39The rate limit of a physical interface specifies the maximum rate for forwarding packets (including criticalpackets).Rate limit also uses token buckets for traffic control. With rate limit configured on an interface, all packetsto be sent through the interface are handled by the token bucket at the set rate limit value. If enoughtokens are in the token bucket, packets can be forwarded. Otherwise, packets are put into QoS queuesfor congestion management. In this way, the traffic passing the physical interface is controlled.Figure 12 Rate limit implementationThe token bucket mechanism limits traffic rate when accommodating bursts. It allows bursty traffic to betransmitted if enough tokens are available. If tokens are scarce, packets cannot be transmitted untilefficient tokens are generated in the token bucket. It restricts the traffic rate to the rate for generatingtokens.Rate limit can only limit traffic rate on a physical interface, and traffic policing can limit the rate of a flowon an interface. To limit the rate of all the packets on interfaces, using rate limit is easier.Configuring traffic policingConfiguration restrictions and guidelinesIn a traffic behavior, do not configure traffic policing with any priority marking action (including localprecedence, drop precedence, 802.1p priority, DSCP value, and IP precedence marking actions) in thesame traffic behavior. Otherwise, you will fail to apply the QoS policy successfully.Configuration procedureTo configure traffic policing:Step Command Remarks1. Enter system view. system-view N/A2. Create a class and enter classview.traffic classifier tcl-name [ operator { and| or } ] N/A3. Configure match criteria. if-match match-criteria N/A
