H3C S5120-EI series Configuration Manual

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H3C S5120-EI series Configuration Manual Manual pdf 66 page image

56Configuring priority markingPriority marking sets the priority fields or flag bits of packets to modify the priority of traffic. For example,you can use priority marking to set IP precedence or DSCP for a class of IP traffic to change itstransmission priority in the network.Priority marking can be used together with priority mapping. For more information about prioritymapping, see "Configuring priority mapping."Color-based priority markingColoring a packetThe switch colors a packet to indicate its transmission priority after evaluating the status of processingresources and the priority of the packet.The switch can color a packet by using one of the following approaches:• Uses the token bucket mechanism (bucket C and bucket E) of traffic policing:{ If bucket C has enough tokens, the packet is colored green.{ If bucket C does not have enough tokens but bucket E has enough tokens, the packet is coloredyellow.{ If neither bucket C nor bucket E has enough tokens, the packet is colored red.• If traffic policing is not configured, looks up the 802.1p priority of a packet in the 802.1p-to-droppriority mapping table, allocates drop precedence to the packet, and colors the packet accordingto the drop precedence.{ Drop precedence 0 represents green packets.{ Drop precedence 1 represents yellow packets.{ Drop precedence 2 represents red packets.The traffic policing functions that support coloring packets include common CAR. For more information,see "Configuring traffic policing, traffic shaping, and rate limit." For more information about prioritymapping tables, see "Configuring priority mapping."Marking packets based on their colorsColor-based priority marking supports re-marking DSCP precedence.You can configure color-based marking in the following ways:• To mark packets based on a color set during traffic policing, configure a priority marking action forthe color in the traffic policing action car. For more information, see "Configuring traffic policing."• To mark packets based on their drop precedence, configure a priority marking action for a color byusing the remark command as described in the subsequent section.