3Com Switch 8800 Configuration Guide
Chapter 33 QoS Configuration
33-17
33.3.6 Configuring Queue Scheduling
Each port supports eight outbound queues except that port of XP4 board only supports
four queues. The switch puts the packets into the queues according to the local
precedence of packets. Queue scheduling is used to resolve problems of resource
contention by many packets. The switch supports SP algorithm and WRR algorithm.
Different outbound queues at the port may use different algorithms. The switch
supports three scheduling modes:
1)
All-SP scheduling mode
2) All-WRR mode: The outbound queues are divided into WRR queue 1 and WRR
queue 2. The switch first schedules the queues in the WRR queue1. If no packets
are waiting for being forwarded in WRR queue 1, then it begins to schedule the
queues in WRR queue 2. By default, all queues at a port are in WRR queue 1.
3) SP plus WRR mode: The outbound queues are put into different scheduling
groups. SP group uses SP algorithm, WRR groups use WRR algorithm. The
select one queue respectively from SP group, WRR group 1 and WRR group 2
and schedule them using SP algorithm.
Perform the following configurations in Ethernet port view or port group view.
Table 33-10
Configure queue scheduling
Operation
Command
Configuring queue
scheduling
queue-scheduler wrr
{
group1
{
queue
-
id
queue
-
weight
} &<1-8> |
group2
{
queue
-
id
queue
-
weight
} &<1-8> }*
Restore the default setting
undo queue-scheduler
[
queue
-
id
] &<1-8>
By default, the switch uses all-SP mode, so those queues not configured with WRR
algorithm are SP mode.
See the corresponding Command Manual for details of the commands.
33.3.7 Configuring WRED Parameters
In the case of network congestion, the switch drops packets to release system
resources. And then no packets are put into long-delay queues.
The switch allocates drop precedence for it when receiving a packet (also called
coloring the packet). The drop precedence values range from 0 to 2, with 2 for red, 1 for
yellow and 0 for green. In congestion, red packets will be first dropped, and green
packets last.
You can configure drop parameters and thresholds by queue or drop precedence.
The following two drop modes are available:
