Implementation of a police criterion calculator based on the leaky bucket algorithm

The usage parameter control (UPC) function for a broadband ATM network is essential for guaranteeing a certain quality level. Though no single UPC algorithm has been standardized, the leaky bucket algorithm is one of the favoured algorithms as it can account for cell delay variation. As each connection has to be enforced separately, a large number of independent leaky buckets is needed for a single link. To make a VLSI implementation feasible that provides a multitude of leaky buckets, the algorithm is slightly modified for time-divided and synchronous operation. After this revision, calculations are simplified to (integer) bit shifts and additions on connection-specific data retrieved from and stored into memory. The required amount of memory is derived directly from the desired performance parameters. For realistic performance assumptions, 42 bits per connection is required. The design requires significantly more memory if an absolute granularity (e.g. a multiple of 16 kb/s) would be implemented rather than a relative granularity. Other parameter changes show a modest influence on the amount of memory needed.<
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