[Cake] ISP Implementation

[Jonathan Morton]

> On 4 Mar, 2021, at 8:31 am, Thomas Croghan <tcroghan at lostcreek.tech> wrote:
> 
> So this would be preferable right? <Theoretically unlimited bandwidth> -- <Cake Instance Limiting bandwidth going left to right> -- <Some sort of limit to 100 Mbps> -- <Cake Instance Limiting bandwidth going right to left> -- <10 x 25 Mbps Customers>

Yes, putting the Cake instances associated with the backhaul link upstream of the link in both directions like that is better for a number of reasons.  You can still have the instances managing individual customers on the right-hand side, or even further to the right.

If the customer links are physically wider in the upstream direction than is made available to the customer, then there's no problem in doing all the per-customer work in an aggregated position.  The difference (in the long run) between the traffic transmitted by the customer and that released to traverse the backhaul is limited to AQM activity on Not-ECT traffic, which will be small, unless they start flooding in which case the overload protection will kick in and start dropping a lot of packets.  This is also what you'd expect to see with a well-behaved policer in the same position.

 - Jonathan Morton