output. The bandwidth limit for the connection may be specified in a traffic contract. A bandwidth limit may be specified as a packet or frame rate, a byte or bit rate, or as an emission interval between the packets. Inefficiency The implementation of the leaky bucket as a queue does not use available network resources efficiently. Because it transmits packets only at fixed intervals, there will be many instances when the traffic volume is very low and large portions of network resources (bandwidth in particular) are not being used. Therefore no mechanism exists in the leaky-bucket implementation as a queue to allow individual flows to burst up to port speed, effectively consuming network resources at times when there would not be resource contention in the network. Implementations of the token bucket and leaky bucket as a meter do, however, allow output traffic flows to have bursty characteristics. Comparison between the two versions Analysis of the two versions of the leaky bucket algorithm shows that the version as a queue is a special case of the version as a meter. Imagine a traffic shaping function for fixed-length packets that is implemented using a fixed-length queue, forming a delay element, which is serviced using a leaky bucket as a meter. Imagine also that the bucket in this meter has a depth equal to the amount added by a packet, i.e. has a limit value, τ, of zero. However, the conformance test is only performed at intervals of the emission interval, when the packet at the head of the queue is transmitted and its water is added. This water then leaks away during the next emission interval (or is removed just prior to performing the next conformance test), allowing the next packet to conform then or at some subsequent emission interval. The service function can also be viewed in terms of a token bucket with the same depth, where enough tokens for one packet are added (if the bucket is not full) at the emission intervals. This implementation will then receive packets with a bursty arrival pattern (limited by the queue depth) and transmit them on at intervals that are always exact (integral) multiples of the emission interval. However, the implementation of the leaky bucket as a meter (or token bucket) in a traffic shaping function described above is an exact equivalent to the description of the leaky bucket as a queue: the