Application Scenarios for Priority Mapping
Networking Requirements
As shown in Figure 3-4, data center users obtain voice, video, and data services from the servers. Service flows are transmitted from the servers to users across the network through SwitchA and SwitchB. The voice, video, and data services must be assigned priorities in descending order so that network devices can provide differentiated services for the service flows based on their priorities.
The precedence field in a packet depends on the network type. For example, packets on a Layer 2 network carry the 802.1p field and those on a Layer 3 network carry the DSCP field. Upon receipt of packets, the device maps packet priorities to CoS values and colors, and provides differentiated QoS services according to CoS values and colors. When transmitting packets, the device re-marks the precedence fields of the packets based on the CoS values and colors. The downstream device can then provide differentiated services based on packet priorities.
- On SwitchA, configure a traffic policy in the inbound direction to re-mark voice, video, and data packets with different 802.1p priorities and DSCP priorities. The priorities of voice, video, and data services are in descending order.
- Configure SwitchA to map 802.1p priorities of incoming packets to CoS values and colors. SwitchA then provides differentiated services according to CoS values and colors.
- Configure SwitchB to map DSCP priorities of incoming packets to CoS values and colors. SwitchB then provides differentiated services according to CoS values and colors.