From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Wed Aug 25 2004 - 06:55:50 GMT-3
I don't know if this is usefull for the exam, but accoring to some
information from cisco, the problem is not that easy...
First of all, bandwidths are calculated at layer 3, where real things
happen at layer 2. Also, some control stuff works out of the thing.
This is where (AFAIK) the 25% started.
The second issue that complicates matters is that there is an implicit
prioritization of traffic queues in 3 levels. All priority queues go
first, but they are also policed, so no starving is possible (as long as
reasonable numbers are configured).
All defined classes with bandwidth go second. Class default goes last.
Oops, no policing is enforced at the standard classes! So starving of
class default is by all means possible (unless we shift it to the second
level by explicitly assigning a bandwidth).
This all depends on having enough traffic fed to the router of each
class, as this assignments are dynamic, and no reservation occur.
gladston@br.ibm.com wrote:
> Let me try it.
> Class-default will get 25% of the bandwidth if we do not specify a value for it.
> If there is congestion, the remaining bandwidth (not assigned to any class) will be shared according to the weight of each class.
>
> ===========
> quoted
> Assume link bw=128kbps and you have 3 classes and assigned a total bandwidth
> of 70%(128kbps*0.7=89.6=90kbps)class 1 bandwidh=10kbps, class 2
> bandwidth=35kbps, class 3 bandwidth=25kbps. What will the bandwidth assigned
> to default-class, is it still 25% of the link bandwidth(32 kbps) or remaining
> bandwidth(38kbps=128kbps-90kbps).
>
> Or else do we need a comand like below to specify to use class-defalt
> bandwidth to the remaining 30% instead of default 25%:
> (config-if)#max-reserved-bandwidth 70<--this number is less than the default
> number(75%)
> ==============
>
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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