3Com Switch 7750 Configuration Guide Guide

QoS Supported by Switch 7750 Family 621
■ When the queue length is smaller than the lower limit, packets are not
dropped.
■ When the queue length is bigger than the upper limit, all inbound packets all
dropped.
■ When the queue length is in the range of the upper limit and the lower limit,
the inbound packets are dropped at random. In this case, a number is assigned
to each inbound packet and then compared with the drop probability of the
current queue. If the number is bigger than the drop probability, the inbound
packet is dropped. The longer a queue is, the higher the drop probability is.
However, there is a top drop probability.
QoS Supported by
Switch 7750 Family
Setting Port Priority If an inbound packet is not VLAN-tagged, the switch will tag the packet with the
default VLAN of the port receiving the packet. In this case, the port priority of the
port receiving the packet is assigned to the 802.1p priority of the VLAN tag of the
packet. In this case, you can set the port priority.
If the inbound packet is VLAN-tagged, the switch does not perform the operation
above.
Configuration prerequisites
■ The port whose priority is to be configured is specified
■ The priority value of the specified port is specified
Table 487 QoS functions supported by Switch 7750 Family and related commands
QoS Description Related command
Priority mapping
Support only the mapping
between 802.1p priority and
local queues
qos
cos-local-precedence-map
Port priority - priority priority-level
Priority to be used when a
packet enters a queue
- priority-trust
TP - traffic-limit
Priority remark - traffic-priority
Redirect - traffic-redirect
Queue scheduling Support SP and WRR queue-scheduler
Rate limit - line-rate
Bandwidth assurance - traffic-bandwidth
Congestion avoidance Support the RED operation traffic-red
Traffic statistics Supported traffic-statistic
Inbound CAR -
inboundcar { enable |
disable }
Traffic-based flexible QinQ - traffic-remark