Everything what you do not want know about the OSPF! In a Service Provider network, one of the most important part is the IGP (Interior Gateway Protocol). Why? Because the network core convergence and routing strategy is depend on the IGP routing rules. If the IGP can not support some features what  are needed for the traffic engineering, it could be a  future operation or development problem. So SPs select IGPs which are satisfy every operational and business needs, and it will be a future proof protocol. Many of service providers typically choose OSPF or ISIS for IGP, because: - they are RFC and ITU-T conform, vendor independent protocols (in general) - they support MPLS traffic engineering features (OSPF opaque LSA 10 11) - link-state routing protocols, which means  that these can provide faster convergence than vector-path or distance vector protocols, and they are more scalable. What is OSPF?  OSPF (Open Shortest Path First) protocol is a dynamic link-state based routing protocol