True ADSL bandwidth resets to normal after plugging in phone set?

[WorriedNoodle]

We have a 13mbps basic 599THB/month ADSL account with True Online in Bangkok.

I have noticed that the downstream speed on the 192.168.1.1 router display settings should normally be at 15,328kbps to give the full account speed, but this drops off for no reason to something slower, usually in the 9,000kbps or 10,000kbps area.

* This is what I don't understand, if I am stuck around 9,000kbps no amount of rebooting modem or checking cables fixes it. But if I plug in a phone set and line to the wall used by modem, dial the phone from another number then remove phone set and re-plug in modem I am back to full throttle 15,328kbps.

Can anyone explain why this happens?

[ThaidDown]

Sounds like it could be a dodgy connection on the phone line between you and the exchange.(something slightly loose and oxidised?)

Calling the phone will pulse the full ringing voltage on the line and the increase in current can temporarily clean up the bad connection.

To check if this is the case, check, via the modem, the signal level and signal to noise ratio when the speed is good and again when the speed is low.

[RichCor]

^^^ Yep

The modem is falling back to a lower speed due to line conditions.

When the phone is plugged in and dialed, that creates a sealing current (or a wetting current).

"In electrical engineering, wetting current is the minimum electric current needing to flow through a contact to break through the surface film resistance. The film of oxidation occurs often in areas with high humidity. Providing a sufficient amount of wetting current is a crucial step in designing systems that use delicate switches with small contact pressure as sensor inputs. Failing to do this might result in switches remaining electrically "open" when pressed, due to contact oxidation."

[Pib]

Yeap...probably a corroded/loose connection upstream of the modem...somewhere between the modem and the exchange/DSLAM. Could be a funky connection within your residence walls...on the poles....it could be anywhere upstream. With a good physical line connection all the way to the exchange/DSLAM your sync speed should remain rock steady at the 15,328Kbps, but not to imply your actual surfing will be that fast due to possible chocking of the bandwidth data flow somewhere.

[WorriedNoodle]

Really appreciate your replies guys. I am not qualified to figure that myself, but what you say sounds very believable.

I figured this out myself when the True service tech came around last month to fix our low speed of around 7mbps and I noticed all he did without saying anything was plug in some listening device, probably called but I didn't notcie, then the Iine was suddenly back to speed. He left it like that and the next day speed dropped off again.

It seems that is all True service is prepared to do about it. I thought I'd plug in a phone set even tho we don't use the land line for phone service, called in and was surprised to see the speed go back up. I guess I'll fix it myself each time like this unless it gets really tiresome/too slow and next time True service gets a call up I'll have a bit more knowledge about it.

[Pib]

You can do a search on ThaiVisa regarding ADSL Downstream Attenuation, Upstream Attenuation, and Signal to Noise Ratio metrics which are excellent indicators of whether you got a physical line problem (i.e, funky connection) or the problem is just with the ADSL service providers servers. I would search and point you to a few of the posts but I need to run right now.

Heck, even True DOCSIS (cable) lines have issues. I'm on a True DOCSIS 15Mb/1.5Mb plan here in Bangkok....Wednesday morning my surfing speed was very slow...almost unusable to many sites (even in-Thailand sites)...I figured it would clear up in an hour or so like I seen before. But at lunch time still slow...at 5pm still slow. But when looking at my modem firmware metrics the sync speed, upstream and downstream power levels were fine, signal to notice ratio was rock solid...just like always.

Ok, I call TrueOnline...explain the problem, expect to be told to reset the modem (they almost always ask you to do that), but the customer service rep did not this time...instead she said hold one, she came back online in about 15 seconds, asked me to try my surfing speed again, and it was back to normal/fast speed. She said she switched me to a different gateway and they need to do this occasionally to balance-out bandwidth load. it's been fine since. Gotta run...

[Pib]

Here are some ADSL metrics which may be helpful to determine if you have a physical line problem or not. You should be able to go into your modem's firmware menu and find some metrics for comparison. May give you more ammunition the next time the True tech comes out to check your line.

Signal-to-noise ratio
Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering measurement defined as the ratio of a signal power to the noise power corrupting the signal.
In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is. The concept can also be understood as normalizing the noise level to 1 (0 dB) and measuring how far the signal 'stands out'. In some instances interleaving can help raise the noise margin to an acceptable level.
In general, higher signal to noise is better; the signal is 'cleaner'.

Attenuation Rate
Attenuation is the gradual loss in intensity of any kind of flux through a medium(i.e. the reduction in signal strength due to length of your phone line). For instance, sunlight is attenuated by dark glasses, and X-rays are attenuated by lead.In ADSL the signal is attenuated by length of copper lines. Attenuation is normally directly linked to the length of your line. Copper is traditionally used in the local loop and the higher gauge of copper will give the best signal, however some lines may have some aluminium or aluminium joints on the line which will increase resistance... as will oxidization of joints. Attenuation is mesured in db or noise. The more noise the weaker the data signal
In general, lower Attenuation is better; the signal is 'stronger'.


Heres is my table of comparisons
SNR:

6dB or below is very bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with little or no sync problems
20dB-28dB is excellent
29dB or above is outstanding

Attenuation:

20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

The following guide (distance vs. attenuation vs speed) gives you an guestimate what you can achieve:
<1km should be 23-24Mbit (nice speed, but doesn't it bug you that Telkom people walk through your bedroom?)
1.0km = 13.81dB = 23Mbit
1.5km = 20.7dB = 21Mbit
2.0km = 27.6dB = 18Mbit
2.5km = 34.5dB = 13Mbit
3.0km = 41.4dB = 8Mbit
3.5km = 48.3dB = 6Mbit
4.0km = 56dB = 4Mbit
4.5km = 62.1dB = 3Mbit
5.0km = 69dB = 2Mbit
>5.0km (you are pretty much poked --- sorry for you)

[WorriedNoodle]

Excellent help thanks. I'm away for weekend, but when I left I checked the SNR and Attenuation after I had bumped the line back up to 15,328kbps by myself using the phone call technique, and I was getting

• SNR Down/Up 15.1dB/32.0dB
• Attenuation Down/Up 10.0dB/2.4dB

which is good or outstanding from the table provided above.

I'll check again on these when the data rate drops again.

I have also in past contacted True Support via their web site/email (they are prompt and helpful I find) and they always first check the line from their end and then the line speed suddenly gets fixed and they reply by email that all is OK without saying why - or they send a guy around to fix it as described earlier.

[Pib]

I have also in past contacted True Support via their web site/email (they are prompt and helpful I find) and they always first check the line from their end and then the line speed suddenly gets fixed and they reply by email that all is OK without saying why - or they send a guy around to fix it as described earlier.

That's telling me you do not have a physical line problem at least to the exchange/DSLAM (but there could be problems at the exchange). Probably just choked local bandwidth or problems at their central servers....and True is just moving you to a different gateway/changing your routing (apparently temporarily in your case) to get you speed back up to normal....giving you a higher priority of service temporarily.

Pretty much like the example I gave in how True fixed my DOCSIS slow-ass speed on Wednesday...called them up...took them a few seconds to switch me to another gateway/different routing...and just like snapping fingers my speed was back to normal. However, my VOIP phone system still had problems making calls to like the U.S....sometimes the number would ring...sometimes it wouldn't....probably long latency problems due to routing. But Thursday morning VOIP was working fine again...each and every call went through on first dial and my surfing speed was still fine.

I think what happened is on Wednesday a truck took down about 10 poles carrying electric, telephone, cable, etc., lines a few kilometers as the crow flies from where I live here in western Bangkok....and people in that area lost electric and other utilities...probably their cable TV/internet and ADSL internet service also. I saw the damage on Thursday when driving by....just amazing...10 concrete poles along approx a 350 meter stretch had to be replaced as the old ones fell like dominoes...some broke off at ground level...some about half way up.

While the repair crews did emergency repairs/pole replacements I expect there was a lot of rerouting of phone/internet services which chocked up bandwidth for some folks (like me). And since I called before they had completed the repair and in order to shut me up they just changed my gateway/routing....I expect if I hadn't called Wednesday evening by Thursday morning everything would have been back to normal anyway.