Bandwidth command under interface confusion

Dear Experts,

I have a confusion relating to QOS. The bandwidth command under the
interface as far as i know doesn't affect the data rate, as the data rate is
a function of the physical link speed & hardware characteristics. The
bandwidth command under the interface is related to routing protocols metric
calculation (OSPF & EIGRP) metrics for instance. However, when configuring
QOS, the bandwidth configured under the interface affects the output queue
calculation (the reservations made for the classes and the priority) and
thus affects the traffic flow.

Can someone help elaborate on this confusion (whether the bandwidth command
which only is said to relate to routing protocols metrics and has nothing to
do with the data rate on one hand; on the other hand the bandwidth command
is the basis for output queue calculations (bandwidth
reservations...priority command..etc).

Thank You for your help & support..

-- 
KJ
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