DLM behaviour on a non-21CN FTTC line?

My old 20CN line is due to move to FTTC on the 11th Sept - thanks to BDUK.

The exchange still doesn't offer 21CN/ADSL2+ products so I'm going straight from 20CN 'up to' 8Mb to FTTC.

Hopefully moving to an FTTC connection will also move me away from the painful DLM that comes with 20CN lines? i.e. Up to 5 days for an IP profile to recover if you happen to suffer from a low sync due to a storm etc.

Anyone able to say how things should work?
Thanks.

DLM is still in use on FTTC lines.

It won't do anything for the first few days just to see how the line handles. Then it will step in if needed.

You actually get two DLMs dealing with your line, but both are far better than the 20CN one.

The one controlling your line is the Openreach one running on the cabinet DSLAM. SIN 498 says:-

Dynamic Line Management (DLM) is employed in GEA-FTTC. DLM constantly manages lines to maintain a target link quality (speed and stability). It does this for as long as the product exists.

At provision, the line is put on �wide open� VDSL2 line profiles allowing the upstream and downstream line speeds to run at the upper limit of the product option selected.

On the first day of operation, DLM will intervene if severe instability is detected. Otherwise, DLM will wait until the day after provision before deciding if it must intervene, provided that the line has been trained up for at least 15 minutes during the preceding day.

Sitting behind that on non LLU broadband is part of the WBC (21CN) BT Wholesale one. It sets the IP Profile but doesn't appear to do much else.

The IP Profile on FTTC is 0.9679 of the sync speed and normally adjusts immediately on change of sync. If you run a BT Wholesale Performance Test and continue to the Further Diagnostics from the initial results page, you see the IP Profile. Divide that by 0.9679 or multiply by 1.033 and you get your approximate sync speed.

and normally adjusts immediately on change of sync

Profile adjusts on a new PPPoE connection. Usually a change of sync will force a PPPoE connection, but you can also force this from the router.

The main complaint about FTTC DLM is that it is quite quick to downgrade a line to lower speeds or to add interleaving after some error condition. However, once the error condition is cleared it often takes 2 to 3 weeks to reestablish higher speeds or non-interleaved connection. The customer has no say in the tradeoff between speed/stability/latency applied by DLM; gamers are often disappointed when they move from ADSL to FTTC and latency goes up.

I was trying to keep it simple, and correct the previous reply . Yes, I agree with what you say.

@b4dger: The fibre connection from the cabinet goes to a 21CN exchange, which is why you get the 21CN (WBC) IP Profile setter.

Sounds better than my current situation

As I mentioned the new fibre goes directly to my current 20CN exchange. Hence the post. I even checked with OR when the cable was being laid as I thought it might go to a near by 21CN one.

It will be passing straight through. It has to terminate on an Openreach switch that is then linked to a 21CN MSAN. (Or LLU one).

In reply to a post by StephenTodd:

The customer has no say in the tradeoff between speed/stability/latency applied by DLM; gamers are often disappointed when they move from ADSL to FTTC and latency goes up.

The customer might have no say, but the ISP is able to order (from BTW) with three different grades of speed-vs-stability.

Both BTW and Openreach offer 3 grades, but name them slightly differently. BTW use "standard", "stable" and "super-stable", while Openreach use "speed", "standard" and "stable".

I haven't yet seen an ISP allow a user to specify the setting, and I assume they choose behind the scenes.

In reply to a post by b4dger:

Sounds better than my current situation

As I mentioned the new fibre goes directly to my current 20CN exchange. Hence the post. I even checked with OR when the cable was being laid as I thought it might go to a near by 21CN one.

Your 20CN exchange will likely just house (Apart from the existing equipment) a Fibre Splitter serving all of the cabinets in the area - The exchange won't really have any other FTTC related equipment. The fibre cables on the other end of the splitter will go back to a larger 21CN exchange which has a Handover Node installed. FTTC doesn't operate over the 20CN network .

Edited by chris6273 (Mon 01-Sep-14 01:25:33)

No I've never seen that. To my knowledge the small exchanges don't house anything regarding FTTC. All of the splitters are outside, I think part of the reason behind that is so that eventually they'll be able to close the small exchanges.