FECN (1 bit) (Frame Relay)

Protocol: Frame Relay Frame Relay PCI

Field: forward explicit congestion notification

Length: 1 bit

Contents: congestion alarm / to be recognized by access nodes.

If a frame handler (i.e. Frame Relay router) suffers from congestion, it will notify the corresponding access nodes by FECN (C/R=0) and BECN (C/R=1) bits set to one. The access nodes won't accept frames that exceed the CIR any longer unless the congestion alarm has stopped (FECN=0, BECN=0).