[Bloat] [Rpm] [Make-wifi-fast] Traffic analogies (was: Wonderful video)

[Rich Brown]

> On Oct 19, 2022, at 7:36 PM, Stephen Hemminger via Rpm <rpm at 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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