3Com 10014298 manual Setting Port Priority, Operation Command Set port priority

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.

Table 169 Setting Port Priority

Operation	Command
Set port priority	priority priority-level
Restore the default priority	undo priority

The switch supports eight priority levels, numbered 0~7, according to your needs.

By default, the port priority level is 0.