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Standard User woodyblade
(newbie) Fri 27-Jan-12 21:56:04
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Attainable Rates dropped


[link to this post]
 
Not sure if I'm posting in the correct forum (might fit in Technical Issues as well).

Anyway I've been trying to work out why attainable rates have suddenly dropped on my line, had it installed 3 months ago and a couple of weeks later (after unlocking the modem) found that attainable rates on the line fluctuated between 70-85mbps(15-19~ SNR)/25-26mbps (22-23~ SNR).
Went to check it at the beginning of this week and found rates had dropped considerably to 52mbps(10~ SNR)/20mbps(13~ SNR), so went to reboot the modem and no change still stuck at those attainable rates and it doesn't budge from those either, unlike before where the SNR moved between the ranges I mentioned above.

I've had a look at the wire between the old master socket and new one, it is fastened to the skirting board with those small metal pins (it's crushing the wire down at points which doesn't look right to me) and upon looking closer one of them looks to have pierced the wire (or at least the edge) though am not overly sure if that would cause such a massive drop in rates.
Errors on the line haven't increased, or at least those shown on the modem interface, at those attainable rates it won't be worth upgrading but at 70mbps it would have been.

I'm wondering if there is anything else I should try or look into to find what the problem is?

As networking isn't my strong point, more my weak point of technology, also I've pasted below previous (these were middle of the SNR range I mentioned) and current stats.

Before:
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 26974 Kbps, Downstream rate = 78428 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 26974 kbps 78428 kbps
Actual Aggregate Tx Power: 6.9 dBm 13.4 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 4.6 21.9 31.4 N/A 11.7 27.0 41.1
Signal Attenuation(dB): 8.1 21.4 30.2 N/A 11.7 27.0 41.1
SNR Margin(dB): 22.4 21.9 22.8 N/A 17.5 17.8 17.6
TX Power(dBm): -4.1 -24.8 6.4 N/A 10.8 7.6 6.0

Now:
# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 20685 Kbps, Downstream rate = 52316 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 20685 kbps 52316 kbps
Actual Aggregate Tx Power: 6.9 dBm 13.7 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 4.6 21.9 31.5 N/A 11.7 27.1 41.1
Signal Attenuation(dB): 8.2 21.0 30.2 N/A 11.7 27.1 41.1
SNR Margin(dB): 13.5 13.6 13.5 N/A 9.5 9.8 10.2
TX Power(dBm): -4.1 -24.6 6.5 N/A 11.0 8.0 6.6

Edited by woodyblade (Fri 27-Jan-12 21:58:04)

Standard User Bald_Eagle1
(member) Fri 27-Jan-12 23:34:31
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Re: Attainable Rates dropped


[re: woodyblade] [link to this post]
 
Hi woodyblade,

Comparing your attenuation & power stats I can see some very minor fluctuations, probably not enough for any concern.

I would have thought that any cable defects would have increased attenuation levels quite substantially.

However, I can see that your SNRM levels have lowered substantially:-

Text
1
23
45
6
Before:
                         U0      U1      U2      U3      D1      D2      D3SNR Margin(dB):          22.4    21.9    22.8    N/A     17.5    17.8    17.6
 Now:
SNR Margin(dB):          13.5    13.6    13.5    N/A     9.5     9.8     10.2


That would suggest to me that either your connection has become generally "noisy", or that the connection has re-synced at "noisier" times e.g. evenings.
Thus the lower attainable rates.

SNRM tends to rise during daylight hours, peaking between noon & 2:00 p.m. & is at its lowest between 11:00 p.m. & 1:00 a.m.

You could try a re-sync / reboot between noon & 2:00 p.m. tomorrow to see if that improves matters.

If not, you could try to find the cause of the "noise" - maybe some new electrical equipment, electrical equipmnet beginning to "fail", or possibly simply increased cross-talk from one or more new broadband subscribers in your area.

It could even be radio interference. Has a radio ham recently started transmitting at high or higher power levels?

If it's none of the above, I can't think what to suggest.

Do you have any PuTTy or other logs from when attainable rates were higher & any recent ones to compare against each other (graphically)?

The most useful commands, run one after the other are:-

xdslcmd info --pbParams
xdslcmd info --Bits
xdslcmd info --linediag
xdslcmd info --show
xdslcmd info --stats


Paul.

Edited by Bald_Eagle1 (Sat 28-Jan-12 00:01:19)

Standard User woodyblade
(newbie) Sat 28-Jan-12 00:27:01
Print Post

Re: Attainable Rates dropped


[re: Bald_Eagle1] [link to this post]
 
Thanks for replying, yeah I would have expected more noise as more people may have moved over to fibre in my area, but haven't seen too many HH3 routers signals popping up, not that I go around checking every street mind you, just what I notice if I walk down the street.
But wouldn't expect such a big drop in a short time, unless the whole street has joined and the BT installers have been going around like blue proverbial flies.

I've checked the noise margins at a few times during the day, 8am/5pm/12am it seems to be fixed at the figures I quoted give or take a couple of .1/.2's here or there.
I would have thought a couple of digits variation like I saw previously and on ADSL as well where I saw similar 3-4 digit variations in SNR would be the norm, just seems odd for it to be fixed like that.

We personally haven't installed any new electrical equipment recently, not sure if the neighbours have, but only those next door (live in a semi-detached) should affect us if at all because other neighbours I would think are a big enough distance away for any interference to not affect us.
I don't think there are any new radios in the area, though wouldn't be sure, I know all cell masts are at least a mile away looking on Sitefinder, though doubt they would cause anything to go wrong.

Looks like I'm running out of reasons, I know your own problems with your actual speeds dropping below 30mbps, so glad I'm lucky enough to get the full speeds which will be good for the foreseeable future (and a damn sight better than 3mbps on ADSL), but obviously quite disappointing to see such a potential speed drop as I see it as more future proofing against BT's slow and dithering approach to investing in fibre, obviously the Government could help but won't, it's spending £30bn on HS2 but won't place more money into 4th utility.
At the rate BT is investing (from previous decades as well) we'll be behind again in a decade and playing catch up all over again.

Unfortunately I've never graphed or recorded the connection details, I'll give you the --show, --stats and --pbParams printouts taken now but not sure what I'm meant to do to get the data for the --Bits and --linediag outputs.
--pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 20715 Kbps, Downstream rate = 52316 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 20715 kbps 52316 kbps
Actual Aggregate Tx Power: 6.9 dBm 13.7 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 4.6 21.9 31.5 N/A 11.7 27.1 41.1
Signal Attenuation(dB): 8.0 21.0 30.2 N/A 11.7 27.1 41.1
SNR Margin(dB): 13.6 13.6 13.6 N/A 9.5 9.8 10.2
TX Power(dBm): -4.1 -24.6 6.5 N/A 11.0 8.0 6.6


--show
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 20696 Kbps, Downstream rate = 52532 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 9.9 13.5
Attn(dB): 0.0 0.0
Pwr(dBm): 13.7 6.9
VDSL2 framing
Path 0
B: 239 111
M: 1 2
T: 64 50
R: 0 16
S: 0.1909 0.7101
L: 10055 2704
D: 1 1
I: 240 120
N: 240 240
Counters
Path 0
OHF: 58413296 1283270
OHFErr: 722 191
RS: 0 4192607
RSCorr: 0 78
RSUnCorr: 0 0

Path 0
HEC: 4202 0
OCD: 0 0
LCD: 0 0
Total Cells: 858445265 0
Data Cells: 176966326 0
Drop Cells: 0
Bit Errors: 0 0

ES: 625 188
SES: 0 0
UAS: 22 22
AS: 179161

Path 0
INP: 0.00 0.00
PER: 3.05 8.87
delay: 0.00 0.00
OR: 65.46 55.88

Bitswap: 1076 1476


--stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 20719 Kbps, Downstream rate = 52316 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 9.8 13.6
Attn(dB): 0.0 0.0
Pwr(dBm): 13.7 6.9
VDSL2 framing
Path 0
B: 239 111
M: 1 2
T: 64 50
R: 0 16
S: 0.1909 0.7101
L: 10055 2704
D: 1 1
I: 240 120
N: 240 240
Counters
Path 0
OHF: 58424055 1286859
OHFErr: 722 191
RS: 0 77079
RSCorr: 0 78
RSUnCorr: 0 0

Path 0
HEC: 4202 0
OCD: 0 0
LCD: 0 0
Total Cells: 860976654 0
Data Cells: 177004199 0
Drop Cells: 0
Bit Errors: 0 0

ES: 625 188
SES: 0 0
UAS: 22 22
AS: 179194

Path 0
INP: 0.00 0.00
PER: 3.05 8.87
delay: 0.00 0.00
OR: 65.46 55.88

Bitswap: 1076 1476

Total time = 1 days 1 hours 46 min 57 sec
FEC: 0 0
CRC: 722 0
ES: 625 188
SES: 0 0
UAS: 22 22
LOS: 0 0
LOF: 0 0
Latest 15 minutes time = 1 min 57 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 0 0
CRC: 2 0
ES: 2 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Latest 1 day time = 1 hours 46 min 57 sec
FEC: 0 0
CRC: 18 0
ES: 18 7
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 0 0
CRC: 350 0
ES: 309 97
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Since Link time = 2 days 1 hours 46 min 33 sec
FEC: 0 78
CRC: 722 191
ES: 625 188
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0


Thanks

Edited by woodyblade (Sat 28-Jan-12 00:33:15)


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Standard User Zarjaz
(knowledge is power) Sat 28-Jan-12 08:35:57
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Re: Attainable Rates dropped


[re: woodyblade] [link to this post]
 
All the sources of potential interference mentioned by Bald Eagle are going to be tricky to find, unless it's REIN based.

In your first post you mentioned the wire between the sockets, is this a 'data extension' cable, does the the socket where the modem plugs in have a small computer symbol on it ? If so, are these cleats or staples that have been used to fix between the two ? Staples are a big no-no, they too easily pinch the twisted pairs.

The cross talk, if it is that causing this issue, is more likely to be nearer the cabinet end, as you pair goes through larger cables and increases it's chance of laying near another VDSL circuit. It *might* be this, who knows.

You also mentioned just the 'b' light going off on the HH3, it's not unknown for these to pack up.

Have you been brave and spoken with BTBB tech support ? Jump through all the hoops and see if they can raise an 'FTTC Boost' task and get an engineer out. If you have any joy with this, let us know and I'll tell you what you need to be looking for when they attend.

p.s. I suspect it's best to keep it simple when you speak to BTBB, no mention of varying attainable rates, just, 'it keeps disconnecting'.

Standard User Bald_Eagle1
(member) Sat 28-Jan-12 08:41:16
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Re: Attainable Rates dropped


[re: woodyblade] [link to this post]
 
Hi woodyblade,


Right, what I see from your stats so far is:-

Your connection is actually making use of all 3 of the 17a band plans:-
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)

My own conection is only able to make use of some of the first 2 band plans.

DS & US Power levels look O.K:-
Pwr(dBm): 13.7 6.9

Interleaving is OFF for both DS & US (value for each = 1):-
D: 1 1

(O)ver(H)ead (F)rame (E)rrors look quite low:-
OHFErr: 722 191

Corrected errors are low & only on your US:-
RSCorr: 0 78

Uncorrected errors are non-existant:-
RSUnCorr: 0 0

Error seconds are low:-
ES: 625 188

Serious error seconds are non-existant:-
SES: 0 0

Unavailable seconds are low:-
UAS: 22 22

Your connection has been up for almost 50 hours (179161 seconds since re-sync)
AS: 179161

Impulse Noise Protection isn't needed:-
INP: 0.00 0.00

There is no delay:-
delay: 0.00 0.00


In other words, so far, so good.

However, what is also needed from info --linediag & info --Bits is details of:-

attenuation over frequency (Hlog)
Signal to Noise Ratio (SNR, not SNRM)
Quiet Line Noise (QLN)
Bit-loading per tone (Bits)


With all the various xdslcmd info data (ideally in a single log file, bit at a pinch in separate log files), we could graph your stats each time your attainable rates changed (or at least obtain a snapshot of how they look at any given time)
It's a million times easier to study a graph than thousands of rows of raw data.

e.g. My poor connection:-
Poor Connection

Another user's much better connection:-
Better Connection

Your own connection would probably have looked a lot like the better connection example when your attainable rates were higher.

I can graph my stats whenever I wish, which is O.K. & I can see minor fluctuations.
The problem in trying to diagnose my connection's much lower speeds & current instability is that I do not have any stats from when my connection was much better.
That was at the time before we had access to our stats.

It's a shame you don't have the data from when your attainable rates were higher as that MIGHT have given a really good comparison against your current stats & a possible bargaining tool to prove that an engineer's visit is required to "fix" a line fault.

You MIGHT be able to get all the data into a single log file via telnet:-
telnet -f telnet.log 192.168.1.1

However, telnet times out & loses connection part way through for me.

Or, you could use PuTTy, freely available from:-
Putty Download

Or, if you are a Windows user and you are prepared to spend a little time setting things up, you could use the batch files & other downloads as per the link in the first pos in this thread:-

Huawei HG612 Modem - Stats & Graphs for Windows Users

Once set up, it just takes a simple double-click to graph a snapshot like the examples above, or to graph your ongoing stats showing any changes over the last few minutes, hours or days.
A lot more ongoing data is collected than is currently plotted, that can be viewed as raw data, or with a little tweak here & there could be plotted.


Paul.

EDIT:
I have to mention that any data/stats as mentioned above would be obtained "unofficially" & possibly in breach of your terms & conditions for the use of the Openreach owned modem.

So as Zarjaz mentions, initially keep it very simple.

Just a last one, is there any noise from a quiet line test by dialing 17070 & picking option 2 and/or does your modem's GUI show any big reductions in SNRM levels while using the phone?
I had that issue for a while, SNRM dropping to as low as 1.5dB while using the phone, & causing occasional connection re-syncs (although the phone was quiet at the time).
An engineer replaced a good few metres of drop wire & that particular issue was resolved.

Edited by Bald_Eagle1 (Sat 28-Jan-12 09:00:02)

Standard User Bald_Eagle1
(member) Sat 28-Jan-12 08:45:54
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Re: Attainable Rates dropped


[re: Zarjaz] [link to this post]
 
I have also read about, but not personally experienced, a modem power supply starting to fail, causing a similar effect.

A straight swap of the power supply cured the problem.

A direct PC to modem connection might be worth a try, as you could then eliminate the router from the equation as a potential source of the problem.

Edited by Bald_Eagle1 (Sat 28-Jan-12 08:47:52)

Standard User Bald_Eagle1
(member) Sat 28-Jan-12 09:07:29
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Re: Attainable Rates dropped


[re: Zarjaz] [link to this post]
 
Hi Zarjaz,

In reply to a post by Zarjaz:
All the sources of potential interference mentioned by Bald Eagle are going to be tricky to find, unless it's REIN based.


For curiosity, as it may just be having some effect on my own connection's reduced speeds, have you had any personal experience with successful REIN investigations?

I have read that it is a very specialised field & that ISPs/BT are usually VERY reluctant to take on REIN issues.
No doubt it can take many hours & therefore be very costly.


Paul.
Standard User RobertoS
(sensei) Sat 28-Jan-12 09:25:28
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Re: Attainable Rates dropped


[re: woodyblade] [link to this post]
 
haven't seen too many HH3 routers signals popping up
A bit of useless info re solving the problem, but FTTC isn't just BT Infinity with Home Hubs. There are many ISPs supplying FTTC and a wide variety of routers around, as with ADSLx and modem/routers.

Other ISP takeup is very low compared to Infinity, I grant you that, but BT love us to think there is no alternative, and I don't like to see the misconception reinforced for any newbies reading smile.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
Standard User Zarjaz
(knowledge is power) Sat 28-Jan-12 10:50:55
Print Post

Re: Attainable Rates dropped


[re: Bald_Eagle1] [link to this post]
 
have you had any personal experience with successful REIN investigations?

Yes. To be fair, have only seen one guaranteed REIN fault on an FTTC line. Due to v.dodgy lighting in a factory, killing it stone dead.
I have read that it is a very specialised field & that ISPs/BT are usually VERY reluctant to take on REIN issues.

Yes, only a handful of engineers have the skill set/equipment to deal with these. I have been on to my boss to get me the 444 meter used to help locate these faults, as I have borrowed them in the past and successfully located sources, but they are hideously expensive [sad].

No doubt it can take many hours & therefore be very costly.

Yes !

Standard User Bald_Eagle1
(member) Sat 28-Jan-12 11:03:04
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Re: Attainable Rates dropped


[re: Zarjaz] [link to this post]
 
Cheers Zarjaz,


In reply to a post by Zarjaz:
Yes. To be fair, have only seen one guaranteed REIN fault on an FTTC line. Due to v.dodgy lighting in a factory, killing it stone dead.


Just to give us a bit of insight into this, how close would you say the factory was to the cabinet/connection/end user & what sort of lighting was involved?

Paul.
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