Assigning an Application to a Traffic Class

Notices and Disclaimers
Revision History
Introduction
- QoS/Flow Control Limitations on the 800 Series
Background
Link-Level Flow Control
- LFC Setup Instructions
- Symmetric vs. Asymmetric LFC
Priority Flow Control - Fundamentals
Congestion Management – Tuning Parameters
Priority Flow Control - Planning and Guidelines
- Steps
- Example Configurations
Priority Flow Control - Verification
Troubleshooting

In Linux, when using DSCP mode, there is a chain of mappings for VLAN PFC that starts with setting the ToS field in the IPv4/6 header, ultimately determining the traffic class:

Type of Service (ToS) → Kernel Priority (sk_prio) → User Priority (UP) → Traffic Class (TC)

If using DSCP, the chain of mapping is:

Type of Service (ToS) → DSCP → User Priority (UP) → Traffic Class (TC)

QoS values, like bandwidth allocations or drop/no-drop characteristics, can then be applied to each TC. This applies whether you're using explicit VLANs or VLAN 0.

The rest of this section outlines the steps taken in designing and implementing this mapping.

Step 1: Determine Flow Control Design Needed

Determining PFC Priority Mode: PCP vs. DSCP Step 1: Determine Flow Control Design Needed