Abstract: Data is written into a circular buffer at an address pointed to by a write pointer. A number is written into the address with the data. Each time the circular buffer is traversed by the write pointer this number increments modulo a predetermined number. This number makes the circular buffer appear longer than it really is and can be used to identify underruns. The buffer has application in a segmentation and reassembly device for ATM constant bit rate services.

Abstract: Data is written into a circular buffer at an address pointed to by a write pointer. A number is written into the address with the data. Each time the circular buffer is traversed by the write pointer this number increments modulo a predetermined number. This number makes the circular buffer appear longer than it really is and can be used to identify underruns. The buffer has application in a segmentation and reassembly device for ATM constant bit rate services.

Abstract: A method of managing buffers in a SAR (Segmentation and Reassembly) device in a cell-relay network in dynamic bandwidth circuit emulation mode involves reading out TDM data from a buffer at a location determined by a read pointer, and writing data from incoming cells commencing at a buffer location determined by a write pointer. The write pointer is incremented as data from incoming cells are written into said buffers. On arrival of an incoming cell a determination is made as to the location of said write pointer. If the location of the write pointer lies between a first value equal to the location of the read pointer plus a predetermined maximum lead plus a predetermined DBCES buffer less the number of bytes per active channel and a second value equal to the location of the read pointer plus said predetermined DBCES buffering, an overrun condition is declared.

Abstract: In a method of managing buffers in a SAR (Segmentation and Reassembly) device operating in DBCES (Dynamic Bandwidth Circuit Emulation Service) mode, first an active channel buffer limit is determined. This is dependent on the number of active channels in the virtual circuit. Next, the amount of buffering for each active channel is set equal to the CDV (Cell Delay Variation) plus the active channel buffer limit. This prevents underruns over overruns from occurring when the number of active channels suddenly changes.