> On Oct 19, 2022, at 7:36 PM, Stephen Hemminger via Rpm
> <r...@lists.bufferbloat.net> wrote:
>
> Grocery store analogies also breakdown because packets are not "precious"
> it is okay to drop packets. A lot of AQM works by doing "drop early and often"
> instead of "drop late and collapse".
Another problem is that grocery store customers are individual flows in their
own right - not correlated with each other. Why is my grocery cart any more (or
less) important than all the others who're waiting?
I continue to cast about for intuitive analogies (and getting skunked each
time). But I'm going to try again...
Imagine a company with a bunch of employees. (Or a sports venue, or a UPS depot
- any location where a bunch of vehicles with similar interests all decide to
travel at once.) At quitting time, everyone leaves the parking lot where a
traffic cop controls entry onto a two-lane road.
If there isn't any traffic on that road, the traffic cop keeps people coming
out of the driveway "at the maximum rate".
If a car approaches on the road, what's the fair strategy for letting that
single car pass? Wait 'til the parking lot empties? Make them wait 5 minutes?
Make them wait one minute? It seems clear to me that it's fairest to stop
traffic right away, let the car pass, then resume the driveway traffic.
This has the advantage of distinguishing between new flows (the single car) and
bulk flows (treating vehicles in the driveway as a single flow). But it also
feels like QoS prioritization or a simple two-queue model, neither of which
lead to the proper intuition.
Any "traffic" analogy also ignores people's very real (and correct) intuition
that "cars have mass". They can't stop in an instant and need to maintain space
between them. This also ignores the recently-stated reality (for routers, at
least) that "The best queue is no queue at all..."
Is there any hope of tweaking this analogy? :-)
Thanks.
Rich
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