Priority Mapping

Priority mapping maps QoS priorities in packets to internal priorities (also called local priority, which is used by the device to differentiate CoS values of packets) to ensure QoS in the differentiated services (DiffServ) model based on internal priorities.

Packets carry different types of precedence fields depending on the network type. For example, packets carry the 802.1p field in a VLAN, the EXP field on an MPLS network, and the DSCP field on an IP network. The mapping between the priority fields must be configured on the network devices to retain priorities of packets when the packets traverse different networks. When the device functions as the gateway between different networks, the external priority fields (including 802.1p, MPLS EXP, and DSCP) of all packets received by the device are mapped to the internal priorities. When the device sends packets, it maps the internal priorities to external priorities.