Low Margin?

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..? 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

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 deleted (Wed 01-May-13 22:31:23)

I took a look at my socket, and it looks like its already got a filtered faceplate: http://d.pr/i/8byi

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)

Looks alright to me

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?

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.

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!

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

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

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?

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.

Thanks for the response. I'll take a look at the master socket in the morning. I believe there's an extension (I think probably a cheap B&Q style one) fitted to the socket itself (it goes back into the wall and through to another room in the house). But i'll check the wiring and let you know - thanks.

Yeah, I know the upstream isnt the problem, really - that was mostly just anecdotal But the fact I can get 16Mbps download speeds but yet not be able to stream reliably drives me up the wall, especially when I know the exchange is so close by (0.3 miles).

I'm intrigued as to why i'm on the Interleaved path rather than the fast path - would that be because of the low margin?

Thanks again, its really great having knowledgeable folks to bounce these questions off.

In reply to a post by mungler:

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?

Sorry I didn't mean to imply that your very short line is a bad thing, on the contrary it's actually a very good thing

If you do try another router it might be a good idea to initially plug it into the test socket behind the filtered faceplate via a dangle micro filter and check to see if there is any difference in the broadband performance. By plugging into the test socket that eliminates the chance of extensions or the filtered faceplate being the cause of any noise issues. Then refit the faceplate, plug the adsl lead into adsl socket and check the router stats and speed tests (throughput) again...

Hopefully you can get the iPlayer to work properly in due course - I usually use this for testing http://www.bbc.co.uk/iplayer/diagnostics

Haha no worries - glad I have a short line!

I actually did just unscrew the filtered faceplate and plugged in via a 'dangly' microfilter. Just connected back up and the router is now reporting:


DSL Status: Connected
DSL Modulation Mode: ADSL2+
DSL Path Mode: Interleaved
Downstream Rate: 21146 kbps
Upstream Rate: 1015 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

Which doesn't seem like a whole lot different to me... ?

Just did another speed test: http://d.pr/i/J2Zs

I dont understand how, with those numbers, I have issues from iPlayer at all.

Plus, how come my downstream margin is bad, this close to the exchange?

EDIT: here's what the iPlayer diagnostics thingy said: http://d.pr/i/Uo8L

Edited by deleted (Thu 02-May-13 01:05:29)

Can you try a http://www.bbc.co.uk/iplayer/diagnostics test now?

In reply to a post by mungler:

The ISP is UKFSN, an Entanet reseller - i'm 99.9% certain its not LLU

Entanet is an LLU ISP, at 20 exchanges. Is yours? Which exchange?

Glenrothes North: http://www.samknows.com/broadband/exchange/ESGLN

iPlayer result: http://d.pr/i/Uo8L

In reply to a post by mungler:

Plus, how come my downstream margin is bad

It isn't! 3 dB is quite normal nowadays. Only worry if it goes below 2dB. My 3dB NM rarely goes below 2.8dB at night.

Is there some way of your router reporting error stats?

Keep taking the iPlayer diagnostics!

Heh, ok. I originally started the thread because the router was reporting 1db margin, which seemed very low indeed.

Thanks for your help. I think im going to get a second line and do the sharedband thing to get better speeds.

Yes, you are running on BTw WBC ADSL2+, where 3dB NMs are normal on stable lines.

Your iPlayer diagnostics are good, tho' slower than mine, esp. Streaming (1), on a faster line, but well good enough to get good streaming.

Just noticed your low Down Power:

In reply to a post by mungler:

Downstream Transmit Power: 9 db
Upstream Transmit Power: 16 db

There has been talk of BTw lowering power on v. short lines to reduce cross-talk. That might explain why you are not getting the full 24 Meg Monty, but should not hinder streaming.

Down NM was 1dB only once as reported, but has been 3dB ever since. May be too early to call.

In reply to a post by mungler:

I think im going to get a second line and do the sharedband thing to get better speeds.

Why? What speed are you trying to improve? Why do you need faster upstream? It won't help streaming. Is there some other use, that you haven't mentioned as far as I can tell, that you need faster?

Whatever it is, surely it is better to see why you aren't getting it now, rather than spend money and find the same problem still exists?

In reply to a post by mungler:

There is, however, an extension fitted to it (behind the socket) that was put in by our builder...

In reply to a post by mungler:

I actually did just unscrew the filtered faceplate and plugged in via a 'dangly' microfilter.

But you haven't answered the following question (preferably with pictures);

In reply to a post by XRaySpeX:

Remove the filtered faceplate by the 2 screws. Are there any wires connected to the terminals on its reverse?

If the extension socket continues to work after you've removed the filtered faceplate, you've located the problem.

Yes, you're right - the second line / increased upload is really because I work from home, and quite often have to upload large files. What prompted my frustration the other day was an upload of a ~2GB virtual machine image that just took forever, and kept timing out etc.

I understand faster upstream wont help streaming - sorry, it was a bit offtopic really.

Going to hit the hay now - thanks for all the help!

There were wires connected to the part that came off when I unscrewed the faceplate, yes. Four, I think, in total. I have the modem hooked directly to the test socket now.

Current status:


DSL Status: Connected
DSL Modulation Mode: ADSL2+
DSL Path Mode: Interleaved
Downstream Rate: 21146 kbps
Upstream Rate: 1015 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

Find out about annex m may double upstream speed but drop downstream slightly.

As for iplayer is it just iplayer or does youtube suffer?

Are speeds sustained, the graphs on our speedtest will show that http://www.thinkbroadband.com/speedtest

As you now know a stable line can be sync'd at 3dB.

It is quite possible for the SNR to actually drop to a negative level - I have seen -0.7dB on mine. And it would stay synced for week/months

I did manage to capture a screen shot at 0.5dB. Mgn1 is the sync SNR, Mgn2 the snapshot SNR with the last being 0.5dB.

Have a look at SNR variation over a day to see how much it can move.

Hi Andrew,

Thanks - I have already requested Annex M as well as a regrade to a business plan from my provider which has lower contention, so hopefully that'll be my home working problem sorted out.

I ran your speed test - here's the result: http://d.pr/i/mZTL

Im not really that sure how to interpret the results, but it looks ok... I guess?

Results do NOT look good.

The two download lines should be very close, and your latency was high too. If this was done over an Ethernet connection, then I would be tempted to suggest that maybe some ISP congestion is sneaking in, and combined with the iPlayer comments that looks to be the case.

BTW no need to bother with droplr our test lets you link to the images of the result (below the main test window is a URL).

If it was me I would be looking for a different provider and not a different contention product.

Hi Andrew,

Sorry, I tested via our wifi (802.11N 5Ghz via Airport Extreme 2012). I guess I should plug in to the router and try again, right?

Thanks

I always like to try an alternative router/modem before coming to any conclusions or proceeding any further, even if that only verifies that the current router/modem is working OK

Not a bad idea, though i'd probably need to go out and buy one. Any recommendations for a cheap-but-good one?

Will you need wireless "N"?

If "G" is adequate then there are plenty of good brand new routers available at about the £20 mark - I personally like Speedtouch/Thomson 585 v7's but I'm sure others will have alternative suggestions particularly as you are considering Annex M (which I've never used.)

I have a standalone N base station (Airport Extreme) which i'd continue to use, so the modem/router doesnt really need wifi at all. My current one has G, which I only use if i need better range (laptop / tablet in the garden or whatever). Thanks

Probably no need to buy an expensive router then - I can run a Gigabit LAN using a Gigabit switch without any problems together with an inexpensive router. But please find out about the best choice for an Annex M connection before you buy anything...

will do, thanks dude

upload of a ~2GB virtual machine image

On ADSL lines, given that the rate of upload will only be up to ~100KB per second, it is going to take at least 20000 of those seconds.
If the upload is via a web-based form you can't guarantee it will complete if it takes longer than 15-30 mins (the session may timeout).

An FTP client that can resume an upload may do better but you have to accept this can a good chunk of your day, and you may prefer to limit the upload in the client to 80% of what is available (otherwise your downstream and latency may also be affected).
(edit) FileZilla can do this, and can talk to both FTP and SSH servers.

Even if you get a 2Mbit upload it is probably going to take longer than 3 hours.
This is where you need to consider different class of internet connection rather than bonding 2 lines.

If you were regularly exchanging virtual machine images, with only small progressive changes, something to look at is rsync which can send differential files rather than the whole thing. I believe Dropbox is based on this too.
or
with virtual machines, depending on the nature of the project, it is feasible to place the (changing) data on a separate smaller disk image from the operating system, if you only need to exchange that (and maybe a tar.gz or zip of any configuration folders (such as /etc).

Edited by prlzx (Thu 02-May-13 22:23:20)

thanks prlzx - im familiar with rsync and techniques for minimising the content in the VM - unfortunately its a massive database that takes up the room.

thanks again all