Exam 350-801 topic 1 question 317 discussion

Selected Answer: B

QoS Baseline recommendation for **Streaming-Video*** marking is AF32, AF33 & CS4 which is not AF42. Interactive Video (Video Conferencing) is marked AF41, AF42, AF43. The Correct Answer is D 10000% https://www.ciscopress.com/articles/article.asp?p=357102&seqNum=2 & https://www.researchgate.net/figure/Mappings-between-DSCP-and-MPLS-EXP-Bits-Sogay-2013-To-provide-the-QoS-we-have_fig86_325988616

https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Collaboration/hybrid/12x/hybcvd/bwm.html

D seems to be the correct one. Interactive-Video " When provisioning for Interactive-Video (video conferencing) traffic, the following guidelines are recommended" https://www.ciscopress.com/articles/article.asp?p=357102&seqNum=2 Interactive-Video traffic should be marked to DSCP AF41; excess videoconferencing traffic can be marked down by a policer to AF42 or AF43.

AF42 specifically indicates a certain level of priority or service quality for a particular type of traffic. In this case, AF42 is typically used to mark streaming video traffic, which requires a moderate amount of bandwidth and a low to moderate level of delay and packet loss tolerance. Therefore, option B (streaming video) is the correct answer. While AF42 can be used for video conferencing traffic in some cases, it is more commonly used for streaming video traffic. This is because video conferencing traffic requires a higher level of QoS to ensure good call quality, and is typically marked with a higher priority value such as AF41 or EF (Expedited Forwarding) to ensure that it receives the necessary bandwidth and low latency it needs to function well.

AF42 is a DSCP value that indicates Assured Forwarding (AF) class 4, which provides medium-high drop probability and moderate latency for traffic with a class selector (CS) value of 4 and a drop precedence (DP) value of 2. This type of marking is commonly used for video conferencing traffic. Therefore, the correct answer is D, video conference.

https://www.cisco.com/en/US/technologies/tk543/tk759/technologies_white_paper0900aecd80295a9b.pdf

Interactive-Video traffic should be marked to DSCP AF41; excess videoconferencing traffic can be marked down by a policer to AF42 or AF43.

I vote B. Streaming. Interactive Video - Sensitive but can tolerate packet loss of about 1% and latency almost same as voice = AF41 per Cisco guidance. Streaming Video - Less sensitive - can tolerate about 4-5% packet loss and latency of about 4-5 seconds...stands to reason that Streaming as it is less sensitive should have a higher drop probability (AKA DSCP42) as compared to Video Conference. https://community.cisco.com/t5/collaboration-applications/qos-why-dscp-af-41-for-video/td-p/2241293

D is the correct answer: Interactive Video (Video Conference) is marked AF41. if a Policing solution exists on the path, and the Bandwidth limit for the queue is reached, excess traffic would be marked down to AF42 or AF43 which makes them more likely to be dropped.

The correct answer is B (Streaming Video). Opportunistic video - AF42; 36 - Includes video streams (main video and presentations or content) and related RTCP packets. https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Collaboration/hybrid/12x/hybcvd/bwm.html#95240

Interactive-Video When provisioning for Interactive-Video (video conferencing) traffic, the following guidelines are recommended: Interactive-Video traffic should be marked to DSCP AF41; excess videoconferencing traffic can be marked down by a policer to AF42 or AF43.

I thought video conference was AF41 and not AF42. We sure this is D?