Rate limit
Rate limit controls the rate of inbound and outbound traffic. The outbound traffic is taken for example.
The rate limit of an interface specifies the maximum rate for forwarding packets (excluding critical packets).
Rate limit also uses token buckets for traffic control. When rate limit is configured on an interface, a token bucket handles all packets to be sent through the interface for rate limiting. If enough tokens are in the token bucket, packets can be forwarded. Otherwise, packets are put into QoS queues for congestion management. In this way, the traffic passing the interface is controlled.
Figure 10: Rate limit implementation
The token bucket mechanism limits traffic rate when accommodating bursts. It allows bursty traffic to be transmitted if enough tokens are available. If tokens are scarce, packets cannot be transmitted until efficient tokens are generated in the token bucket. It restricts the traffic rate to the rate for generating tokens.
Rate limit controls the total rate of all packets on an interface. It is easier to use than traffic policing in controlling the total traffic rate.