Operation Manual – QoS-QoS ProfileH3C S3100-52P Ethernet Switch Chapter 1 QoS Configuration1-93) Local precedenceLocal precedence is a locally significant precedence that the device assigns to a packet.A local precedence value corresponds to one of the eight hardware output queues.Packets with the highest local precedence are processed preferentially. As localprecedence is used only for internal queuing, a packet does not carry it after leaving thequeue.II. Priority trust modeAfter a packet enters a switch, the switch sets the 802.1p priority and local precedencefor the packet according to its own capability and the corresponding rules.1) For a packet carrying no 802.1q tagWhen a packet carrying no 802.1q tag reaches the port of a switch, the switch replacesthe 802.1p priority of the received packet with the port priority, searches for the localprecedence corresponding to the port priority of the receiving port in the 802.1p-to-localprecedence mapping table, and assigns the local precedence to the packet.2) For an 802.1q tagged packetWhen an 802.1q tagged packet reaches the port of a switch, you can use the prioritytrust on the receiving port to configure the port to trust packet priority or use thepriority command on the receiving port to configure the port to trust port priority. Bydefault, port priority is trusted and the priority of a port is 0.z Trusting port priorityIn this mode, the switch replaces the 802.1p priority of the received packet with the portpriority, searches for the local precedence corresponding to the port priority of thereceiving port in the 802.1p-to-local precedence mapping table, and assigns the localprecedence to the packet.z Trusting packet priorityIn this mode, the switch searches for the local precedence corresponding to the 802.1ppriority of the packet in the 802.1p-to-local precedence mapping table and assigns thelocal precedence to the packet.Table 1-5 shows the default 802.1p priority-to-local precedence mapping table. You canmodify the default mapping tables at the CLI. For detailed configuration procedure,refer to Configuring the Mapping between 802.1p Priority and Local Precedence.Table 1-5 802.1p priority-to-local precedence mapping table802.1p priority Local precedence0 21 02 1
