On Thu, 6 Apr 2017, Pete Heist wrote:

Suppose there is a cooperative ISP that has some members who access the network 
through a single device (like a router with NAT), while others use multiple 
devices and leave routing to the ISPs routers. (No need to suppose, actually.)

There’s fairness at the IP address level (currently with esfq, maybe soon with 
Cake), but it's not fair that members with multiple devices effectively get one 
hash bucket per device, so if you have more devices connected at once, you win. 
There is a table of member ID to a list of MAC addresses for the member, so if 
there could somehow be fairness based on that table and by MAC address, that 
could solve it, but I don’t see how it could be implemented.

well, if the congested link is not the last-mile link to a user, the right answer is probably to increase the capacity of the link, and fairness issues would be a temporary thing until the link was upgraded.

remember that the fairness is a means to an end, good reponsive service. As long as the result is responsive for all users, a bit of unfairness is acceptable.

David Lang

Is it possible to customize the hashing algorithm used for flow isolation, 
either with Cake or some other way?

The only options I can think of now:

- force each member to use only one IP address (probably impractical at this 
point with hundreds of members)
- use one queue per member in an HTB hierarchy, for example, with filters 
matching each member’s devices, but that seems difficult to manage
- wait years for IPv6 deployment, allocate subnets to each member and wait for 
qdiscs that have the ability to hash by IPv6 subnet :)

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