Proactive Rerouting in Network Overlays

Virtual overlay network technology provides important benefits to large data centers and to service providers. These benefits include traffic isolation and ease of service provisioning. When the underlying network supports traffic engineering, tunneling brings another important benefit: the ability to control the exact route of all packets without handling each independent flow. This paper addresses the problem of rerouting when the core network supports traffic engineering. We introduce the novel concept of proactive (time-driven) rerouting, which we distinguish from the well-known concept of reactive (event-driven) rerouting. One important advantage of proactive rerouting is reducing the communication between the core network controller and the edge network controller. Another advantage is that new flows do not have to wait before they are admitted into a rerouted tunnel. Unlike a reactive rerouting algorithm that knows which tunnel has to be rerouted, a proactive rerouting algorithm does not receive as an input the identity of a specific tunnel. Thus, its main goal is to predict which tunnel to reroute in order to increase the probability that future flows will be accommodated. Our main contribution is the development of a proactive rerouting algorithm that performs very well, sometimes even better than the reactive algorithms.