Question about profiles, latency and fastpath

I used to get between 7 and 9ms on my connection when I first switched to FTTC (Zen Internet) but due I believe to a mis-configuration in my router, which caused it to keep dropping the internet connection, some level of interleave was switched on causing an increase in latency (now about 15ms) and a decrease in line speed.

The issue with the router has long since been rectified (many months) and I believe my line is quite capable of operating quite happily without interleave on (indeed it was doing so initially aside from the router misconfiguration causing frequent resets).

I have on two occasions asked Zen if I can be switched back but they flat refuse to do it, claiming they can't do it, as BT does not provide that option on these products.

My question is, is this true?
Is there a way to get BT to switch me back on to fastpath?
Does that extra 7ms really have any impact (I am an FPS player) anyway?

As a software developer, having developed several performance critical database systems, I tend to want to optimise optimise optimise (every little bit counts) to get the best possible overall performance, which may be why I am being a bit anal about those unwanted extra ms.

Edited by deleted (Thu 01-Nov-12 15:52:01)

Yes, it's true. Are you using the Openreach modem or a router with built-in VDSL2 modem?

Basically, no, Zen can't get BT to change the fastpath on FTTC; that is determined by DLM (digital line management).

To confuse things, there are three BT companies involved. This is approximately (I'm sure I'll be corrected if this is wrong):
- Openreach provides the low level hardware and makes the cabinet connections, etc.
- BT Wholesale provides the FTTC service based on that hardware. That includes administering the DLM software in the cabinet.
- BT Retail sell the end user product (if you have Infinity). Not relevant to Zen, they sell the retail product bought in from BT Wholesale.

BT Wholesale are very reluctant to do any manual management at the cabinet. They can reset the profile at the retailer's request (Zen), but not at the customers direct request, but are difficult to persuade. That might put you back on fastpath. However, DLM would probably switch you back again pretty soon if that is what it felt the line needed.

The issue is unlikely to be due to router issues; unless you have provided your own router/modem combined. It could be because of modem problems.

I'm not sure your router configuration would affect anything, unless you were reconnecting the modem in your attempts to fix the problem. I feel there may be an unfortunate coincidence.

Unless of course you are using your own VDSL2 router rather than the Openreach modem and a router connected to that.

I don't think there is any user control of interleaving. That isn't even in the BT Wholesale province for FTTC, it is Openreach.

A few people in the past have reported interleaving coming and going automatically. The delay before switching back to Fast Path isn't yet established. I'm waiting to see if mine goes back, having hit interleaving for some reason this Sunday. Not messing is probably the key.

It could simply be that there is now higher takeup on your cabinet and crosstalk has caused it.

(I'm sure I'll be corrected if this is wrong):

...
BT Wholesale provides the FTTC service based on that hardware. That includes administering the DLM software in the cabinet.

Indeed you will .

The cabinet DLM is BT Openreach and BTW have no real control of it. BTW only get hold of the connection over an Openreach GEA link at the exchange, as do TalkTalk and Sky.

BTW then feed the connection into their WBC DLM to set IP Profiles and the like, but the line configuration itself is the OR one.

Thanks for the replies.

I am using the open reach modem (PPPoE). Specifically the issue with my router was the detection of internet access was set to use ping instead of arp and that proved very unreliable, and the router would drop the PPPoE session regularity. I can see that, now you mention it, that should not affect the DSL connection of the modem, so probably was not a factor (unless it was tripping the modem up causing it to reset?).

I guess I will just have to live with it, if resetting the profile is not something that can be done easily. Tried twice to get Zen to request it and both times they declined.

Edited by deleted (Thu 01-Nov-12 19:21:42)

In reply to a post by RobertoS:

A few people in the past have reported interleaving coming and going automatically. The delay before switching back to Fast Path isn't yet established. I'm waiting to see if mine goes back, having hit interleaving for some reason this Sunday. Not messing is probably the key.

On the three occasions interleaving has appeared on my connection it's reverted back to fastpath after between 1 and 4 weeks.

Thanks Simon. So there's hope for the OP, and for me .

(anonymous posting by wwwombat)

I've had 2 different lines, and 2 different experiences of DLM...

On our old line, we initially got 40/10 service, but with a high error rate - leading to 4% packet loss. DLM intervened after 48 hours to add interleaving (adding 8ms latency), and we lost some speed, dropping to 36/10.

The line stayed like that until the new frequency plan was introduced, as BT prepared for full 80/20 services. Our sync went back to 40/10, but stayed interleaved.

The new line has been working at 80/20 without interleaving, with a 12 ms latency. We had a physical line problem in August that caused interleaving to be added (latency up to 20ms), and a small drop in speed. It took 3 weeks for interleaving to be removed again, and another couple of days for the speed to recover.