Exam 350-401 topic 1 question 3 discussion

not correct, both answer with delay and jitter must be swap... (from Policing to shaping) https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html Shaping implies the existence of a queue and of sufficient memory to buffer delayed packets, while policing does not.

Traffic Policing causes tcp retransmitions Introduces no delay and jitter drops excessive traffic Traffic Shapping buffer excessive traffic Introduces delay and jitter typically delays , rather than drops traffic

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.

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.

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. "

Based on AndresV 1, policing generates more TCP retransmissions than shapping. then, for tcp retransmissions to be generated, you have to wait for their timers (acknowledgment) to expire in order to carry out the retransmission, in the case of shaping you do not wait for those timers to retransmit (or at least not as long as in the case of policing) In conclusion, I think that policing does introduce latency and jitter due to the elimination of packets that it does and shaping does not (at least not directly since it only makes the packets wait) since it does not eliminate packets.

DRAG AN DROP IT´S CORRECT BOOK: ccnp-350-401-official-cert-guide Chapter 14. QoS -Implement traffic policing to drop low-priority packets and allow high-priority traffic through. Then: " Drops excessive traffic" - Implement traffic shaping to delay , is not recommended for RTP,it relies on queuing that can cause jitter. Then: "introduces delay and jitter" whereby: traffic policing = "introduces no delay and jitter" -Shapers: Buffer and delay egress traffic rates ***deleted for space*** then: "Buffers excessive traffic" -Policers for incoming traffic ***deleted for space***. A downside of policing is that it causes TCP retransmissions when it drops traffic. the: "Cuase TCP retransmission when traffic is dropped" - Shapers are used for egress traffic ***deleted for space***. Shaping buffers and delays traffic rather than dropping it, and this causes fewer TCP retransmissions compared to policing. then: "typically delays ,rather than drops traffic"

given answer is correct

hint ~jitter & delay: packet gets neither delay nor jitter when it gets dropped

1,3,5 - TP 2,4,6 - TS

provided answer is correct

Traffic policing cause TCP retransmissions when traffic is dropped. introduce delay and jitter. drops excessive traffic. Traffic shaping buffers excessive traffic. introduces no delay and jitter. delays, rather than drops, traffic.

The provided answer seems correct. Policing drops packets which will cause TCP retransmission and no need for delay. Shaping buffers instead of dropping packets which will lead to queuing causing delays. Based on many comments, the provided answer is also valid.

Shaping definitely introduces delay due to queuing.... So 'Introduces delay and jitter' should be under 'traffic shaping'..

Shaping places packets into queues when the actual traffic rate exceeds the traffic contract, which causes more delay, and more jitter. Policing when making a simple decision to either discard or forward each packet causes more packet loss, but less delay and jitter for the packets that do make it through the network

Traffic Shaping according to the book: Implement traffic shaping to delay packets instead of dropping them since traffic may burst and exceed the capacity of an interface buffer. Traffic shaping is not recommended for real-time traffic BECAUSE IT RELIES ON QUEUING THAT CAUSE JITTER.

policing drops and shaping buffers the traffic