Statistics Collection in MPLS LSPs
In IP networks it is never possible to distinguish between different traffic end points. Only the inbound and outbound traffic of the interface can be calculated.
Consider that the traffic from M1 to M2 is 1Mbps and from M2 to M3 is 1Mbps. We cannot infer from IP as to what percentage of traffic present between M1 and M2 is actually destined to M3.
In MPLS, two different FECs can be assigned to destination M2 and M3 and then statistics can be calculated on per FEC basis. This workout is of significant importance in traffic engineering.