HP (Hewlett-Packard) 2500 Switch User Manual


 
132
Enhancements in Release F.04.08
Configuring Port-Based Priority for Incoming Packets
Configuring Port-Based Priority for Incoming Packets
When network congestion occurs, it is important to move traffic on the basis of relative importance.
However, without prioritization:
Traffic from less important sources can consume bandwidth and slow down or halt delivery
of more important traffic.
Most traffic from all ports is forwarded as normal priority, and competes for bandwidth with
all other normal-priority traffic, regardless of its relative importance.
Traffic received in tagged VLAN packets carries a specific 802.1p priority level (0 - 7) that the switch
recognizes and uses to assign packet priority at the outbound port. With the default port-based
priority, the switch handles traffic received in untagged packets as "Normal" (priority level = 0).
You can assign a priority level to inbound, untagged VLAN packets. (The switch does not alter the
priority level of 802.1p tagged VLAN packets it receives.) Thus, for example, high-priority tagged
VLAN traffic received on a port retains its priority in the switch. However, you have the option of
configuring the port to assign a priority level to untagged VLAN traffic the port receives.
The Role of 802.1Q VLAN Tagging
An 802.1Q-tagged VLAN packet carries the packet’s VLAN assignment and the 802.1p priority setting
(0 - 7). (By contrast, an untagged packet does not have a tag and does not carry a priority setting.)
Generally, the switch preserves and uses a packet’s priority setting to determine which outbound
queue the packet belongs in on the outbound port. If the outbound port is a tagged member of the
VLAN, the packet carries its original priority to the next, downstream device. If the outbound port is
not configured as a tagged member of the VLAN, then the tag is stripped from the packet, which then
exits from the switch without a priority setting.
Feature Default Menu CLI Web
Assigning a priority level to traffic on the basis
of incoming port
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