A versatile architecture for the design of UPC functions for ATM

摘要

The Usage Parameter Control (UPC) function in a broadband ATM network is essential for guaranteeing a certain quality level. For some applications a simple peak cell rate enforcement is adequate. Other applications desire a more flexible traffic contract and thus require a more flexible policing function. As the policing function must be performed at virtually any access to the network, adequate performance has to be paired with easy implementation. This article focuses on the implementation of such a UPC function for a large number of simultaneous connections.An architecture is proposed to yield a maximum of flexibility at modest implementation cost. In the architecture the following functionalities are distinguished: Cell Storage, Extraction of cell header information, Police Criterion Calculation, a Decision Function, a Translation Function and the obvious Auxiliary Functions.The proposed partitioning of functionalities leads to an architecture that provides both versatility and scaleabil-ity. Simple and complex UPC functions may be realised without adverse impact on implementation complexity, just by combining the functionalities in different ways. To illustrate this versatility, two examples of a more complex UPC function are given. In the first example the user cell stream is enforced using different time scales, e.g. the peak cell rate and a long term (sustainable) cell rate. The second example shows how a connection containing cells with mixed settings of the Cell Loss Priority bit can be controlled according to the requirements set in the ITU-TS recommendation.