Kitz Forum
Broadband Related => Broadband Hardware => Topic started by: shmertmoans on February 19, 2008, 05:49:42 PM
-
Hi,
First off, thanks to kitz for a great site ive used it quite a fait bit over the last few months.
Anyway heres my story.
I have been having problems with my sync droppin then reconnecting straight away(30secs or so)..no good for gaming
It was intermitting and could be stable for a day or so or disconnect as much as 4 times in an hr.
I was using a ZyXel P-660HW-T1 and it was syning at 2600kbps -3000kbps with theses line stats-
Downstream stats-
noise margin downstream: 6 db
output power upstream: 18 db
attenuation downstream: 61 db
upstream stats-
noise margin upstream: 19 db
output power downstream: 12 db
attenuation upstream: 31 db
From what i read i did think it was snycing too fast but as i have no control over this, i couldnt experiment.
Anyway, i spoke with my service provider and they asked bt to do some snr profile changes....things have been better but it still was dropping every day/second day....I was fairly pleased with this improvment but tbh i want it stable for longer than this..
So after reading this site and some others i found that people were recommending the netgear DG834G router as one that would maitain a stable connection on crappy lines.
Ive just set it up and i am now on the net but after checking the stats on my line now it has synced a great deal slower..heres my new stats-
ADSL Link Downstream Upstream
Connection Speed 1024 kbps 448 kbps
Line Attenuation 61.0 db 31.5 db
Noise Margin 16.8 db 18.0 db
As you can see it has synced alot slower than the zyxel router (which should help my line stay stable i recon) but why is this??
Is this router making a "better connection for my poor line" or is ther a setting on the netgear i may dont know about.
-
Hi and welcome.
What seems to have happened is that the automatic DLM process in the exchange has determined that your line is unstable, and has increased the target noise margin to stabilise it. This results in a more stable, but lower speed, connection. With a line as long as yours (61 dB downstream attenuation) that may be the best option. I imagine that if you were to put the Zyxel back its stats would now be similar.
Just to confirm that this is the case, you could check the router stats immediately after a re-sync. If the downstream noise margin is in the region of 15 dB at that time, then this would confirm the point.
With a long line like yours, you're always going to be a bit on the edge, so the most useful thing you can do is make sure that your own internal telephone wiring is as perfect as you can make it. There are some tips here (http://www.kitz.co.uk/adsl/lowSNR.htm).
-
Thanks,
I've had this problem for a while though so why wouldnt the dlm process have dropped the speed before??. Every time it re-sync's it has been @ 2600-2700kbps (for a good few months) lol
Just before i changed router to netgear one the zyxel had been up for 45hrs(longest in months) @ 2700kbps. Then i swap it and straight away netgear is 1024kpbs.
I changed 1 setting on netgear(DSL MODE) to ADSL(G.DMT), it had been AUTO (Muliti-mode before) and i now get 1312 kbps.
I will check zyxel one again later ...im going to leave this one in and see how long it works at this speed.
Thanks again
btw- thanks for the tips/link but ive already did this...
-
By the looks of your post the change in margin could be a change by the Dynamic Line Management taking drastic action or BT manually changing the SNR margin at the request of your ISP.
In theory the target noise margin will be dropped and the sync rate improve if the line remains stable for a period of time. As roseway suggested, look at the advice on the website for improving your lines performance.
If you have already optimised your internal configuration, think about any potential sources of interference which might be causing your problems. In the majority of cases a line will not want to resync 4 times in an hour with a 6dB noise margin without some obvious cause of interference.
As for the routers, the DG834 is one of the most stable available and will hold sync well as the noise margin varies throughout the day. The line performance with the Netgear is governed by the exchange and if you reconnect the Zyxel, you might find the stats even worse depending on how well they perform in DSL terms.
-
thanks alot.
Yes i think bt (at request from service provider) have changed my SNR margin on downstream just at weekend. This must be it taking effect now.
Ill leave new router on and hopefully ill stay up forever(ish). Ive also put routerstats on to monitor the situation.
When you say it will "drop the target SNR and sync rate should improve if the line remains stable for a period of time"..what sort of time frame? Ive read elsewhere 3days.
-
No, the three days refers to something else - the period which it takes for an IP profile to be raised after getting a higher connection speed. In fact this period is now anything between 4 hours and 5 days, depending on how big the change is (big changes happen more quickly).
The progressive reduction in target noise margin takes longer, and the process doesn't seem to be well documented. As far as I know, the target should be reduced by 3 dB after 14 days of stability, then another 14 days for the next 3 dB, and so on.
-
Thanks alot.
I'll leave my router connected for at least the next 2 weeks(provided it dont disconnect itself). Hopefully the speed will increase after this.
Should the target noise margin change whilst connected or will it need a re-boot/reconnect to show this reduction in the routers stats? why i want to know is so that i could check the stats to see if they change without having to dissconnet. I could wait till it shows a 3db reduction then try a reboot if this was the case.
-
As youv'e changed routers, one point worth loking at, are you using the same lead from the microfilter to the router ? If your using the new one for the new router is it still coiled up or sitting predominately around other transformers/mains cables.
This usualy dosn't make any difference but some times you may be picking up some noise via this lead because in a typical set up this may be clumped togeter with other transformers mear the mains supply.
Also a lot of people will coil any spare cable up to keep things tidy. Avoid doing this with the dsl lead from the filter to your router/modem (also the same with any data cables such as the ethernet cable). Best practice lay this cable out as long as you can, maby back & forth a couple of times, away frombeing directly by any transformers and not running parallel within 50mm of any mains/power cable if you can.
Also some times it may be wrth trying to move the cable/router modem away from any plumbing/ pipe work in case this makes a difference. sometimes if something electrical is dumping current back doem the earth, then this can be retransmitted via metal plumbing.
As I said this isn't very typical but might be worth trying, it's a nice easy fix when trying the above youy suddenly find, Hello my stats/sync have improved.
-
As youv'e changed routers, one point worth loking at, are you using the same lead from the microfilter to the router ? If your using the new one for the new router is it still coiled up or sitting predominately around other transformers/mains cables.
This usualy dosn't make any difference but some times you may be picking up some noise via this lead because in a typical set up this may be clumped togeter with other transformers mear the mains supply.
Also a lot of people will coil any spare cable up to keep things tidy. Avoid doing this with the dsl lead from the filter to your router/modem (also the same with any data cables such as the ethernet cable). Best practice lay this cable out as long as you can, maby back & forth a couple of times, away frombeing directly by any transformers and not running parallel within 50mm of any mains/power cable if you can.
Also some times it may be wrth trying to move the cable/router modem away from any plumbing/ pipe work in case this makes a difference. sometimes if something electrical is dumping current back doem the earth, then this can be retransmitted via metal plumbing.
As I said this isn't very typical but might be worth trying, it's a nice easy fix when trying the above youy suddenly find, Hello my stats/sync have improved.
thanks for reply..
yes im now using the new cable and filter but they are totally uncoiled and are running the same way to socket as before-(well away from mains cables, plumbing etc and oly 1m long or so)..ive ordered a new screened rj11 anyway so will swap it asap.
think its more likely that is due to bt changing my SNR margin from 6db up to 16.8db....
hopefully this will retrain and ill get a little more speed but still maintain a stable line.......maybe i need a bit more than 6db but i doubt i need as much as 16.8db(neva know tho)
saw that i could get firmware(not official netgear tho) that you can frig this value to get more...may try this after a few months or "retraining"
-
after day 1 of new netgear with router stats i got these results from 4 am to 7am it was like this..... at all the other times of the day it was reasonably flat at around 16db and no drop in speed.
the router has not disconnected at all(good) but on the graph it shows a drop in speed(see pic)
Any help appreciated
Also- what is the most likely place this noise is getting picked up on - the rj11 cable from router to wall or the bt line comin into my house picking up streetlights etc. I will be trying a screened rj11 cable shorlty so that should eliminate the rj11 from the problem surely.
All i can think that switches on around this time is my white meter heaters and hot water tank(12-7am) but the closest heater is about 6 meters away from router and cable and water tank is other side of house.
[attachment deleted by admin]
-
You've got several fairly devastating noise spikes over a short period, and switching of heaters and similar things are the most likely suspects. This sort of interference can be conducted over the mains wiring, which seems quite likely in view of the physical distances you mention. If it weren't the middle of winter I would suggest that you switch off the heating for 24 hours and see what happens, but I don't expect you want to do that. :)
Unless anyone has got any better ideas, I think you may have to think about using mains suppressors, or even running your router from a UPS, to keep the noise spikes out.
-
As eric says - looks like some serious noise spikes thats taking your connection out.
Whats the SNRM like during the rest of the day? ... or is it just 4am ish?
-
You've got several fairly devastating noise spikes over a short period, and switching of heaters and similar things are the most likely suspects. This sort of interference can be conducted over the mains wiring, which seems quite likely in view of the physical distances you mention. If it weren't the middle of winter I would suggest that you switch off the heating for 24 hours and see what happens, but I don't expect you want to do that. :)
Unless anyone has got any better ideas, I think you may have to think about using mains suppressors, or even running your router from a UPS, to keep the noise spikes out.
thanks for reply.
Say it is caused by spikes on my mains wiring, is this coimg through the power adaptor for router and onto adsl line?
I will try leaving the heating(white meter) off tonight. I can use an electric fire later i to heat the place..
If it is this i will try a mains suppressor as well as the screened rj11 ive ordered.
-
As eric says - looks like some serious noise spikes thats taking your connection out.
Whats the SNRM like during the rest of the day? ... or is it just 4am ish?
the graphs for the rest of the day are a failry straight line @ about 16dB. this was just earlier and were like this apart from a few hrs i metioned (4am-7am)
[attachment deleted by admin]
-
>>> Say it is caused by spikes on my mains wiring, is this coimg through the power adaptor for router and onto adsl line?
The problem with REIN faults (http://www.kitz.co.uk/adsl/rein.htm) is that it can come from various sources.. it may not even be something in your own home. Theres a list on that page of typical culprits (kindly provided by Ezzer)... but that list is by no means exhaustive :/
-
>>> Say it is caused by spikes on my mains wiring, is this coimg through the power adaptor for router and onto adsl line?
The problem with REIN faults (http://www.kitz.co.uk/adsl/rein.htm) is that it can come from various sources.. it may not even be something in your own home. Theres a list on that page of typical culprits (kindly provided by Ezzer)... but that list is by no means exhaustive :/
cheers,
yes just read that page as you were typing. good info. cheers.
defo switching heaters off tonight and will be buying one of these surge protectors (http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=PL04049)
-
The worst thing about REIN faults is that they may not necessraily come from your property. Your mains cableing is shared with you neighbours an can act as an antennea broadcasting the inteference evenly no matter where the source is.
2 recent REIN faults I've had to work on were like that. The last one took 6 visits i the area before I could pinpoint which address it came from.
As for the cable from the micro filter to the router, this is a very small part of where you can pick up the interference, my previous post refered to a quick way of eliminating one aspect. Screened cables will never hurt.
As for the source of the interference, ANYTHING electical. The more energy it uses, the more likely it will become an issue. Previous sources I've found. transformers, central heating timer/switches, TV's. UPS units (several times), pc LCD screen, electric fan heater, Street lights, 500w halogen security light, TIG welding equipment, routers, x-mas lights
-
I checked today and there were no nasty spikes/drops, i left heaters etc on.
Im thinking these could have been caused by the (lead up to) power cut. I had power cut at 7am so it couldve been noisy on the lead up to this.
I will just have to monitor it for the next wk or so.
Thanks
-
>> I checked today and there were no nasty spikes/drops, i left heaters etc on.
Hopefully it has stabilised
.. although I'm not sure about the leading up to the powercut.. but then again Im not into electrics so couldnt really say Im afraid.
-
Sometimes in the time before a power cut you get poor quality power and brief outages (brown-outs... when the lights will visibly dim for a second or so), which because of the cheap consumer-grade power transformers that are supplied with most pieces of electrical equipment, can cause havoc if the device is reliant on a nice steady voltage to operate properly.
So yeah, it's possible (in my mind anyway, but then again I'm no electrician) that your router dropped a few times in a short space of time just before the power cut or something, causing the line to appear unstable.
I don't understand how DLM works.. in fact I'm rapidly coming to the conclusion that it's buggy as hell, because there seems to be little consistency between different reports I've read on here and other forums of how it actually works. I myself had my SNR raised automatically even though my line was stable at 6db for months - and then after a small handful of resyncs it shot up to 9dB, then very quickly up to 12dB, again after just one or two resyncs whilst I was trying to time the sync just right to get the highest speed possible (no DMT tool tweaking for my DG834Gv2, you see).
And conversely I've seen cases where people have had to manually tweak their SNR UP because the DLM steadfastly refuses to increase from the default 6dB even though the line is dropping several times a day. Madness!
For people in your situation, there ought to be a route for ISPs to ask BT to get the target SNR reduced, no questions asked, if the user can give a legit reason for the unusual instability (i.e. factors other than phone line quality, e.g. power cut, new router, etc). But I doubt that'll happen anytime soon, I had hoped DLM would have been tweaked a bit better by now!
-
Sometimes in the time before a power cut you get poor quality power and brief outages (brown-outs... when the lights will visibly dim for a second or so), which because of the cheap consumer-grade power transformers that are supplied with most pieces of electrical equipment, can cause havoc if the device is reliant on a nice steady voltage to operate properly.
So yeah, it's possible (in my mind anyway, but then again I'm no electrician) that your router dropped a few times in a short space of time just before the power cut or something, causing the line to appear unstable.
I don't understand how DLM works.. in fact I'm rapidly coming to the conclusion that it's buggy as hell, because there seems to be little consistency between different reports I've read on here and other forums of how it actually works. I myself had my SNR raised automatically even though my line was stable at 6db for months - and then after a small handful of resyncs it shot up to 9dB, then very quickly up to 12dB, again after just one or two resyncs whilst I was trying to time the sync just right to get the highest speed possible (no DMT tool tweaking for my DG834Gv2, you see).
And conversely I've seen cases where people have had to manually tweak their SNR UP because the DLM steadfastly refuses to increase from the default 6dB even though the line is dropping several times a day. Madness!
For people in your situation, there ought to be a route for ISPs to ask BT to get the target SNR reduced, no questions asked, if the user can give a legit reason for the unusual instability (i.e. factors other than phone line quality, e.g. power cut, new router, etc). But I doubt that'll happen anytime soon, I had hoped DLM would have been tweaked a bit better by now!
thanks for reply.
yes it must have been due to the power cut/problem.
ive been watching routerstats and i dont get any nasty spikes, it only fluctuates by maybe around 1db.
the snr has also dropped to around 13db hence my sync going up to about 1800kbps. I just need the snr to get back to 6db or so and i should get my 2700kbps - 3000kbps i used to have.
wish i knew how to manually tweak snr on the netgear DG834 v4...i got the wrong router, need the GT model...dammit...if anybody knows a way id be greatful for the info....
-
In theory one router should give similar results within 2-3 db to another.
Just one thing about surge protectors, if you suffer from power cuts or you notice say your room lights often flickering then it's worth while investing in a surge protector for use with any thing that has delicate electronics. PC,s Modern TV's & dvd's etc.
I doubt if the surge protector would make any difference to the noise spikes you get, however by fluke you might get lucky.
And never rely on a surge protector for lightning protection, no matter what the manufacturer may say. The protector will give you a 50/50 chance with a lightning surge. If you get enough energy coming down the line it will go straight through the protector and cook whatever is at the end before it can do it's job if at all.
If there's a hint of thunder on it's way the only way to protect yourself is to physicaly unplug as much as possible from from both mains & telephony. Both can act like casting a big net so even if your house dosn't get hit, the cableing might bring a current back home
Ahh thats 3 things........ ::)
-
>> i knew how to manually tweak snr on the netgear DG834 v4...i got the wrong router, need the GT model...dammit
The v4 is relatively new out therefore there isnt that much info about it yet... but it is supposed to use the broadcom chipset similar to the GT.
Therefore (Im not sure on this) but you may be able to manually configure it using the following instructions as a guide?
http://www.kitz.co.uk/routers/dg834GT_targetsnr.htm
-
You are right Kitz.
The new version4 does utilise the broadcom chipset. I would personally not recommend that anyone changed thier target SNR value. This is something that the BT servers should be able to set, and if you are not with BT then the LLU provider should set it with the DSLAM manually.
Azzaka
-
I would personally not recommend that anyone changed thier target SNR value.
In an ideal world you would be right. But BT's DLM is far from an ideal world. In my experience SNR margins can get bumped up for transient line issues. Once they are up they never seem to come down again, which is frustrating. It seems to be compounded by the lack of good communication channels between the ISP's and BTW, which would enable SNR margin changes to be made more rapidly.
-
... But BT's DLM is far from an ideal world. In my experience SNR margins can get bumped up for transient line issues. Once they are up they never seem to come down again, which is frustrating...
The communication between BTW and the ISP can be arduous i agree with you completely. and can definitely be frustrating and disconcerting. My only point which i was trying to make and i realise now was not very clear, is that when you change the SNR it can cause a lot more issues with the line and cause BT systems to think that your line is stable when it isn't.
This from my point of view is a big issue and can be the cause of many a headache. Often the SNR does stay at the set target without moving. However if the line settles and you believe it can be set lower and still remain stable, you can ask for the 10 day training period to be restarted. This in effect will either leave the target SNR where it is or it will drop the SNR to a lower value giving you more speed without sacrificing stability.
When you try and manually set the SNR you can have adverse effects on your line, or you can even spend more time trying to keep the stability because you keep tweaking it.
I hope this is a little clearer, and I welcome any feedback.
Leo
-
Yes, I do rather agree with you Azzaka. People need to realise that tools like DMT can't fix the target noise margin at a specific value, they can only offset the value set by the DLM process by a few dB. And if this results in the line becoming more unstable then DLM will increase the target noise margin still further.
DMT can have some practical use on a stable line. For example, sometimes a small tweak can get you up into the next IP profile band. But small tweaks like this are really all that should normally be applied, and it's probably better not to try at all with a connection which is at all unstable.
-
Exactly... and if the DLM system worked in a more predictable way, and IP profiles updated at each sync rather than this stupid wait up to 5 days malarky, then we'd all probably be a bit more tolerant of it.
I bet there's probably more processing going on to determine whether to raise/lower the profile than there would be by simply resetting it everytime someone logs on!
Grr!
-
yes... but think of how much bandwidth on the VP backhaul "gets saved" when someone has a low IPprofile. ;)
/cynic
-
One way of looking at the DLM, rather like driving along and then discovering your going patches of ice, so you slow down, after a while you get more confident and speed up, but if you feel another patch if ice you get nevous and slow down again :-\
If the DLM has slowed things down then something has triggered this. With getting capped then the line becoming unstable chances are the DLM has noticed this the other way around.
Tweeking things TOO much as Azzaka stated; back too car in ice, it's like a passenger saying "go-on put your foot down" then planting their own foot hard on the accelerator :lol:(oh I love my analogies :blush:)
-
I think you're giving the DLM far too much credit there, Ezzer :P
-
EZZER is 99% correct and an insignificany 1% wrong.
The DLM is not humanoid but works only to set parameters, its "go" or "No go" . How can it think?
-
I was actually being flippant when making that remark.
Nobody has ever suggested that the DLM system can "think" at all. What I am suggesting, and I will hold to that, is that it does not appear to always work in the same way, which causes frustration for those involved.
I think you're over-simplifying it by saying it's "go" or "no go". The changes it makes to lines certainly don't seem to follow any straightforward rules - and there are instances of people stuck on 15dB with very solid lines after a temporary freak condition caused a few disconnects. Conversely there are people stuck on the default of 6dB with problems, who would love for the SNR to be raised automatically.
If it was (a) made public exactly how it did work (or how it is indended to work), and (b) it always worked in a predictable and sensible way, then perhaps end users who fall foul of its logic decisions would be more forgiving of it.
EZZER is 99% correct and an insignificany 1% wrong.
Please do elaborate? I'd be interested (as I'm sure Ezzer himself would!) in what he is wrong about?
-
Im sure that any resonable request to BT and its suppliers would or should result in the formal explanation in the "Plain English language" they should be proud to extol its virtues to all your site members.
-
Hmm, to be honest I never really thought of asking BT for an explanation - I suppose I expected that if they were willing to make it public that it would be on the BT wholesale or Openreach sites somewhere.
I did find a STIN document (suppliers trial information note) that stated somewhere that when Wholesale Broadband Connect is brought out of trial and fully launched as a product, that improvements to DLM will, amongst other things, "improve response times" - which hopefully means it will improve the time taken for it to react to changes! Apart from that, I couldn't really find any other official information.
Do you have any more info about it's workings at all? Because I'd love to understand why exactly it does what it does in different situations!
Thanks :)