A backbone carrier is approached by an ISP_A which provides L3VPN services. The ISP_A requires MPLS VPN services from the backbone carrier to establish connectivity between the two POPs of the ISP_A. Which label protocol should the backbone carrier use to provide the proper connectivity that the ISP_A requires?
A. L2TPv3
B. L2TPv2
C. LDP
D. GRE
E. mGRE
F. BGP
