Latency changes

tehidyman · May 22, 2011, 13:35:15

Checking my download speed using Speedtest.net I noticed recently that my latency was now 87-89ms and my upload speed was 0.37- 0.40Mb/s. However earlier tests in March this year gave values of 45/46ms latency and 0.62-0.65Mb/s upload speed. Currently my reported download speed is 1.95 Mb/s and earlier it was between 1.47 and 2.17Mb/s. For both series of tests my Attenuation has been 49-51db and my sync on the earlier set about 2720Kbps and currently is 2272Kbps. What might have caused the change in latency? Could this be the cause of slower browsing responses? If so how can I get it back to the earlier level? My signal type on the line was changed from ADSL2+ to standard ADSL in August last year. The only change I can think of is upgrade Firefox to v 4.0.1

Steve · May 22, 2011, 14:54:41

Your broadband connection seems to have degraded whether that's due to line degradation,noise interference increasing or poor router/modem performance I can't say at present. The latency may have increased due to the imposition or an increase in the level of interleave on the line. To dig deeper we need a BT speedtest and router stats.

tehidyman · May 22, 2011, 16:04:46

BT Speed Test.....1965kbps down, 612 up, IP 2000 kbps, upload 736 DSL 2272

My line has intermittent high noise which has been the case for last few years. Test socket results showed cause was external. ADSL nation filtered faceplates, Cat 5 extension, short Pro+ ethernet cable, all in place for several months to try and reduce effect of noise.

Current router stats
ADSL Link    Downstream    Upstream
Connection Speed    2272 kbps    736 kbps
Line Attenuation    49 db    15.5 db
Noise Margin    14 db    11 d

Router is Netgear DG834G v3 using ethernet cable, wireless disabled.

Rik · May 22, 2011, 16:06:50

That noise margin is depressing your speed, suggesting that DLM is trying to compensate for the instability.

tehidyman · May 22, 2011, 16:16:03

I thought I had put all the detail in my first post but on a re-read realise I left out that my noise margin has been up to 15db for most of the last few years.

Rik · May 22, 2011, 16:18:04

Even when you had the higher speeds?

tehidyman · May 22, 2011, 16:25:08

Quote from: Rik on May 22, 2011, 16:18:04
Even when you had the higher speeds?

Yes, rechecked in my notebook and confirm that when the lower latency was recorded the noise margin was up to 15db.

Rik · May 22, 2011, 16:26:24

In which case it sounds like DLM is now deploying greater interleaving to achieve the result.

Steve · May 22, 2011, 16:45:53

Below will give you your interleave status with the v3 although I suspect it's on

http://192.168.0.1/setup.cgi?todo=debug

telnet 192.168.0.1

cat /proc/avalanche/avsar_modem_stats

Just wondering whether another router may perform better on your line cheapest option I guess is a BT 2700 from ebay. The other thing that springs to mind is the downstream sync rate which is at the upper limited of a banded profile

ADSL2+ profiles

7168 - 14336
4864 - 9728
3328 - 6656
2272 - 4544
1472 - 3072
1152 - 2272
576 - 1152
288 - 576
160 - 288

Although since you've been modulated back to plain adsl on a adsl2+ enabled exchange I'm not sure how this fits in. Perhaps check with support?

tehidyman · May 22, 2011, 17:12:15

Quote from: Steve on May 22, 2011, 16:45:53
Just wondering whether another router may perform better on your line

I have a box full of Routers! Netgear 834G v4 and v5. I do have a BT 2700 but overnight it resyncs at a high speed when the noise is very low (neighbour has gone to bed!) I then find that BT have "reset" my download speed and then when my neighbour generates all the RF noise I crash and resync at a slow rate. DLM reacts very quickly and I am often back at an even lower IP. Have found that the V3 seems to be the most stable. I will however check with Support tomorrow to see if it is worth trying to resync. I have been working to an old Line sync speed to IP profile chart which has 2272 to 2847Kbps gives 2Mbps

Steve · May 22, 2011, 17:27:00

The banded profile is used by BT to limit the maximum downstream sync on adsl2+ lines which have high noise levels or high error rates. The IP profile is as you state still the same and related to the downstream sync. I guess it may well be a red herring as a banded profile normally results in a rise in the downstream margin when it's applied and yours has I believe stayed the same.

tehidyman · Jun 03, 2011, 10:04:29

Having configured my RouterStats for Telnet information as Rik recommended I found that interleaving was on. For the next 6 days it stayed on, I synced at 2433kbps and a BT speed test gave IP of 2145kbps down and a download speed of 2131kbps. The best stable speed I have enjoyed for a long time. My noise margin was the usual variable up to 15db. This morning I had lost my internet connection. Having rebooted I was now synced at 1920kbps and my interleave has been turned off. I then took the opportunity to switch from Netgear DG834G v3 to v4. Is there any way I can get interleave turned back on and ensure it does not get turned off again? I did note yesterday that my total error count was 10. l I would then try to get back to the better speed which in some applications does make an appreciable difference.

Rik · Jun 03, 2011, 10:07:04

Give support a ring, they can have it switched on for you.