Occasional plummeting attainable rate

Hive mind of TBB - I seek your help

I had FTTC installed in Feb 2015, basically the moment it became available to me - it was estimated (and I knew this to be hopelessly optimistic) that I'd get 50-68M down... the day arrived and it actually managed 42.

Since then it has been basically entirely stable, although it slowly dropped to around 33-34 and after changing from the Openreach ECI modem (plus a LinkSys router) for a FritzBox (to get G.INP and to condense the installation into a single device) it rocketed up to be stable around 43-45M.

Over time, the maximum permitted rate by the remote end (started at 80000) has dropped in steps - 60000, 44000, 40000,35000, 32400.

Nothing has changed at my end - there is no CPE attached other than the router, there is no premises wiring (I had that disconnected before the VDSL install happened). It's entirely underground fed for the entire distance to the exchange.

I've had a dig around in the historical mails the FritzBox sends me about the connection and I notice the periodic drops in attainable rate (light blue line) and the actual sync (green line), you can see in the linked picture - http://imgur.com/7mJap4k - those drops started on March 15th and occur 0-2 times per day ever since.

Now I know I'll never get near 80M (I'm 250m from the cabinet but the line actually goes at least 900m to get to me) - but having been happily receiving 43-45 for the last 6 months, I'm now seemingly condemned to 32...

Any ideas what the likely cause is? I'm guessing it's a ham-fisted jumpering of a nearby line that's started it...

edit: The attainable rate is still constantly in the 43-45M range (apart from the drops in the picture - which typically last approximately 1 hour at no particular time of day)

Edited by hunnymonster (Tue 26-Apr-16 10:17:19)

REIN, SHINE or crosstalk.

Suddenly - it appears on one day after 12 months and only occurs for short bursts?

Edited by hunnymonster (Tue 26-Apr-16 10:07:36)

I got connected in January 2016 on a 330 metre pair. sycning at 116000Kbps DS and 31000Kbps US without any error correction such as G.INP being required...

Then crosstalk took wee chunks of my bandwidth away (3-4Mbps downstream per line connected it seemed)

Was sat at 79000/25000kbps quiet happily for a couple of weeks then all of a sudden one afternoon I lost 16000/3000kbps in one hit...

After 2 engineers visits (3 hours total investigation time) which included a pair swap, all that could be done was a wee 2000kbps downstream speed boost.

Seams the issue is REIN combined with poor alumium cabling which is a crosstalk nightmare in the area.

After investigation by BT retail Openreach & Wholesale have said they aren't going to investigate further as they can't force noise emitters to cease the activity/equiopment and they're not prepared to replace bad cabling.

BT has since given me a discount for staying and revoked my contract as they're speed estimates where broken.

My line speed without error correction is 56000kbps.... 60Mbps below its day 1 rate

Unfortunately my building wasn't connected to the Virgin Media network that runs 2 metres in front of the building... next to the BT network : so stuck until further notice.

Further info - the sudden drops only happen Sunday to Thursday (never on a Friday or Saturday) and mostly in the 1600-2000 timeframe - always apparently lasting for about an hour...

What makes the least sense about it all is that it never drops below 40M attainable (even when at the nadir of the drop) yet my maximum allowable rate is now almost 25% below even that (and no doubt going to fall further)

Sounds like bursts of noise hitting the line. If you know the route your line takes, does it go past any factories or small businesses? Perhaps one which do not open on Fridays such as ones run by adherents to certain non-Chiristian religions?

You could have decent bit loading across the full spectrum and when te noise hits, it takes out a block of tones and does not affect others which continue as normal. hence the 40Mbps limit.

This is in a very small town (more like a village but don't let the locals hear that)...

The number of "alternative weekend" businesses is zero. Most of the time the attainable sync is in the range 43500-45300 - but I haven't seen a drop in attainable rate below 40000 at any point (so I would assume that should be my attainable rate not 25% lower than that - and that would be ok - not great, but ok)

Other than one business (runs Monday to Friday) diagonally opposite the cabinet, the line only passes domestic premises, all underground. Oldest cabling should be no more than 15 years old (given local layout).

I was just trying to think of why it only happens Sunday to Thursday and only for short periods.

You're not alone in trying to work that out...

Is there any certain times of day it happen's??

Perhaps evening when someone's TV or Recevier is on....

Here are the periods when the attainable rate has dropped in a step (of about 4M), rising back to where it was...

Max allowable rate 60000 / actual sync at that point 44300
Tu March 15 - 1900-2000

Max allowable rate 44000 (dropped on March 16 around 0600)

Max allowable rate 40000 (dropped on March 22 around 1200 - great time to do it)
Tu March 22 - 1800-1900
We March 23 - 1700-1800 & 2300-0000
Tu March 29 - 1900-2000
We March 30 - 1900-2000

Max allowable rate 35000 (dropped on April 01 around 1200 - again great time to do it)
Su April 03 - 1700-1800
Mo April 04 - 1700-1800
Tu April 05 - 1800-1900
We April 06 - 1300-1400 & 1700-1800
Su April 10 - 0700-0900 & 1700-1900
Mo April 11 - 1900-2000
Tu April 12 - 0000-0100 & 1200-1300
We April 13 - 1700-1800
Th April 14 - 1600-1700 & 1800-1900
Su April 17 - 1500-1700 & 1800-1900
Mo April 18 - 1700-1800
Tu April 19 - 1700-1800 & 2200-2300
We April 20 - 1400-1500 & 2200-2300
Th April 21 - 1900-2000

Max allowable rate 32400 (dropped this morning at 0650)

No observed attainable rate drops since 2000 on April 21...

Edited by hunnymonster (Tue 26-Apr-16 12:55:47)

Does your line still show a max attainable of 60000 ?

How are you reading your lines speeds?

Max attainable is showing as (right now) 44453 - which is hovering around where it has since I acquired the FritzBox

Line speeds from the interface of the router (and they match up with the data my ISP has in his control panel - which is populated from the MSAN/DSLAM at line sync time)

Are those EXACT times when it changes or rounded? Or have you set up monitoring to check on the hour?
A pity you cannot run DSLstats.or Routerstats to generate some graphs.


Do you have an alternate modem that you could install for a day or two and produce some graphs of what is happening?

Those are time frames only - better data not available, certainly not historically

As for alternate router/modem - sadly nothing that can be inserted easily (allowing for suppression of spousal eye rolling)

Are you connected to the test socket or an extension?

Direct into the master socket (which has the VDSL service specific "lump" on it)

There is definitively no premises wiring - I removed that before the VDSL was even available to order here.

Could be a line fault. Is the phone line noisy?

Don't know - no longer have an instrument to test Fed up with getting cold calls so it got disconnected and the instrument binned.

I may have to borrow one from a neighbour to test...

Or five quid at argos http://www.argos.co.uk/static/Product/partNumber/552...

Plus 2 gallons of fuel to get there

Well the BT chap was here today - lots of teeth sucking and peering down personholes...

He remade joints at the two DPs closest to my house (revealing there that when I thought my line went N to get to the cabinet that is E of me - I was wrong - it goes W for a few hundred extra metres, then N, then E, then N... making for 1300m cable length for a 290m crow fly distance) and the cabinet. He also replaced the NTE5 & the VDSL Mk3 plate.

Despite having found nothing - the end result is that there are no longer thousands of CRC errors when the line is called (no instrument to answer, so no idea when the calls are happening).

Time will tell if the plummets are a thing of the past...