A 4 bit field in the ATM cell header with local significance (i.e. it's value is not carried end-to-end and is overwritten in ATM switches). Though not currently used (as of 95-07-19) this field is intended to provide standardized local functions (e.g. flow control). One possible use bantered about is to use the GFC to arbitrate cell transfer when more than one end systems shares a UNI.