Dell 3548 manual CoS Services

Table 9-1. CoS to Queue Mapping Table Default values (continued)

CoS Value Forwarding Queue Values

5q3

6q4

7q4

Packets arriving untagged are assigned a default VPT value, which is set on a per port basis. The assigned VPT is used to map the packet to the egress queue.

DSCP values can be mapped to priority queues. The following table contains the default DSCP mapping to egress queue values:

Table 9-2. DSCP to Queue Mapping Table Default Values

DSCP Value	Forwarding Queue Values
0-15	q1 (Lowest Priority)
16-31	q2
32-47	q3
48-63	q4

DSCP mapping is enabled on a per-system basis.

This section contians the following topics:

•"CoS Services" on page 442

CoS Services

After packets are assigned to a specific egress queue, CoS services can be assigned to the queue(s). Egress queues are configured with a scheduling scheme by one of the following methods:

•Strict Priority — Ensures that time-sensitive applications are always forwarded. Strict Priority (SP) allows the prioritization of mission-critical, time-sensitive traffic over less time-sensitive applications. For example, under Strict Priority, voice over IP traffic can be prioritized so the IP traffic is forwarded before FTP or e-mail (SMTP) traffic.

•Weighted Round Robin — Ensures that a single application does not dominate the device forwarding capacity. Weighted Round Robin (WRR) forwards entire queues in a Round Robin order. All queues can be configured to WRR or SP queues. If WRR is selected, the following weights are assigned to the queues: 1, 2, 4, 8.

442

Configuring Quality of Service