3-3Figure 3-1 Priority mapping procedure for an Ethernet packetWhich priority istrusted on theport?Receive a packeton a portUse the port priorityas the 802.1p priorityfor priority mappingNLook up the dot1p-dpand dot1p-lpmapping tablesMark the packet withlocal precedence anddrop precedenceIs the packet802.1q tagged?YDSCPin packetsLook up the dscp-dp,dscp-dot1p, and dscp-dscp mapping tables802.1pin packetsMark the packet with802.1p priority, dropprecedence, and newDSCP precedenceLook up the dot1p-lpMapping tableMark the packet withlocal precedenceLook up the dot1p-dpand dot1p-lp mappingtablesMark the packet withlocal precedence anddrop precedenceSchedule the packetaccording to its local anddrop precedenceUse the portpriority as the802.1p priority forpriority mappingLook up the dot1p-dp, and dot1p-lpmapping tablesMark the packetwith localprecedence anddrop precedencePort priorityThe priority mapping procedure presented above applies in the absence of priority marking. If prioritymarking is configured, the device performs priority marking before priority mapping, and then uses there-marked packet-carried priority for priority mapping or directly uses the re-marked scheduling priorityfor traffic scheduling depending on your configuration. In this case, neither priority trust modeconfiguration on the port nor port priority configuration takes effect.Priority Mapping Configuration TasksYou can modify priority mappings by modifying priority mapping tables, priority trust mode on a port, andport priority.You are recommended to plan QoS throughout the network before making QoS configuration.Complete the following task to configure priority mapping:
