From: Ivan (ivan@iip.net)
Date: Mon Jan 29 2007 - 06:25:30 ART
I haven't IEWB. Therefore i can say only general consideration. Congestion
appear if output queue is not empty. Next router has two threshold.
1) if size of queue less than threshold 1 than packet transmit with no action
2) if size of queue more than th1 and less or equal th2 packet must be
CA(congestion avoidance) action apply with some probability. Action can be
mark ECN (FECN, IP ECN) or drop. Note that FR-switch mark with FECN not BECN.
3) if size of output queue more than th2 than packet unconditionally drop.
I send you unicast mail with more explanation about IP ECN. Not for GS cause
it composed with Russian language.
> In IEWBv3 Vol II Lab 7 Task 8.1 there is a task about enabling ECN when
> congestion occurs.
> But I misunderstand when the ECN starts marking packets.
> And how can we explicitly configure threshold of interface load when ECN
> marking should be started?
>
> In UniverCD there are only poor examples and explanations (such as ECN is
> switched on when congestion occurs - that's all)
-- Ivan
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