MPLS - Multi Protocol Label Switching is the basic private networking technology that most large carriers worldwide have moved to by upgrading their networks.  The two primary features of MPLS networks are that they more secure and they enable controllnig Quality of Service (QoS) for each media types such as voice, video, and data.  MPLS is more secure because the header on each data packet is labeled in such a way that each is uniquely identified relative to it's destination and the source.  So the packet is more secure than former VPN packet labeling methods.