Technical Discussion
  >> Home Networking, Internet Connection Sharing, etc.


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Standard User mungler
(newbie) Wed 01-May-13 22:23:58
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Low Margin?


[link to this post]
 
Hi,

I'm kind of fed up with having a relatively slow upload, so i've been looking around at various options (from satellite - high latency - yuck! to bonding multiple ADSL2+ lines together) and during my research i've stumbled across something odd.

I'm 0.3 miles from the exchange (the 'DSLAM', right..? wink and I get around 16.5Mbps down and 0.7Mbps up, on my ADSL2+ connection in speedtests. I was looking at the numbers on the router's stats page and figured i'd do some research into how good/bad they are. The modem (a Linksys WAG200G) reports:

DSL Status: Connected
DSL Modulation Mode: ADSL2+
DSL Path Mode: Interleaved
Downstream Rate: 21174 kbps
Upstream Rate: 912 kbps
Downstream Margin: 1 db
Upstream Margin: 8 db
Downstream Line Attenuation: 11 db
Upstream Line Attenuation: 3 db
Downstream Transmit Power: 9 db
Upstream Transmit Power: 16 db

As I understand it, the attenuation etc isnt bad, but the downstream margin of 1db is horrifically awful. I also notice that i'm in Interleaved mode, which I understand is to combat line noise.

I'm guessing that at 0.3 miles from the exchange, this is not normal, right? I have not yet done an isolation test (that'll be my next step), and am considering buying one of those faceplates with the separate ADSL port, which I understand are generally A Good Thing.

I guess for a standard ADSL2+ connection, I cant really complain about the rate im connected at - is the speedtest result i'm seeing consistent, though? I know you should expect to lose some bandwidth to overheads etc, just want to make sure im on the right track. I'm just wondering if the modem is having to do a lot of error correcting etc, slowing things down.

Apologies for all the noob questions smile

Any guidance would be greatly appreciated!

Thanks

EDIT: I meant to say, i'm *pretty* sure I have a proper master socket in the house, and thats what the DSL modem is connected to. There is, however, an extension fitted to it (behind the socket) that was put in by our builder...

Edited by mungler (Wed 01-May-13 22:31:23)

Standard User mungler
(newbie) Wed 01-May-13 23:12:59
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Re: Low Margin?


[re: mungler] [link to this post]
 
I took a look at my socket, and it looks like its already got a filtered faceplate: http://d.pr/i/8byi
Standard User tommy45
(knowledge is power) Wed 01-May-13 23:20:46
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Re: Low Margin?


[re: mungler] [link to this post]
 
You should be getting the full 24mbps sync & thats on a 6db margin on a short line like that you appear to have (11db attenuation ) Why you are not seeing the full sync , could be the modem/router in use,not being a good match with the chipset in the line card at the exchange,
the filtered faceplace may not be working properly, or it could be that DLM has messed things up in some way,

You should in theory be able to run that line at 3db with Fast path without any issues
Who is the ISP? If it isn't BTretail then you may be able to get interleaving sawitched off, as this is now possible on 21cn WBC ADSL

Edited by tommy45 (Wed 01-May-13 23:24:27)


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Standard User 4M2
(fountain of knowledge) Wed 01-May-13 23:27:10
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Re: Low Margin?


[re: mungler] [link to this post]
 
Looks alright to me smile

What time of day were the stats recorded - if it was in the late evening then a 1dB downstream SNRM might be expected if the sync time SNRM was 3dB? Are you having any problems with the DSL dropping or is the router holding the connection OK?
Standard User mungler
(newbie) Wed 01-May-13 23:29:59
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Re: Low Margin?


[re: 4M2] [link to this post]
 
Hi,

Thanks for the reply. It was about an hour or so ago (say about 10pm). It does drop now and again, maybe every few days or so? Its generally alright, and as I said I cant really complain too much, but things like streaming SD iPlayer screws up and buffers umpteen times during a single Doctor Who, which is maddening.
Standard User mungler
(newbie) Wed 01-May-13 23:32:25
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Re: Low Margin?


[re: tommy45] [link to this post]
 
Its an older router right enough, but ADSL2+ capable.

http://support.linksys.com/en-eu/support/gateways/WA...

The ISP is UKFSN, an Entanet reseller - i'm 99.9% certain its not LLU or anything, and my exchange was upgraded to 21CN a year or so ago.

Thanks for the response. Good to know i'm not crazy! smile
Standard User mungler
(newbie) Wed 01-May-13 23:34:14
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Re: Low Margin?


[re: tommy45] [link to this post]
 
Just checked the router again, its now reporting:

DSL Status: Connected
DSL Modulation Mode: ADSL2+
DSL Path Mode: Interleaved
Downstream Rate: 21174 kbps
Upstream Rate: 912 kbps
Downstream Margin: 3 db
Upstream Margin: 8 db
Downstream Line Attenuation: 11 db
Upstream Line Attenuation: 3 db
Downstream Transmit Power: 9 db
Upstream Transmit Power: 16 db
Standard User 4M2
(fountain of knowledge) Wed 01-May-13 23:49:54
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Re: Low Margin?


[re: mungler] [link to this post]
 
In reply to a post by mungler:
...but things like streaming SD iPlayer screws up and buffers umpteen times during a single Doctor Who, which is maddening.


Yet your speed tests are quite acceptable...

As tommy45 suggests there could be an issue with your connection. Also one would normally expect the upstream attenuation to be about half of the downstream attenuation, the fact that it's not could simply be explained by the way your router registers it. Maybe you could try another router and that might handle ADSL2+ and your very short line a little better smile
Standard User mungler
(newbie) Thu 02-May-13 00:23:14
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Re: Low Margin?


[re: 4M2] [link to this post]
 
Thanks, i'll try to source another router to try. Also, the way you said 'very short line' made it sound like a bad thing... is that the case?
Standard User XRaySpeX
(eat-sleep-adslguide) Thu 02-May-13 00:34:07
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Re: Low Margin?


[re: mungler] [link to this post]
 
In reply to a post by mungler:
There is, however, an extension fitted to it (behind the socket)
Behind? How far behind? Fitted to the faceplate or to the wall-mounted box?

Remove the filtered faceplate by the 2 screws. Are there any wires connected to the terminals on its reverse? That'll answer my Qs.

Now find yourself a dangly filter and plug that into the hidden test socket that has now been revealed. Plug your router into the ADSL side of the filter and get your router stats, speedtests and try out streaming. Best to reconnect in daylight. That'll eliminate a faulty BT V10 filtered faceplate (such a faulty one I have in front of me) and possibly your extension.

A slowish Upstream sync (and it's not really slow) should not hinder TV streaming which is predominantly downstream.

A short line is good; the shorter it is the faster it should go, but anything below 12dB attenuation will give the max ADSL capability of 24 meg.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
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