Cos Services - Dell PowerConnect 2708 User Manual

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. DSCP mapping is enabled on a per-system basis.
The following table contains the default DSCP mapping to egress queue values:
Table 7-2. DSCP Mapping to Egress Queue Default Values

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 — Strict Priority (SP) allows the prioritization of mission-critical and time-
•
sensitive traffic over less time-sensitive applications. Thus, ensuring that time-sensitive
applications are always forwarded before traffic with lower priority. For example, under Strict
Priority, voice over IP traffic is forwarded before FTP or e-mail (SMTP) traffic.
• Weighted Round Robin — Ensures that a single application does not dominate the Ethernet
switch forwarding capacity. Weighted Round Robin (WRR) forwards entire queues in a
Round Robin order. All queues can participate in WRR.
70
D S C P Va l u e
0-15
16-31
32-47
48-63
F o r w a r d i n g Q u e u e Val u e s
q1 (Lowest Priority)
q2
q3
q4 (Highest Priority)