Patent ID: 6118764
Filing Date: 2000-09-12
Classification: H04L,H04Q

Abstract:
A method of controlling the flow of ABR ATM (available bit rate asynchronous transfer mode) cells in an ATM network wherein a plurality of connections through the ATM network are each guaranteed a MCR (minimum cell rate) including an ABR connection, cells above the ABR connection's MCR being referred to as ABR elastic cells; comprising signalling a CI (congestion indication) and an NI (no increase) to a source of cells on the ABR connection, the signalling being carried out by way of passing along the ABR connection an RM (resource management) cell containing the Ci and NI, each switch along the ABR connection in sequence receiving the RM cell containing the CI and NI, having an opportunity to set the values for CI and NI in the RM cell before transmitting on an output port in the switch to the next switch in the ABR connection; wherein the new values of CI and NI are obtained by executing the steps of:determining an estimate of an input ABR elastic cell rate Port.sub.-- EIR of cells destined for transmission on the particular output port;determining an estimate of an output reservation output at the output port for cells having a higher priority than ABR elastic, HPE.sub.-- reserve;determining a port elastic allocatable rate Port.sub.-- EAR as a function of the output port's capacity, and HPE.sub.-- reserve;determining a local.sub.-- CI and local.sub.-- NI for the connection to be zero and zero respectively for the case where port.sub.-- EIR is less than port.sub.-- EAR*(1-delta.sub.-- NI), to be zero and one respectively for the case where port.sub.-- EIR is greater than port.sub.-- EAR*(1-delta.sub.-- NI) and less than Port.sub.-- EAR*(1+delta.sub.-- CI), and to be one and one respectively for the case where port.sub.-- EIR is greater than port.sub.-- EAR*(1+delta.sub.-- CI), when delta.sub.-- NI is between zero and delta.sub.-- CI is greater than zero; anddetermining CI and NI by ORing local.sub.-- CI with the CI in the RM cell, and by ORing local.sub.-- NI with the NI in the RM cell respectively.