LevelOne GSW-4876 - Manual (Page 202)

C HAPTER 4 | Configuring the Switch
Quality of Service
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system. Drop precedence (DP1~DP3) is normally set from a lower to
higher Quality of Service levels for red, yellow, and then green. The
internal DSCP map is used to mark inbound traffic based on priority bits
in the VLAN tag or Layer 2 traffic, or the IP Precedence or DSCP value
for Layer 3 traffic.
As shown in the following figure, Max. DP 1-3 is the drop probability
when the average queue level is 100%. The Min. Threshold is the
average queue level at which the queues randomly start dropping
frames. Note that frames marked with Drop Precedence Level 0 are
never dropped. While the drop probability for frames marked with DP
level n increases linearly from zero (at Min. Threshold average queue
level) up to Max. DP n (at 100% average queue level).
Figure 86: WRED Drop Probability
◆ WRED can only be applied to queues 0-5. Queues 6-7 are reserved for
real-time applications (such as voice) and network control, and are
therefore not suited for aggressive traffic management policies.
P ARAMETERS
These parameters are displayed:
◆ Queue - The queue number (QoS class).
◆ Enable - Enables or disables RED for each queue.
◆ Min. Threshold - Controls the lower RED threshold. If the average
queue level is below this threshold, the drop probability is zero.
(Range: 0-100)
◆ Max. DP 1~3 - Controls the drop probability for frames marked with
Drop Precedence Level 1~3 when the average queue level is 100%.
(Range: 0-100)