[e2e] Why was hop by hop flow control eventually abandonded?

Michael Welzl michawe at ifi.uio.no
Wed Jul 17 15:10:47 PDT 2013

On Jul 17, 2013, at 11:16 PM, dpreed at reed.com wrote:

> I would dispute underutilization being a problem.   Most engineers confronted with an extremely bursty load (where the burstiness must be supported to get the kind of interaction responses desired - i.e. very low latency on complex web requests, etc.) would understand and *accept* the need for the network to be *on the average* very lightly loaded.
> That is, even on the creaky old Bell System digital phone network, the actual capacity was over provisioned by a large factor - a factor of 10 or so - because of *Mother's Day* phenomena.

"even on" => but this was connection oriented. "especially on" seems more likely to me. Mother's Day phenomena won't be so bad when things are more dynamic, that's the whole point. FWIW you could fill a net with LEDBAT-like traffic all the time… this might not be "green", but it won't cause a problem on Mother's Day.

> If you aim for full utilization, even if you are a government sanctioned *monopoly*, you will serve your customers badly if you try to fill up your entire fixed capacity to > 50% on the average.
> Of course, in the minds of academics, this is intolerable!  But academics rarely bother to think about the real world of engineering, preferring to invent problems (like using all available capacity *on the average*) that give them well-formed mathematical optimization problems.

Yes, I said that I consider underutilization a problem, but I didn't say what you say here.

> Are you serving your students well?   Are you serving your research community well?  Not bloody likely.

I beg to differ  :-)     Academics should be forward-looking, no?


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