[Cake] Query on ACK

[Jonathan Morton]

>> The ACK filter runs on enqueue, so if a queue has only ACKs in it, it
>> will never accumulate anything in the first place...
> 
> but the side effect is that on dequeue, it flips it into the fast
> queue drr rotation, not the slow, so it can't accumulate
> as many acks before delivering the one it has left.
> 
> Or so I thought, way back when....

The ack filter converts a stream of acks that might be treated as a bulk flow into a sparse flow, which is delivered promptly.  This is a good thing; an ack should not be held back solely to see whether another one will arrive.

I think of it as an optimisation to reduce delay of the information in the ack stream, not solely as a way to reduce the bandwidth consumed by the ack stream; the latter is a happy side effect.

 - Jonathan Morton