A fundamental question on CBWFQ:
My understanding of ?bandwidth? statement on CBWFQ is: 1. Minimum bandwidth guarantee; 2. Weigh(ratio) for bandwidth allocation: For instance, bandwidth 20% to class A and 5% to class B, if there are only two classes traffic on the pipe and if the pipe is congested (means Queuing mechanism kicks in), IOS will start to allocate bandwidth based on weight, 20 to class A, 5 to class B with total weigh of 25. The end result of that is roughly 80% bandwidth will be used by A and 20% bandwidth will be used by B.
Is my understanding correct? I opened a TAC case, TAC engineer told me that bandwidth statement is only used for minimum bandwidth guarantee, after that, everything is evening located, so in above example it will be close to 50:50.
My testing on small pipes <4Mbps shows that IOS IS using bandwidth statement as allocation ratio quite closely, but on large pipe, like DS3, the ratio doesn't work any more. Any one has any idea? Is there anything I need to tune to make it work? I try to tune queue-limit, it works to certain extend (10%), but still far from "where it should be".
Any experience or insight info is appreciated.