Line management, SNR and profiles

btb22 · Mar 18, 2012, 19:20:37

A bit of background - when I first got ADSL over the BT network their DLM system profiling crippled my sync rate due mainly to evening noise and occasional interference. I went over to Be LLU when it came available and asked them to switch off line management and I've got used to things that way, I don't mind the odd resync when the SNR drops the line. The line went from a 2500kbps profile under BT to a mostly syncing at nearer 10,000kbps on Be.

Now I've got the opportunity to come over to Infinity, but I'm dreading the prospect of going back onto BTs line profiling and DLM again. I've already read a few posts where great sync rates drop progressively as DLM controls the line.

So what I'm really asking here is for any comments and views on Infinity DLM before I come over? I can't decide whether to go for it now, and accept DLM, or wait for my current ISP to go fibre and be DLM free. I don't know how close the cabinet is, but the checker suggests 20/5.8 as likely speeds.

If BT would just drop DLM!

Simon · Mar 18, 2012, 19:37:16

I'm no good at the tech stuff, but someone will be along to advise shortly.

Steve · Mar 18, 2012, 19:39:45

I'm not sure, if you were going to see a dramatic improvement in line speeds I'd say go for it, but your predicted speeds are not great. I'm 500m or so from the cabinet and I get a full sync on 40/10 and the connection is very stable with a constant IP profile of 38718, I've never seen aggressive line management on FTTC like we used to see on adslmax.( not saying it doesn't exist).

mervl · Mar 18, 2012, 23:29:43

I'm 600m from the Cab on a known poor underground local loop from the cab (with joints at every dwelling) and down sync has increased up to a full 38717 profile (38Mbps throughput) and 6642 upload/10 despite getting tones only on the lower frequencies (with a moderately high 20 attn. because of the poor quality line and I suspect, reduced power levels to reduce interference with the much-weakened ADSL signals in the locality, that gave me 4Mbps maximum and kept a a 9dB SNR). The original prediction (on profile 8c) was 25Mbps. From your speeds your line looks better. So I'll stick my neck out and say that unless you are prone to a high level of disconnects and/or have a known/suspected HR fault on your line you should be OK. My line always had high error rates and still has interleaving but there is a dramatic reduction in uncorrectable errors on VDSL. The Engineer install should test the line, though you need to be proactive to get the info, and have a co-operative engineer. I didn't. Line stats aren't available unless you are in to unlocking the supplied modem.

The DLM is OpenReach's and not at all the same as that BT Wholesale use in the exchange for ADSL, apparently; and I think it definitely shows.

That being said I have a 10Mbps+ up/down Fixed Wireless service (from the days when my ADSL was hopeless) and except the shorter time for big uploads/downloads (a 2/3rds reduction), the performance is not noticeably different!

Tacitus · Mar 19, 2012, 07:25:53

Quote from: mervl on Mar 18, 2012, 23:29:43
......That being said I have a 10Mbps+ up/down Fixed Wireless service (from the days when my ADSL was hopeless) and except the shorter time for big uploads/downloads (a 2/3rds reduction), the performance is not noticeably different!

I don't really want to hijack this thread but I've been looking at a wireless service as an alternative to my current line and was wondering how you've gone about installing it. For example, do you have a rooftop aerial and a wireless modem, how far are you from the mast etc. I'm about a mile equidistant from two masts - one O2 and the other Orange, but I'm not sure who else, if anyone uses them.

Solwise seem to have some decent kit and, on the face of it installation wouldn't be a problem, but given the prices it could be an expensive way of finding out that either it doesn't work or produces no real benefits. OK it might be useful for backup but that's not really the point.

btb22 · Mar 19, 2012, 08:36:10

Thanks very much for the welcome and the replies. I meant to say before that the Home Pro Fibre (with a year paid up front), looks like the best deal around that would suit us. I'm so tempted.

I'm hoping the prediction from the checker is as pessimistic as the ADSL one is and that once connected I'd actually get the full whack as it were. I've been for a walk around and reckon the nearest cabinet is about 600m away as you would walk to it, its a newish estate all undergound to the premises. The connection is stable at 3dB SNR though interleaving is on and working hard, ADSL2+ gives us a bit more than just ADSL2, the tones that are lacking are around a couple of frequencies due to a radio station (I forget which now, so long ago when I went into it all). I'd like to think the interference is picked up along the line prior to the cabinet, and not just the last few hundred metres.

I appreciate the information, glad to hear that the Infinity DLM is not the awful crippling system ADSL suffered with. I'm trying to be realistic with my guesses as to where the line will sync. I negotiated a special price with Be so I'll be paying an extra £20 a month, if we get the full 40 I'll justify it, if its down to 20 I'm not so sure.

Is there a way to find for sure which cab the line is connected to before ordering?

Thanks again for the info, I think I'll do the neccssary rewiring in preparation, then bite the bullet...oh, decisions, decisions.

Steve · Mar 19, 2012, 08:45:06

I'm unsure how you can tell which cabinet your connected to, mine was obvious as it was the only one within a 1km radius. OR know but it's getting the information out of them. The FTTC estimates do appear to be conservative, I was quoted 30/6 and get 38/8.5 on a good day.

Glenn · Mar 19, 2012, 08:50:09

A post on Thinkbroadband's Firbe forum including your postcode should give you your cabinet, as several people there have a copy of the database.

btb22 · Mar 19, 2012, 08:57:21

Quote from: Steve on Mar 19, 2012, 08:45:06
I'm unsure how you can tell which cabinet your connected to, mine was obvious as it was the only one within a 1km radius. OR know but it's getting the information out of them. The FTTC estimates do appear to be conservative, I was quoted 30/6 and get 38/8.5 on a good day.

Thanks for that, out of interest what do you get on a bad day, and does a bad day mean it takes a fews day to creep back up?

About a year ago there was a link to an OR page that had all the phone numbers and their associated cabs. I thought I'd saved it but can't find it now. Seems like what was public info has gone in house.

By-the-way, a quick one, is off-peak also all day at weekends? I'm guessing not or it would be clearly stated.

And, what do they do with your master socket, I've got an ADSL Nation faceplate, if they remove I'll put a standard one back on on the day of installation!

btb22 · Mar 19, 2012, 08:59:08

Quote from: Glenn on Mar 19, 2012, 08:50:09
A post on Thinkbroadband's Firbe forum including your postcode should give you your cabinet, as several people there have a copy of the database.

I cross posted and missed your reply, that must be the one I found before, do you have a copy of the database?

Glenn · Mar 19, 2012, 09:06:55

No, sorry.

Off peak is only 00.00 - 09.00 everyday, any uploads are not included in your allowances.

The BT chap will replace the faceplate and test the line. I'm around 650m from my cabinet, currently I get about 34mb, but the BT eng got 40/10 from his tester.

btb22 · Mar 19, 2012, 09:08:19

Quote from: Glenn on Mar 19, 2012, 09:06:55
No, sorry.

OK, thanks, sorry to say I did and lost it!

mervl · Mar 19, 2012, 09:12:01

btb22: There is an OR schedule (latest published version March 2012, I believe) which gives projected uplifts and cab details - well nos - for postcodes - I found the reference on the TBB fibre forums. If all else fails I think I downloaded it somewhere, and might be able to extract some info if you're able to PM me your postcode.

Tacitus: EDIT: you'd have to find a local supplier for Fixed Wireless - the only list I've found is on ISP Review.

Fixed wireless is point to point i.e. doesn't use the mobile masts, and hence does require a small squarish roof receiver, which usually can be put on the TV aerial pole. The important thing is the need for line of sight to the transmitter, so buildings, hills and dense woodland in the way can be evil. I'm about 5 miles from my transmitter (across the edge of an urban area but also a river valley). Things to find out about are the backhaul, and nothing beats asking the supplier (which will probably be a local company) for contact details of a couple of customers as references. The install cost is like that for a TV aerial, as well as a usually competitive monthly subscription (though as an early customer and the first in my sector a few years ago I got mine free of the monthly subscription!). Weather hasn't been a problem nor has interference, though the service is contended which can give you problems with a local bandwidth-hogger especially on a feeder transmitter depending on their bandwidth management which tends to be primitive. That said I've had no problems, the Sky gigabit backhaul which my supplier uses is excellent, and latency is only a bit higher than the IDNet fibre. There's a bit of jitter and can at times be a small amount of packet loss, not sure the extent to which that is due to the up/down transmission being sequential not simultaneous. Find out their speed and throughput limits which do vary but the kit (if Ubiquiti Nano) is top notch and comparable with FTTC. The supplied dumb modem requires a cable router (or single PC) setup the same as for cable, and the air is a fantastic transmission medium, without the vagaries of copper! Unfortunately service often comes secondary to installation, but that being said after an initial problem with the older kit, I've had no problems for over 18m.

Steve · Mar 19, 2012, 12:37:58

Quote from: btb22 on Mar 19, 2012, 08:57:21
Thanks for that, out of interest what do you get on a bad day, and does a bad day mean it takes a fews day to creep back up?

And, what do they do with your master socket, I've got an ADSL Nation faceplate, if they remove I'll put a standard one back on on the day of installation!

Good and bad relate purely to throughput my sync rate and IP profile have remained constant since install at the beginning of December.

As far as I'm aware the adsl faceplate is compatible with VDSL, should you decide to use it probably best to ensure for future OR engineer visits that you keep BT's VDSL master plate. The VDSL master plate and VDSL modem are part of the install package.

Tacitus · Mar 19, 2012, 15:14:56

Quote from: mervl on Mar 19, 2012, 09:12:01
Tacitus: EDIT: you'd have to find a local supplier for Fixed Wireless - the only list I've found is on ISP Review.

Ah thanks - I've obviously misunderstood what you were referring to. Internet Central http://www.ic.co.uk/ operate not far from here so it might be worth trying to interest the Parish Council in a feasibility study since clearly BT are not going to do much, if anything.