Refactoring Router Software to Minimize Disruption

Network operators are under tremendous pressure to make their networks highly reliable to avoid service disruptions. Yet, operators often need to change the network to upgrade faulty equipment, deploy new services, and install new routers. Unfortu-nately, changes cause disruptions, forcing a trade-off between the benefit of the change and the disruption it will cause. This disruption comes from the very design of the routers and routing protocols underlying the Internet’s operation. First, since the Internet is composed of many smaller networks, in order to determine a path between two end points, a distributed calculation involving many of the networks is necessary. Therefore, during any network event that requires a calculation, there will be a pe-riod of time when there are disagreements among the routers in the various networks, potentially leading to the situation where there is no path available between some end points. Second, selecting routes involves computations across millions of routers spread over vast distances, multiple routing protocols, and highly customizable rout-ing policies. This leads to very complex software systems. Like any complex software