Configuring Priority Mapping; Overview; Introduction To Priorities; Priority Maps - HP FlexFabric 5700 series Configuration Manual

Configuring priority mapping

Overview

When a packet arrives, a device assigns a set of QoS priority parameters to the packet based on either
a 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 according to the priority
mapping rules. The set of QoS priority parameters decides the scheduling priority and forwarding
priority of the packet.
Priority mapping is implemented with priority maps and involves the following priorities:
802.1p priority.
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• DSCP.
IP precedence.
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Local precedence.
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Drop priority.
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Introduction to priorities

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

Priority maps

The switch provides various types of priority maps. By looking through a priority map, the switch decides
which priority value 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 only to IP packets.
dscp-dp—DSCP-to-drop priority mapping table, which is applicable only to IP packets.
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dscp-dscp—DSCP-to-DSCP priority mapping table, which is applicable only to IP packets.
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