Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) Practice Mode

Community Discussion

Written by other learners. Comments can disagree with the marked answer — check the official documentation when in doubt.

• 1

  Traffic shaping is more likely to introduce delay and jitter. Since traffic shaping buffers and queues excess traffic to smooth out the rate, packets may be held in the buffer for some time. This buffering process can cause variable delays for different packets. As a result, the time it takes for packets to travel through the network (latency) becomes less consistent, introducing jitter. In contrast, traffic policing usually drops packets that exceed the rate limit without significant buffering for the purpose of rate control, so it generally doesn't introduce as much delay and jitter as traffic shaping.

• 4

  Answer is Correct. Policing Advantages: - Drop (or remark) excess packets over the committed rates. Does not buffer. - Controls the output rate through packet drops. Avoids delays due to queuing. Policing Disadvantages: - Propagates bursts. Does no smoothing. - Drops excess packets (when configured), throttled TCP window sizes and reduces the overall output rate of affected traffic streams. Overly aggressive burst sizes can lead to excess packet drops and throttle the overall output rate, particularly with TCP-based flows. Shaping Advantages - Buffer and queue excess packets over the committed rates. - Controls bursts and smooths the output rate over at least eight-time intervals. Uses a leaky bucket to delay traffic, which achieves a smoothing effect. - Less likely to drop excess packets since excess packets are buffered. (Buffers packets up to the length of the queue. Drops can occur if excess traffic is sustained at high rates.) Typically avoids retransmissions due to dropped packets. Shaping Disadvantage: - Can introduce delay due to queuing, particularly deep queues.

• 1

  Not correct. The following text is take from Cisco Official Guide. " Policers: Drop or re-mark incoming or outgoing traffic that goes beyond a desired traffic rate. Shapers: Buffer and delay egress traffic rates that momentarily peak above the desired rate until the egress traffic rate drops below the defined traffic rate. If the egress traffic rate is below the desired rate, the traffic is sent immediately. A downside of policing is that it causes TCP retransmissions when it drops traffic. Shaping buffers and delays traffic rather than dropping it, and this causes fewer TCP retransmissions compared to policing. "