I wrote in the previous post about traffic engineering, how it could help to utilize the secondary link in case when primary link is congested. MPLS TE is used set up the tunnels from headend to tailend routers. Intermediate routers are only responsible to forward the tarffic. MPLS TE uses RSVP signalling which is aka Resource Reservation Protocol. It uses two messages to acomplaish this signaling: Path Messages & Resv Messages.