Cisco CCNA (200-301)IP ServicesHard
A network administrator is implementing Quality of Service (QoS) on a Cisco router to prioritize voice traffic over data traffic. Which QoS mechanism is primarily used to classify and mark traffic based on its characteristics?
- AClassification and Marking
- BLink Efficiency
- CPolicing and Shaping
- DCongestion Management
Show answer & explanationAnswer & explanation
Correct answer: A. Classification and Marking
Classification and Marking is the foundational QoS mechanism where traffic is identified (classified) based on various criteria (e.g., source/destination IP, port numbers, protocols) and then tagged (marked) with a specific value (e.g., CoS, DSCP) to indicate its priority or class. This marking is then used by other QoS mechanisms.
Why the other options are wrong
- B. Link Efficiency mechanisms (e.g., LFI, cRTP) optimize bandwidth usage but rely on traffic being already classified.
- C. Policing and Shaping are mechanisms used to *control* the rate of traffic, often based on previous classification and marking, but they don't perform the initial identification.
- D. Congestion Management (e.g., queuing mechanisms) *uses* the classification and marking to decide how to handle traffic when congestion occurs.
QoS Classification and Marking
The process of identifying specific types of network traffic and assigning them a priority or class label for differentiated treatment.
- First step in a comprehensive QoS strategy.
- Classification criteria: IP address, port number, protocol, ACLs.
- Marking methods: CoS (802.1p), DSCP (IP Precedence), MPLS EXP.
Memory trick: First, you Classify and Mark, then you Manage and Shape.