A Linear Programming Model for Traffic Engineering in 100% Survivable Networks under combined IS-IS/OSPF and MPLS-TE Protocols

The paper concers the problem of minimizing the maximum link utilization of IP telecommunication networks under the joint use of the traditional IS-IS/OPSF protocol and the more sophisticated MPLS-TE technology. Both working conditions and single link failure scenarios are addressed. An innovative Linear Programming mathematical model is proposed that, while optimizing the network utilization, provides optimal user performance, efficient use of network resources, and 100\% survivability in case of single link failure. The hybrid approach takes advantage of both IGP and MPLS-TE technologies providing a flexible tool for IP networks traffic engineers. The proposed model is validated by a wide experimentation performed on synthetic and real networks, both in working and failure conditions. The obtained results show that the new approach considerably reduces the maximum utilization of the network, thereby allowing a more efficient use of the network resources; setting a limited number of LSPs yields better results than those obtained by simply optimizing the IGP weights. In addition, an optimized set of IGP weigths allows to further improve the network performance in case of failures. The computational time needed to solve the LP model is very limited and it well matches the real time requirements.