Originally designed to improve the efficiency of packets forwarding, MPLS provides support for Traffic Engineering and network resilience. Constrained-based path computation is a key building block for Traffic Engineering in MPLS networks, since it allows to set-up LSPs along paths that satisfy QoS constraints. This paper deals with on-line and offline path computation algorithms and, more specifically, introduces and compares the performance of three novel offline path computation algorithms which aim at improving the performance of their standard version by means of some heuristics. All these algorithms have been developed in NS2 as an extension of OSPF-TE\ns and integrated with RSVP-TE\ns.