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[qpop]

Hi all.

You may have seen this post on other forums, but I'm hoping you guys will be able to offer me some help here...

Basically I'm in a new build flat, recently moved in, XILO are providing an ADSL2+ line through Cable & Wireless.  The Kitz line checker says I'm about 900m from the exchange. I bought a Zoom ADSL modem and plugged it into an old DIR-615 with DD-WRT installed, full bridge. The connection at 9dB SNR margin was about 14mbps.

Using telnet I tweaked the SNR margin, and the modem reported a sync speed of 19mbps. Great thought I. But throughput is still 14mbps.

To cut a long story short I was convinced it was the modem, but I today installed a Netgear DGT834 GT with DGTeam firmware installed, and same story.

Here's the line stats from routerstats:

   
              
       System Up Time 01:01:17            
                          
       Port           Status           TxPkts           RxPkts           Collisions           Tx B/s           Rx B/s           Up Time           WAN           None           102431           125259           0           0           0           00:00:00          --     
       LAN           10M/100M           129820           106970           0           33061           11710           01:01:14             
      WLAN          11M/54M          0          0          0          0          0          00:00:00                                
                     
      ADSL Link         Downstream         Upstream            
      Connection Speed          18777 kbps          1023 kbps             
      Line Attenuation          17.0 db          9.0 db             
      Noise Margin          5.6 db          6.1 db                              

Speed Test Results
Date    12/09/11 19:10:25
Speed Down    12862.44 Kbps ( 12.6 Mbps )
Speed Up    804.98 Kbps ( 0.8 Mbps )
Port    8095
Server    speedtest2.thinkbroadband.com


And this is replicated here:
https://twitpic.com/6iefz5/full
and here:
https://twitpic.com/6hfvqc
in various different setups.

So guys, any ideas? I'm at a total loss! My conclusion is that C&W unbeknownst to Xilo (as they've said the link speed isn't limited) are limiting my connection to 14mbps. Is this possible/realistic?

[waltergmw]

Hi Qpop and welcome here,

As it's a new build have you checked the house phone wiring ?
Builders' electricians are not always the best of phone engineers.
Has the ring wire been removed so you only have wires in pins 2 & 5 ?

Kind regards,
Walter

[qpop]

Hi Walter, it's currently plugged into the test socket in the main BT socket so the ring wire shouldn't be an issue.

I just don't understand how the connection appears to be entering one side of the modem at 18mbps and exiting the other side at 14mbps. no matter what settings I give it!

[roseway]

That's not what's happening. The modem connection speed just defines the capability of the connection. the actual speed is being limited somewhere else. I don't know if C&W uses a form of DLM, but if so this might be the cause. Or it could be a specific speed cap applied by C&W, or network congestion. Your ISP must be able to find out if any speed limits are being applied.

[qpop]

Hi roseway, I previously asked Xilo and they said that C&W don't have any kind of banding/speed limiting as far as they knew. The congestion argument is possible as I think the exchange serves a wide area, but not very densely populated and I can't imagine that many people on C&W LLU kit round here. Also, the "speed limit" is constant, regardless of time of day/night.

I've just tried the quiet line test and had a nice quiet line, I've got rid of the DIR-615 from the equation because it was periodically disconnecting me from PPPoE, so I'm just on the GT now.

https://twitpic.com/6k1u4m is the DMT tool info about the line, this is after setting the SNR margin manually.

I've just posted another support query with Xilo I'm just worried about having to pay if an engineer is called out and concludes there's no fault.

[qpop]

Hi all, woke up this morning and lo and behold the connection wasn't working, so it isn't hardware based, these connection drop-outs. Unfortunately, despite leaving routerstats running it had crashed (don't think I'd set it up properly) so I don't have much info as to why. The GT reported that the line was still synched but it seemed to be an authentication error. A disconnect/reconnect brought the line back. So this is an addition to my issues, that I thought was local/hardware related, that it turns out isn't! D'oh!

Anyway I'm leaving routerstats running/logging and will check that and the GT log later to see if anything obvious is going on (which I doubt)

[roseway]

That sounds suspiciously similar to the PPP dropouts which you got with the other router. It definitely points the finger at the interface between the exchange and your ISP, or the ISP itself. As you say, not a local hardware problem. It's up to your ISP to sort this out, so hopefully you'll get a helpful response to your new support query, otherwise you'll need to push it harder with them.

[qpop]

Hi Roseway,

It's exactly the same symptoms as before and I've changed every piece of kit in the property; filters, modem, router, computer.

Interestingly router stats when re-started and before I rebooted the connection was reading the SNR margin as being something like 1.4dB. Noise wasn't unusually high though, and at <1km from the exchange with a quiet line I'm supposing this shouldn't have caused an issue; and if it did, it would be a dropped sync, not a sync that is apparently up but non-functional.

[jeffbb]

Hi
quote: was reading the SNR margin as being something like 1.4dB.
 that is very low margin !this implies that the line had some noise that had lowered your SNR margin.When you resynched what was your SNR margin and synch rate ?
Regards Jeff

[qpop]

OK so this morning I did a bit of experimentation;

I upped the SNR margin on the DGTeam router, giving me the following details:
   
              
       System Up Time 20:53:35            
                          
       Port           Status           TxPkts           RxPkts           Collisions           Tx B/s           Rx B/s           Up Time             
       WAN           PPPoA           4608177           1479706           0           72442           7424           11:38:22             
       LAN           10M/100M           66293           8068           0           203           15           20:53:32             
      WLAN          11M/54M/108M          2800666          6097555          0          17360          748          20:34:38                                
                     
      ADSL Link         Downstream         Upstream            
      Connection Speed          15915 kbps          1023 kbps             
      Line Attenuation          17.0 db          9.0 db             
      Noise Margin          10.3 db          6.1 db                              

I left routerstats running all day. Incidentally it's no surprise that despite the sync rate of 15mbps my throughput is 13.8mbps.

Anyway, this is interesting:

https://twitpic.com/6kfe5j/full


The SNR dropped to 0, then spiked back up to exactly where it is now. This is the first time it happened all day (looking through the routerstats log) and it didn't kick me offline. I'm guessing, though, that on a lower SNR margin, if that happened it would knacker my connection. It still doesnt explain why when the drop-outs happen I get a sync but no throughput.

Any ideas on this new and exciting(?) development?

[roseway]

That spike is probably a red herring. If the router is busy at the time Routerstats connects to take a sample, RS will sometimes return empty handed, and zero values are entered into the graphs.

[qpop]

d'oh! for a moment there I thought I was nearing a eureka moment...

[HighBeta]

Seems more like a exchange backhaul issue ?

An SFI lift and shift maybe an option to push for.?

[qpop]

OK so I have some screengrabs of the situation when its happened.
Absolutely no throughput, and the various points to note:

https://twitpic.com/6kh7qe/full

Thats DMT tool, and routerstats. I'm guessing the line dies at the point the SNR margin drops to 8dB.

When dropping into the GT's webGUI pressing "connect" on the ADSL screen yields this result:

https://twitpic.com/6kh8sv/full

The line dies completely and the only thing that saves it is a reboot of the modem.

Incidentally since rebooting the modem my laptop won't use DHCP to connect to the wireless :\ I have to connect using a manual IP on the wifi connection - and windows gives me an odd warning that I've not seen in ten years of fiddling with Windows network settings that says I shouldnt combine different intranet / extranet gateways :\. Anyhoo, any way of forcing Windows 7 to "identify" a network? (prod the DHCP server into assigning an IP address, I guess) The DHCP server seems to be assigning everything else IP's.

WILL MY PROBLEMS NEVER END?!?!?

*cough*

[HighBeta]

Hmm

Have you got electric underfloor heating or any other timed electric device In/around your flat ?

That 9pm time stamp is a timer fav.