Improving IGP Convergence through Distributed OSPF in Scalable Router

Fast convergence in IGP is very important for widespread deployment of real time applications. Many efforts, such as fast hello and fast flooding, have been proposed to reduce the convergence time in IGP. However, these solutions need to consume a large amount of CPU and memory resources in routers. Furthermore, they require collaboration of two neighbor routers. In this paper, we analyze the limitations in traditional open shortest path first (OSPF), which causes slow (or not so fast) convergence based on failure data collected in real ISP networks. To address these issues, we propose a distributed OSPF (DOSPF) scheme to schedule routing computation through self-adaptively adjusting SPT waiting time. We analyze the convergence performance with DOSPF with Petri net. We then build a simulation tool to with routing trace in China Education and Research NETwork 2(CERNET2) to evaluate our DOSPF scheme. Our simulations show that DOSPF can effectively improve the IGP convergence performance.