| 摘要 |
A method and system for Connection Admission Control (CAC) in a communications network, such as an ATM formatted B-ISDN network, is provided. Using end-to-end virtual path structures and class-of-service separation, various network virtual connections may be administered using a connection server based on a weighted round robin or similar connection-serving algorithm. Network users aware of the network structure and the means by which queue lengths are determined may easily calculate a Sustainable Cell Rate (SCR) for the traffic they wish to introduce into the network path for transmission to a given destination. The user declared SCR, in addition to other user declared traffic parameters, determines the queue lengths allocated in the network switches, such that a required level of Quality of Service is maintained. A measurement of certain types of transmitted cells in a virtual path, such as idle, unassigned, or low-priority cells, is made at any single point along the virtual path, such as at the source switch. This measurement of cells that may be considered to be "empty", i.e., available for use by high-priority cells, is used as the basis for a determination of the allowable connections that can be admitted to a virtual path. A relationship between the mean number of "empty" cells per scheduled cycle of the connection server and the cell rate bandwidth in cells-per-second that may be allowed to enter a virtual path that is already considered to be "full", based on the sum of the sustainable cell rates of its existing component connections, is used as the basis of CAC. Virtual connections may be admitted to a "full" virtual path if the cell rate of the requested connection is less than the allowable cell rate statistically determined from the mean number of "empty" cell timeslots in the path available for use by high-priority cells.
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