Low connection speeds & varying SNR

[CrossTalk]

Hi,

Sometime today, my connection router lost connection and resynced at around 1 mbps - prior to this sync speed had been just short of 3mbps.

I watched the line stats for an last hour or so and the SNR has wandered between 7dB & 15dB.  In the (not so distant) days before I joined IDNet I was on a fixed 1MB connection and the same setup yielded a rock solid SNR of 21 dB.

I've moved my router to the BT socket behind the NTE 5 faceplate and in the last 30 minutes, the SNR has been down as low as 8dB and up to 12dB.

Other than wait till Tuesday to give CS a ring, is there anything else I can try ?  Also, when I do contact CS, is there likely to be anything that can be done - or will I just get slopey shoulders from BT ?

Regards,

Phil.

[jupiter]

SNR behaves differently on fixed speed connections and on Max. Your Max connection will seek the best compromise between speed and stability, so your SNR is likely to be around 6db to 9db or so, depending on how the exchange equipment is handling your connection.

Varying SNR at the test socket could be caused by external noise affecting your line, especially at night, when AM radio signals cause interference.  You seem to be getting similar SNR at the test socket as before, which suggests that your internal wiring is not gathering further interference.  Lost connection can be caused by bursts of noise.

You may find it useful to look at the help thread here:
http://www.idnetters.co.uk/forums/index.php/topic,1904.0.html
which covers some of these connection issues.

[DorsetBoy]

Sorry to hear about this,I see that you are also in Dorset........which bit?

I too have suddenly experienced this problem,12 days back my normally stable line dropped and ever since I have had major problems with speed/stability and rapidly fluctuating SNR.

CS have lent me a different router and that is being monitored ,I am also running router stats to try and pin down the cause(which is definitely external).

Gather all the stats that you can for CS and phone through on Tuesday.

[Lance]

CS have lent me a different router

How many other ISPs offer that as a service I wonder!

I am also running router stats to try and pin down the cause(which is definitely external).

In case you struggle to find it, you can download Router Stats from here

I'm afraid I can't really add to anything else already said, but it would be interesting to find if it is specifically a problem in Dorset.

[Rik]

Phil

What router are you using, what is your attenuation?

[DorsetBoy]

How many other ISPs offer that as a service I wonder!

Indeed,and how many times do the MD's of other ISPs phone you from their home on a saturday afternoon to discuss the problem and what can be done about it?

Haven't sorted the problem yet but the lengths Idnet go to are quite amazing.

[Rik]

As you know, Dorset, Simon once emailed me at 4:34am to check on a problem. I don't think he ever sleeps.

IDNet are truly amazing in the lengths they will go to.

[CrossTalk]

DorsetBoy:
I'm in Wimborne - if you're on the same exchange send me a private message & I I'll be more specific.

Rik:
Router is a Draytek 2600Plus. 

Full ADSL status info
adsl status
--------------------------- ATU-R Info (annex A) ----------------------------
  Running Mode            :    G.DMT       State                : SHOWTIME
  DS Actual Rate          :  1056000 bps   US Actual Rate       :   448000 bps
  DS maximum Rate         :  1696000 bps   US maximum Rate      :   896000 bps
  DS Path Mode            :  Interleave    US Path Mode         :  Interleave
  NE Current Attenuation  :    55.0  dB    Cur SNR Margin       :    17.5  dB
  DS actual PSDM(C)       : 00000007       US actual PSDM(R)    : 0000319d
  ADSL Firmware Version   : 41e2be2c
-------------------------------- ATU-C Info ---------------------------------
  Far Current Attenuation :    31.5  dB    Far SNR Margin       :    15.0  dB
  CO ITU Version[0]       : 000f414c       CO ITU Version[1]    : 43420000
  DSLAM CHIPSET VENDOR    : < Alcatel >
-----------------------------------------------------------------------------
  INTL, DSTREAM bytes/depth=  16, symbols/codewords  =   0, latency= 0*0.25ms.
      , USTREAM bytes/depth=   8, symbols/codewords  =   0, latency= 0*0.25ms.
  CODE, DSTREAM fast parity bytes=   0, fast codeword=   0.
        DSTREAM intl parity bytes=  12, intl codeword= 148.
  CODE, USTREAM fast parity bytes=   0, fast codeword=   0.
        USTREAM intl parity bytes=  16, intl codeword= 136.
  Setting>>
      FDQ : Enable, TCM : Enable, EC : Disable, Framing Mode : 3.
  Running>>
      FDQ : In Use, TCM : In Use, EC :    Off.
      DS : Framing Mode 3, US : Framing Mode 3.
  ADI ADSL Firmware Version: 41e2be2c

Previously I was getting line syncs of over 3.5 mbps on a good day, around 3 mbps typical
When on a 1 MB fixed, the SNR was solid at 21 +/- 0.5 dB, (the DS Maximum rate in the above info was always around 4MB)

Line attenuation has remained constant throughout.

What's most alarming is the wide spread of SNR I saw last night (It's settled down for now). But it was swinging by over 10 dB over a few seconds.   - And that's on the same line, with  a lower connection speed that I used to achive a rock solid 21 dB.  Something wierd's going on.

[Rik]

Hi Phil

We have the same attenuation. I had my target noise margin raised to 9db to stabilise the line, and I sync at around 3200kbps, with a profile of 2500. Occasionally, I manage to sneak up to a 3000 profile for a while.

I, too, had a 2600+ when I was on a fixed 1Mbps service, with an attentuation of around 20db. However, I found that the Draytek did not handle Max terribly well on my line, and moved to a Netgear DG834. That has proved rock solid. I've read other reports of people finding Draytek's not being terribly successful with Max on longer lines, despite their reputation on fixed-rate.

Could you borrow another router to try?

What your noise margin does suggest is that the dynamic line management (DLM) software has decided your line is unstable, and is trying to overcome this by pushing your target noise margin higher. Have you checked your wiring, and particularly tried connecting at the test socket if you have one? Check the sticky here for detailed instructions.

[DorsetBoy]

Netgear router stats.

System Up Time 93:51:08
Port   Status   TxPkts   RxPkts   Collisions   Tx B/s   Rx B/s   Up Time
WAN   PPPoA   609201   905201   0   345   7964   40:57:55
LAN   10M/100M   1853779   1346571   0   6943   389   93:51:04


ADSL Link   Downstream   Upstream
Connection Speed   6624 kbps   448 kbps
Line Attenuation   27 db   7 db
Noise Margin     15 db   25 db


My exchange is Wareham South, so not that far away but not the same either.

[CrossTalk]

Rik,

Thanks for the info about Drayteks on a Max service - interesting & surprising.  I still have my really old ASUS AM6000 router kicking around, but that wasn't even great on a fixed speed link.

I use the 2600+ because of it's VPN endpoint facilities, which I don't think any of the NetGears offer.  (I have some embedded devices & a NAS device that I sometimes need access to when away from home).  Do you have any other router recommendations.

I had the router plugged into the back of the NTE 5 socket for about an hour last night and didn't see any noticable difference between that and the internal wiring.  I use a centrally filtered faceplate (from www.clarity.it) with a 6 metre continuous run of cat 5 cable from the rear of faceplate to the RJ11 wall socket next to the router.  When I installed that a couple of years ago my router didn't show any difference between the back of the NTE 5 & the installed wiring.  Prior to that I lost about 2dB with my internal phone wiring.

That said, the Draytek has been working fine since joining IDNet 2 months ago, the drop off in performance yesterday was dramatic and sudden, which still makes me think that something changed - I think I've ruled out any internal influences - so I assume it's still worth asking CS to get BT to investigate.


With regard to the DLM system - I assume that once stable this will recover over a period of days, is this correct or do I need to ask CS to do something.

[Rik]

Hi Phil

The most commonly recommended routers for Max seem to be the Netgear and Speedtouch, but that may just reflect market share, given these are user recommendations. Zyxel and D-Link are also mentioned, but not as often. I was very surprised by the inversion of my Draytek's performance when I went to Max, but I found I was not alone. It would be worth checking to see if they have any updated firmware.

With the filtered faceplate and Cat5 cabling in place, you've done just about everything you can and from what you say, I think a call to support is the only way forward. Before you do, run a BT speed test, so that you can quote the results to them.

DLM will recover with regards to profile, but may need a nudge on noise margin. Support will be able to arrange that once the cause of your problems has been tracked and sorted.

[CrossTalk]

Well, I rebooted my router around lunchtime because I was playing with the VPN configuration - I was a bit worried, but the SNR had been stable at 17dB all morning (much improved over last night's 5dB!)

It resynced at 2656000 bps - not the best it's been, but OK (for round here!).  SNR was 11.5 dB.  Since then it's dropped slightly to 10dB - but again 1.5dB drop for mid evening peak is OK.  So fingers crossed that last night's SNR rollercoaster was a one off.

I've been running RouterStats as suggested by DorsetBoy - As my Gran used to say when waiting for a brew [no, I'm  not a Dorset Native] "A watched kettle never boils"


Still, I might try a DG834 to see if that can improve matters - however that would just leave me with the issue about what to do for VPN connectivity - The main reason I bought the Draytek in the first place.  (perhaps ebay for a Draytek 2900 ?).

Does anyone know if particular variants of the DG834 are better (or worse) than others ?



Phil

[CrossTalk]

However....

SNR still holding around 9.5 - 10 dB

But things still felt very slow so I did the BT speedtest as Rik suggested it looks like last night's problems killed my profile:

Speedtest results:

Test1 comprises of Best Effort Test: -provides background information.
    IP profile for your line is - 500 kbps
    DSL connection rate: 448 kbps(UP-STREAM)  2656 kbps(DOWN-STREAM)
    Actual IP throughput achieved during the test was - 393 kbps

So what next ?

[jupiter]

The DLM equipment at the exchange will look for three days of stability before upping your profile - frustrating but that is how it has been designed.

I suggest though that you phone CS tomorrow and explain what has been happening.

I have used the DG834v2 with good results on a max line with higher attenuation than yours.  Good luck.

[Rik]

Phil

If memory serves me correctly, the 834 and 834G use the TI chipset, and the GT uses the Broadcom. The best results seem to occur if you can match your chipset to that of the DSLAM you are connected to, but that may be apocryphal.

Jupiter's advice is sound on all counts.