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Configuring QoS 161
This random number is compared with the discarding probability for the
current queue. Any packet whose random number is greater than the
probability is discarded. The longer the queue, the higher the discarding
probability . However, there is a maximum discarding probability.
Through randomly discarding packets, RED avoids global TCP synchronism. When
some packets of a TCP connection are discarded and the transmission speed is
lowered, other TCP connections can still keep the higher transmission speed. In
this way, there are always some TCP connections with higher transmission speeds,
that make a better use of the line bandwidth.
Configuring QoS Before you create a QoS configuration, you must define an ACL. Packet filtering is
enabled when you create an ACL so packet filtering configuration is not described
here.
The following sections describe QoS configuration tasks:
■ Setting Port Priority
■ Setting Port Mirroring
■ Setting Queue Scheduling
■ Entering QoS View
■ Configuring the Traffic Limit
■ Setting Line Limit
■ Setting Traffic Bandwidth
■ Setting Traffic Redirection
■ Relabeling the Priority Level
■ Configuring the RED Operation
■ Configuring Traffic Statistics
■ Displaying and Debugging QoS
The 20-Port 10/100/1000BASE-T and 20-Port 1000BASE-X-SFP I/O modules only
support QoS configuration for the inbound packets.
Setting Port Priority
If the received packets contain no VLAN labels, the switch adds the default VLAN
and modifies their 802.1p priority levels with port priority levels.
Perform the following configurations in Ethernet interface view.
The switch supports eight priority levels, numbered 0~7, according to your needs.
By default, the port priority level is 0.
Table 169 Setting Port Priority
Operation Command
Set port priority priority priority-level
Restore the default priority undo priority