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[altq 48] Re: altq-diffserv
>> I give EF traffic at least 50% of the bandwidth (40 Mbit/s) and BE at
>> least 25% (20 Mbit/s).
>> Since I allow EF and BE to borrow the rest of the bandwidth (20 Mbit/s)
>> from their parent class ("DefaultClass"), I expected that
>> EF would receive: 40 + (40/60)*20 = 53.3 Mbit/s
>> BE would receive: 20 + (20/60)*20 = 26.7 Mbit/s
>> This would be the case with a fair queue.
Unfortunately, CBQ does not define how the excess bandwidth is
shared. It only says that underlimit classes are served before
overlimit classes. The current CBQ algorithm employs a heuristic
I have to admit that this is a weak point of CBQ but it is not
simple to share the excess bandwidth among classes with different
priorities, bandwidth assignments, delay requirements, packet sizes...