Priority Mapping Features Supported by the Device
This section describes priority mapping features supported by the device.
Priority Trust Modes
After packets reach the device, the device allocates priorities to packets based on the type of priority trusted by the inbound interface. An interface can be configured to trust 802.1p priorities in Layer 2 packets, DSCP priorities in Layer 3 packets.
You can configure the device to trust any of the following priorities:
802.1p priority
The inbound interface maps 802.1p priorities of tagged packets to internal priorities based on the default mappings; the device adds the default 802.1p priority of the interface to untagged packets and maps the default 802.1p priority of the packets to internal priorities.
DSCP priority
The system searches the DSCP priority mapping table based on DSCP priorities in packets and obtains the mapped 802.1p priorities, DSCP priorities, or drop priorities.
IP priority
The system searches the IP priority mapping table based on IP priorities in packets and obtains the mapped 802.1p priorities or IP priorities.
By default, priorities of packets are not trusted.
Priority Mapping Modes
When packets reach the device, the device maps packet priorities to 802.1p priorities. The device then maps 802.1p priorities in packets or the default 802.1p priority of an interface to local priorities, determines the queues that packets enter based on the mapping between internal priorities and queues, and performs traffic shaping and queue scheduling. When packets are sent out from the device, the device re-marks priorities of packets so that the downstream device can provide differentiated QoS based on packet priorities.
The device supports the following priority mapping modes:
- Mappings from DSCP priorities to 802.1p priorities, drop priorities, or new DSCP priorities
- Mappings from IP priorities to 802.1p priorities or new IP priorities
Table 2-1 and Table 2-2 list the mappings between 802.1p priorities and internal priorities, and between internal priorities and queues.
802.1p Priority |
Internal Priority |
|---|---|
0 |
BE |
1 |
AF1 |
2 |
AF2 |
3 |
AF3 |
4 |
AF4 |
5 |
EF |
6 |
CS6 |
7 |
CS7 |