Why is FTTC Limited to 80/20

On ADSL connections the line is ran at the maximum speed it will handle.

So why is FTTC/VDSL limited to 80/20?

Is there a reason its not allowed to run at the maximum speed the line can handle?

Manly I expect to have more users able to hit headline speeds, having adsl2+ run at 24mbit was a bad idea in my view, and especially bad to market it at that speed. Also it improves stability if a line is hitting a cap rather than its maximum physical limit.

In reply to a post by Seansmit17:

On ADSL connections the line is ran at the maximum speed it will handle.

So why is FTTC/VDSL limited to 80/20?

Is there a reason its not allowed to run at the maximum speed the line can handle?

Because BT Wholesale limit ADSL (capped at 8Mbps) ADSL2+ (capped at 21Mbps) and FTTC (capped at 76Mbps)

There is nothing that many isp's can do. Only BTW will limit us all.

In my view that BTW should capped the following:

ADSL (9Mbps)
ADSL2+ (28Mbps)
FTTC (86Mbps)

Edited by adslmax (Tue 27-May-14 02:08:29)

Wasn't it to limit the amount of crosstalk effect on lines? By running it slower it should reduce the impact. And I suspect there is a relatively small percentage of lines that would see a speed increase compared to the number that could be impacted by the increased crosstalk from running the lines hot.

You're mixing up the sync speed which is 80/20 and TT/Sky can do what they like with that, and BT Wholesale IP Profiling which doesn't actually limit the throughput very much at all. Most of what it removes accounts for some unavoidable overheads which also affect TT and Sky throughput.

28 mbps.....

what people are living in the exchange?

I would say roll on Vectoring but from what I have read the Modems BT are using are only 100mbps lan ports and not gigabit so anyone getting a speed over 100mbps would not be able to use anything over.

The router they are using may also be a limitation if its only 100mbps for the lan/wan

In my opinion, because with FTTC there will be people living on top of every cab (at the end of their drive, against their wall, etc).

This means that one of these people could end up with, potentially, a 120mbit sync. This would cause lots of crosstalk to the lines that were longer.

By limiting such a customer to 80mbit, you can reduce the bitloading and power levels, meaning less crosstalk to longer lines.

It's a bit of robin hood going on, taking from the fastest to give to the slowest.