cancel
Showing results for 
Search instead for 
Did you mean: 

FTTC VERY unstable at night

Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

FTTC VERY unstable at night

I had my Fibre installed a week ago today. I was slightly disappointed to get an attainable rate of 16Mb down and 1Mb up. I am (give or take a few meters) 850M from my cab. (yes i know its quite a long way). 2/3 of that is on poles, I suspect it's Aluminium.
I am (was) using a Draytek Vigor 2750N with the very latest 1.5.2 firmware.
It was really stable. I checked the router quite often for the first two days and the SNR margin didn't drop below 5.5 at any time.
Then I went away for a couple of days.
I've been back for two days. I still get reliable (16Mb/sec) service during the day, but from about 7pm each evening unitl roughly midnight last night, and again this evening) the Vigor looses sync every few minutes. It always comes up at least 15Mb/sec downstream speed until it next re-syncs, just a few minutes later.
So for the last hour or so I've been up on the BT modem and Plusnet Router. Can't get any stats out of these, but pingplotter is telling me I'm getting >10% packet loss, and speedtest.net tells me I'm getting a very erratics download speed of 2-4mbsec. Web surfing seems slow too.  This from a machine with a wired connection to the router to rule out Wifi issues I've ruled out local RF issues.
The modem is connected by CAT6 to the idc connectors in the new faceplate, but I tried an RJ11 cable too, with no improvement.
I've disconnected the smal amount of internal wiing and this hasn't helped.
Two things of note:
During last weekend while was watching the vigor perfom well, The cab was brand new and I know I had the only connection in the cab. Since then who knows how many installs there has been.
The Vigor reports quite a lot of stats. It reports quite a lot of FEC during the day, but not that concerning. It does also tell me that even after all these dozens of re-syncs the line is still working in fastpath (0ms latency due to error correction is reported).
So I guess I need to report a fault, but what's likely to happen - Engineer Visit? Can/will plusnet force Interleaving on? (I dont play games)
24 REPLIES
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

Still on the BT modem/PN Router I've tried to do a test at
http://www.speedtester.bt.com/
But it always seems to time out on the upload test. Perhaps they never expected anyone with FTTC to only have a lossy 1Mb/sec upload speed  Cry
Quietline test on the phone shows up no noises.
Of course it has been very wet and quite windy since the thing was stable too......It's too difficult to see if the cables have been affected in any way, there are two multicore cables on the poles and they are not very tidy, running through several trees, and at one point they even wrap around each other.
Ther cables are mostly away from civilisation, and even if more people have been added to FTTC on the cab, it;s unlikely there would be any of them on the same d-side run as me yet. There would be ADSL on it though, but not many (10-20 tops I'd guess)
Community Veteran
Posts: 1,412
Thanks: 4
Registered: ‎29-01-2009

Re: FTTC VERY unstable at night

Quote from: Lorian
I had my Fibre installed a week ago today. I was slightly disappointed to get an attainable rate of 16Mb down and 1Mb up. I am (give or take a few meters) 850M from my cab. (yes i know its quite a long way). 2/3 of that is on poles, I suspect it's Aluminium.

Yes, perhaps a little slow on downstream for that distance, but the upstream looks really bad.
Is there a way to graph the SNR or bit-loading data from the Draytek?
Quote
So for the last hour or so I've been up on the BT modem and Plusnet Router. Can't get any stats out of these, but pingplotter is telling me I'm getting >10% packet loss, and speedtest.net tells me I'm getting a very erratics download speed of 2-4mbsec. Web surfing seems slow too.  This from a machine with a wired connection to the router to rule out Wifi issues I've ruled out local RF issues.

Once you are getting significant packet loss, there isn't much point in testing the download speeds - too many packets are going missing and need to be resent. When I had 5% packet loss, I'd lose about 10% of my throughput (37Mbps down to 33Mbps), so it looks like 10% loss is perhaps a serious limit.
Quote
The Vigor reports quite a lot of stats. It reports quite a lot of FEC during the day, but not that concerning. It does also tell me that even after all these dozens of re-syncs the line is still working in fastpath (0ms latency due to error correction is reported).

That is very strange - the FEC process isn't enabled until interleaving is switched on, so the FEC counter shouldn't be increasing until then.
At 5% packet loss, DLM certainly turned on interleaving for me - and used about 23% overhead for carrying the FEC parity data. It did this at precisely 48 hours after my line was converted.
Therefore I'd have expected a 10% packet loss to have triggered DLM (at least after the first 48 hours), and for you to be able to notice easily on the higher latency and a probable drop in speed from the 16Mbps.
Have you tried a ping meter from TBB: http://www.thinkbroadband.com/ping/monitors.html?
Quote
So I guess I need to report a fault, but what's likely to happen - Engineer Visit? Can/will plusnet force Interleaving on? (I dont play games)

It certainly could be an engineer visit, and in fact probably would be. DLM ought to be trying enough to make your sync stable - and is either not trying, or is failing to cope.
PN probably can't force interleaving to any particular state. It is all down to DLM on the cabinet.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
Bald_Eagle1
Grafter
Posts: 313
Registered: ‎24-06-2011

Re: FTTC VERY unstable at night

Quote from: Lorian

I had my Fibre installed a week ago today. I was slightly disappointed to get an attainable rate of 16Mb down and 1Mb up. I am (give or take a few meters) 850M from my cab. (yes i know its quite a long way). 2/3 of that is on poles, I suspect it's Aluminium.

I saw similar speeds when my connection was in need of repair.
I'm a little further from the cabinet (900m to 1000m), but my connection now syncs at up to 30Mb & I see throughput speeds of up to around 28Mb.
Currently synced at 29Mb:-

Today's stats from my connection are attached.
Although my FEC & CRC graphs still state the data is from the HG612's GUI, it is actually from the telnet command xdslcmd info --stats (The modem's GUI reports them INCORRECTLY).
square
Grafter
Posts: 28
Registered: ‎08-06-2011

Re: FTTC VERY unstable at night

I had probelms in the evening some years back. The telegraph pole is next to a street light. The light had failed and was causing interference when it would have been lit. Worth checking.
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

There are no street lights (or anyother lights) anywhere near the overhead cables. They do pass through a couple of trees and quite close to some mains cables though, which they cross over with maybe 3 feet of air between them.
With luck Plusnet will arrnage an OR engineer who knows what he's doiing. The iinstaller did seem more keen on getting home in time for lunch than conside the sync speed was pants.
I haven't found a way to get proper bit loading out of the Vigor yet, but I can see its only using the lowest frequencies.
I'm starting to understand the Draytek code in the firware, I've made some enhancements that might mean it will hold-off resyncing for longer when the line gets lossy. We'll see soon.
adie:quote
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

Nice graphs Mr Eagle, I presume you have a new stats program, nice (do let me know if it's available for use).
In the meantime I've used the existing graphing scripts on my recently hacked Huwaei modem. please see below.
Some other notes.
1. Tried another faceplate filter - no change
2. Disconnected all internal wiring - no change
3. Found my laptop PSU was causing a 2mb/Sec drop in attenable rate - Fixed that before producing the graphs.
4. Although the OR engineer provided a Huwaei modem I think I'm probably comnected to a ECI96 Cabinet.
5. Stopped using the Vigor as it's attainable rate is 4mb/sec less than the huwaei, it drops out more, and it has a bug in pppd that means it takes 4-5 minutes to reconnect after a drop. I can see the problem, and will fix that in the source code sometime. Concentrating on the BT modem for now.
5. Connection this evening >10% packet loss (even soon after a re-sync to redistribute bit loading) and thtoughput remains 2-4Mb/s this evening (ok during the day).
6. My d-side from the cab is maybe 50M more than I thought, as when I walked the route there is at least 4 on-pole joins, with the loops to the joint boxes perhaps another 50M in total.
Here are the stats - be interested in your analysis.

http://www.bug-byte.co.uk/vdsl_stats.png

Bald_Eagle1
Grafter
Posts: 313
Registered: ‎24-06-2011

Re: FTTC VERY unstable at night

Quote from: Lorian

Nice graphs Mr Eagle, I presume you have a new stats program, nice (do let me know if it's available for use).

I haven't released the new ongoing stats harvesting program yet. It is still being tested.
It is a .EXE program rather than batch file scripts that works much quicker & hopefully reliably.
Quote
In the meantime I've used the existing graphing scripts on my recently hacked Huwaei modem. please see below.
Some other notes.
1. Tried another faceplate filter - no change
2. Disconnected all internal wiring - no change
3. Found my laptop PSU was causing a 2mb/Sec drop in attenable rate - Fixed that before producing the graphs.
4. Although the OR engineer provided a Huwaei modem I think I'm probably comnected to a ECI96 Cabinet.
5. Stopped using the Vigor as it's attainable rate is 4mb/sec less than the huwaei, it drops out more, and it has a bug in pppd that means it takes 4-5 minutes to reconnect after a drop. I can see the problem, and will fix that in the source code sometime. Concentrating on the BT modem for now.
5. Connection this evening >10% packet loss (even soon after a re-sync to redistribute bit loading) and thtoughput remains 2-4Mb/s this evening (ok during the day).
6. My d-side from the cab is maybe 50M more than I thought, as when I walked the route there is at least 4 on-pole joins, with the loops to the joint boxes perhaps another 50M in total.

Looking at the tone band plans, you are connected to a Huawei DSLAM.
The ECI DSLAM uses slightly different tones.
Something looks quite wrong though.
The stats state that all 3 DS tone bands are in use (Medley Phase), yet attenuation is far too high or is an invalid value (from pbParams & Hlog).
Supposedly only US band U0 is in use (Medley Phase), but some US bitloading can be seen in U1 band.
Other than unlocking the HG612, have you adjusted any other settings?
Are you using a separate ROUTER, or just the HG612 as a MODEM/ROUTER?
Are you able to zip a Plink log & post it as an attachment for me to have a closer look at the data & graph at my end?
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

The HG612 is unmodified except for uploading the unlocked firmware. It's connected to an unmodified Plusnet Technicolor Router.
There is a plink log here, thanks for taking the time to look:
http://www.bug-byte.co.uk/Plink_20120930-2018.log
Isn't there also a an unusal hole at about Tone 150/200, if I'm interpreting the graph correctly?
Bald_Eagle1
Grafter
Posts: 313
Registered: ‎24-06-2011

Re: FTTC VERY unstable at night

Quote from: Lorian

Isn't there also a an unusal hole at about Tone 150/200, if I'm interpreting the graph correctly?

There is also a corresponding "disturbance" in the Hlog graph (attenuation over frequency).
I'm not 100% sure, but I think a peak means high capacitance & a valley means high resistance.
You seem to have both, which possibly signifies either a physical fault or maybe a change of cable types (maybe a short section of aluminium on a mainly copper line or vice-versa).
Maybe bit swapping accounts for the US bitloading despite that band supposedly not being in use, but I have no theory as to why all 3 DS bands are supposedly in use.
Just as a reference, I have attached your graphs & mine for comparison on a similar length line.
FWIW, I used to occasionally see valleys in my connection's Hlog graphs, before a faulty underground cable to pole top DP joint was repaired.

I notice that Interleaving is OFF for your connection that either suggests it is very stable (possibly due to low speeds), or that DLM has been recently reset.

QLN & Hlog data is only updated during resyncs, but bitloading & SNR are dynamic.
Do you see much better SNR & bitloading graphs during daytime?
I see slightly deteriorated SNR graphs in the evenings for my connection - probably due to the usual & general evening "noise" interference.
Finally, have you tried the 24/7 graphing? That may just identify what might be causing evening slowdowns (I would guess at a massive increase in various error counts & errored seconds (perhaps due to noise interference), otherwise you may just be suffering from really excessive contention.
EDIT:
I forgot to add that your US Output Power levels are high, suggesting that the connection is having to work unusually hard to provide the already low US speeds. Are you on Plusnet's old 40/2 service or the new 40/10 service?
A BT speed test should confirm your US IP Profile.
I had to downgrade my version of Java to build 1.6.0_31-b05 to get the BT test to complete properly
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

Thanks. The hlog graph is interesting.
The plink log I attached before was produced not long after a re-sync so I doubt there had been time for any significant bitswapping to have occured.
I wonder if the distrubance could signify the presence of a really long bridge tap? The reason I ask is that the overhead cable that goes past my house continues on for maybe a further mile, and I wonder if they have somehow tapped my connection in, rather than disconnecting from the rest of the run. I don't want to go jumping to conclusions though.
I only unlocked the modem yesterday afternoon, so I will produce a graph this morning to see what the bit loading looks like, and will post up, then leave it on 24/7 for a whie.

Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

I'm very suprised interleaving has stayed off. With the Huawei modem the link stays up but is very lossy, but with the draytek on the line it would re sync more than a dozen times in an evening.
Back-reving java fixed the bt speedtest - it says 19.x mb down profile and 10Mb up - I would have thought it should have said 20Mb up profile as I ordered the new Fibre extra producst (install was only a week ago),
The hlog graph shows no kink nowm but I think a small hole at the same location? Aslo I see some very high fequency traces on the one from this morning.
http://www.bug-byte.co.uk/Plink_20121001-0844.log
Lorian
Grafter
Posts: 699
Registered: ‎31-07-2007

Re: FTTC VERY unstable at night

Update from PN Customer Services:
Quote
Problem Explanation: [GEA503] An issue has been identified. Appointment Not required.
Resolution/Recommendation: Report fault to BTW for OR investigation.

The issue seen is high SES/ES (errors) recorded during the test. They said they will raise a call with OR.
Community Veteran
Posts: 1,412
Thanks: 4
Registered: ‎29-01-2009

Re: FTTC VERY unstable at night

On bridged taps: I don't know much, but I found this JDSU document on identifying them from HLOG, QLN and SNR data: http://www.jdsu.com/ProductLiterature/sctpsbridgedtap_an_tfs_tm_ae.pdf
On packet loss, and interleaving:
You've mentioned that you get 10% packet loss, but you haven't said how you know this. Where do you get it from?
Your stats certainly seem to show that interleaving is off (zero RS count, depth 1, block size 239/240, delay of 0).
However, your stats show some anomolies related to time:
- That stats part suggest that the plink data came 20 minutes & 38 seconds after startup - some 1238 seconds.
- But AS and UAS combined only total 66 seconds. Strange - time ought to accumulate under one or the other of these counters.
- Even though AS is only 26 seconds, apparently there were 458 seconds with errors in them.
- 458 ES suggests that the error counts must total *at least* 458 - yet there were only 3 OHFErrs, 7 HEC, and 0 RSUncorr. The count is high in the "CRC" section of the stats, but they ought to be high elsewhere too
- The OHF count, of 4293, looks low too for 20 minutes.
There's *something* going on with the statistics that doesn't make sense.
And the bad news:
While there may be one or two things that can help "twiddle" your speed, the basic graphs suggest that your line really does degrade badly over that distance, suggesting aluminium. Improvements may give you a few Mb here or there, but I don't think you are going to get any astounding results. Of course, that's just talking about sync. There are still improvements to be sought to find why your download is still significantly below sync, and what that 10% loss is about.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
Community Veteran
Posts: 1,412
Thanks: 4
Registered: ‎29-01-2009

Re: FTTC VERY unstable at night

Offtopic aside:
Want to feel really jealous?
Here's a link to someone who has a diary of his FTTC install: http://beusergroup.co.uk/technotes/index.php?title=Diary_of_an_FTTC_Install
On the page, he includes some graphs of the bit-loading of an almost-impossibly perfect line. That is - the same level of bitloading all the way up to tone 3950. Sickening  Cry
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.