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[commless]

Hi everyone. I’m new to this site so treat me gentle!

It’s funny how we all moan about line speeds but I think its amazing what we can now pump down a pair of wires (remembering my Hayes 9600 modem at a cost of £300!)

OK, the real reason for logging in was to pick the brains of all you “techies”. I have 0.5MB line with a BT Voyager 2110 wireless router. Being at the end of the exchange, I’m told I can’t expect much more than that. This is fine and I have had no problems with line or router for the past 8 months.

Over the past 3 weeks I have experienced line dropout. DSL flashes on router and synch fails. I removed the backplate and plugged in direct. I only have the master socket on that line. I changed all cables and filters and also removed all other equipment connected. Problem still there. BT engineer came out - and would you believe it…the dam thing stayed up! He ran some tests on the line and said SNR was 26db and what he would expect for that line. 2 hours after he left, BANG! Down it went again. I found yet another filter and plugged that in and so far it’s stayed up for 4 hours.

Any thoughts guys?

BTW…I have no fairy lights or garden lights and neither have I added any new equipment to the house!

James.

[roseway]

Hi James and welcome

The first thing I have to ask is what are your router stats? If you're unsure how to get this information, see here.

This information will help us to judge what's possible on your line.

[commless]

Thanks for a very prompt reply.

Here are my router stats:


 Line Mode     G.DMT   Line State        Show Time 
 Latency Type Fast     Line Up Time    00:04:28:51 
 Line Coding Trellis On   Line Up Count 1 
   
 Statistics                   Downstream      Upstream 
 Line Rate                  576 Kbps           288 Kbps 
 Noise Margin            22.4 dB              18.0 dB 
 Line Attenuation      63.0 dB               31.5 dB 
 Output Power          16.1 dBm            11.8 dBm 


 K (number of bytes in DMT frame) 19 10 
 R (number of check bytes in RS code word) 0 0 
 S (RS code word size in DMT frame) 1 1 
 D (interleaver depth) 1 1 
 Super Frames 1020910  1020908   
 Super Frame Errors 95  0   
 RS Words 0  0   
 RS Correctable Errors 0  0   
 RS Uncorrectable Errors 0  0   
 HEC Errors 31  0   
 OCD Errors 0  0   
 LCD Errors 0  0   
 ES Errors 0 


As you can see Line Attenuation is at 63.0dB  I'm right at the end of the exchange.

James

[kitz]

Hi James and welcome.
- Hope you dont mind, but I split your topic from the other thread to try make it a bit easy for anyone replying to you so that they can concentrate on your line issues only.


----

63dB is like you say a very long line.. its also the limitation at which many routers will report, so there is a possibility that your line may even be longer.
Your SNR Margin however looks very good and based on those stats there should be plenty of spare to maintain a decent sync.
You seem to have been doing some reading up and have done all the correct things that we would advise so far.

Have you noticed any particular time pattern to the loss of syncs?  In view of the amount of spare SNRM you have I would imagine it would perhaps be something like a large noise spike which is taking out your line.
This sort of thing can be whats known as a REIN fault and the first stage of diagnostic would be monitoring whats happening with your SNRMargin to see if theres any clues as to when the SNRM starts to decline.

The best tools to help monitor this type of problem are listed on the bottom of that page.  Routerstats will work with the Voyager but requires a bit of manual configuration.
DMT tool works with the Voyager and may be a bit easier to set up, but the logging isnt as easy for someone else to read.  For your voyager you will need DMT v8.   

Set either one of these up and leave it running logging your SNRMargin for a day and let us have a look at the results to see if it pulls anything up.

[commless]

Thanks Kitz.

I'll run some tests and let you know the outcome.  I came across this site today and I must congratulate you on a very informative and well laid out site. I'm an ex telecoms guy, going back to the old strowger electo-mechanical days. Stat muxs, TDM's Kilo and megastream lines were my lot. It was all analog then! I do grasp an understanding of the new technology but clearly not in your field.

I have learnt a lot from this site in the few hours I have browsed through it and it has restored my interest in the new technology. Thank you so much once again for an excellent site.

James.

[Ezzer]

can i just say 63db is a magic figure. A lot of routers as well as a woosh test tops out at 63db where your line loss can be  lot more however, the line loss can be an awfull lot more, sounds as if your on a long line. although drop outs at a specific time will usualy dipict a possible RETN issue

[UncleUB]

Just a quick question about line attenuation.Why can't routers read anything above 63db?There are a lot of broadband users with this (as ezzer puts it) magic figure.Is there a reason why they can't be made to be more accurate?Don't mean to hi-jack your thread,just curious thats all,as I'm sure many other 'long line' users are.

[roseway]

At a guess I would say that it's down to binary numbers. 63 (decimal) is the largest number which can be stored in 6 bits, so maybe there's a 6-bit limitation somewhere. If that isn't the specific reason it'll be something like that.

[commless]

My thanks to all of you who have replied to my thread.

Can someone explain what all the errors mean (i.e ODC, HEC)  On the subject of my new problem, I changed the micofilter, yet again! And found the line came up and stayed up for 48 hours. I came home this evening to find the router showing a solid DSL light but no internet light. Logging into the router and selecting the ‘connect’ option re-established the link.  I wonder why it dropped out but stayed in synch?
I have never had a problem with this line - until about a month ago – and wondered if it could be the result of some work carried out at the exchange?  Everything that can be changed has been changed, removed, and or switched off. I even bought a new router!  Still, at least I now have a spare (he says, trying to stay positive).

James

[roseway]

>> I wonder why it dropped out but stayed in synch?

There are two stages in your connection to the internet: the first is the ADSL link to the exchange, and the second is the connection from there to your ISP. What can happen sometimes is that the ADSL part stays in sync, but the connection with your ISP gets dropped for some reason - this can be caused by something BT have done, something the ISP has done, or a glitch, and it's not something you have any control over.

Hopefully someone more knowledgeable than me will explain the errors.

[UncleUB]

My thanks to all of you who have replied to my thread.

Can someone explain what all the errors mean (i.e ODC, HEC)  On the subject of my new problem, I changed the micofilter, yet again! And found the line came up and stayed up for 48 hours. I came home this evening to find the router showing a solid DSL light but no internet light. Logging into the router and selecting the ‘connect’ option re-established the link.  I wonder why it dropped out but stayed in synch?
I have never had a problem with this line - until about a month ago – and wondered if it could be the result of some work carried out at the exchange?  Everything that can be changed has been changed, removed, and or switched off. I even bought a new router!  Still, at least I now have a spare (he says, trying to stay positive).

James

Hi James,I had a similar experience a couple of months ago,my router lights were on but there was no connection to the internet.I found out the reason was some work in my exchange.If you are with BT you can find out if there is a any outages in your exchange by getting updates on 0800 169 0199.I've just had a look on the BT service update page and see there was a BT broadband connection problem the same time as you were have problems.I don't know your ISP,but I'm sure others have service updates.I like yourself am a complete novice,but if you can get half the help I have received in this forum then you will be doing fine.

[kitz]

The errors are various places were packets have been lost/corrupted and your router has gone "pardon".
Depending on the type of error it shows you on what level the error has occured.
HEC (Header Error Check checksum/control) are those that have occured at the ATM level.
OCD is Out of Cell Delineation errors, and occur when you have 7 consecutive HEC violations.


>> I wonder why it dropped out but stayed in synch?

As eric says, its when a problem has occured on the PPP part of your connection as opposed to the ATM part.
This normally occurs if your ISP has disconnected you for some reason, usually its load balancing or an ISP problem, but there are a couple of other places where it can occur on the later stages of the BT network waaaaay down the line, before it hits your ISP.

Theres a diagram that helps show the routing here:- How adsl works. PPP parameters start just after Colossus which is the main BT backbone in the UK.
ATM is mostly the bit up to the RAS, which is a kind of central hub for exchanges, of which theres 11 in the UK.

[kitz]

PS
I'm sorry but I thought I had responded to your post yesterday - I can certainly remember also typing some things to you along the lines of


Thank you for your kind comments

>> I'm an ex telecoms guy,

That would perhaps explain you having done most of the usual stuff we normally recommend first already


Unfortunately it would appear I let myself get distracted by someone who I've wasted far too much time on and apologising for over the past few weeks,  which is time that could have been far better spent actually helping someone

[PhilT]

Can someone explain what all the errors mean (i.e ODC, HEC) 

HEC is header error correction errors, referring to the bit of the data packet (the header) that was corruptl

I haven't met ODC in the context of errors. CRC is cyclic redundancy check which looks for discrepancies across the data packet . FEC is forward error correction used in interleaving to correct errors - FEC errors are OK as it means the fancy maths has spotted and fixed the error. A lot of FEC errors and a few CRC errors would be typical on interleaved lines.

As a fixed speed BT line you don't have interleaving but I would recommend having it turned on if go to MaxDSL to get the speed up.

Phil

[kitz]

The 2110 doesnt show a "CRC" errors :/

Although the stats at that snapshot do show a large SNR Margin.. 
Not sure that this particular line would be better on Max until the source of the existing loss of  connection can be found first.
If this line is already dropping on a fixed rate 576/288 product now,   then theres strong possibility that on Max it would be clobbered by the DLM and could actually see even lower speeds.