Priority Mapping Configuration; Priority Mapping Overview; Introduction To Priority Mapping; Introduction To Priorities - HP A5120 EI Series Configuration Manual

Priority mapping configuration

Priority mapping overview

Introduction to priority mapping

When a packet enters a device, depending on your configuration, the 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 device status. The set of QoS priority parameters decides
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.

Introduction to priorities

Priorities fall into the following types: priorities carried in packets and priorities locally assigned for
scheduling only.
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 the chapter ―Appendix B Introduction to packet
precedences.‖
The locally assigned priorities only have local significance. They are assigned by the device for
scheduling only. These priorities include the local precedence and drop precedence.
 Local precedence is used for queuing. A local precedence value corresponds to an output queue. A
packet with higher local precedence is assigned to a higher priority output queue to be
preferentially scheduled.
Drop precedence is used for making packet drop decisions. Packets with the 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 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.

dot1p-lp: 802.1p-to-local priority mapping table.

dscp-dot1p: DSCP-to-802.1p priority mapping table, which is applicable to only IP packets.

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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