Configuring Priority Mapping; Overview; Priority Types; Priority Mapping Tables - HP A6600 Configuration Manual

Configuring priority mapping

The features in this chapter are available only on routers with a SAP interface card working in bridge mode.

Overview

When a packet arrives, a router assigns a set of QoS priority parameters to the packet based on a certain
priority field carried in the packet or the port priority of the incoming port, depending on your configuration.
This process is called ―priority mapping.‖ During this process, the router may modify the priority of the packet
depending on router 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 802.1 1e priority,
802.1p priority, DSCP, EXP, IP precedence, local precedence, and drop precedence.

Priority types

Priorities fall into the following types: priorities carried in packets, and priorities locally assigned for
scheduling only.
The packets carried in 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 locally assigned priorities have only local significance. They are assigned by the router for scheduling
only. These priorities include the following types.
 Local precedence—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—Used for making packet drop decisions. Packets with the highest drop precedence

are dropped preferentially.

Priority mapping tables

The router provides various types of priority mapping tables, or rather, priority mappings. By looking up a
priority mapping table, the router decides which priority value to assign to a packet for subsequent packet
processing.
The default priority mapping tables (as shown in
for priority mapping. They are adequate in most cases. If a default priority mapping table cannot meet your
requirements, modify the priority mapping table as required.
―Appendix B Packet precedences.‖
Appendix A Default priority mapping
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tables) are available