An OSPF enhancement for energy saving in IP networks

This paper deals with a strategy to save energy in an IP network during low traffic hours allowing a subset of IP router interfaces to be put in sleep mode by means of an Energy Aware Routing (EAR) strategy. The EAR is fully compatible with OSPF and is based on the “Shortest Path Tree (SPT) exportation” mechanism, consisting in sharing the SPTs among couple of routers. The EAR strategy is able to control the set of links to be put in sleep mode through the concept of “move”. This approach gives the network operator the possibility to control the network performance and allows a smoothed QoS degradation strategy to be implemented. A formulation of the EAR problem is presented and will be demonstrated that this problem can be traced back to the well-known problem of the maximum clique search in an undirected weighted graph. A heuristics, called Max Compatibility, is presented and, as shown in the performance evaluation study, it allows to save about 30% of network links with a negligible increase of network path lengths and link loads.