[Ecn-sane] [tsvwg] per-flow scheduling

[Jonathan Morton]

> On 22 Jun, 2019, at 10:50 pm, David P. Reed <dpreed at deepplum.com> wrote:
> 
> Pragmatic networks (those that operate in the real world) do not choose to operate with shared links in a saturated state. That's known in the phone business as the Mother's Day problem. You want to have enough capacity for the rare near-overload to never result in congestion.

This is most likely true for core networks.  However, I know of several real-world networks and individual links which, in practice, are regularly in a saturated and/or congested state.

Indeed, the average Internet consumer's ADSL or VDSL last-mile link becomes saturated for a noticeable interval, every time his operating system or game vendor releases an update.  In my case, I share a 3G/4G tower's airtime with whatever variable number of subscribers to the same network happen to be in the area on any given day; today, during midsummer weekend, that number is considerably inflated compared to normal, and my available link bandwidth is substantially impacted as a result, indicating congestion.

I did not see anything in your argument specifically about per-flow scheduling for the simple purpose of fairly sharing capacity between flows and/or between subscribers, and minimising the impact of elephants on mice.  Empirical evidence suggests that it makes the network run more smoothly.  Does anyone have a concrete refutation?

 - Jonathan Morton