[Sephiroth]

I posted this in answer to a similar question on the VM forum:

It works like this (but can vary in different parts of the country according to who was the original cable supplier):

1/
A small street cabinet connects either 16 or 32 customers. A larger street cabinet connects 48.

2/
The cable from a cabinet passes along to another cabinet configured as above.

3/
5 or 6 cabinets go to an optical node and it's fibre from there.

4/
In high density population areas, you might get 20 coax cabinet feeding the optical node.

5/
The optical node originally would have supported only 2 upstream channels and these might have been split between two nodes at the VM end line card. So that's a heck of a lot of users who think they're getting, say 5 meg upstream sharing just 40 meg upstream capacity.

6/
A bonding group currently has 4 downstream channels with c. 200 meg capacity to share across one or two optical nodes.

So that explains how overutilisation can occur.

The current infrastructure upgrade programme should double all the capacities I've mentioned. For high contention areas, VM should be adding more optical nodes and line cards and CMTS devices at their end to cope with the additional channels allocated. That's what they say they're doing.

So there you have it. The full explanation. I might get corrected on some piece of detail, but that's basically it.

I hope that helps you somewhat.