H3C SR6600 Configuration Manual

Also see for SR6600 SPE-FWM: Configuration guide Configuration guide Command reference Command reference Command reference

Contents

17-3Figure 17-3 How a token bucket worksIn the token bucket approach, packets requiring flow control is evaluated by the token bucket beforetransmission. If the number of tokens in the token bucket is enough for sending these packets, thepackets are allowed to pass through, in other words, the packets are forwarded normally. Otherwise,these packets are assigned to the FR class queue (namely, the FRTS queue in FRTS implementation).Once enough tokens are available in the token bucket, the packets are taken out of the FR class queuefor transmission. In this way, you can control the traffic of a certain class of packets. Tokens are in theunit of bits.The CIR ALLOW, CBS, and EBS define the token bucket as follows:z The sum of CBS and EBS equals the token bucket size.z CIR ALLOW defines the number of tokens put into the token bucket per second.For efficiency sake, the FRTS solution introduces the concept of dynamic Tc. Tc (Tc=size of packet/CIR)is in the range of 10 milliseconds to 100 milliseconds, and allows of dynamic adjustment depending onthe transmitted packet size. That is, the router allocates the required tokens to the current packetswaiting for transmission within the latest Tc regardless of the packet size (which is smaller than 1500bytes).Figure 17-4 Relationship between Tc and CIRTc (ms)Size of packet (byte)K=1/CIR51015400 800 1200