Plusnet Annex M?

A few questions for the reps.

Will Annex M be available to residential customers in the forseeable future?

Why is there a monthly charge for it? (As opposed to a one off activation fee)

Is the rise in upload speed relative to the drop in download speed?

Does the overall line quality improve or suffer if using Annex M? (i.e. pings, errors etc.)

Info re the relationship between upload and download speeds.

Annex M pinches for upstream the lower frequencies usually used for downstream. If the line is relatively short there will be plenty of spare bin capacity higher up for the downstream to be unaffected, and there will also be the maximum upstream gain.

If the line is relatively long then the attenuation on the higher frequencies will be such that those higher frequency bins will be smaller so already fully utilised. The attenuation on the lower frequencies will also be high so the speed gain on Annex M is reduced. So it's win/win or lose/lose.

From observing O2/Be lines there seems to be a rule of thumb. Below an Annex A downstream sync of 16Mbps, forget about Annex M. It is likely to be lose/lose. Above 20Mbps Annex A downstream sync, almost certainly no effect on downstream but a significant gain in upstream. Win/win.

In-between, it depends on the individual user how valuable increased upstream speed is.

I haven't been looking out for error rates, but I would guess that downstream rates would increase due to higher utilisation of the higher frequency bins. The scope for bit-swapping has to be reduced, with the knock-on effect of that. My guess could be garbage!

Hope that helps.

Mmm. 30.0dB / 19.0dB (down / up). See my stats (sync / profile) on sig or profile for more.

Out of interest, since my last reboot (1 day 11 hours) I have errors of:

Downstream :
FEC : 0
CRC : 292
HEC : 215
Upstream :
FEC : 65535
CRC : 0
HEC : 65535

I assume 64K of memory for the errors.

Annex M only applies to ADSL2+.

On your ADSL stats you would be just around the borderline. Looks like a no-no.

As a consolation prize, if you got onto ADSL2+ with PN, then an uncapped upstream should be well over 1Mbps actual. They cap it to 448kbps by default, as I expect you know.

Edited by RobertoS (Wed 29-Feb-12 00:07:28)

In reply to a post by RobertoS:

They cap it to 448kbps by default, as I expect you know.

Salt. Wound. Rub.

Yup. Was speculating on Annex M viability when ADSL2+ comes.

LOL
I did say "by default". They'll remove the cap on request I believe. I don't think they then cap it at 832.

I was on the Annex M trial with a marginal line ~42.5dB IIRC and with occasional noise bursts too. Upstream went from about 900kbps to 1.2Mb/s and I lost about 1Mb/s down.
Sometimes (twice in a couple of years) the system dropped the Annex M and I had to raise a ticket to get it back as the line management didn't revert automatically. I doubt that would happen with your line, though.