Always we can see that in service provider network there will be primary link & Secondary link but only one link will be utilize. Implementing Policy base routing somehow we manipulate the route,
But still it required man force to monitor the link & manipulate the route as per requirement. It becomes very chaotic to do route manipulation every time in service provider network. So the solution is to have a technology where we can use un-equal load balancing or path manipulation as per requirement. So it give us scalability to use or chose any path that we required, may be it can primary path, backup path or both path i.e. un-equal circuit load balancing . So the solution isMPLS- Traffic Engineering, using MPLS traffic engineering we can manipulate the route as per our requirement where you can use each circuit or you can have route path on-demand.
MPLS Traffic Engineering (MPLS TE) is a growing implementation in today's service provider networks. MPLS adoption in service provider networks has increased manifold due to its inherent TE capabilities. MPLS TE allows the MPLS-enabled network to replicate and expand upon the TE capabilities of Layer 2 ATM and Frame Relay networks. MPLS uses the reachability information provided by Layer 3 routing protocols and operates like a Layer 2 ATM network. With MPLS, TE capabilities are integrated into Layer 3, which can be implemented for efficient bandwidth utilization between routers in the SP network.
Below link show an example where we have redundant link in service provider network, Without MPLS Traffic engineering we can see that we can only one link will be utilized . But after implementing MPLS Traffic engineering we can use both circuit as per our requirement or on-demand path manipulation per VRF.
Below link contain the complete document for MPLS TE with Per VRF/VPN