48 | Rapier Switch User Guide |
Quality of Service
The switch hardware has a number of Quality of Service (QOS) egress queues that can be used to give priority to the transmission of some frames over other frames on the basis of their user priority tagging. The user priority field in an incoming frame (with value 0 to 7) determines which of the eight priority levels the frame is allocated. When a frame is forwarded, it is sent to a QOS egress queue on the port determined by the mapping of priority levels to QOS egress queues. All frames in the first QOS queue are sent before any frames in the second QOS egress queue, and so on, until frames in the last QOS egress queue, which are only sent when there are no frames waiting to be sent in any of the higher QOS egress queues.
The mapping between user priority and a QOS egress queue can be configured using the command:
SET SWITCH QOS=P1,P2,P3,P4,P5,P6,P7,P8
The switch has four QOS egress queues. It has a default mapping of priority levels to QOS egress queues as defined in IEEE Standard 802.1Q (Table 7).
Table 7: Default priority level to queue mapping for four QOS egress queues
Priority level | QOS Egress Queue |
01
10
20
31
42
52
63
73
To display the mapping of user priority to QOS egress queues, use the command:
SHOW SWITCH QOS
Figure 13: Example output from the SHOW SWITCH QOS command
Priority Level QOS egress queue
0 | 1 |
1 | 0 |
2 | 0 |
3 | 1 |
4 | 2 |
5 | 2 |
6 | 3 |
7 | 3 |
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Rapier Switch Software Release 2.2.1
