MPLS is a networking protocol or technique designed to segment data flow channel of an wide area IP network. Specific channels may be configured for priority of data packets to control the Quality of Service (QoS). The conventional IP simply addresses each data packet individually and sends it on its way through the network with out regard to its relative importance, and the data packets for any given session can take multiple paths traveling from the sender to the receiver. Instead, with MPLS, all packets in an IP session are grouped together into a single "flow" and then tagged for priority handling through the network routers. The group of packets, or flow, is mapped onto a dedicated path in an ATM or frame relay virtual circuit, or any other data link for delivery. MPLS mapping, in the OSI Layer 2), is actually accomplished by swapping layer 3 labels for layer 2 labels in a data packet header, hence the term label switching. In this manner, data transmissions can be assigned different levels of priority so that financial file transfers, or VoIP traffic, get higher priority than e-mail.