MPLS and Next-Generation Networks: Foundations for NGN and Enterprise Virtualization

MPLS-based L3VPNs were first defined in the Informational IETF RFC 2547. It came about as a result of a tag switching invention from Cisco. The RFC 2547 was later revised to draft-ietf-2547bis. This is now a final approved RFC 4364. RFC 4364 adds the capability to support Inter-AS, Inter-Provider VPNs, and Carrier Supporting Carrier VPNs. The RFC 4364 also describes how MPLS VPNs can be built over an IP core using point-to-point GRE tunnels or IPSec tunnels.