What is the Generic Flow Control (GFC) header in an ATM NNI cell used for?

A.
Rate control between the ATM NNI switches

B.
Rate control between UNI devices

C.
GFC has local significance, only, and the value encoded in the field is not end-to-end.

D.
None of the above

Explanation:
http://www.pulsewan.com/data101/atm_basics.htm