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Author Topic: 352kbps upstream sync 95% of the time  (Read 4140 times)

sgour

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352kbps upstream sync 95% of the time
« on: October 19, 2009, 12:36:07 PM »

Hi,

I'm having a rather annoying problem with my upstream sync to the exchange, about 95+% of the time it is 352kbps and the other few percent it is 736kbps, which is around what it should be since I am on a ipstream adslmax business package. My downstream sync is OK and Ive no problems with it, its just the other.

I have had this problem since before summer but I never really bothered with it since I hoped it would just sort itself out, but it didnt so I recently notified my ISP and they got their technicians to look at it. Low and behold, knowing my luck the time they looked at it I had sycned at 736kbps and thus they see no problem.

I have tried different routers (dg834g v2 + dg834gt), different microfilters and connecting from behind the master face plate - all to no improvement. I have also tried the quiet line test on my phone and there is no fuzzyness or any other sort of noise during it. Whenever the upstream does rarely sync at 736kbps it is either at night or during the weekend.

As of this point at time, my line stats are like they usually are -

Code: [Select]
ADSL Link  Downstream  Upstream
Connection Speed 3776 kbps 352 kbps
Line Attenuation 57.0 db 31.5 db
Noise Margin 10.6 db 6.0 db

Code: [Select]
# cat /tmp/adsl-stats
/usr/sbin/adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 0
Channel: INTR, Upstream rate = 352 Kbps, Downstream rate = 3776 Kbps
Link Power State: L0
Mode:                   G.DMT
Channel:                Interleave
Trellis:                ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):       10.7            6.0
Attn(dB):       57.0            31.5
Pwr(dBm):       18.6            12.4
Max(Kbps):      4320            520
Rate (Kbps):    3776            352


Is there anything I can do around the house, or so to see if any interference is causing this or will I just have to keep nagging at my ISP to get this resolved?


Thanks
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roseway

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Re: 352kbps upstream sync 95% of the time
« Reply #1 on: October 19, 2009, 02:47:04 PM »

Hi and welcome.

Your upstream noise margin is at the default minimum level (6 dB) so I think the only reasonable explanation is that your line is getting strong interference in the upstream part of the frequency range. This is often associated with a crackly telephone line, but as you've tried the quiet line test this would seem not to be the problem.

I think your best option would be to install Routerstats and monitor the noise margins to see if it gives any clue to the type of interference. If we could see a copy of the graphs it may help us to see what's happening.
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  Eric

sgour

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Re: 352kbps upstream sync 95% of the time
« Reply #2 on: October 19, 2009, 03:21:32 PM »

Hi,

Thanks for your reply. Ive installed that program and will let it log for some time to see what it comes up with.

I had a BT engineer out several months ago to repair the phone line as it was crackling and affecting my adsl connection. He connected up a spare wire (or something) going alongside the one to my home and that fixed the crackling and the sync. The crackling hasnt returned since. Though personally I have rarely, if ever recall seeing my upstream noise margin above 6dB, even when I was on a non-business package.

I was doing some reading and it seems the upstream sync is to do with low frequencies(??), maybe this graph is of some use? - http://i35.tinypic.com/rj077n.jpg

I'll post images of the noise margin graphs once Ive let them ran for a while.

Thanks for your help

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roseway

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Re: 352kbps upstream sync 95% of the time
« Reply #3 on: October 19, 2009, 03:42:28 PM »

Quote
I was doing some reading and it seems the upstream sync is to do with low frequencies(??), maybe this graph is of some use?

Yes, the green section at the left hand side is the upstream part of the frequency range. If you want to learn more about it, see Kitz' article on ADSL technology.
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  Eric

sgour

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Re: 352kbps upstream sync 95% of the time
« Reply #4 on: October 19, 2009, 06:31:16 PM »

My sync died and I resynced with my upstream at 736kbps at about 6:10pm. This is the first time it has synced at 736kbps during the week for many months, from atleast what I can remember.

Here are the graphs from during this period, hopefully they are of some use -

Downstream noise graph - http://i36.tinypic.com/wl5dax.jpg
Upstream noise graph - http://i33.tinypic.com/2ng7g49.jpg
Upstream sync graph - http://i37.tinypic.com/106f3w1.jpg
Bits/SNR tone graph - http://i38.tinypic.com/2ptt0cp.jpg


Thanks
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jeffbb

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Re: 352kbps upstream sync 95% of the time
« Reply #5 on: October 19, 2009, 06:32:36 PM »

Hi

There seems to be some noise at the bottom end of the DL graph. The bit loading appears to be low below tone 63 when compared to tones 65 to 84.

Your DL SNR margin is a little High at   10.7db suggesting your target is at least 9db . Have you been having disconnection problems ?

Regards Jeff

edit
  Just seen last graphs   very odd ??? how its improved
« Last Edit: October 19, 2009, 06:38:19 PM by jeffbb »
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sgour

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Re: 352kbps upstream sync 95% of the time
« Reply #6 on: October 19, 2009, 06:43:01 PM »

Hi,

My noise margin increased a few years ago from when there was bad weather when I was out. Other than when there is very heavy rain, my connection is stable enough. I use DGTeam firmware to get it back down to around 9dB or so. Every little counts when you're the last on the exchange!

It seems from just looking at those graphs as if something has been switched off somewhere ( :hmm: ) because it just seems to cut out completely, on both upstream and downstream without, to put it one way, decreasing slowly to 0dB and then losing sync.
« Last Edit: October 19, 2009, 06:48:56 PM by sgour »
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roseway

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Re: 352kbps upstream sync 95% of the time
« Reply #7 on: October 19, 2009, 06:56:30 PM »

The Netgear routers don't seem to report upstream margin correctly, but just measure it once at sync time, and then report that value until the next re-sync. So what's possibly happening is that the upstream noise margin slowly falls to an unsustainable level, which triggers a re-sync.

However, as it's reconnected with a higher upstream speed, what seems more likely to me is that a short burst of noise triggered the re-sync. This burst could come from something being switched (as you suggested) and you need to think about things like thermostats and timer switches (central heating for example). Almost anything electrical could be the culprit, and we've seen things like TV sets causing this sort of problem.

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  Eric

waltergmw

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Re: 352kbps upstream sync 95% of the time
« Reply #8 on: October 19, 2009, 07:39:04 PM »

To confirm or otherwise Eric's thoughts re Netgear inaccuracies you might be able to do a BT Speedtest which reports the DSL Connection Rates which I've assumed are the modem sync rates. I'm monitoring a pretty lousy connection using a DG834 V2 with V3.01.31 - DGTeam Rev. 0849 firmware. This configuration currently reports the same upload and download connection speeds as does the BT Speedtest's DSL connection rates of 448 and 608. This produces a 500 kbps IP profile and a 417 kbps download throughput speed. The corresponding TBB throughput speeds are 360 and 459 respectively. The netgear reports Attenuation at 15.5 and 63 dB with Noise at 10 & 8 dB respectively. I believe the upstream attenuation is about half what it really is.

Make what you will of these figures !

Kind regards,
Walter
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