Exam 300-430 topic 1 question 215 discussion

To preserve the QoS marking sent by the Cisco Jabber software running on PC1, the DSCP (Differentiated Services Code Point) value must be trusted on port Fa 0/6. Cisco Jabber, like many modern applications, uses DSCP to mark IP packets for QoS prioritization at Layer 3. Trusting the DSCP value ensures that the QoS markings set by the application are preserved as traffic traverses the network. Explanation of the options: A. DSCP: This is correct. DSCP is a Layer 3 marking used in the IP header for QoS prioritization. Trusting DSCP ensures that the markings set by Cisco Jabber are preserved. B. 802.1p: This is a Layer 2 marking used in the Ethernet frame for QoS prioritization. It is not relevant for preserving markings set by Cisco Jabber, which operates at Layer 3. C. CoS (Class of Service): This is another term for 802.1p, which is a Layer 2 marking. It is not applicable for preserving Layer 3 DSCP markings. D. IP precedence: This is an older Layer 3 QoS marking method that has been largely replaced by DSCP. It is not the correct choice for modern applications like Cisco Jabber.