Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Pages: [1] 2 3 ... 7

Author Topic: Loop loss (attenuation) question  (Read 25891 times)

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Loop loss (attenuation) question
« on: June 13, 2012, 03:05:39 PM »

Hello,

I wonder if anyone can explain the reasons for what follows.

I have been a customer of Plusnet since I moved to my present address in June 2007. At that time my newly connected line provided a constant 8Mbps with attenuation of 32db. During the period that BTs 21CN was being introduced I signed up to join what was called, at the time, a WBC 21CN trial. Initially, my line did seem to increase in speed, and the attenuation went up from around 32db to 35db, which I later found out was quite normal when switching to 21CN. Over a period of many months, some better than others, the overall trend was a decrease in synch speed and wavering attenuation. Whenever I contacted the ISP they seemed to be of the view that my line was performing very well overall, considering the distance from the exchange. I assume they were basing that on the attenuation, but could be wrong about that.

As this went on and on for many months, and mainly because of the frustration that I was experiencing, I looked into having a new line installed by O2. I was already an O2 mobile customer and this provides me with a £5 per month discount on the broadband service that they provide. It had been my intention to run these two lines in parallel in order to compare their performance for a short time, but I still have both in service. Now, I do realise that the O2 broadband service is LLU, whereas the service provided by Plusnet, as far as I know uses standard BT equipment, and is therefore NOT 'unbundled'

The bit that I don't understand is why the O2 line synchs up at around 15Mbps at 29db attenuation, and has suffered only one outage as far as I can recall. Whereas the BT/Plusnet line appears incapable of connecting at much over 11Mbps with an attenuation of 36db, and is up and down like the proverbial lady of the nights underthings. As I said before, I have brought this to the attention of Plusnet on many occasions, but their attitude seems to be that I'm very lucky indeed to be able to use their service at all !!!!! Go figure.

Any thoughts on this would be very welcome


toulouse
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 43467
  • Penguins CAN fly
    • DSLstats
Re: Loop loss (attenuation) question
« Reply #1 on: June 13, 2012, 03:47:22 PM »

Your BT line is certainly underperforming. Assuming that the original 32 dB / 8 Mbps are accurate, then you should get something in the region of 14 Mbps on ADSL2+. However, do check that you are actually on ADSL2+ and not just ADSL2. If you could copy your router stats here we might see something else which would explain the issue (e.g. high noise margin).

LLU shouldn't make any difference (in principle at least). It still uses the same ADSL2+ protocol, and on the same line it should give much the same results. The fact that your second line has a lower attenuation and higher speed implies that the second line follows a slightly different route to the exchange.
Logged
  Eric

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #2 on: June 13, 2012, 04:15:54 PM »

Thanks for those comments Eric. I will try and get the Routerstats 'stuff' included. I'm currently using a Netgear DGND3300 on that line, but will revert it to my trusty DG834 over the next few days. I'm not sure that Routerstats works with the DGND3300, but I know it does with the DG834

The 8Mbps on the original Plusnet product is accurate, although of course I no longer have any proof of that.

Yes, indeed Plusnet did tell me that I should see speeds of Up To 14Mbps prior to me upgrading to their ADSL2+ service. I signed up for the ADSL2+ (WBC/21CN) product, but the line has never achieved anywhere near that - I think the highest I have seen is around 12Mbps, and that was during the trial that I mentioned. And the line is always up and down like a yo-yo.

I should perhaps have mentioned that when the O2 line was installed, the OR engineer just tapped into what he referred to as a DP (Distribution Point) within the building in which I live. In other words, both lines as far as I am aware, share the same cable and route from the exchange to the local cabinet, and thence on to my building terminating at a rather ancient looking box hanging off the wall, where the individual lines to each of 12 separate flats are distributed from.

I'll be back with the Routerstats stuff later,
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 43467
  • Penguins CAN fly
    • DSLstats
Re: Loop loss (attenuation) question
« Reply #3 on: June 13, 2012, 04:40:30 PM »

When I said 'router stats' I meant the stats reported by your router, i.e. upstream/downstream speed, attenuation and noise margin. I wasn't referring to the Routerstats program.
Logged
  Eric

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #4 on: June 13, 2012, 04:57:40 PM »

Ok, sorry about that misunderstanding Eric.

The current stats as reported by the Netgear DGND3300 (Plusnet Line) are :


         Down                            Up
       11239  Connection Speed  440
         36.0     Attenuation        17.3
           5.9    Noise Margin        28.2

This is following a further test of the line by Plusnet approximately 3 hours ago, i.e. around 13:50 this afternoon.

By way of comparison the O2 line is currently showing the following :

         Down                            Up
        14888 Connection Speed  1256
          29.0    Attenuation         16.0
            4.5   Noise Margin          6.5

and has been connected continuously for in excess of 53 days.


I am right in thinking that something isn't right here, aren't I ?


TTFN


toulouse


 
« Last Edit: June 13, 2012, 05:02:46 PM by toulouse »
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

Black Sheep

  • Helpful
  • Addicted Kitizen
  • *
  • Posts: 5717
Re: Loop loss (attenuation) question
« Reply #5 on: June 13, 2012, 05:50:58 PM »

Could be routed over a higher attenuated E-side than the other circuit ?? Plus, different routers have different resistance.

I'd hedge my bets on it being the former. ;) :)
Logged

GigabitEthernet

  • Kitizen
  • ****
  • Posts: 2243
Re: Loop loss (attenuation) question
« Reply #6 on: June 13, 2012, 06:12:18 PM »

different routers have different resistance.

Might be worth posting the stats from another router just to make sure :).
Logged

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #7 on: June 13, 2012, 06:19:26 PM »

Thanks for those additional comments.

@Black Sheep - if your first suggestion is correct I guess it's never going to get any better than it's been

@Black Sheep and @arobertson - as far as I am aware, the figures are pretty much the same using the present Netgear DGND3300 and a Netgear DG834G v4 with current firmware.

I'll revert back to the DG834 probably tomorrow just to confirm this.

TTFN

toulouse
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #8 on: June 14, 2012, 10:04:58 AM »

Just a quick update, now that I have reconnected the Netgear DG834G v4 on the Plusnet line

            Down                           Up
          11216 Connection Speed  440
            36.0    Attenuation        17.3
             6.4     Noise Margin       30.4

These figures were taken approx. 4 hours after connection.

Is it safe to assume, that if what Black Sheep suggested about the E-side pair is correct, then that's as good as it's ever going to get.

Thanks to all those who have commented thus far.
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 43467
  • Penguins CAN fly
    • DSLstats
Re: Loop loss (attenuation) question
« Reply #9 on: June 14, 2012, 10:25:08 AM »

Your BT line is still underperforming in relation to its attenuation. It's probably affected by some sort of interference, crosstalk or whatever. This is where Routerstats (the program) could be useful in plotting the variation in noise margin over time. But first you ought to connect the router directly to the test socket, just to eliminate your own internal wiring as a possible cause of the problem.

A separate issue is that the upstream speed seems to have been capped at 440 kbps. Plusnet should be able to correct this for you.
Logged
  Eric

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #10 on: June 14, 2012, 12:11:15 PM »

Ok, once again thanks for those comments Eric.

Just out of interest, could you tell me what kind of speed should be expected for the attenuation that is being reported by the router. I have had a look around this site, but haven't been able to track it down, as I remember seeing a chart displaying attenuation plotted against expected speeds, which I thought was on here. Maybe I'm mistaken about that though.

Regarding the internal wiring situation, it's all pretty basic really. I live in a building which contains 12 flats. The local cabinet is around 50 metres from my building. A cable runs from there to a distribution point in a communal area and then each flat has a connection from there. In my case, on the ground floor of the building, although the wiring is quite old and there was at one time an extension socket running off of the main socket, that has been disconnected for some time as far as I know. But I will definitely check that again. Since the O2 line was installed in January 2011, and that line has given no problems since then, I assume that if there were any internal wiring problems that would affect both lines - or am I wrong about that. The two lines are terminated at NTE boxes side by side both with splitter/ ADSL filters installed.

As regards the Upstream speed on the Plusnet line, I was aware that customers can request uncapping of the Upstream rate, but I have no real need for an increase in Upstream speed, whereas I could use a bit more on the Downstream. Thanks for mentioning it though.

Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 43467
  • Penguins CAN fly
    • DSLstats
Re: Loop loss (attenuation) question
« Reply #11 on: June 14, 2012, 12:45:11 PM »

If there are no extension sockets fed from the NTE boxes, then you can forget the suggestion to try the test socket, as there's no extension wiring to be eliminated. So Routerstats monitoring would be a helpful next step.

Although you don't particularly need an increased upstream speed, you might as well have the cap removed anyway, because you won't lose anything on the downstream by doing so - there's no trade-off between the two.
Logged
  Eric

toulouse

  • Reg Member
  • ***
  • Posts: 595
  • I like cheesecake !!!
Re: Loop loss (attenuation) question
« Reply #12 on: June 14, 2012, 01:03:34 PM »

Ok, Routerstats has now been running since just before 6:00 this morning when I connected the DG834G.

In particular, which graphs or log features would be appropriate to enable further diagnosis of the situation.

I really do appreciate you taking the time to look at this for me.

TTFN

toulouse
Logged
Utility Warehouse (via TalkTalk)
FTTC 40/10
ZyXEL VMG8924-B10A
ECI (approx 750 metres)

People tell me that I ought to get out more. But in the words of the great Homer J Simpson, "Yeah, but what ya gonna do ?"

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 43467
  • Penguins CAN fly
    • DSLstats
Re: Loop loss (attenuation) question
« Reply #13 on: June 14, 2012, 01:46:46 PM »

The noise margin graph is the first port of call. By default I think you get about three hours' worth on one Routerstats page, and you can configure it to save each page automatically as it fills up. Any sections which show large variations in noise margin would be useful evidence.
Logged
  Eric

HPsauce

  • Helpful
  • Kitizen
  • *
  • Posts: 2606
Re: Loop loss (attenuation) question
« Reply #14 on: June 14, 2012, 01:55:27 PM »

Your BT line is still underperforming in relation to its attenuation.
Are you sure, it's pretty much spot on uses Kitz' own calculator?
36dB, 11mbps...
Logged
Pages: [1] 2 3 ... 7