METHOD AND APPARATUS FOR MANAGING THE STATISTICAL MULTIPLEXING OF DATA IN DIGITAL COMMUNICATION NETWORKS

摘要

An apparatus and method for supporting a plurality of virtual channel (VC) connections within a single virtual path (VP) in a digital communications network operating in the Asynchronous Transfer Mode (ATM) is described. The apparatus (56) is combined with the cross-connect part of a conventional VC switch (54) to form a Data Switch (40). A VP switch (42) switches and terminates incoming bandwidth-resourced VPs on lines (48), some of which are carrying non-bandwidth-resourced VCs and switched onto lines (50) on the output side of VP switch (42). VPs on lines (50) are switched and multiplexed by the Data Switch (40). The apparatus (56) comprises buffers (66) for storing cells and a VP rate server. The buffers (66) are significantly larger than in a conventional VC switch to enable smoothing of data flow peaks associated with data flowing from multiple bandwidth resourced VP tributaries into single resourced VP tributaries. Notwithstanding the large buffers in the Data Switch (40) there may still be congestion when data bursts occur on several converging streams. When buffer overflow is threatened, the Data Switch (40) discards whole frames, i.e., whole VPI-VCI sequences marked with an end of transmission delimiter in the PTI, rather than individual cells originating from different frames as would be the case with normal ATM cell multiplexing. The Data Switch also employs rate shaping by virtual scheduling and implemented by linked lists used to read data from the Data Switch buffers into bandwidth resourced VPs.