Kitz Forum

Broadband Related => ISPs => Topic started by: UncleUB on November 20, 2007, 10:13:32 AM

Title: Speed Variations
Post by: UncleUB on November 20, 2007, 10:13:32 AM
Hi all,when I put my telephone number into ISP,s availability checkers it says my line can support up 1mb adsl,yet when I put my next door neighbours number in it says his line can support up 3.5mb.Our lines come from the same telegraph pole.He does not have broadband so I can,t ask him what speed he is getting.Why can there be such a difference in such I small distance?
Title: Re: Speed Variations
Post by: roseway on November 20, 2007, 11:13:52 AM
The premier line checker is of course http://www.kitz.co.uk/adsl/adslchecker.php so you should try that one if you haven't already.

The figures which you get from checkers are based on what's in the BT database, and this will quite often be inaccurate or out of date. They're only an estimate, and don't limit your actual performance in any way. If you post your present router stats (upstream/downstream attenuation, noise margin and connection speeds) as described in http://www.kitz.co.uk/adsl/frogstats.htm we could give you a fair estimate of your line's actual capability.
Title: Re: Speed Variations
Post by: UncleUB on November 20, 2007, 01:54:01 PM
Hi eric,just run the kitz adsl checker.It says I can get 1mb fixed and 1mb dsl max.My next door neighbour 1mb fixed 3.5mb dsl.We are both 1.85km straight line to exchange,3.54km via road.
my line stats are

1248kbps down/448kbps up  IP profile 1000kb

SNR 14.9 down/12.0 up

line att 63.0 down/31.5 up.

Title: Re: Speed Variations
Post by: roseway on November 20, 2007, 03:34:26 PM
I see that you're already on Max, but it looks as though the DLM process has increased your target noise margin in order to stabilise your line. With the default target noise margin of 6 dB you should be able to sync at just over 2000 kbps which would increase your profile to 1500. I suspect that the speed estimate for your neighbour's line is inaccurate, unless by some oddity it follows a completely different (and shorter) route to the exchange.

With an attenuation of 63 dB you're never going to get a lot more than you are at present, and long lines are also more vulnerable to interference problems, which probably accounts for the increase in the target noise margin.

Sorry I can't be more optimistic. :)
Title: Re: Speed Variations
Post by: kitz on November 20, 2007, 06:02:25 PM
Agree with everything erics said.

With the default Target SNR of 6dB then you may get a tad higher speed... but it does indeed look like the DLM has had to increase it to 15dB to get stability on your line and avoid frequent disconnects.

The BT database is an estimate if records about the line are not actually held.  Yours will be based on the reality.
A 63db atten  line is pretty long and more likely equates to 4.5 - 5km from the exchange, so its possible that the line may "go all round the houses" before getting to you. :/

The only thing I could suggest is perhaps plugging the router directly into the test socket behind the master socket to eliminate any problems with internal wiring.
http://www.kitz.co.uk/adsl/troubleshooting.htm

If you get better line stat readings from the test socket, then it points to a possible problem with the internal cabling.
Title: Re: Speed Variations
Post by: UncleUB on November 21, 2007, 08:33:04 AM
Hi,just to add that I do not have any extensions in my home just the main socket which is at the side of my computer desk.The cabling runs about 10 feet from entering my home to my phone socket.This was fitted by BT in March.As I pointed out in another thread my router manager stopped working so I was told by kitz tha t a reboot should sort it.I refrained from doing this as I was getting good stats(for my line) 1856 down/448up.snr margin 14.1down/10.0 up IP profile 1500kb.What I didn't notice was because the router manager was not working i was unable to use the broadband phone line to make free evening and weekend calls.So under pressure from 'er indoors I rebooted.The router managers fine now but my speed dropped 0.5mb.What would be the best snr margin to try a reboot to get my speed up again.At the moment it is 14.8 down/12.0 up.
Once again thanks for all your help and comments.
Title: Re: Speed Variations
Post by: roseway on November 21, 2007, 09:58:23 AM
It looks as though your target noise margin has been set at 15 dB, and this isn't something you have any direct control over, unless you can use the DMT tool to tweak your router. You can ask your ISP to get the noise margin target manually reduced but you may find it hard to persuade them, and you risk making your connection unstable. Short of this, if you monitor your router stats frequently and see that the margin goes up and down through the day, then if it gets well over 15 dB and you reboot when it's at its high point, it should re-sync at a higher speed.
Title: Re: Speed Variations
Post by: UncleUB on November 25, 2007, 11:24:16 AM
Hi all,been monitoring my stats for 8 days now.My snr margin was 15.1 downstream when I rebooted and in the 8 day period has gone at its lowest 14.6 to 14.9 highest.The upstream snr was 12.0 all the time.What if anything does this tell me about my line.Do you think I would get anything higher than 1248 down/448 up at the moment if I rebooted.
Title: Re: Speed Variations
Post by: kitz on November 25, 2007, 11:40:23 AM
>> its lowest 14.6 to 14.9 highest

If it doesnt go outside that range then the variation isnt going to be enough to get a higher speed if your target SNR is 15dB. 

Unfortunately you dont stand any chance of syncing at a higher speed until that SNR Margin goes above that figure. :/

UB remind me again which router you use - sorry I cant remember
Title: Re: Speed Variations
Post by: UncleUB on November 25, 2007, 11:42:58 AM
Hi Kitz,its the Bt Voyager 220v ADSL voice router
Title: Re: Speed Variations
Post by: kitz on November 25, 2007, 03:27:14 PM
>> its the Bt Voyager 220v ADSL voice router

I was hoping it was one of the routers known to work with DMT tool

Ive just been doing a bit of digging and it would appear that it has a broadcom chipset and there may (or may not )be a link with the V2100 routers.

You could always have a "dabble" to see if DMTtool v8 works and if it does use DMT to lower your target SNR a bit.

DMT tool v8 tutorial (http://www.kitz.co.uk/tute/DMTv8.htm)

Title: Re: Speed Variations
Post by: UncleUB on November 26, 2007, 08:46:30 AM
Hi Kitz,just to update you,my router re-synced at 08.30,it went from 1248 to 1344 downstream and the snr went from 14.8 to 15.6.I then rebooted immediately and went from 1344 to 1536,the snr went to 14.8 down/448 up.I know this is not much but according  to your IP and bras chart I should now get 1250 kbps.


Edit, just done a bbmax speedtest which was 968down/379up.this is the same speed I was getting before.If my speed has gone from 1248 to 1536,why is the speed test showing the same.Tried to do a speedtester.bt.com but it said busy try later.
Title: Re: Speed Variations
Post by: roseway on November 26, 2007, 10:06:46 AM
Your IP profile doesn't go up immediately. It can take up to 5 days for a small change in connection speed like this (large changes are supposed to update more quickly).
Title: Re: Speed Variations
Post by: UncleUB on November 26, 2007, 10:13:43 AM
I should have remembered that eric,what a plank,sorry  :-[
Title: Re: Speed Variations
Post by: kitz on November 26, 2007, 11:24:37 AM
Good stuff - getting there.  Just got to wait for the iP profile to update :)
 
Title: Re: Speed Variations
Post by: mr_chris on November 26, 2007, 12:23:57 PM
Cross your fingers and hope nothing sneezes on your phone line!
Title: Re: Speed Variations
Post by: UncleUB on November 27, 2007, 01:50:34 PM
Hi all,My IP profile has risen to 1250kb  :) .It only took 1 day 5 hours to rise,I guess thats pretty good.BBMax speedtest which was 1211downstream/378upstream.I know its not gone up much but on my long line your glad of every little kb.  :)
Once again guys thanks for all your help/input.  :)
Title: Re: Speed Variations
Post by: roseway on November 27, 2007, 04:16:36 PM
That's pretty good for your line. As Chris said, try not to sneeze. :)
Title: Re: Speed Variations
Post by: UncleUB on December 02, 2007, 08:17:09 AM
Hi all,My connection was lost yesterday at about 4pm.I was online when it went,logged off and back on but still the same.Did a reboot which was still the same.I then ran a diagnostic check which brought up the following.

Test ATM OAM FS segment ping----Fail
Test ATM OAM end to end ping-----Fail
Test PPP server connection---------Fail.

Can anyone tell me what these mean.Also when my connection came back about 3 hours later my downstream has gone from 1536kbps to 1848kbps and my snr has gone from 13.6 downstream to 15.9


Edit.Just found out there was a problem at my exchange yesterday.
Title: Re: Speed Variations
Post by: roseway on December 02, 2007, 09:46:56 AM
>> Edit.Just found out there was a problem at my exchange yesterday.

I guess that was the problem then. You seem to have gained some speed in the process. :)
Title: Re: Speed Variations
Post by: UncleUB on December 02, 2007, 10:00:28 AM
Thanks eric,are those failure messages telling me there is a problem with the exchange(just for future reference so it saves me from wondering if its something I have done)
Title: Re: Speed Variations
Post by: roseway on December 02, 2007, 10:19:49 AM
I don't really know (I thought an ATM was a cash machine, but it also stands for Asynchronous Transfer Mode) but it certainly seems likely.
Title: Re: Speed Variations
Post by: kitz on December 02, 2007, 11:15:54 AM
ATM is (usually) the BTw part of the network

 (http://www.kitz.co.uk/adsl/images/contention.gif)


More info: -BTs ATM Backhaul (http://www.kitz.co.uk/adsl/equip2.htm)

However just be aware you will obviously also get ATM fail if you dont have sync or youre not connected.

You have to follow the list through - if one of the earlier stages wont work, then obviously the subsequent ones wont.

Connected to the phone line (phone works) >
Connected to the exchange  (Sync) >
BT authentication at the RAS (http://www.kitz.co.uk/adsl/equip2.htm#RAS) (ATM) >
ISP authentication (PPP) >


The above is a very simplified version
- full version of BT login authentication (http://www.kitz.co.uk/adsl/images/l2tpauthentication.gif).

Title: Re: Speed Variations
Post by: kitz on December 02, 2007, 11:22:46 AM
yay you certainly do seem to have benefited in some way from the outage with a faster connection and also a better SNR Margin.

Your SNR must have been pretty good when you did eventually manage a resync.

Did the green dsl light on your router go off?  Thats the easiest and most obvious way to see if youve lost sync with the exchange.
Title: Re: Speed Variations
Post by: UncleUB on December 02, 2007, 11:28:52 AM
Hi Kitz,no the green light did not go off,but the green light which shows I can make calls via the internet went off and I was not able to make broadband calls.the normal phone line was ok.This is what I couldn,t understand.The sync light was green yet there was no connection.
Title: Re: Speed Variations
Post by: kitz on December 02, 2007, 12:57:58 PM
>> The sync light was green yet there was no connection.

Probably the bit between the dslam at the exchange and the RAS then.
Title: Re: Speed Variations
Post by: UncleUB on December 03, 2007, 07:08:08 AM
Thanks kitz,just to update,my IP profile has increased to 1500kb,it only took just over 24 hours to increase.This seems a lot quicker at updating than it used to.  :thumbs:
Title: Re: Speed Variations
Post by: roseway on December 03, 2007, 07:26:05 AM
Excellent. Tread around lightly and try to hold on to it. :)
Title: Re: Speed Variations
Post by: UncleUB on December 03, 2007, 08:06:38 AM
There is no sneezing allowed indoors. ;D