Information about banding

[jezuk1]

Hi all,

Recently I've been doing a little testing with my router which involved restarting it twice, and then about a week later I bought a new router which resulted in effictively 2 more restarts (one to change the router and one after a firmware upgrade).

I noticed that after each reset the ADSL2+ downstream sync speed dropped by approximately 250kbps each time. I'm guessing this is the banding system thinking the line is 'unreliable' yet it seems to be incredibly easy to lose sync speed just by restarting the box a few times. I've noticed BT systems seem to prefer 24-hour routers. Either way just a few restarts and I've effictively lost 1Mbps. If I continue to restart the router randomly the sync speed will eventually drop down from the normal 13Mbps all the way to 4-6Mbps.

If I leave the router online permanently (which I normally what I do) eventually it will resync to a higher speed again but it takes weeks or months to recover. Why is the system behaving this way and is there anything I can do to speed things up? There's a general lack of information about what is happening such as why the equipment at the exchange has decided upon a particular sync speed.

It would be really nice to have some more details about what is going on at the exchange, or some more input from you guys.

Thanks
Jez

[Rik]

What are your current router stats and profile (from a BT speed test)?

[jezuk1]

ADSL Information
DSP Firmware Version    A2pB025f.d22k
DMT Status   No Defect
Operational Mode   ADSL2+
Upstream   444
Downstream   12165
SNR Margin(Upstream)   22.0
SNR Margin(Downstream)   12.3
Line Attenuation(Upstream)   11.2
Line Attenuation(Downstream)   21.5

Interface    Protocol    VPI/VCI
ppp_0_0_38_1   PPPoA   0/38

Received      Pkts    Errs    Drops
2788805167   2526735   0   0

Transmitted   Pkts    Errs    Drops
141528933   2540161   0   0


BT Speed Test

Download speedachieved during the test was - 7781 Kbps
For your connection, the acceptable range of speeds is 4000-21000 Kbps.
Additional Information:
Your DSL Connection Rate :12164 Kbps(DOWN-STREAM), 444 Kbps(UP-STREAM)
IP Profile for your line is - 11000 Kbps

Upload speed achieved during the test was - 340 Kbps
Additional Information:
Upstream Rate IP profile on your line is - 444 Kbps

Speed Test 1


Same test again

[jezuk1]

Thinkbroadband:

[jameshurrell]

ADSL Information
DSP Firmware Version    A2pB025f.d22k
DMT Status   No Defect
Operational Mode   ADSL2+
Upstream   444
Downstream   12165
SNR Margin(Upstream)   22.0
SNR Margin(Downstream)   12.3
Line Attenuation(Upstream)   11.2
Line Attenuation(Downstream)   21.5

Interface    Protocol    VPI/VCI
ppp_0_0_38_1   PPPoA   0/38

Received      Pkts    Errs    Drops
2788805167   2526735   0   0

Transmitted   Pkts    Errs    Drops
141528933   2540161   0   0

The sync seems low for that downstream attenuation. I have an ADSL2+ line with downstream attenuation of 27.5 and I manage to sync at 15130Kbps...

Upstream sync is also low. You should be maxing out upstream on that line (around 1200Kbps)...

Your SNR Margin might be the key to this. It is sitting at 12db which is effectively curtailing your sync speed... looks like there is some noise somewhere which has caused the DLM to increase the SNR margin.

[Rik]

I checked with support, and you're not banded. I agree with James that your speeds seem low for the attenuation, so it's time to do the usual diagnostics, eg move to the test socket, try a different filter, if possible try a different router.

[jezuk1]

I've tried 3 different routers 

They are connected to the BT master socket. There is no internal telephone wiring (well, there is but it's been disconnected). I'm on my 3rd microfilter 

[MisterW]

Upstream sync is also low.

Upstream looks like its capped.

[jezuk1]

Master Socket for reference:



That's a shielded cable to the ADSL router also. The microfilter is new too.

Where should I go from here? Can I get a special faults investigation to determine the cause of the noise?

[Rik]

You can try, but be prepared to spend £200 or so.

[Ardua]

Been there, read the book etc. My advice for what it is worth would be to do nothing. Leave everything connected and sit back and think about FTTC. Three months later you might find that your downstream SNR falls by 3 and your downstream speed increases accordingly; a month later another drop of 3 and so on. I am not sure that changing routers, ripping out wiring etc is always necessary. After 5 months on ADSL2+, my SNR has fallen from 15 to 6 and I now have a very stable connection at 16Mbps. Calling out a BT engineer seems to be a 'win-win' situation for BT not the suffering customer. I should add that the 100% increase in downstream connection speed has come at a cost. My original estimate of 15Mbps on ADSL2+ has now fallen to 13Mbps!

PS You could ask Support to lower your downstream SNR to 6; however, I know from experience that it will not stay there if BT's great box in sky (DLAM) does like the results.

Best of Luck.

[jezuk1]

Thank you all, some nice information here. I do agree that it's probably worth waiting for FTTC although it's yet another variable with an unknown timescale.

[Rik]

If it's anything like mine, allow a year over and above BT's date. 

[jezuk1]

So really the only remaining question I have is why, as of lunch time at some point last week, are all of my downloads capped to approx 6Mbps. On any single download from any location I am unable to get more than 6Mbps. It's capped and won't make full use of the line. Idnet suggested there is congestion at the local exchange but I really doubt that suddenly started at lunch time last week.

This download graph shows 5 different downloads, from totally different servers and locations. They are all capped at 6Mbps.
At the end of the graph I start a 2nd simultaneous download just to demonstrate that the line is perfectly capable of downloading at the sync speec (IP profile is set to 10000kbps on the BT speed tester)

This test was done at 1:30am



Here's the speed tester from a few minutes earlier:

Same story!

Last week I was able to stream YouTube 1080 videos without pausing, now it's not possible because of this 6Mbps cap on a single transfer. What's going on? I've been unable to get any answers so far...

[Rik]

No obvious answer springs to mind. If you want support to look into it, you'll need to run some BT speedtests. I suppose it's possible that you're on a congested VP.

[Lance]

It sounds like an issue with your pc or router to be honest. If kicking off a second concurrent download uses the maximum available bandwidth but one download doesn't I can't think of how that can be a line issue.

[jezuk1]

I've tried 3 different PCs, 3 routers and 2 microfilters over the past week. I don't believe my equipment is faulty in any way. This happened suddenly last week.

[armadillo]

This download graph shows 5 different downloads, from totally different servers and locations. They are all capped at 6Mbps.
At the end of the graph I start a 2nd simultaneous download just to demonstrate that the line is perfectly capable of downloading at the sync speec (IP profile is set to 10000kbps on the BT speed tester)le because of this 6Mbps cap on a single transfer. What's going on? I've been unable to get any answers so far...

Are you on Windows XP?

[jezuk1]

Windows 7

Other PCs have Vista

I assure you it's nothing to do with the PC 

[armadillo]

Windows 7

Other PCs have Vista

I assure you it's nothing to do with the PC 

With those OSs that could well be right. The reason I asked about XP is that the behaviour you describe is consistent with needing to adjust RWIN. I have had similar results in XP and achieved a 4 fold increase in speed of single stream downloads by setting RWIN. Windows 7 and Vista have a different method for setting this automatically and I don't think you can alter it. If you don't know the intricacies of RWIN it still might be worth investigating how Windows 7 and Vista set it. I only know about XP.

[Lance]

It automatically adjusts in vista and 7, but can be manually set through the command line.