water level, and thus make a packet waiting to conform wait longer. Neither Turner nor the ITU-T addresses the issue of variable-length packets. However, the description according to the ITU-T is for ATM cells, which are fixed-length packets, and Turner does not specifically exclude variable-length packets. Hence, in both cases, if the amount by which the bucket content or counter is incremented for a conforming packet is proportional to the packet length, they will both account for the length and allow the algorithm to limit the bandwidth of the traffic explicitly rather than limiting the packet rate. For example, shorter packets would add less to the bucket, and could thus arrive at smaller intervals; whereas, longer packets would add more and thus have to be separated by proportionally larger intervals to conform. Concept of operation A description of the concept of operation of the leaky bucket algorithm as a meter that can be used in either traffic policing or traffic shaping may be stated as follows: A fixed capacity bucket, associated with each virtual connection or user, leaks at a fixed rate. If the bucket is empty, it stops leaking. For a packet to conform, it has to be possible to add a specific amount of water to the bucket: The specific amount added by a conforming packet can be the same for all packets or can be proportional to the length of the packet. If this amount of water would cause the bucket to exceed its capacity then the packet does not conform and the water in the bucket is left unchanged. Uses The leaky bucket as a meter can be used in either traffic shaping or traffic policing. For example, in ATM networks, in the form of the generic cell rate algorithm, it is used to compare the bandwidth and burstiness of traffic on a Virtual Channel (VC) or Virtual Path (VP) against the specified limits on the rate at which cells may arrive and the maximum jitter, or variation in inter-arrival intervals, for the VC or VP. In traffic policing, cells that do not conform to these limits (nonconforming cells) may be discarded (dropped) or may be reduced in priority (for downstream traffic management functions to drop if there is congestion). In traffic shaping, cells are delayed until they conform. Traffic policing and traffic shaping are commonly used in UPC/NPC to protect the network against excess or