Palo Alto Networks Certified Network Security Engineer (PCNSE)Deploy and ConfigureHard
A network security team is configuring Quality of Service (QoS) on a Palo Alto Networks firewall to prioritize voice over IP (VoIP) traffic over standard web browsing. They need to ensure that VoIP packets receive preferential treatment throughout the network. Which QoS mechanism can be used on the firewall to mark VoIP traffic so that downstream devices also recognize and prioritize it?
- ADSCP marking
- BTraffic shaping
- CBandwidth reservation
- DPacket policing
Show answer & explanationAnswer & explanation
Correct answer: A. DSCP marking
DSCP (Differentiated Services Code Point) marking is a QoS mechanism that allows the firewall to mark traffic in the IP header. Downstream network devices (routers, switches) can then read these DSCP values and apply appropriate prioritization based on their own QoS policies.
Why the other options are wrong
- B. Traffic shaping regulates the rate at which traffic is sent, but doesn't inherently mark packets for downstream prioritization.
- C. Bandwidth reservation allocates a fixed amount of bandwidth, but doesn't directly mark individual packets for prioritization by other devices.
- D. Packet policing drops or re-marks packets that exceed a configured rate, primarily for rate limiting, not for marking for preferential treatment.
DSCP Marking (QoS)
A Quality of Service mechanism that modifies the Differentiated Services Code Point field in the IP header to classify and prioritize network traffic.
- Provides a standard way to classify traffic.
- Allows for end-to-end QoS across different network devices.
- Different DSCP values correspond to different per-hop behaviors (PHBs).
- Commonly used for real-time applications like VoIP and video.
Memory trick: DSCP's the stamp, for priority's champ!