LSC²: An extended link state protocol with centralized control

Current link state routing is based on routing decisions made through distributed interactions among routers. Link state is disseminated by means of flooding, which possesses a few limitations, such as excessive message overhead and network-wide computation. Thus, we propose LSC², an extended link state routing protocol with centralized control, in this paper to address this problem. In LSC², link state advertisements (LSAs) are communicated between a centralized element (CE) and a forwarding engine (FE) rather than traditional flooding. Multiple CEs form a separate control network as a representation of the control plane. Through this control network, LSAs are disseminated to FEs in a determinate manner. We also propose a signaling protocol for independent path convergence in the control network, as well as a routing control algorithm to prevent unnecessary routing updates in the forwarding network. We implement a prototype LSC² and evaluate its performance. Our experiments show that with the use of real topologies, LSC² can accelerate network convergence and reduce message overhead compared with OSPF. Moreover, LSC² is robust because having multiple CEs can prevent the occurrence of a single point of failure. LSC² also scales well with network size by adding additional CEs to share in the processing load.