The apparatus and method herein provide a means for actively monitoring a
communications node for datapath disruptions caused within the node. It
was developed to address linecard failures that were detected in the
field and for which traditional error detection mechanisms such as CRC
and OAM CC checks are not feasible. According to one implementation,
statistics are collected over a preset time interval. If any egress cell
counts are zero over a full interval, then the ingress interface for that
datapath is determined, e.g. using the node's cross-datapath information,
and the corresponding linecard of that ingress interface is contacted to
determine the ingress cell count. If the ingress cell count is non-zero
then the datapath is alarmed since the complete lack of cells transmitted
at the egress indicates a datapath disruption. Other implementations that
can detect datapath disruptions without a complete interval of statistics
collection and which do not require a zero egress cell count are possible
for cases where congestion, linecard resets, etc. can be ruled out.