experience, not those of IDNet.

Poverty

Thanks very much for that info, Steve.

I will leave my router permanently on from now on to see what happens.

I have now done a BT speed test as follows:

Test1 comprises of Best Effort Test: -provides background information. Your DSL connection rate: 5600 kbps(DOWN-STREAM), 448 kbps(UP-STREAM) IP profile for your line is - 4000 kbps Actual IP throughput achieved during the test was - 3750 kbps  If you wish to discuss these results please contact your ISP.  If you are experiencing problems with specific applications, servers or websites please contact your ISP for assistance.  


Rik

Speed is OK for the profile, but that's low for the sync speed, it should be 4.5M. It can take up to five days to catch up, though.
Rik
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This post reflects my own views, opinions and experience, not those of IDNet.

Poverty

No, nothing at all has changed in my home.  The only earlier stats are given in my first post as an average.

Steve

Steve
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This post reflects my own views, opinions and experience, not those of IDNet.

Rik

Lines are degrading, partly due to lack of maintenance, partly due to increased noise (crosstalk) as more people connect to broadband. In addition, a noise source may have appeared along the path of your cable, eg an industrial unit. :(
Rik
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This post reflects my own views, opinions and experience, not those of IDNet.

Sebby

:welc: :karma:

I don't think I can add anything to what's been said. :thumb: