ITU used SDLC as a basis to develop LAPF for the Frame Relay environment, along with other equivalents:  LAPB for the X.25 protocol stack, LAPM for the V.42 protocol, and LAPD for the ISDN protocol stack.
ITU utilized SDLC as a basis for creating LAPF in the Frame Relay setting, similar to LAPB for X.25 protocols, LAPM for V.42 protocols, and LAPD for ISDN protocols.