Configuring Priority Mapping; Overview; Types Of Priorities; Priority Mapping Tables - HP 5830 Series Configuration Manual

Configuring priority mapping

This chapter describes how to configure priority mapping.

Overview

When a packet arrives, depending on your configuration, a device assigns a set of QoS priority
parameters to the packet based on either a certain priority field carried in the packet or the port priority
of the incoming port. This process is called "priority mapping." During this process, the device can
modify the priority of the packet depending on the status of the device. The set of QoS priority
parameters determines the scheduling priority and forwarding priority of the packet.
Priority mapping is implemented with priority mapping tables and involves priorities such as 802.1p
priority, DSCP, EXP, IP precedence, local precedence, and drop precedence.

Types of priorities

Priorities include the following types: priorities carried in packets, and priorities locally assigned for only
scheduling.
The packet-carried priorities include 802.1p priority, DSCP precedence, IP precedence, EXP, and so on.
These priorities have global significance and affect the forwarding priority of packets across the network.
For more information about these priorities, see "Appendix."
The locally assigned priorities have only local significance. They are assigned by the device for only
scheduling. These priorities include the local precedence and drop precedence, as follows:
Local precedence—Local precedence is used for queuing. A local precedence value corresponds to
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an output queue. A packet with a higher local precedence value is assigned to a higher-priority
output queue to be preferentially scheduled.
Drop precedence—Drop precedence is used for making packet drop decisions. Packets with the
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highest drop precedence are dropped preferentially.

Priority mapping tables

Priority mapping is implemented with priority mapping tables. By looking up a priority mapping table,
the device determines which priority value is to assign to a packet for subsequent packet processing. The
switch provides the following priority mapping tables:
dot1p-dp—802.1p-to-drop priority mapping table.
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dot1p-lp—802.1p-to-local priority mapping table.
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dscp-dot1p—DSCP-to-802.1p priority mapping table, which is applicable to only IP packets.
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• dscp-dp—DSCP-to-drop priority mapping table, which is applicable to only IP packets.
dscp-dscp—DSCP-to-DSCP priority mapping table, which is applicable to only IP packets.
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The default priority mapping tables (as shown in
available for priority mapping. They are adequate in most cases. If a default priority mapping table
cannot meet your requirements, you can modify the priority mapping table as required.
Appendix A Default priority mapping
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tables) are