Leaky bucket
The leaky bucket is an algorithm based on an analogy of how a bucket with a constant leak will overflow if either the average rate at which water is poured in exceeds the rate at which the bucket leaks or if more water than the capacity of the bucket is poured in all at once. It can be used to determine whether some sequence of discrete events conforms to defined limits on their average and peak rates or frequencies, e.g. to limit the actions associated with these events to these rates or delay them until they do conform to the rates. It may also be used to check conformance or limit to an average rate alone, i.e. remove any variation from the average. It is used in packet-switched computer networks and telecommunications networks in both the traffic policing and traffic shaping of data transmissions, in the form of packets, to defined limits on bandwidth and burstiness (a measure of the unevenness or variations in the traffic flow). It can also be used as a scheduling algorithm to determine the timing of transmissions that will comply with the limits set for the bandwidth and burstiness applied by the network: see network scheduler. A version of the leaky bucket, the generic cell rate algorithm, is recommended for asynchronous transfer mode (ATM) networks in Usage/Network Parameter Control at user–network interfaces or inter-network interfaces or network-to-network interfaces to protect a network from excessive traffic levels on connections routed through it. The generic cell rate algorithm, or an equivalent, may also be used to shape transmissions by a network interface card onto an ATM network (i.e. on the user side of the user-network interface), e.g. to levels below the levels set for Usage/Network Parameter Control in the network to prevent it taking action to further limit that connection. The leaky bucket algorithm is also used in leaky bucket counters, e.g. to detect when the average or peak rate of random or stochastic events or stochastic processes, such as faults or failures, exceed defined limits. At least some implementations of the leaky bucket are a mirror image of the Token Bucket algorithm and will, given equivalent parameters, determine exactly the same sequence of events to conform or not conform to the same limits. However, there are at least two different descriptions of the leaky bucket that can and have caused confusion. (Wikipedia).
