[e2e] [Fwd: RED-->ECN]

[Greg Minshall]

there's a point here i've been mistaken on in the past, and though it is only 
a small thing, it is perhaps worth pointing out.

> However, the average queue size need not be the only measure of
> congestion. Indeed, some recent works suggested measuring the arrival rate
> directly (using some filter to smooth out transients) and using this as
> the measure of congestion. In some sense, such schemes attempts to achieve
> the rightful objective you mentioned; decide whether demand exceeds
> capacity. Both approaches (queue-based or rate-based) have some problems
> that are too involved to detail here.

i used to think that measuring average queue size was really just a proxy for 
measuring average arrival rate.

however, V. Jacobson, K. Nichols, and K. Poduri have pointed out that the 
arrival rate might equal the link bandwidth (their example uses TCP ACK 
clocking, so no new packets show up until old ones leave), but there may still 
be a standing queue.

thus, if i had been measuring arrival rate, i would have decided "no need to 
drop [mark] packets".  whereas, i should have been measuring (and seeing) a 
standing queue and decided "i need to drop [mark] packets".

cheers,  Greg Minshall