They limit it because of a few things - first they need to ensure enough bandwidth to stop any contention and also the higher the data rate the more crosstalk will be present which will slow everyones SYNC down.

James

In reply to a post by Adsl24:

they need to ensure enough bandwidth to stop any contention

Yeah, right

In reply to a post by billford:

In reply to a post by Adsl24:

they need to ensure enough bandwidth to stop any contention

Yeah, right

A contentious issue?

In reply to a post by LeJimster:

I'm not really sure why BT are limiting it to 80/20 as the 17a profile works upto 128Mb ish down 30Mb up before overheads are taken into account.

Doesn't the steep drop in speed with distance from the cabinet mean very few people would get 128Mb? If so managing customer expectations might be more trouble than it's worth to run at full speed and have the majority of subscribers thinking they're being short changed

I had a 40/10 line that pretty much always got the full rate (there were occasional times when the downstream dropped, but my VDSL modem died and had to be replaced so those blips may have been it being unhealthy). The BT checker suggested I should expect ~60/15 but having upgraded a short while ago I've been seeing stable speeds that suggest I'm getting the full 80/20 or close to it. My upgrade took less than a working day to process and I've had no issues then or afterwards (touch wood).

As the upgrade is free, cost isn't an issue to you.

Some people have reported problems due to the switch, so if you have absolutely no need for the upgrade I might suggest you play safe or perhaps save the upgrade for a time when you aren't busy at work or personally so you have time to chase solutions if you do have problems. These problems seem to be relatively rare from what I've read though.

In reply to a post by dspillett:

As the upgrade is free, cost isn't an issue to you.

That might be only on BT. The charge by Openreach is £3.nn per month higher, then whatever BT Wholesale do, then perhaps an ISP markup, plus Vat. BT Retail seem to be swallowing it.

Your connection looks unstable and heavily interleaved both up and down. Which is odd, if it can supposedly hit >100. What are your pings like?

In reply to a post by qasdfdsaq:

Your connection looks unstable.

If you are talking about my connection then I would respectfully disagree. My pings range from 8 to 13 and I get 37Mbps down and 8.9 up at any time of the day. My connection has been up since I last did a firmware upgrade 3 weeks ago and that the stats read Down: 21ES, No SES, FEC 0.01/min and No CRCs: Up; 432 ES No SES, FEC 0.03/min and 0.01CRCs/min. A massive improvement over ADSL Max and ADSL2+ IMHO.

In reply to a post by RobertoS:

In reply to a post by dspillett:

As the upgrade is free, cost isn't an issue to you.

That might be only on BT.

The OP said the offer was for a free upgrade, though you are right that will not be the case with all ISPs. With A&A (my current ISP) there is no monthly price difference but there was a one-off admin fee of £10+VAT for existing 40/10 accounts to be upgraded.

That's why I said it was odd.

In my experience, reduced sync speeds like yours (i.e. anything below 39999/10000) are used by BT DLM to introduce interleaving and INP on unstable lines. For example on my line 39999 would be the default "normal" speed while 39998 meant light interleaving, and progressively lower syncs (39997, 39996, etc) meant progressively more interleaving and INP. The same applied to the upstream - 10000 = no interleaving, 9999 = light interleaving, 9997 = moderate interleaving, and so on.

The reason your line *is* currently stable could be because DLM has compensated for instability through INP and interleaving (you don't say what your pings are to, or what you tested by, so they could be entirely false) - or it could be completely unrelated. But if it is stable and can reach >100mb, I don't see why your sync is only 39976/9992 instead of 39999/10000.