Line attenuation changed by 18db, very confused!

Ok so kind of a long story but ill try to cut it down...

So my line running on my old Linksys WAG200G used to sync as follows which I was very happy with, it was extremely stable:

Linksys WAG200G
DSL Status: Connected
DSL Modulation Mode: G.dmt
DSL Path Mode: Interleaved
Downstream Rate: 8128 kbps
Upstream Rate: 832 kbps
Downstream Margin: 9 db
Upstream Margin: 14 db
Downstream Line Attenuation: 29 db
Upstream Line Attenuation: 7.5 db
Downstream Transmit Power: 12 db
Upstream Transmit Power: 5 db

I then had a fault on my line, this was 'fixed' by BT but since then the router stats on exactly the same router, new RJ11, new microfilter looked like the following:

Linksys WAG200G
DSL Status: Connected
DSL Modulation Mode: G.dmt
DSL Path Mode: Interleaved
Downstream Rate: 6496 kbps
Upstream Rate: 832 kbps
Downstream Margin: 4 db
Upstream Margin: 8 db
Downstream Line Attenuation: 41 db
Upstream Line Attenuation: 13 db
Downstream Transmit Power: 11 db
Upstream Transmit Power: 5 db

As you can see my downstream attenuation has jumped up 12db! Whilst this seems like alot its not high enough and my sync isn't low enough to raise it as a fault. Also my SNR now flicks between 0 - 6db, where as it used to be happily around 9db.

Anyway as I somehow (and probably stupidly thought) ill try another router to help the issues. So I purchased a DGTeam flashed Netgear DG834GT as ive been reading good things about them. I've plugged it in tonight and without tweaking it my speed has increased to 6720Kbps and my SNR is now stable at 6db rather than flicking around all over the place. However my downstream line attenuation has increased further! Its now sitting at 47db and my downsteam is now 23db! Im really confused why it would jump up this high considering all i've done is plug in a different router.

SNR before and after the switch of routers:
http://imageshack.us/photo/my-images/10/capturemwd.png/

Netgear DG834GT
http://imageshack.us/photo/my-images/440/capture2ow....

Also as im new to Netgear routers and the Routerstats app, can someone please explain this graph to me, it looks like my attenuation flys up dramatically for whatever reason, is this normal? I would assume not.

http://imageshack.us/photo/my-images/811/capture3e.png/

Can anyone please help diagnose this for me? I'm lost to say the least.

Many thanks
Dan

Peculiar!

Sounds like BT lengthened your line when they did the fix.

Who's your ISP and package? Can you get your Line Mode out of your Netgear by Telnetting into it? Or try this: http://192.168.0.1/setup.cgi?PATH=/bin:/sbin:/usr/bi...?

1.3km seems a long increase, im only 1.7km away from the exchange!

Results from that page:

adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 1
Channel: FAST, Upstream rate = 832 Kbps, Downstream rate = 8128 Kbps
Link Power State: L0
Mode: G.DMT
Channel: Fast
Trellis: ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 1.1 10.0
Attn(dB): 47.5 23.0
Pwr(dBm): 19.7 11.9
Max(Kbps): 8192 1036
Rate (Kbps): 8128 832
G.dmt framing
K: 255(0) 27
R: 0 0
S: 1 1
D: 1 1
ADSL2 framing
MSGc: 1 1
B: 211 25
M: 1 1
T: 1 1
R: 0 0
S: 1.0000 1.0000
L: 1696 208
D: 1 1
Counters
SF: 53276 53275
SFErr(CRCErr): 190 0
RS: 0 0
RSCorr: 0 0
RSUnCorr: 0 0

HEC: 77 0
OCD: 0 0
LCD: 0 0
Total Cells: 17362441 0
Data Cells: 161826 0
Drop Cells: 0
Bit Errors: 0 0

ES: 459 0
SES: 8 0
UAS: 138 0
AS(Uptime): 906

INP: 0.00 0.00
PER: 1.75 1.75
delay: 0.25 0.25
OR: 32.00 32.00

Bitswap: 0 0
Total uptime: 7389

In reply to a post by XRaySpeX:

Peculiar!

Sounds like BT lengthened your line when they did the fix.

Who's your ISP and package? Can you get your Line Mode out of your Netgear by Telnetting into it? Or try this: http://192.168.0.1/setup.cgi?PATH=/bin:/sbin:/usr/bi...?

Or bad joint increasing attenuation.

Or bad joint increasing attenuation.

or aluminium, or thinner copper

or wet string? ... (sorry someone had to say it!)

to gain 1.3km of cable? really?

Possibly, but the numbers from the router look a little suspect to me...

Downstream Line Attenuation: 29 db
Upstream Line Attenuation: 7.5 db

Downstream Line Attenuation: 41 db
Upstream Line Attenuation: 13 db

Usually upstream attenuation is ~ half the downstream attenuation, but yours appears to be 1/4. Also the power levels appear low for a situation where the line is not syncing at its max speed.

What do you suggest? I'm currently on another router and have posted the stats below.

These latest stats are showing G.DMT 8128/832 kbps, indicative of ADSL Max Premium or IPSC equivalent? What happened to the 6740kbps you posted earlier, and the 1.1dB downstream noise margin suggests to me you have been tweaking. Which isn't a good idea when we are trying to help you troubleshoot.

In reply to a post by c0dec:

Results from that page:

Was that from my //192.168.0.1/... link? I'd be very interested to know if it worked on your flashed router.

In reply to a post by MrSaffron:

Possibly, but the numbers from the router look a little suspect to me...

Agreed! These stats, Attn. & Pwr, from the Netgear look much more normal, which casts doubts on the Linksys.

I had a phone fault a while back and BT replaced some E-side cable between Exchange and Cabinet. Attenuation before was 23 db constant but went up to 25 on ADSL max. Tested with two identical routers but at the same time my 4db SNR before went up to 9db after. Explain that.

And what did the sync do?

If your router is not showing decimal places, then the change may be well under 2dB, depending on its rounding.

9dB suggests a higher target margin, brought about by probably having the router connected while the line was being worked on.

Full rate sync for what one assumes if Max Premium (i.e. up to 8Meg with the faster upstream option)

Robertos has covered the noise margin, if there is no tweaking and router really synced with a 6dB target and these stats are within a minute or so of the resync, then they suggest a noise issue on the line/in the property.

Yup!

In reply to a post by MrSaffron:

And what did the sync do?

If your router is not showing decimal places, then the change may be well under 2dB, depending on its rounding.

9dB suggests a higher target margin, brought about by probably having the router connected while the line was being worked on.

Sync remained 8128 throughout.

Couple of routers both shows 23.0db which went to 25.0db after cable change.

Can't be sure but think target margin was 6db throughout as one day line was on next day phone was dead and took 3 weeks to get reconnected, kept router off until BT engineer rang to say we were reconnected. Think I did everything right.

Thanks for all your replies.

I havn't already said but im on the Plusnet 'up to' 8mbit service with Pro bolt on, on a BT20CN exchange (EAWDB).

I have been tweaking the router last night ill admit, this is only because this has been an ongoing fault for sometime and I wanted to see if I could hold 8128/832 without dropping overnight with some load and idle whilist im at work.

During my fault period BT done various things to my line so I can only assume one of these 'fixes' has had an adverse effect on my line. At least 4 lifts and shifts where carried out and finally a line card swap at my exchange fixed my issue. FYI the issue was my net dropping whenever my phone was rung, however my net stayed up if I was making a call. The fault had been going on for 2 months until it was fixed, then I was left with a 18db higher downstream attenuation, which before any router tweaks where carried out gave me a max sync of 6700 kbps, with an SNR of around 4-6db.

Annoyingly Plusnet won't raise this as a fault due to 6.7mbit still being within fault tolerance for my line, which is somewhat annoying as it does look like BT have done something wrong along the line and I have to suffer because of it. I always synced at 8128/832 before this work was carried out and my downstream noise margin sat 18db lower than it currently does, it was like this for 2 years before the fault occured!

Many thanks for your help so far guys.
Dan

I am surprised noone has said the obvious, you may have had the simple line swap in the cabinet done on you, a common trick done by BT engineers to try and fix faults as its cheap and fast. Then the swap may have put you on a longer routed line or one with poorer cabling as not all cabling is equal on BT local loops, it varies a huge amount.

It was suggested and confirmed on the PlusNet forum

http://community.plus.net/forum/index.php/topic,1005...

In reply to a post by godsell4:

It was suggested and confirmed on the PlusNet forum

http://community.plus.net/forum/index.php/topic,1005...

The statement by Matt Taylor in that thread, that a lift and shift can cause the connection from the user/cabinet to the exchange to be changed isn't correct. That would be an E-side swap.

A lift and shift occurs purely within the exchange and would not do this to the attenuation. (Faulty new connection in the exchange excluded).

Edit! I have now seen

During this time I also had 3 lift and shifts performed along with my line being moved to newer E-side & D-side cabling

in a different thread on those forums. So Matt is still wrong in what he says, but the E-side move looked like what had happened right from the start here.

Edited by RobertoS (Thu 08-Dec-11 18:42:24)

Seconded. Only an E-side swap if going to have such a profoundly marked affect.