| Exam 400-101 | Question id=843 | Infrastructure Services |
You issue the following commands on RouterA:
RouterA(config)#policy-map kyiv
RouterA(config-pmap)#class applications
RouterA(config-pmap-c)#police 100000 5000 8000 conform-action transmit exceed-action set-qos-transmit 4 violate-action drop
When will RouterA begin to drop packets?
| A. |
when the burst rate exceeds 5,000 bits | |
| B. |
when the burst rate exceeds 8,000 bits | |
| C. |
when the burst rate exceeds 40,000 bits | |
| D. |
when the burst rate exceeds 64,000 bits | |
| E. |
when the burst rate exceeds 100,000 bits |
RouterA will begin to drop packets when the burst rate exceeds 64,000 bits. You can issue the police command to explicitly configure a maximum bandwidth limit.
The syntax of the police command is policebps [burstnormal] [burstmax] conform action action exceed action action [violateaction action]. The bps parameter is the average rate specified in bits per second, and the optional burstnormal and burstmaxparameters are specified in bytes. When traffic exceeds the burstnormal rate, the router will perform the exceedaction action, and when traffic exceeds the burstmax rate, the router will perform the violateaction action.
Traffic policing is used to slow down traffic to a value that the medium can support, to monitor bandwidth utilization, to enforce bandwidth limitations at the service provider edge, and to remark traffic that exceeds the Service Level Agreement (SLA). Excess traffic and outofprofile packets are dropped or remarked and transmitted. By contrast, traffic shaping buffers excess traffic and outofprofile packets in memory and drops traffic only if the queue is full. Because traffic shaping does not remark traffic, it can create queuing delay, particularly when queues are large and traffic flow is heavy.
In this scenario, the burstmax rate is set to a value of 8,000 bytes, which is equal to 64,000 bits. The action that corresponds to the violateaction keyword is drop.
The drop keyword configures the router to silently drop packets. Therefore, when burst traffic exceeds 64,000 bits, some packets will be dropped.
RouterA will not begin to drop packets when the burst rate exceeds 5,000 bits or 8,000 bits. The burstnormal and burstmax parameters are specified in bytes, not bits.
RouterA will not begin to drop packets when the burst rate exceeds 40,000 bits. The burstnormal rate is set to a value of 5,000 bytes, which is equal to 40,000 bits.
The action that corresponds to the exceedaction keyword is setqostransmit 4. Therefore, when burst traffic exceeds 40,000 bits, some packets will begin to be reclassified with a Quality of Service (QoS) value of 4 and will be transmitted.
RouterA will begin to drop packets before the burst rate exceeds 100,000 bits. The bit rate indicates the average rate of burst traffic, not the rate at which packets will begin to be dropped.