[R-C] Charter -> congestion avoidance vs. congestion control?

[John Leslie]

Harald Alvestrand <harald at alvestrand.no> wrote:
> 
> When I first learned networking ~30 years ago, "congestion avoidance" 
> was the term used when you managed things so that congestion at the 
> media level could never happen (token ring, ATM), while "congestion 
> control" was the whole area of what you did either to avoid congestion 
> or to deal with it once it happened.

   30-years? A newcomer!!

   IMHO, both terms are kind of accidental -- congestion can only be
prevented if you know the entire path a packet will follow. "Congestion
control" is the term applied to the AIMD algorithm for TCP: IMHO to
indicate a control loop. But we could just as well have talked of it
as "congestion avoidance" since what it actually did is avoid sending
data into a path believed to be congested.

   "Congestion control" has always struck me as an optimistic name --
but then, _all_ names are optimistic! IMHO, what we will do for
congestion-management in RMCAT will look even less like a tight control
loop.

> So I'd prefer "congestion control", since congestion is a fact of life; 
> we're dealing with it, not avoiding it at all cost - but I'm a bit 
> old-fashioned.

   Congestion which drives up delay will _need_ to be avoided in RMCAT.
"Congestion avoidance" to me has never meant "at all cost", but YMMV.
Myself, I'm more sensitive to any suggestion that RMCAT can "control"
overall congestion. We're going to find ourselves at the mercy of and
competing TCP streams (which will always try to fill the pipe); and
if we have any way to "control" them, it's not obvious to me.

   But perhaps the final argument is our name:

RTP Media Congestion Avoidance Techniques (RMCAT)

--
John Leslie <john at jlc.net>