Kitz Forum
Broadband Related => ADSL Issues => Topic started by: roseway on June 17, 2011, 07:08:45 PM
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The question arose in this thread, (http://forum.kitz.co.uk/index.php/topic,9415.0.html) about how DLM responds to the router being switched off periodically, and there was some disagreement which I would like to explore further to try to get to the truth. Basically one party says that switching off the router a few times a day will not trigger DLM into raising the target noise margin, and another party says that even switching it off once a day at night will trigger a response from DLM, which will eventually result in a substantial reduction in the connection speed.
This isn't personal, by the way, and I'm quite happy to be shown to be wrong, but I would welcome any contributions to the debate.
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Thanks Eric.
Also, on the back of this, Eric stated that in the early days of Broadband, most routers were USB powered and as such were switched off as soon as the PC/Laptop was switched off. Back then though, only fixed-rate Broadband was available and wasn't tied-in to the DLM management sytems we now have on rate-adaptive products.
So, my belief (and that of all SP's) is that by turning the router/Hubs off on a regular basis, ie- every evening, then one's speed will suffer enormously after a certain period of time. I'm not saying that turning it off every now and again will affect it, but at least once a day will !!
As per Eric's comments, it's in no way personal .............. I just know I'm right. ;D
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Also, on the back of this, Eric stated that in the early days of Broadband, most routers were USB powered and as such were switched off as soon as the PC/Laptop was switched off. Back then though, only fixed-rate Broadband was available and wasn't tied-in to the DLM management sytems we now have on rate-adaptive products.
I accept that point.
But on reflection, not entirely. As HP says below, lots of USB modems were still in use when rate adaptive ADSL started up.
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Although, just to confuse things, many USB ADSL modems were fully capable of working on rate-adaptive lines at the same speed as a standalone modem-router, and I've seen many in exactly such use.
For BT's DLM to not cope properly with that scenario would be a major oversight. :-X
(not that many around now though)
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I've got a green frog!
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So, my belief (and that of all SP's) is that by turning the router/Hubs off on a regular basis, ie- every evening, then one's speed will suffer enormously after a certain period of time. I'm not saying that turning it off every now and again will affect it, but at least once a day will !!
This is the point which I dispute. Anyone who becomes the subject of a discussion between their ISP and OR will have some sort of undiagnosed problem with their connection. It may well be assumed that the fact that some of them turn off their router periodically is a contributing cause of the problem, but that's a long way short of proven.
Over the years I've seen many examples of people who regularly turn off their routers at night with no ill effect. I can't think of any reason why the designers of DLM would want to make it so sensitive to something which lots of people will want to do, if only for 'green' reasons (or 'granny' reasons :) ).
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Hi:
Smacked wrist for me for posting in the wrong thread, but here is what I wrote regrading the DLM question:
....and a fixed rate is what I have now. I was put onto a 4mb speed (12db) fixed speed as part of the trouble shooting/resolution when I recently had a bad network issue. And personally its suits me perfectly - the connection is stable and now performs very well (touch wood). Bearing in mind that I'm a bit of distance from the exchange I would rather have much improved stability/reliability at the expense of sacrificing some speed. And it means I can turn the router off at night !
Being controversial - Is the DLM worth it unless you have a need for utmost speed?
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I've got a green frog!
I've got a Tiscali Speedtouch 330 and Vista drivers - I can even make it work with Windows 7 64-bit!
(not that I want to - it was just an academic exercise)
But they are still out there so it would be really good to know "the truth".
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http://uk.answers.yahoo.com/question/index?qid=20101105095925AAZn083
http://www.diynot.com/forums/viewtopic.php?p=1969280&sid=b34fbc06ac850b9e9a66b92db9ed08fe
2 quick web finds ...........
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TBH , for every web page I find backing up my sentiments, there's another stating different.
I think there's clarity needed here. I'm saying that if the Hub/Router is turned off every night until the following morning, not switched off then back on again as a lot of the threads seem to infer.
To reiterate, when I have co-op calls with the ISP's they also concur with the fact that switching ones modem off on a daily basis is detrimental to the circuits health.
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Hi Guys,
This is an interesting discussion going on. I just noticed it.
So, when I go on holidays for a week or two, I can turn the router off (for safety reasons) without any worries of being penalised by the DLM. Am I correct in this assumption?
Archie.
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Yes.
IMHO (and the SP's), the DLM likes to be able to 'talk' with the router/Hub at all times. The key is stability. If you turn it off once for 2 weeks, this is hardly 'an ongoing issue'. If however, you turn it off each and every evening for long periods, the DLM quite rightly 'sees' this as an underlying fault and raises the SNR steadily until it acyually 'caps' the line at it's lowest speed.
Please, please do not take my word for this. Ring your SP's techy peeps and ask them. ;D
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Hi
I used a Speedtouch 330 when I first upgraded to 8 Max and had no problem with the target SNR .Had plenty of problems with Tiscaly though,but that was another tale of woe .
Regards Jeff
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I used a Speedtouch 330 when I first upgraded to 8 Max and had no problem with the target SNR .Had plenty of problems with Tiscaly though,
Me too on both counts; 8128kbps sync but it was traffic management nightmare every evening. >:D
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the DLM quite rightly 'sees' this as an underlying fault and raises the SNR steadily until it acyually 'caps' the line at it's lowest speed.
There are two things wrong with this:-
- it's not "quite rightly" if the router sends the dying gasp message to inform DLM that it's doing a power down. It's my understanding that most ADSL routers do send the dying gasp message, but I have no hard information to back that up.
- DLM doesn't keep on slowing down the connection until it gets to the lowest speed. It increases the target noise margin to a maximum of 15 dB, and the eventual connection speed is whatever results from that noise margin on the line in question.
To reiterate, when I have co-op calls with the ISP's they also concur with the fact that switching ones modem off on a daily basis is detrimental to the circuits health.
I'm not doubting that this has been your experience, but I do question whether the ISP reps who agreed with this were really technically qualified. If they were the typical first line support staff employed by the big ISPs then their technical opinions don't really rate very highly. I'm hoping that one or two of the reps with real technical knowledge will contribute here.
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Until two years ago my brother in law's system (running Redmond 'doze XP) was making its broadband connection via a USB port to the ISP supplied "horseshoe crab" (as I called it). When the system was powered off the USB modem was, therefore, powered down. There was never any problem with his throughput speed. Eventually, as he wanted to have wireless capabilities, he contacted his ISP who then provided him with a more up-to-date modem/router/WAP connecting via the system's Ethernet port.
My copper pair is completely unbundled -- I am LLU, with TalkTalk as my ISP. I mention my ISP as it may have some relevance due to being different equipment from that of BT. From day one, I have always powered off my modem/router at the end of the day and switched it back on the next morning. At present, I am not using my 2Wire 2700HGV but my Netgear DG834Gv5. Here are the current statistics --
/ # adsl version
Version : 1.12
DriverVersion : 1.75
APIVersion : GS_API_652
FirmwareVersion : E.25.41.64 A
DspVersion : 0x000000e1
/ # adsl opmode
Current trained adsl mode : G.Dmt
/ # adsl channel
Current trained adsl path : Interleaved
Downstream Bit Rate : 4192000 bps
Upstream Bit Rate : 896000 bps
/ # adsl margin
Downstream Noise Margin : 9.0 dB
Downstream Attenuation : 51.0 dB
Downstream Power : 18.9 dBm
Upstream Noise Margin : 9 dB
Upstream Attenuation : 29.0 dB
Upstream Power : 12.4 dBm
/ # adsl perf
============= NEAR END ===========
FEC : 10
CRC : 0
HEC : 0
============= FAR END ============
FEC : 0
CRC : 0
HEC : 0
/ # adsl defects
============== NEAR END =============
ES (Count of errored seconds): 0
SES (Count of Severely errored seconds): 0
LOS (Count of Loss of signal): 0
============== FAR END ==============
ES (Count of errored seconds): 0
SES (Count of Severely errored seconds): 0
LOS (Count of Loss of signal): 0
Note that although I am connected to 21CN equipment that is ADSL2+ capable, my service is "Up to 8 Mbps" i.e. is capped at 8 Mbps. As a result of that cap and due to the fact that I still have not rationalised my internal wiring :-[ I have set the DG834G to use G.Dmt.
I would appreciate an analysis of the statistics by one of the appropriate experts (you know who you are ::) ) . . . please pretend that I am a novice and know nothing.
Perhaps, once I have rationalised my internal wiring, I should do the required experiment -- contact my ISP and request that my download SNRM be set to 6 dB and then leave my modem/router constantly powered up?
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@ Eric,
Perhaps it would also help if DLM functions were considered in the context of both 20CN and 21CN systems, whether on ADSL or ADSL2?
I have observed the results of the DLM logic on our long lines that most 21CN ADSL lines do not resynchronise nearly as often as 20CN ones.
Also that the IP profile change responds very rapidly and the speed steps are different and I think more of them are defined.
With the new double entry BT speed tests, IP profiles are recorded for both up stream and downstream values.
The sync speed often increases a little and the noise margin decreases.
How much these observations are just down to Huawei / Infineon compatible chip sets and how much might be due to different DLM logic is quite unclear to me.
( I have also noted that TalkTalk + O2 LLU and Orange + possibly some BT services have been configured for ADSL2 on long lines where in theory they should remain on ADSL.)
Kind regards,
Walter
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@ Eric,
Perhaps it would also help if DLM functions were considered in the context of both 20CN and 21CN systems, whether on ADSL or ADSL2?
I have observed the results of the DLM logic on our long lines that most 21CN ADSL lines do not resynchronise nearly as often as 20CN ones.
Also that the IP profile change responds very rapidly and the speed steps are different and I think more of them are defined.
With the new double entry BT speed tests, IP profiles are recorded for both up stream and downstream values.
The sync speed often increases a little and the noise margin decreases.
How much these observations are just down to Huawei / Infineon compatible chip sets and how much might be due to different DLM logic is quite unclear to me.
( I have also noted that TalkTalk + O2 LLU and Orange + possibly some BT services have been configured for ADSL2 on long lines where in theory they should remain on ADSL.)
Kind regards,
Walter
That again flies in the face of what I see on a daily basis, and with my own circuit as well. My 'uptime' when on 20CN was measured in many months, my 'uptime' on 21CN is measured in very few days. 21CN is far more unstable with it trying to transmit data at the higher end of the 2.2Meg frequencies imo.
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@razpaq - Do you think that instability is ADSL2+ vs ADSL1, or something specific to your circuit/locality or a "feature" of the BT implementation of ADSL2+?
Obviously if it is generally less stable on ADSL2+ (and colloquially I'd say that agrees with what I hear, on all ISP's) then how DLM works and whether it is different on ADSL2+ is significant.
I'm in the fortunate position of "Being" on an LLU non-DLM ADSL2+ connection, which has been running at 19444kbps (interleaved) with a nominal 3dB target noise margin since the last router reboot - 402 hours ago (over 2 weeks). (I can't run non-interleaved for any length of time due to variable interference from an unknown source)
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Sorry HP, i've read your post a couple of times and am not 100% sure what you are asking mate ?
All I know and can comment on, is what I see on a day-to-day basis. Add to that my own personal experience of my home circuit, and I can honestly say that 21CN is far, far more unstable than 20CN. I personally put it down to the high ammount of 'errors' on 21CN circuits (due to the extremely high frequencies utilised), which in turn makes the DLM go into overdrive.
As I say, this is IMHO. Walter has obviously got his own findings from his own customers.
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am not 100% sure what you are asking mate
Sorry, sometimes I ramble....
Anyway your answer is clear enough, thanks.
My own experience (which includes many of my clients) is that ADSL2+ is indeed inherently less stable and that DLM can be quite brutal in dealing with that.
(though on my own exchange the only ADSL2+ is LLU so my immediate area isn't "afflicted" so much)
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@burakkucat: The stats you posted above look quite reasonable for your 51 dB attenuation, but it looks as though your target noise margin may have been raised to 9dB by DLM at some point. We could only be sure of this by seeing what your noise margin is immediately after a router reboot.
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We could only be sure of this by seeing what your noise margin is immediately after a router reboot.
That is easily obtained --
/ # adsl margin
Downstream Noise Margin : 8.5 dB
Downstream Attenuation : 51.0 dB
Downstream Power : 19.2 dBm
Upstream Noise Margin : 10 dB
Upstream Attenuation : 29.0 dB
Upstream Power : 12.4 dBm
/ #
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So your target noise margin has almost certainly been raised to 9 dB.
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Now I've just seen something interesting in the PlusNet forums.
A customer was complaining about slow speeds. PN staff confirmed he was ADSL1 and no ADSL2+ was available through them.
They then said:
"Looking at your recent speedtest, your IP profile has dropped down from 7150kbps to 500kbps. Our connection logs are also showing that your router is powered off during the night. Can you confirm to us if you are turning the router off?. If you are, can you ensure you keep your router switched on so your IP profile will raise back up to 7150kbps"
Now, reading that CAREFULLY they're not actually saying that turning it off caused the problem, but are saying recovery will be helped by leaving it on 24*7. :graduate:
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That would indeed make some sense.
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Hi
I am going to have to read up again on the way the DLM updates the profile (Target snr and interleave ). 2 things I remember is that ar ecord is kept for errors and or Resynchs in 96 15 minute blocks over for every 24 hrs , and this data is assessed every 24 hrs .Then the DLM actions profile changes as appropriate . BUT there are other factors as well. All this is related to Target snr and interleave
Nowhere have I seen anything that actually has any bearing on the IP profile ,this is a direct result of a bad synch and it is known that there is a variable recovery time depending on the % difference. Obviously many bad synchs would result in the Target SNR and or interleave depth to be increased .
Now whether switching off router overnight slows any recovery of the IP profile I am not sure . Even during initial training period you are nor required to leave router on 24/7 . All connections of 15 minutes or more are valid for assessing the line.
Regards Jeff
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Gentlefolk,
Sorry I have been away. I expect the reason I observe the good 21CN stability is that we try to insist that all long line services remains on ADSL (1) G.DMT which I think should not allow the higher frequencies to be used.
I suspect that many are not heeding the advice from e.g. here:-
http://support.zen.co.uk/kb/KnowledgebaseArticle.aspx?ArticleID=11125
My experience suggests that it's well worth being transferred to 21CN even on long lines PROVIDED you stay on ADSL 1. We still have pretty awful speeds but the stability does seem to help prevent wider throughput speed fluctuations we experienced on 20CN ccts. In any case I understand that eventually there will be no option but to be transferred.
Hence my original queries about how DLM works differently on a 21CN line.
Here's my best example where you will see the service was transferred on 15 March 2011 with the line card changing from TI to Infineon.
Kind regards,
Walter
[attachment deleted by admin]
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Now I've just seen something interesting in the PlusNet forums.
A customer was complaining about slow speeds. PN staff confirmed he was ADSL1 and no ADSL2+ was available through them.
They then said:
"Looking at your recent speedtest, your IP profile has dropped down from 7150kbps to 500kbps. Our connection logs are also showing that your router is powered off during the night. Can you confirm to us if you are turning the router off?. If you are, can you ensure you keep your router switched on so your IP profile will raise back up to 7150kbps"
Now, reading that CAREFULLY they're not actually saying that turning it off caused the problem, but are saying recovery will be helped by leaving it on 24*7. :graduate:
Thanks for the 'post up' HP. Reading that CAREFULLY heavily suggests, that turning your router off every evening is detrimental to the circuit. ;D
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Thanks for the 'post up' HP. Reading that CAREFULLY heavily suggests, that turning your router off every evening is detrimental to the circuit. ;D
Only detrimental in that, in the opinion of the writer, switching off the router at night may delay the recovery of the IP profile after it was depressed by a low speed re-sync.
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Eric, you're a tough nut to crack old boy. ;D
"Looking at your recent speedtest, your IP profile has dropped down from 7150kbps to 500kbps. Our connection logs are also showing that your router is powered off during the night. Can you confirm to us if you are turning the router off?. If you are, can you ensure you keep your router switched on so your IP profile will raise back up to 7150kbps"
Granted, the above doesn't actually say in 'Bold, New Roman underlined' text that turning the router off every night, is the definitive cause of the EU's problem. But my neighbours 8yr old child could draw the conclusion that it is highly likely to be the issue.
I don't think your ever going to agree with me on this Eric, so lets draw a line under it and you keep switching your router off and I'll keep mine on. ;D
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Remember this is a CS agent talking to a non-technical customer, caution is advised. ;)
They're just advising the customer what to do to get their service back ASAP, I'm wary of trying to read too much into it.
But it's all "grist to the mill" as they say.....
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Hear hear HP !
Might I suggest that Eric is not a tough nut, but is attempting to establish systems design characteristics and parameters.
IMHO circumstantial evidence can help but is no substitute for the actual design specification.
Now all we need is for the design engineer to come forth!
Kind regards,
Walter
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There seems a very simple solution to this discussion.
2 of you on stable BT connections must experiment over a 2 week period then report back, one turns the router off every night and the other doesn't.
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I'm tempted to do just that, but realistically it would need lots of participants to get a statistically significant result.
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@ Oranged,
I'm afraid it's not so simple for me as I'm remote-monitoring a number of 2Wire 21CN ADSL1 services for different friends who might well be very peeved if I tried to ex-communicate them !
I can and do reboot modems remotely with some caution, but I can't actually switch them off remotely, nor would I wish to disturb their nocturnal activities !
Kind regards,
Walter
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I don’t know if this helps or hinders the debate, but I’m on an ADSL2 4 Mb (Virgin National) fixed line (4mb capped according to RP and I must bow to his superior knowledge). I understand this is fairly a long line from the exchange and has a 54Mb attenuation downstream.
The line was configured to be fixed/capped in this way as a result of lots of problems I was experiencing a few months ago with stability of the connection and was done as part of the troubleshooting by the ISP. As you might expect the connection speeds were going all over the place during this period. Finally what was probably a network fault was fixed as a result of the OR engineer changing the copper in the network and remaking connections.
However the fixed (capped) speed was left as it was after the network problem was resolved..
I now ALWAYS connect at 4Mb downstream and 864K upstream. It never ever ever varies. The router is turned off overnight and also sometimes on/off several times during the day as the PC is used by several users.
I’m more than happy with this as the connection is stable and reliable (fingers crossed!).
I’ll be the first to admit I’m not an expert, but I would ask: Is the DLM facility worth it unless you are a attempting to wring the last ounce of speed out of the line?
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Hi
Quote : However the fixed (capped) speed was left as it was after the network problem was resolved..
I now ALWAYS connect at 4Mb downstream and 864K upstream. It never ever ever varies.
Because you are capped You will always connect at that capped speed . There is no negotiation to get the optimal speed for your line. You will either connect or not connect .
so switching off is not an issue . Every time you connect each time it will try to connect at that one speed .
Regards Jeff
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Quite recently I have disclosed that I have a LLU connection provided by TalkTalk for my telephone and broadband service. Taking a little bit of a deeper look, it can be seen that the backhaul is that of Opal Telecom -- so no surprises there.
In view of RP's recent advice with regards to a modem/router being left constantly powered up, I decided to ask at the TalkTalk Members' Forum what TT themselves would advise. Here follows the response I received --
Talk Talk has DLM (Dynamic Line Management) active on all lines by default, and this will try to give you the best balance of speed and stability.
If your router keeps switching off, DLM can see this as instability and consequently slow your speeds to the slowest available in order to 'stabilise' the line.
Because of this, it is best to leave the router on 24/7 365 days, and indeed all routers are designed to be used this way, the router is waiting for a device to need it, and they use very little power when left switched on.
If you do want to switch it off, it will in most cases cause no ill effects with DLM as long as there is a period of several hours between such power down/power up, so it is as always 'up to you', however in the same way that DLM can slow your line, if the router is left 'on', DLM will see a stable line and speed the connection up to the fastest available profile that your line can handle, however if the router is always switched off/on, then it will remain always on the default profile which is somewhat conservative for many lines in terms of speed.
For completeness, this is my acknowledgement --
Thank you for the welcome and your reply. Once I have finally finished rationalising my internal wiring and, hence, the odd disturbance to the connection I will then follow that advice.
Currently my target SNRM is set to 9 dB so, once everything is finished at my end, I will then request a reset to 6 dB. But that will be in the future.
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Gentlefolk,
Does this not suggest that we need to record the workings for LLU and BT W DLM functions as it is unlikely that they will all use exactly the same logic?
Before 21CN I seem to remember that several people selected O2 services precisely because they did not like the way the BT DLM worked.
Kind regards,
Walter
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You're quite right Walter. Some years ago, BT applied for a patent for the system which we call DLM, but undoubtedly the LLU operators use their own differently configured systems.
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Quite recently I have disclosed that I have a LLU connection provided by TalkTalk for my telephone and broadband service. Taking a little bit of a deeper look, it can be seen that the backhaul is that of Opal Telecom -- so no surprises there.
In view of RP's recent advice with regards to a modem/router being left constantly powered up, I decided to ask at the TalkTalk Members' Forum what TT themselves would advise. Here follows the response I received --
Talk Talk has DLM (Dynamic Line Management) active on all lines by default, and this will try to give you the best balance of speed and stability.
If your router keeps switching off, DLM can see this as instability and consequently slow your speeds to the slowest available in order to 'stabilise' the line.
Because of this, it is best to leave the router on 24/7 365 days, and indeed all routers are designed to be used this way, the router is waiting for a device to need it, and they use very little power when left switched on.
If you do want to switch it off, it will in most cases cause no ill effects with DLM as long as there is a period of several hours between such power down/power up, so it is as always 'up to you', however in the same way that DLM can slow your line, if the router is left 'on', DLM will see a stable line and speed the connection up to the fastest available profile that your line can handle, however if the router is always switched off/on, then it will remain always on the default profile which is somewhat conservative for many lines in terms of speed.
For completeness, this is my acknowledgement --
Thank you for the welcome and your reply. Once I have finally finished rationalising my internal wiring and, hence, the odd disturbance to the connection I will then follow that advice.
Currently my target SNRM is set to 9 dB so, once everything is finished at my end, I will then request a reset to 6 dB. But that will be in the future.
Nice post B*Cat ......... ;D However, I think we'll have to take photgraphic evidence of the actual DLM stripped intp pieces, before some of the lads will accept this advice ??!! ;) ;D
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Nice post B*Cat ......... ;D However, I think we'll have to take photgraphic evidence of the actual DLM stripped intp pieces, before some of the lads will accept this advice ??!! ;) ;D
Sorry to be argumentative, but the advice from TT doesn't support your viewpoint. For a start, it refers to a TalkTalk LLU connection, and their version of DLM is undoubtedly different to that used by BT. Secondly, they agree that switching off the router periodically doesn't carry a risk of triggering their DLM into slowing down the connection. What it may do in their system is result in a stuck profile.
I've never disputed that leaving the router on 24/7 is the best option in general, but switching it off each night won't result in the progressive slowdown which you have asserted.
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Nice post B*Cat ......... ;D However, I think we'll have to take photgraphic evidence of the actual DLM stripped intp pieces, before some of the lads will accept this advice ??!! ;) ;D
Sorry to be argumentative, but the advice from TT doesn't support your viewpoint. For a start, it refers to a TalkTalk LLU connection, and their version of DLM is undoubtedly different to that used by BT. Secondly, they agree that switching off the router periodically doesn't carry a risk of triggering their DLM into slowing down the connection. What it may do in their system is result in a stuck profile.
I've never disputed that leaving the router on 24/7 is the best option in general, but switching it off each night won't result in the progressive slowdown which you have asserted.
This is just getting plain silly. :) To reiterate, not only have I 'asserted' that switching the router off every evening can and does harm the speeds provided, I've also said that the ISP's I deal with on a daily basis give this information.
B*Cat has offered up this from his SP ........ "If your router keeps switching off, DLM can see this as instability and consequently slow your speeds to the slowest available in order to 'stabilise' the line."
There's no conspiracy here Eric mate, this is what the engineers and ISP's have found to be the case. You may spend all day and night on here looking for the one exception to the rule that there always seems to be, but on the whole the message is switching your router off is detrimental to your speeds.
Accept defeat graciously sir. :P ;D
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Gentlefolk,
I second Eric's comments. Unless and until we have the complete design of ALL DLMs published (Under suitable patent protection for the investors), we are all blundering around in the dark. Furthermore just because one piece of hearsay / advice works in one particular set of circumstances I cannot see there is any guarantee that it will be universally suitable.
Kind regards,
Walter
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Walter ...... it wouldn't be you sir if you'd said anything different. I just know you and Eric are gonna join forces and become one. Good luck, but flogging a dead horse springs to mind. ;D ;D ;D
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I'm sorry RP, but you're crossing the line there and making this a personal issue. It isn't as far as I'm concerned, nor do I believe that it's personal for Walter. And we're not involved in any joining of forces, but each expressing our views, based on our individual experiences and knowledge.
If anyone has anything further to contribute I would like to hear it, but this sniping has got to stop.
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Unless and until we have the complete design of ALL DLMs published (Under suitable patent protection for the investors), we are all blundering around in the dark.
Not necessarily.
We "could" treat the DLM as a "black box" and do some testing, though as noted above just 2 users would prove nothing. It would need a lot of people prepared to "sacrifice" their line speed, probably allied with a fair bit of detective on what sort of exchange equipment and services they are connected to.
Probably impractical. :(
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Just to join in the fun ;D, In my case DLM is not working...I had an interruption to my power on Friday due to NIE replacing poles and cutting branches...ip profile now as follows
Download speedachieved during the test was - 1801 Kbps
For your connection, the acceptable range of speeds is 400-2000 Kbps.
Additional Information:
Your DSL Connection Rate :4352 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 2000 Kbps
The intersting thing to note is "acceptable range 400-2000kps" which means I'm on an "up to 2 meg service" rather than 8...each time this happens (ANY disconnection) I have to get BT to reset the profile manually...it really sucks!!!
BTW, does anyone know of the new profile system being implemented nationwide, were after a re-sync your profile immediately goes to 88.2% of your sync speed?
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I don't agree that just 2 users cannot prove this point one way or the other.
A BT IPStream interleaved connection with DLM will operate the same for every user but to be certain the 2 users must have BT as their ISP.
The DLM doesn't differentiate users, so using just 2 examples will, if razpag is correct, prove the point.
LLU DLMs all operate, I believe, in different ways. I think TT and Sky operate 24/7 but O2/BE only operate in the initial few days of a new connection and is then turned off. So it is a pointless exercise trying to compare different LLU users or even comparing LLU to IPStream/WBC.
The other aspect is I thought that BT were making technical changes to the way their DLM functioned in respect of how it manages the recovery after a noise incident.
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The other aspect is I thought that BT were making technical changes to the way their DLM functioned in respect of how it manages the recovery after a noise incident.
Apparently it will be 88.2% of the sync speed but I'm not sure if it's 21CN exchanges only...but someting seems to be going wrong at the moment as the BT forum is full of people with stuck profiles like myself....
On a side note, does anyone know of ANY instance of when DLM rectified target SNR from, say 15dB< to 6dB in ANY timescale as from my experience the whole thing is a lie used to cap EU's bandwidth...Someone really should explain this "complicated algorthim" :'(
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On a side note, does anyone know of ANY instance of when DLM rectified target SNR from, say 15dB< to 6dB in ANY timescale as from my experience the whole thing is a lie used to cap EU's bandwidth...Someone really should explain this "complicated algorthim" :'(
My target margin has been up to 15 dB and back down to 6 dB over a period of months without any manual intervention. And I know at least one other member here has also been though it - in his case he deliberately tweaked his target noise margin up to reduce the error rate, and this does seem to have speeded up the process of noise margin reduction.
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My target margin has been up to 15 dB and back down to 6 dB over a period of months without any manual intervention. And I know at least one other member here has also been though it - in his case he deliberately tweaked his target noise margin up to reduce the error rate, and this does seem to have speeded up the process of noise margin reduction.
Thanks for that...so DLM isn't like "the Tooth Fairy"?...however, I have to question if this "period of months" isn't in the interests of capping End-Users through-puts, rather than stability, as the time-scale you refer to is surely a bit draconian?...
Many rural customers (like myself) will struggle to maintain a connection for a period of months as high winds and storms can cause frquent electrical outtages..I do use a netgear to tweak it, but there is something afoot with BTwholesales system for profiles at the minute as it seems beyond co-incidence that so many customers are having stuck profile issues..
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I agree that DLM in the form it's taken to date has been too harsh on the user - it does make it feel as though you're being punished for something you haven't done. Whether it was done that way with the deliberate intention to reduce throughput I really can't say.
There does seem to be some adjustment taking place at the moment. DLM on ADSL2+ works a bit differently anyway, and maybe they're updating DLM on ADSL to work the same way.
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Gentlefolk,
I also concur that something has changed with the line management functions on the BT Wholesale 7 km ADSL (1) 21CN rural line with an average attenuation of about 79 dB that I'm monitoring.
Since the change-over date of 15 March 2011 there have, remarkably, been no power outages. (I know this as the 2Wire clears down the diagnostic data after a power fail or a system soft-reset.) The line re-synced after change-over from 576 Kbps up to 896 Kbps and then twice on 7 May to 960 Kbps and 5 times on 19 May up to 1056 Kbps and back down to 960 Kbps but has since remained absolutely stable. Given the otherwise stable line it could well be human intervention caused the 19 May multiple resyncs. I am unable to say how much of this is due to the new Infineon line card in the exchange and the Infineon chip in the 2Wire 2700HGV and how much is due to the possibly different line management functions. However I think we can deduce that the synchronisation logic possibly together with monitoring function outputs have changed since the BT line speed tester now reports both up and downstream speeds and IP profiles and the numerical values of the IP Profile steps are different.
Conversely others have reported a deterioration in 21CN ADSL2+ stability.
If one considers all the possible permutations I suggest it will be a significant challenge to define how observations on even a few lines can define precisely how BT's line management functions work.
Please note in this context I have deliberately not used the DLM acronym as some of these observations could be the result of other algorithms. Hence my suggestion that detailed specifications would provide a far more satisfactory solution albeit that is probably wishful thinking.
Kind regards,
Walter
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I'm sorry RP, but you're crossing the line there and making this a personal issue. It isn't as far as I'm concerned, nor do I believe that it's personal for Walter. And we're not involved in any joining of forces, but each expressing our views, based on our individual experiences and knowledge.
If anyone has anything further to contribute I would like to hear it, but this sniping has got to stop.
WHAT ??? Hells bells Eric, tad sensitive aren't we ??
How on gods earth am I making it personal ?? You say switching the hub off at night has no effect on speed, I say it does. It's called a difference of opinion, not a personal attack. Just because I posted up "Admit defeat graciously", followed by blatantly obvious emoticons to show it was meant in a jokey fashion, doesn't warrant you suggesting "I've crossed the line".
Likewise the comment about Walter, I genuinely meant that as a moment of mirth and would like to think everbody else reading this thread thought so too ??
You've got it sooo wrong there Eric. I like to post not only informatively, but also as a person would speak in a face-to-face situation. Not - just - posting - like - a - robot - without - any - sense - of - humour. ;D
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RE: my problems with DLM...just got a resync on my router and see the target SNR is 6dB again...also got an email from one of the mods on their forum that
"occasionally lines can be set outside of DLM control following a difficult fault. It is possible that this was done previously with your connection and left this way."
Does anyone know how often this is the case?
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Being a academic research scientist earlier in my life taught me many things. (Fortunately I haven't yet forgotten everything. ::) )
From practical experience gained over 45 years (minimum) I have discovered that GPO, BT & now OR Engineering staff are extremely knowledgeable people who, if they have the time to spare, are more than willing to discuss the technology involved in their daily work. (b*cat raises his paw to salute Messrs Razpag, Ezzer & Gumble (His Lordship thereof), to name just a few.)
If it came down to having to decide upon advice provided by an ISP's CS representative versus that provided by an OR employee, the latter would always have higher status. For my particular case -- which is LLU -- both are in agreement. As of yesterday, I started a crude experiment -- I did not power off my DG834Gv5 last night. I intend to leave it alone and just check its vital statistics once per day. Obviously until I complete my rewiring job, my situation is not optimal. (The DG834Gv5 is fed by a RJ11 plug to RJ11 socket extension lead from the ADSL socket on the filtered faceplate at the NTE5A. Oops. :-[ ) However I still hope that some information may be forthcoming.
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Thank you for vote of confidence B*Cat. But all I try to do is share first hand experience with others, regarding my day-to-day work.
I'm not some sort of deity that knows it all, far from it in fact as somebody pointed out on a REIN thread on this DG, where one of my comments was incorrect.
I will always stand corrected as I'm not (nor is anybody) perfect. I got the REIN situation slightly wrong due to not being trained in that particular area, but am due to be at the end of this month.
But, for this rather emotive subject of switching the router off, I do have knowledge of its effect and this is backed up by every ISP's technical people that I speak with on a daily basis. I don't have reams of paper backing up each individuals router stats taken over a month, nor do I have the circit diagram of the DLM's inner workings. I do however have a Field Log Book detailing umpteen EU visits where the cause of their 'slow-speeds' has indeed been due to switching off ones router. There has not been a single re-visit on these jobs that I am aware of, since making the EU conscious of the need to leave the router powered up 24/7.
Another common thread to these type of jobs is they are usually (but not always for the pedants :)) what we would calss as 'Early Life failures' (ELF's), as the EU will have reported a problem with their circuit within the first month of connection. There are no underlying electrical fault conditions, only the fact they switch their router off every evening.
Columbo I am not, but if it looks like a penguin and it walks like a penguin, then there's a good chance it is a penguin !! ;D ;D Yes, that's jokingly aimed at you Eric. No hard feelings please, I genuinely wasn't making this a personal thing in any way, it just happened to be your good-self that had the 'other point-of-view', and thats why my postings were mainly addressed to you. ;D
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Thank you RP, we'll shake hands and agree not to come to blows. But I do still disagree with you. :)
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That'll do for me. ;D
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I got the REIN situation slightly wrong due to not being trained in that particular area, but am due to be at the end of this month.
Mr Pag,
Once that has occurred and you have a few "good" REIN stories noted down in your log book, perhaps you could provide us with some interesting technical anecdotes?
Something for the future, please. ;)
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I think informed information from myself, regarding REIN, will be a good while away yet B*Cat. Would you believe that the course is only 5 hours long ?????!!!!!!!
I'm hoping that just to cover the 'legals', as I'm sure one of my old friends on OR who also happens to be a trainer, mentioned that the trainee has to assist on a 'live' REIN fault before gaining full accreditation. I do hope so, as I have been on a couple of jobs where i've sourced the REIN myself, but they were easy. I want to be assisting on an extremely hard-to-find fault.
TBH, I think i'll acquire more relevant info from you guys on here, until i'm au-fait with it all. ;D
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Hi
quote :until i'm au-fait with it all
That may take a long time ,its one of those odd things . The more you learn the more you realise how little you Know ;D
Regards Jeff
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That is so true Jeff. That's why I'm hoping to prise info from you guys in the know !!!
The problem is, actual 'live' REIN faults aren't as common as you might think within an engineers PWA (Preferred Work Allocation). I'll probably be lucky to get to 3/4 in a year. ;D
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I think people often believe that they are subject to REIN when it's actually just ordinary electrical interference, which is common, probably universal.
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Hi
quotes from Talk talk
quote 1 :If your router keeps switching off, DLM can see this as instability and consequently slow your speeds to the slowest available in order to 'stabilise' the line.
quote 2 : If you do want to switch it off, it will in most cases cause no ill effects with DLM as long as there is a period of several hours between such power down/power up
quote 3 :if the router is left 'on',DLM will see a stable line and speed the connection up to the fastest available profile that your line can handle, however if the router is always switched off/on,then it will remain always on the default profile which is somewhat conservative for many lines in terms of speed.
quotes 1 and 2 are as understood by most people and are the sort of advice given from this site .
quote 3 well that's a little different but its correct as far as it goes . Again it states as we all understand that continually switching "on"and "off " will result in the line being seeing as unstable .The quote is correct as the DLM will see the line as stable ,it does not imply that switching off once a day will jeopardise that .
Again this is totally in line with the normal advice given from this site
There are other factors to be considered which may have a bearing on the case . Some areas get more problems with stability during different times of the day and it may be better to switch OFF during those hours ,if the router is not required .
Mr RP
this link http://uk.answers.yahoo.com/question/index?qid=20101105095925AAZn083
as far as I can see the consensus was that there was no reason to link the slow down with the switching off the router nightly .
although I have noticed one of the responses is from BT Engi. :)
this one http://www.diynot.com/forums/viewtopic.php?p=1969280&sid=b34fbc06ac850b9e9a66b92db9ed08fe
I must have missed something its about telephone sockets ?
Regards Jeff
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Hi Jeff, whilst I appreciate your input into this debate, and can see where you are coming from ....... I will stick with my own thoughts on this subject, that turning the router off every evening does have a detrimental effect on performance on most lines controlled by DLM.
Again, the 'evidence' provided are just peoples personal views, and whilst they do form an arguement/alternative view to my own, they are just opinions. I can only go from what I know to be fact, and part of that fact is that (copied from my previous posting) ...... 'I have a Field Log Book detailing umpteen EU visits where the cause of their 'slow-speeds' has indeed been due to switching off ones router. There has not been a single re-visit on these jobs that I am aware of, since making the EU conscious of the need to leave the router powered up 24/7.'
Add to the other fact that the ISP's technical people (not sales or front-line) I speak with on regular co-op calls, also have this same opinion, then who am I to argue ???
I really don't know what more I can add to this subject ???. ;D .There are always going to be scenarios that fly in the face of what I'm saying, but I reiterate that my particular stance on this appears to bring about long-standing results for the EU's. That, at the end of the day, is what I'm employed to do.
Cheers Jeff.
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Hi
Something interesting from
EP 2 169 980 A1 EUROPEAN PATENT APPLICATION
Table 2
Stability Metric Very Poor Poor OK Good
Aggressive Re-Trains >10 per hour mtb<3600 mtb<8640 mtb≥8640
Aggressive Errors - mtb<10 mtb<8640 mtb≥8640
Normal Re-Trains >10 per hour mtb<7200 mtb<8640 mtb≥8640
Normal Errors - mtb<300 mtb<8640 mtb≥8640
Stable Re-Trains >10 per hour mtb<28800 mtb<86400 mtb≥86400
Stable Errors - mtb<1000 mtb<28800 mtb≥28800
[0081] In table 2 "mtb" stands for "mean time between" and thus corresponds to the normalised metrics calculated by
dividing the total time in seconds for which the respective line has been in synchronisation over the past 24 hour period
of the monitoring by the number of re-trains or errors recorded in that period. For all cases, in the present embodiment,
if there are more than 10 re-trains in any one hour period, the line is assumed to be very poor, regardless of the number
of errors recorded. For lines operating at an aggressive stability level, if the average time between retrains is less than
once per hour (=3600 seconds) (e.g. 6 re-trains in less than 5 hours of "up-time") or if the average time between errors
is less than one per 10 seconds of up-time, then the line is deemed to be poor; if the average time between re-trains is
less than once every 2.4 hours (but more than once every hour) or the average time between errors is less than once
every 2.4 hours (but more than once every 10 seconds) then the line is deemed to be ok, whereas if the average time
between re-trains is greater than or equal to once every 2.4 hours or if the average time between errors is greater than
or equal to once every 2.4 hours, then the line is deemed to be good. From Table 2 above, it is clear what the thresholds
are for the other stability levels in the same way.
[0082] In an alternative embodiment, the stability levels could operate such that for the most aggressive stability level
the DLM function attempts to keep sync loses to below 12 per 24 hour period (including switching off modems/routers
which count as a sync loss) and to keep the line error free for 98.3% (59/60 seconds) of uptime measured over a 24
hour period; for the normal stability level the DLM function attempts to keep sync loses to below 6 per 24 hour period
and to keep the line error free for 99.8% (599/600 seconds) of uptime measured over a 24 hour period; and for the stable
stability level the DLM function attempts to keep sync loses to below 3 per 24 hour period and to keep the line error free
more than 99.98% (5999/6000 seconds) of uptime measured over a 24 hour period.
Regards Jeff
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Hello
I will give you my experience as to the effects of routine router switch off.
I never used to leave my router on 24/7 because I was a light user and always had a 63+ down attn so was happy to get 1mb speeds. In February this year the broadband became very poor due to HR fault which OR engineer fixed enabling me to connect at 3mb+ with a 53 db attn and 9 db TSRN. I decided to leave HGV2700 on 24/7 because of the improved speeds. However I am on a long rural line and experienced a few random disconnects which could knock my IP Profile down below 2mb.
In May the disconnects became worse and my TSRN had increased to 12 db. BT call centre could see no fault, but said would do some thing to help the stability. I managed to remain connected for 6 days at about 3400 but the profile was still at 2mb. Then I had another noise spike which knocked me down to 1500 IP. After 2 days the IP had increased to 2.5 Mb as I was connecting at 3000 after which I began switching the router off. That speed is all I need and as I connect at about 3400 during the afternoon, it should leave enough leeway.
So I am switched on for about an hour most days. I’ve done this for the last 2 weeks and today I checked the IP Profile which has gone up to 3 Mb which goes against all I’ve heard about needing to leave the router on 24/7 for 3-5 days to get an increase. I don’t think my local exchange has been updated to the new profiling system.
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There's no doubt in my mind that, with a long and slightly dodgy line like yours, switching off at night is a much better option than leaving the router switched on and risking instability during the night. Switching off the router is only a single loss of sync event, whereas a burst of interference when it's connected could result in multiple connection drops.
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Hi Mike W,
I don’t think my local exchange has been updated to the new profiling system.
If you are referring to BT's 21CN you can tell if you have been changed over as the BT Speedtest will now show both a downstream and an upstream entry, whether or not you have asked to remain on ADSL1.
Kind regards,
Walter
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Hi
quote I checked the IP Profile which has gone up to 3 Mb which goes against all I’ve heard about needing to leave the router on 24/7 for 3-5 days to get an increase.
I have not ever thought that, . It might take 3 to 5 days to reset IP profile (which is NOT the same as resetting Target SNR etc .) The actual time it takes is dependant on the % difference between current profile and the final IP profile you could expect.But this is not dependant on being connected 24/7. As far as the IP profile is concerned your synch rate is the governing factor . If you connect with Low synch rate (because of temporary noise on line) then your profile drops . Then within a few days either still connected or if you connect as you require at a good synch rate the the profile will go back up .
Regards Jeff
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@ Jeff,
I am perplexed about the different ways IP Profiles work depending upon whether or not the line is a 21CN one.
For a 21CN line, I believe that the IP Profile now reacts almost immediately and precisely as 88.125 % of the sync speed, presumably whenever the modem re-syncs.
If I'm mistaken somebody please tell me !
Kind regards,
Walter
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Hello all
Walter, my exchange is using G.DMT Annex A and only downstream on BT speedtest.
Jeffbb, I support what you say, I'm only going off the BT forum advice which always says to never disconnect the router in order to get the IP profile higher. It has been better for me, with my unstable line, to turn off the router when not in use, usually off about 23 hrs a day. Of course you need to be re-connecting in a speed range to support the higher profile and my best time is during daytime as long as the weather is not stormy. I know this would not suit a lot of people but it needs to be pointed out more that switching off can be a benefit to those on unstable lines.
Regards Mike
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One point I should mention is that I had a 9 db Target Signal Noise Ratio for over 4 years, being switched off most of the day. Then this year when I left my router on 24/7 and had some bad sessioins of disconnections, the TSRN was increased to 12 db. I conclude that switching off my router had no effect on the TSNR but leaving it on resulted in my TSNR increasing.
Regards Mike
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Hi
I think that the real point is that there is NO absolute correct way for ALL situations . Leaving the Router on 24/7 which is what I tend to do( * see note ).,Is probably the best option for most stable lines . Selective switch off for those that are not on all/ most of the time will do no harm providing its not a case of rebooting many times per day . For others It may be actually beneficial to switch off router during Known bad noise periods . Its a case of making a valued judgement .
Note . If for some reason I have had a unforeseen re synch (power cut ) at the wrong time, (I do have some periods during the day where the SNR margin drops by up to 3db.) ,then I will have re connected at a lower synch rate than normal ,so dropping The IP profile. Monitoring the SNR margin using RS I will reboot when the SNR margin is at the appropriate higher level to give me my normal synch rate .Then the IP profile will return to normal after 2 to 3 days .This is an occasion where leaving my router on 24/7 would leave me with a lower synch rate for many weeks .
Regards Jeff
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Hello Jeffbb
I agree with that last post.
Having gained some Knowledege how broadband works from websites like Kitz has enabled me to get the best out of my broadband. I think the best solution for most people would be the new profiling system.
Regards Mike
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When i had a bad line fault that lasted a year i was told that turning off my router at night would not cause the DLM to raise my SNR or lower my sync, After my line was fixed i was called by someone from BT and told to keep my line on 24/7 for the first 10 days i think it was.
After that i could return to turning it off every night when i went to sleep.
He informed me that the dlm would not consider this as a fault if i was only doing it at night and not every time i switched of my pc.
I have been doing this since march and i still have an IP profile of 5mb and snr has never moved from 6.
So if you ask me from my own experience, turning off the router once a day before you goto sleep has no effect on your SNR or IP profile.
Ps i am now on the new profile system so no longer get 1,1.5,2,2.5 and so on, think its 5.3mb or something stupid like that for my profile now