On the Cisco ASR9K router, when using the bandwidth command to specify the minimum
guaranteed bandwidth to be allocated for a specific class of traffic, what will be used as the
queuing algorithm?
A.
custom queuing
B.
CBWFQ
C.
WFQ
D.
FIFO
E.
priority queuing
Explanation:
Class based weighted fair queuing (CB-WFQ) was initially released without the support of a
priority queuingsystem, thus it could not guarantee the delay and jitter (delay variation)
requirements of real-time, interactivevoice and video conversations. Since for CBWFQ, the weight
for a packet belonging to a specific class isderived from the bandwidth assigned to the class,
which in turn determines the order in which packets are sent.
All packets are serviced fairly based on weight and no class of packets may be granted strict
priority. Thisscheme poses problems for voice traffic that is largely intolerant of delay, especially
variation in delay
CBWFQ – used to guarantee bandwidth (BW) to classes; supports user-defined traffic classes; a queue is reserved for each class; packets satisfying the match criteria for a class constitutes the traffic for that class; to characterize a class, you assign a BW to it; BW assigned to a class is the minimum BW allocated to the class during congestion; each queue has a size: max # of packet it can hold and is platform dependent; if queue limit has been reached, tail drop (the default dropping scheme) within each class