So is it time for BTWS to ditch DLM?

Not really a poll but I'm keen to hear from ISP staff and others with in depth working experience of xDSL from BT wholesale & full LLU providers.

Is it time for BTWS to ditch the wonderfull DLM system that causes more problems than it fixes.

If not then why not (technical only)

Is it time for BTWS to drop IP profiles and banded profiles (technical only)

Is it time the full LLU providers embraced this lack of DLM as a way to win customers to there networks (commercial only)

How best to deal with REIN (in the 'real world' on an ageing BTOR network)

How best to compensate for blocks of missing tones (e.g. Brookmans Park, Hertfordshire)

How to best manage X-Talk on VDSL lines without further reducing the TX power of the MSAN

Are you aware that LLU providers can have their own form of DLM, i.e. TalkTalk and Sky decide what target noise margin is good for the line

Be let their users tweak the settings themselves.

REIN is not just an OR issue, its world wide and possibly worse in the US where bridge taps are part of the network

I think what you're really asking is: "Is it time service providers dropped copper except for the last mile"

As I see it, ADSL technology was always only ever an emergency stop gap using ever-increasingly ingenious ways to defeat the laws of physics!

Instead of treating fibre like something special and, inevitably, going to cost us more, it should be treated like something we should have had in the first place! The water and gas boards have just completely renewed their networks around here to provide a better pressure and more consistent serve but they haven't charged us extra for it!

John.

http://www.water-guide.org.uk/rates.html

There are a few reasons that water rates have to rise, to cover cost of renewing water pipes and treatment plants to keep the quality of water at a good level and also to improve the service that the customers receive.

Yes, but that's a rise that's applied to everyone regardless of whether their particular bit of pipe has been renewed. Or, put another way, those people who have had their supply improved don't pay any more than those who haven't.

John.

I think BTw should give the ISP's renting from BTw (Including BT) the option to bypass the DLM which in turn, the decision would be up to the end consumer. If not, they should/could at least do some tests by disabling the DLM for some areas and if it works out okay, then they expand the areas/bRAS's where it is disabled.

Another idea - The DLM could/should be disabled for people who's line syncs above a certain speed. For instance, if your line has an attenuation of below 45 (Or if you sync at more than 4.5mbps) then the DLM will be disabled.

There are lots of things which BTw should do - the most important and best option would be to leave it up to the customer (who's broadband it is) to decide on whether they want the DLM disabled or not.

Another idea - The DLM could/should be disabled for people who's line syncs above a certain speed. For instance, if your line has an attenuation of below 45 (Or if you sync at more than 4.5mbps) then the DLM will be disabled.

In simplistic terms it's the stability of the line that counts not the attenuation with regard to the DLM and the way it changes the noise margin to suit.

People have connections with attenuation figures greater than 45dB and still have stable connections

DLM does make lines more stable. If stability and reliability is important to you (telco engineers are brought up on these things as being utmost importance) then DLM is a good idea. If you lay awake at night worried that you've lost 500k off your connection speed you might not like DLM, but you might if it keeps the line up 24/7. WBC has I believe a range of settings for the DLM fastest through to most stable - which would help accommodate individual preferences.

IP profiles are I believe an important part of efficiently running a mult-service multi-provider network. I have seen a router think it had a 622M connection and act accordingly, because the IP Profile was not correctly passed to it. The service was unusable until the router was told the right capacity and acted accordingly. LLU ISPS don't need these as they are single provider operations and often have IP DSLAMs rather than ATM or PPTP tunneled services to retail ISPs. All the traffic mixes at the exchange and can leave in one virtual pipe, not N. The IP profiles define the VP sizes.

Most customers won't understand DLM so you're appealing to a few anoraks. Many can't get LLU or have not heard of the companies or positively dislike them. If you don't have a Sky dish you won't want Sky, Talk Talk have awful customer relations, Be/O2 can hardly give their service away for some reason.

VDSL lines have multiple profiles available to them, I don't know what are being used but you can mask and shape the frequencies to reduce clashes.

Seems unfair then, those with no improvements paying for those that had them?

In reply to a post by yarwell:

DLM does make lines more stable. If stability and reliability is important to you (telco engineers are brought up on these things as being utmost importance) then DLM is a good idea. If you lay awake at night worried that you've lost 500k off your connection speed you might not like DLM, but you might if it keeps the line up 24/7. WBC has I believe a range of settings for the DLM fastest through to most stable - which would help accommodate individual preferences.

DLM has a place to play I aggree with that - I'm not so much thinking the odd 500k off a profile, more a few mbit and the time it takes to recover etc etc.
There are *lots* of options on BTWS DLM I forget how many that *could* be configured for each line (something like 44) but BT have no interest in doing anything with those settings as yet. There are trials going on I'm told, and enhancements in the pipeline, but as with most things BT are not saying a lot yet.

In reply to a post by yarwell:

IP profiles are I believe an important part of efficiently running a mult-service multi-provider network. I have seen a router think it had a 622M connection and act accordingly, because the IP Profile was not correctly passed to it. The service was unusable until the router was told the right capacity and acted accordingly. LLU ISPS don't need these as they are single provider operations and often have IP DSLAMs rather than ATM or PPTP tunneled services to retail ISPs. All the traffic mixes at the exchange and can leave in one virtual pipe, not N. The IP profiles define the VP sizes.

I have had this problem before with an endoing going mad - trying to get an 8mbit upstream link! however do we need such huge profiles & gaps between profile and sync? A profile could match or follow within 10's of kbit a stable sync.

In reply to a post by yarwell:

Most customers won't understand DLM so you're appealing to a few anoraks. Many can't get LLU or have not heard of the companies or positively dislike them. If you don't have a Sky dish you won't want Sky, Talk Talk have awful customer relations, Be/O2 can hardly give their service away for some reason.

True to a point - but customers do understand a 13mbit sync but only 8mbit throughput, or having to wait anything upto a week for the network to catch up and lift the profile.

o2 do OK if you have a phone on contract, BE where/are picky as to which lines they will accept. BE have at least started selling wholesale - hopefully a few more ISP's will start to buy in these alternate services.

In reply to a post by yarwell:

VDSL lines have multiple profiles available to them, I don't know what are being used but you can mask and shape the frequencies to reduce clashes.

VDSL a bit like ADSL has lots of options BT won't tell you about, neigh let you configure! There is only so much you can chop off freq wise till you start to impact the speed vs distance curve. Chop too much and you get another product that's never going to live up to its marketed potential, or the spec its built against.

Granted you have to tweek things within the network and I have no problem with BTWS rejecting orders that will sync <12mbit - however where this happens they *should* ensure that the line will be able to get ADSL2/2+ at *at least* 12mbit even if that means replacing/repairing line plant.