Policing, Queueing, and Scheduling: True Statements | CCIE Data Center Exam

# Policing, Queueing, and Scheduling

### Question

Which two statements about policing, queueing, and scheduling are true? (Choose two.)

### Explanations

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A. B. C. D.

BC.

Sure, I'll explain each statement and its validity:

A. The Weighted Random Early Detection (WRED) algorithm is a proactive approach to manage congestion, not a reactive one. WRED works by randomly dropping packets before a link becomes congested, in order to avoid a sudden and severe increase in packet loss. Therefore, statement A is false.

B. Policing is a traffic management technique that involves limiting the rate of incoming traffic to a specified rate or burst size. This can be useful to ensure that a particular class of traffic does not exceed a certain level of bandwidth usage. The device can monitor both the data rate and packet sizes associated with the traffic being policed. Therefore, statement B is true.

C. Weighted Random Early Detection (WRED) can be applied to a class of traffic to manage congestion. WRED works by randomly dropping packets before a link becomes congested, and it can use the Class of Service (CoS) field to determine which packets to drop first. However, WRED does not drop packets based on the CoS field alone, but rather uses a combination of factors such as packet size and queue depth. Therefore, statement C is partially true.

D. Traffic scheduling is a method of managing bandwidth by assigning a maximum data rate to a class of traffic. If the traffic exceeds this rate, packets may be dropped. This technique is known as shaping. Shaping is different from policing in that it buffers excess packets instead of dropping them immediately. Therefore, statement D is false.

In summary, statements B and C are true, while statements A and D are false.