Configuring QoS

The switch hardware's architecture and the corresponding QoS packet flow (described in Figure 20-3 above) determines the logical sequence and the types of configurations that can be utilized to achieve the desired results.

The network administrator should determine what kind of functionality is required and how that functionality should affect the traffic (TCP, UDP, non-IP, etc.). Therefore, advance knowledge of the user applications and their traffic patterns aids in the process of configuring QoS. For example, ingress traffic can already be marked appropriately by the upstream devices, so QoS policies can directly rely on such marking. On the other hand, some traffic may lack marking or may be marked differently from what is desired. In such case the network administrator needs to implement appropriate policies. Granular and accurate traffic classification is of paramount importance to optimizing traffic flows: for that purpose, vFlow policies can represent a powerful tool for selecting and (re)marking traffic according to the network design’s requirements.

Below are the QoS functionalities described in the sequence from ingress to egress:

• Ingress Port Trust 
• DSCP Map
• Policing (Rate Limiting)
• Traffic Remarking
• Port Buffering
• Queue Scheduling and Shaping
• Strict Priority Queuing