Question Thread

[#1]

The router's system log information below shows the disconnects that occurred between the 14th and 16th December.  I've attached a graph, produced by Router Stats, to show the downstream SN Margin earlier today.  Also attached are a couple of snapshots produced by DMT before and after the disconnect today.
Router System Log:
Dec 16 12:11:18 PPP link up (Internet)
Dec 16 12:11:01 PPP link down (Internet)
Dec 16 12:10:42 xDSL linestate up (downstream: 12463 kbit/s, upstream: 855 kbit/s; output Power Down: 22.5 dBm, Up: 12.5 dBm;
                                    line Attenuation Down: 33.5 dB, Up: 17.5 dB; snr Margin Down: 6.5 dB, Up: 5.0 dB)
Dec 16 12:10:20 xDSL linestate down
Dec 15 12:13:05 PPP link up (Internet)
Dec 15 12:12:42 PPP link down (Internet)
Dec 15 12:12:25 xDSL linestate up (downstream: 13893 kbit/s, upstream: 855 kbit/s; output Power Down: 23.0 dBm, Up: 12.5 dBm;
                                    line Attenuation Down: 33.0 dB, Up: 17.5 dB; snr Margin Down: 3.5 dB, Up: 5.0 dB)
Dec 15 12:12:02 xDSL linestate down
Dec 14 12:32:48 PPP link up (Internet)
Dec 14 12:11:03 xDSL linestate up (downstream: 13886 kbit/s, upstream: 447 kbit/s; output Power Down: 23.0 dBm, Up: 12.0 dBm;
                                    line Attenuation Down: 33.5 dB, Up: 17.5 dB; snr Margin Down: 3.5 dB, Up: 21.0 dB)
Dec 14 12:10:40 xDSL linestate down

[#2]

I was holding off a report on before and after speeds until my line settled - but it's never settled, and I actually appear to have royally stuffed up my profile and the initial adaptive goings on at the DSLAM end.
I stupidly didn't check the ADSL settings on my Draytek Vigor 2800V ADSL Router, and I've been forcing it to sync as "ADSL1" (G.DMT) up until last night!! 😞
The problem now is that I don't know whether my "problems" (I use that term loosely as all it's been doing really is reducing the speed repeatedly each day) over the past 7 days have been down to forcing syncs as ADSL1, or if there is just a general problem due to ADSL2+ and my line length.
The router has been resyncing every 3/6/12/24 hours or so. I've summarised what I've seen below into just a few major points...
All showing: Date Downstream/Upstream SNR(Down) Att(Down)
DSLAM=ADSL1 / MODEM SYNC = ADSL1
8th 4832000/448000  8.0 50.0
My modem's been pretty stable on this for some time. It had leapt up recently from a more normal 3.8meg or so.
The true download speed has always been around 3.3Mbps regardless.
DSLAM=ADSL2+ / MODEM SYNC = ADSL1
8th 5024000/448000  9.0 50.0
8th 5568000/864000  7.0 45.5
8th 5280000/864000  7.5 45.5
8th 5536000/896000  8.0 45.5
9th 4864000/800000 10.5 45.5
10th 4256000/832000 13.5 45.5
11th  576000/288000 33.0 45.5 (Only for a few minutes)
11th 3936000/832000 14.0 45.5
12th 3776000/832000 16.5 45.5
14th 3680000/768000 17.0 45.5
14th 3808000/928000 16.5 45.5
15th 3072000/896000 20.5 45.5

I then discovered last night that I was actually syncing using ADSL1 G.DMT, so changed this to ADSL2+. I also left the router unplugged last night for an hour to let things settle/reset at the DSLAM end (but to no effect).
DSLAM=ADSL2+ / MODEM SYNC = ADSL2+
17th 3070800/655000 13.0 45.5
17th 3067400/632000 12.0 45.5

The question is - have I screwed up my profile?!?
I didn't expect much uplift in downstream on ADSL2+, in fact, I'd even happily accept a slight reduction to 3.8meg maybe even 3.5meg if it got me a higher upstream.
I had interleaving on before, and still have interleaving on now. I do get CRC errors, etc. Always have though, and ADSL1 seemed to "deal" with a certain level of this without going into a panic.
Has my incorrect forcing of the syncing to ADSL1 done this? Can my profile or whatever be reset again so it can learn the correct speeds again now I've actually got the correct setting on the modem?

[#3]

Interleaving should be enabled on both lines some time today.
pnf - just been through the RADIUS logs and these are the times of the connection drops around 12:10 that I can see since you moved across to 21CN, you first connected at 12:17 on 4/12 and apart the 8th where it didn't drop and 14th where you weren't able to connect at all it is dropping within 8 minutes.
4/12 connected 12:17
5/12 12:13
6/12 12:09
7/12 12:09
8/12 did not disconnect
9/12 12:16
10/12 12:13
11/12 12:17
12/12 12:10
13/12 12:14
14/12 did not connect until 12:32
15/12 12:12
16/12 12:09
I'm wondering 2 things. First is there anything unusual about the 8th? It may be worth focusing on why it didn't drop then rather than why has dropped every other day.

[#4]

Thanks Dave. 
How will I know when interleaving has been switched on?  Is there anything that will indicate it either in the Member Centre or on my router?
There wasn't anything unusual about the 8th as far a I know, but I will check through the router stats that I have been taking to see if anything stands out.

[#5]

Line still stable here at 4480 / 672 on ADSL1. No Interleaving. Excellent.
Question - do I still have to pay for the Increased Uplink speed with 21CN and ADSL1?
Apologies for the outbreak of morse code earlier please ignore it - it was a reply to Barry's signature which was in morse.

[#6]

Quote from: gaptag

The question is - have I screwed up my profile?!? I didn't expect much uplift in downstream on ADSL2+, in fact, I'd even happily accept a slight reduction to 3.8meg maybe even 3.5meg if it got me a higher upstream. I had interleaving on before, and still have interleaving on now. I do get CRC errors, etc. Always have though, and ADSL1 seemed to "deal" with a certain level of this without going into a panic. Has my incorrect forcing of the syncing to ADSL1 done this? Can my profile or whatever be reset again so it can learn the correct speeds again now I've actually got the correct setting on the modem?

I don't think so, the DLM works differently on 21CN to 20CN. It will recognise that you've made a change (changed from ADSL1 to ADSL2+) and will pick that up in the back end systems. Now depending on what the DLM has already done to stabilise the line it could take between about a day and week or so before it makes any changes but it will learn. The easiest way to imagine, consider if you had a faulty modem at the point of activation causing a low sync rate or dropping connection and then swapped it after a week. The DLM in the first week may have applied interleaving and upped your target SNR a couple of times or even put you on one of the new special capped profiles but when it sees the new modem has caused the line to be more stable it will start to undo what it's done. It's cautious and won't change everything in one go, but it will go back to normal in a few days.

[#7]

Quote from: pnf

How will I know when interleaving has been switched on?  Is there anything that will indicate it either in the Member Centre or on my router?

Your router might tell you, some do and some don't depends what sort it is. It's usually with the line stats.
At the moment the Member Centre interleave option isn't available on 21CN as the ordering process is entirely manual.

[#8]

Quote from: dave

I don't think so, the DLM works differently on 21CN to 20CN. It will recognise that you've made a change (changed from ADSL1 to ADSL2+) and will pick that up in the back end systems. Now depending on what the DLM has already done to stabilise the line it could take between about a day and week or so before it makes any changes but it will learn. It's cautious and won't change everything in one go, but it will go back to normal in a few days.

Thanks Dave. I'll keep an eye on it and report back in a week or so.
Probably something to add to the list of findings from the trial - ensuring that when the customer migrates to 21CN that they make sure they have their router setup correctly to make use of it! 
In general though, the migration was seamless (despite the above issue and the continuing dropping of downstream speed below that of ADSL1!). Certainly one of the reasons I have the Draytek is because of the years it was the only modem I could confidently leave and never have to worry about it failing to reconnect if the connection dropped. The daily/hourly(!) drops have been annoying, but for the most part only because I run SSH sessions and occasionally a VPN which of course break when the modem resyncs. The average user will probably not noticed or be disturbed by it.

[#9]

Quote from: gm4jjj

Question - do I still have to pay for the Increased Uplink speed with 21CN and ADSL1?

No, that'll have been removed as part of the trial. Because it's a trial stage we've just set the download and upload speed to be the max each line can get and not made any limitations on what products can go on the trial or anything like that. At this stage with only a small number of people it's about getting different people with different routers and different lines and different usage patterns and see what happens. This may well change when we move beyond the trial, I couldn't say for sure but it makes sense to do it this way to try and get the as much information as we can early on.

[#10]

Any one know why you see little or no increase in sync speed on adsl2 if your bettween  2-5mb on adsl1. Yet if your under 2mb you see an improvment in sync speed on adsl2.
i find it odd that it can improve really long lines but not  the 50+ db atten lines.
so whats the tech bit then that stops the average long lines improving yet improves really really long lines?

[#11]

Quote from: dave

... I'm wondering 2 things. First is there anything unusual about the 8th? It may be worth focusing on why it didn't drop then rather than why has dropped every other day.

During the trial I have taken snapshots from the router and, having looked at these, there is nothing that really stands out about the day that the line did not disconnect.  During this stable period, when the line remained up for 44 hours, from the observations that I have made, the downstream SN Margin didn't drop below 6.5 dB, it remained between 6.5 db and 8.5 dB throughout.  At the relevant time on the day that the line did not disconnect, the downstream SN Margin was at 8 dB.  On other days, the downstream SN Margin was lower than this at the time the line disconnected. 
I have from time to time monitored the line using 'Router Stats', but I have done this mainly in the evening, as that is normally the time that the noise levels tend to fluctuate the most. I did however monitor the 'lunch time period' on the day of the switchover, the day after the switchover and, fortunately, on the 8th when the line did not disconnect.  I also monitored the lunchtime period yesterday and today to see if that would reveal anything.  I've attached a pdf file that contains edited 'highlights' which may or may not be useful in identifying the problem.
Apart from the regular 24 hour disconnections, my experience of the ADSL2+ trial has generally been good.  It was not so good when I lost Internet connectivity for 24 hours last weekend but  hopefully, interleaving will reduce the chance of that happening again.  Download speeds have increased and upload speeds have been equal to, if not better than on ADSL1.  The speeds are still being adjusted and have been reducing since I had the loss of Internet connectivity last weekend, so it will be interesting to see how things end up.  Unfortunately, my IP profile according to the BT speed tester has now gone down to 10,000 kbps.  It is still at 11,000 kbps in the Member Centre.

[#12]

Good news - no disconnect today! 
I rebooted the router this morning just in case it was necessary as a result of the interleaving change.  I have no way of knowing that interleaving is now on the line, but I assume it to be the case.  Download speeds have been lower today at about 7700 kbps but the download sync speed is 11,847 kbps.  I haven't been able to get any readings from the BT speed tester so I am assuming that my IP Profile is still 10,000 kbps.  I'll report speed readings in a few days when the line has had chance to settle down.

[#13]

I am syncing at 4416 on ADSL1 non interleaved,  and according to PN my line speed is 3500. However I seem to be clamped to only 3000 download? Last week I was getting 3268 downloads at similar sync speeds. I was also getting better upload sync speed at that time. Currently Upload is syncing at 672.
Edit: Now appears to be faster no longer clamped at 3000. 

[#14]

Quote

Looking at the upstream on 21CN we have a choice of setting a fixed rate of 448kbps or setting it to “uncapped” which will allow the line to sync at the maximum speed it will support (up to 1Mbps). For the trial we’ve set all the lines to be uncapped and again so far all of the lines have seen increase in upload speed with some of them sync’ing at speeds above 1,000kbps.

(JELV also quoted this text on 20/11/2008)
What happens to the upload speed/sync rate at the end of the trial?
Will it be limited to 448kb/s?
  EDIT: Oops!  I see that my question has already been answered in item/answer #68. 

[#15]

Quote from: LNNFN

Quote Looking at the upstream on 21CN we have a choice of setting a fixed rate of 448kbps or setting it to “uncapped” which will allow the line to sync at the maximum speed it will support (up to 1Mbps). For the trial we’ve set all the lines to be uncapped and again so far all of the lines have seen increase in upload speed with some of them sync’ing at speeds above 1,000kbps.

I'm getting only slightly better speeds as the old ADSL 8Mbps

Quote

Bandwidth (Up/Down) [kbps/kbps]: 1,157 / 7,699

It is also less stable than ADSL 8Mbps - and I've been moved from a 6dB to 9dB noise margin.
If a reduced upload rate allowed a slight increase in download speeds, then I'd definitely go for it (given the choice).
The ADSL2+ does bounce back from disconnections etc much more quickly than ADSL 8Mbits.