Event-based technique for determining instantaneous cell bandwidth in a digital communications network

Abstract

A method and associated apparatus for determining the bandwidth or transmission rate of a desired type of cell in a cell stream occurring over a digital communications network connection during a time interval between occurrences of a first and second predetermined event. The transmission rate of the desired cell, such as an Asynchronous Transfer Mode (ATM) Available Bit Rate (ABR) user cell may be measured only when certain conditions exist, eliminating unnecessary calculations from being performed. Furthermore, the cell bandwidth may be determined immediately upon occurrence of the predetermined events, providing real-time feedback and analysis to test and measurement and/or network nodes. In an ATM ABR environment, for example, this enables the implementing system to immediately compare the actual cell transmission rate calculated in accordance with the present invention to the rate at which the cell stream was transmitted by a source node, as identified by a resource management (RM) control cell in the cell stream. Such information may then be immediately provided to the virtual or actual source nodes in the network in a backward-going RM cell for subsequent use in determining the transmission rate of a future cell stream. One implementation is in an event-based cell bandwidth determinator for determining a transmission rate of a first type of cell in a cell stream occurring over a digital communications network connection during a time interval between an occurrence of first and second events, such as successive occurrence of a second type available bit rate ABR cell stream. Here, the first type of cell is a user cell and the second type of cell is a resource management (RM) cell. The connection may be one or more virtual channels or paths in the ATM network.