Operation Manual – QoSH3C S3610&S5510 Series Ethernet Switches Chapter 5 Priority Mapping5-1Chapter 5 Priority MappingWhen configuring priority mapping, go to these sections for information you areinterested in:z Priority Mapping Overviewz Configuring a Priority Mapping Tablez Configuring the Port Priorityz Configuring Port Priority Trust Modez Displaying Priority Mapping5.1 Priority Mapping OverviewWhen a packet reaches a switch, the switch assigns the packet parameters accordingto it configuration, such as 802.1p priority, DSCP precedence, IP precedence, localprecedence, and drop precedence.The local precedence and drop precedence are described as follows.z Local precedence is the precedence that the switch assigns to a packet and it iscorresponding to the number of an outbound queue on the port. Local precedencetakes effect only on the local switch.z Drop precedence is a parameter that is referred to when dropping packets. Thehigher the drop precedence, the more likely a packet is dropped.For packets without 802.1q tags, the switch uses the priority of the receiving port as the802.1p precedence of the received packets, and then obtains the local precedence ofthe received packets by mapping the 802.1p precedence.For packets with 802.1q tags, the switch provides the following two priority trust modes:z Trusting packet priorityThe switch looks up the 802.1p precedence of the received packets in the802.1p-precedence-to-local-precedence or 802.1p-precedence-to-drop-precedencemapping table for the corresponding local precedence or drop precedence and assignsthe precedence to the received packets.z Trusting port priorityThe switch uses the priority of the receiving port as the 802.1p precedence of thereceived packets, looks up the 802.1p precedence in the802.1p-precedence-to-local-precedence or 802.1p-precedence-to-drop-precedencemapping table for the corresponding local precedence or drop precedence, and thenassigns the precedence to the received packets.The default 802.1p precedence to local precedence/drop precedence mapping table isas shown below.
