This read-only counter tallies cells discarded because the egress port queue serving this channel's service type became completely full, with the counter specifically reflecting the shared queue for the port/service-type combination this channel belongs to rather than a purely per-channel queue. Admins use this to identify when the egress side of a port - shared across all channels of the same service type - has run out of buffering capacity under load. For example, if several CBR channels sharing the same port all show increasing chanEgrPortQfullDiscardCells, the admin knows the shared CBR egress queue on that port, not any single channel's own queue, is the bottleneck.