Web Management Guide-R01

Chapter 9 | Class of Service
Layer 2 Queue Settings
– 241 –
Mapping CoS Values
to Egress Queues
Use the Traffic > Priority > PHB to Queue page to specify the hardware output
queues to use based on the internal per-hop behavior value. (For more information
on exact manner in which the ingress priority tags are mapped to egress queues for
internal processing, see “Mapping CoS Priorities to Internal DSCP Values” on
page 247).
The switch processes Class of Service (CoS) priority tagged traffic by using eight
priority queues for each port, with service schedules based on strict priority,
Weighted Round-Robin (WRR), or a combination of strict and weighted queuing.
Up to eight separate traffic priorities are defined in IEEE 802.1p. Default priority
levels are assigned according to recommendations in the IEEE 802.1p standard as
shown in Table 13. The following table indicates the default mapping of internal
per-hop behavior to the hardware queues. The actual mapping may differ if the
CoS priorities to internal DSCP values have been modified.
The priority levels recommended in the IEEE 802.1p standard for various network
applications are shown in Table 14. However, priority levels can be mapped to the
switch’s output queues in any way that benefits application traffic for the network.
Command Usage
◆ Egress packets are placed into the hardware queues according to the mapping
defined by this command.
◆ The default internal PHB to output queue mapping is shown below.
Table 13: IEEE 802.1p Egress Queue Priority Mapping
Priority 01234567
Queue 20134567
Table 14: CoS Priority Levels
Priority Level Traffic Type
1 Background
2(Spare)
0 (default) Best Effort
3Excellent Effort
4 Controlled Load
5 Video, less than 100 milliseconds latency and jitter
6 Voice, less than 10 milliseconds latency and jitter
7Network Control
Table 15: Mapping Internal Per-hop Behavior to Hardware Queues
Per-hop Behavior 0 1 2 3 4 5 6 7
Hardware Queues 2 0 1 3 4 5 6 7