Preemption in MPLS network

In a MPLS network LSPs preemption is based on their set-up and holding priority values. According to (de Oliveira, 2004), this preemption strategy can lead to excessive re-routing decisions. A preemption optimization is based on three criteria:

•  Number of LPSs to be preempted 
•  Priority of the LPSs 
•  Preempted bandwidth 

In (de Oliveira, 2004), an adaptive scheme is proposed to select lower priority LSPs that can afford having their rate reduced.
Besides prioritizing access policies preemption can also be used for restoration policies in event of a network failure.
In order to establish, maintain and tear-down a LSP the Label Distribution Protocol (LDP) and the Resource Reservation Protocol (RSVP) are use (Awduche, 2002).

de Oliveira, J.; Scoglio, C.; Akyildiz, I. & Uhl, G. (2004), 'New preemption policies for DiffServ-aware traffic engineering to minimize rerouting in MPLS networks', IEEE/ACM Transactions on Networking (TON) 12(4), 733—745.

D. O. Awduche and B. Jabbari, “Internet traffic engineering using multiprotocol label switching (MPLS),” Comput. Netw., vol. 40, pp. 111–129, 2002.