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Reduced Sync Speed

dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

Since being upgraded to maxdsl last year my line sync speed has consistently been between 4000 & 5000kbps,even during the BB+ speed problems in Feb my sync speeds were OK.

I transferred from BB+ to BBPAYG at this time because of slow speed problems, and from then until mid April, I consistently recorded speed tests between 2500 & 3500kbps.

I then did not connect to the internet at all for one week, and since then my sync speed has reduced to between 2000 & 2800kbps and speed tests are all below 1900kbps.
As far as I can tell nothing has changed on my line, and there is no change to my equipment.

How do I go about finding out the cause of this?
19 REPLIES
chrisc
Grafter
Posts: 688
Registered: 19-04-2007

Reduced Sync Speed

I've had a look at your account and can see that your BRAS profile was dropped to 1500 on the 21st April. This is the profile that BT use to determine the speeds you will receive.

It may have been dropped for a number of reasons - noise/interference on the line, a line fault or a problem with your internal setup for example.

Although the profile can be dropped instantly it takes 72 hours for it to be increased again - this is only if your router is syncing at a higher rate with the exchange.

Make sure that your router is plugged directly into the master socket and you remove all other devices from the phone line. disconnect and reconnect at least 3 times a day for the next 3 days.

If you are syncing at a higher rate than 1500 this will force an increase in the BRAS profile and you speeds will increase accordingly Wink
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

To ccotterill
Thanks for your response

The Bras profile setting was still at 4000 when I first connected (16 April) after the break, but the sync speed was down to 2500 ish. Later I noticed it had reduced to 2000, and as you point out it is now 1500.

My sync speed is now consistently between 2000 & 3000; if 4000 to 5000 sync speed was possible before,somewhere there is a defect.

I've done all the checks at my end, changing filters, connecting only to the master socket, doing quiet line test etc, etc.

I can't help feeling that somehow there is some downgrading gone on because I've not connected for a week.

What's the next move, do I have to contact BT or is it a plusnet issue?
N/A

Reduced Sync Speed

Have you run a quiet line test (dial 17070 option 2) and checked to see if you can hear any noise (static, buzzing, beeps and so on)? If you hear noise with only the handset on the line (through a filter) at the master socket then change the filter and try again. If you still get noise then swap the handset for another if you can. If there's still noise then raise a line fault with BT on 150.

If there's no audible noise on the line (and you already seem to have eliminated an internal problem) then raise a fault here.
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

I have run a quiet line test and trawled my way through the Broadband Fault Checker as suggested by lestones only to be told that "my speed is within the limits of acceptable performance"

Next move?
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

When I carry out an ADSL Availability test on the BT wholesale site, I get the following message
“Your exchange is ADSL enabled, and our initial test on your line indicates that your line should be able to have an ADSL broadband service that provides a line rate up to 2Mbps.
Our test also indicates that your line should be able to support a potential ADSL Max broadband line rate of 2.5Mbps or greater.”

After being upgraded last year by PN to 8Mbps, this message used to say

“Your exchange is ADSL enabled, and our initial test on your line indicates that your line should be able to have an ADSL broadband service that provides a line rate up to 8Mbps.
Our test also indicates that your line should be able to support a potential ADSL Max broadband line rate of 4.5Mbps or greater"

Until about April 8th I used to sync at around 4.5Mbps but it has now reduced to around 2.5Mbps.

It looks as if I have been downgraded back to the 2Mbps service. Could someone at PN please take this up with BT.
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Reduced Sync Speed

Can you post your line stats? This page shows how to get them on post routers/modems:

http://www.kitz.co.uk/adsl/frogstats.htm

I'd also suggest taking a look through this:

http://usertools.plus.net/tutorials/id/13

any incorrect wiring or filters could easily cause a decrease in sync speed.
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

To dtomlinson

The whole reason for my last post was to make the point that BT appear to have downgraded my connection to fixed 2Mbps.
If that's the case your comments are irrelevant, aren't they?
chrisc
Grafter
Posts: 688
Registered: 19-04-2007

Reduced Sync Speed

The line stats will show what sync speeds and throughput speeds you are getting.

If these are not in line with the bRAS profile then we can look at getting this investigated further for you.
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

My understanding is that BT's "ADSL Availability Checker" is exactly that, an availability checker. So if you put your phone number in, no actual tests are carried out, it merely checks what type of service is avaiable at your exchange, and estimates the likely speed based on the distance from the exchange. So the figures it returns are the best achievable for your line. The speed I am getting is approximately as they predict.

My point is that until 2 weeks ago I was achieving higher speeds as per my previous posts, which indicates to me that something must have changed on BT's system, and also implies that there is no fault on my equipment.

Is my understanding correct or am I missing something?
chrisc
Grafter
Posts: 688
Registered: 19-04-2007

Reduced Sync Speed

The availability checker is just that but what we need to see are the stats from your router showing your specific connection details.

We can then compare these with your BT profile to see if any problems exist.

Details of how to obtain the stats can be found here.
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

I will send you the line stats info later today, when I get home.
But I don't see the point, the conclusion will surely be, "the speed is within the limits of acceptable perfomance for your line" or words to that effect.
I will then be forced to ask the question again, "So why has my speed halved"?
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

Line stats as promised

My modem is a Voyager 105

Data Rate (Rx/Tx): 2976 / 448
Line Rate (Rx/Tx): 3232 / 544
Heading: Local / Remote
Attenuation (dB): 36.5 / 24
SNR Margin (dB): 12 / 9.5

I presume these are the figures you need
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Reduced Sync Speed

I can probably make a guess at what's happened. The important figure to look at is this one:

SNR Margin (dB): 12

I suspect that BT dynamic line management systems thought that your line was unstable at some point and as a consequence increased the target SNR on your line. By default the target SNR is 6dB but in the event of any instability the BT systems can increase it to 9, 12 or 15dB. Doing so improves the stability of the line but at the cost of decreasing the speed.

That's I think has happened here, the target SNR has gone up to 12dB from 6dB and has decreased the speed. This is worth a read though as well in case it's wiring or filter related:

http://usertools.plus.net/tutorials/id/13
dejjones
Grafter
Posts: 86
Registered: 31-07-2007

Reduced Sync Speed

I'm not sure I understand this.My knowledge of line stats is pretty much non existant.

But if you are saying that SNR Margin is a "setting" rather than a measurement then I think your guess is correct, because I'm pretty sure when I've looked at line stats previously SNR Margin has been 6db.

So 2 more questions:-
1. Why would BT change the setting when I have had a perfectly stable connection for many months? and
2. How do we get them to change it back?