Design principles for ISP networks with consideration to overlay routing behaviors

In recent years, network applications and services, such as P2P (Peer-to-Peer) file sharing, CDNs (Content Delivery Networks), and IP-VPNs (IP Virtual Private Networks), have been deployed over the Internet. These applications and services configure their own overlay networks. Each overlay network adopts its own routing algorithm to optimize users’ criteria. On the other hand, the underlay network employs the IP routing. However, the IP routing does not necessarily take into account metrics for the overlay routing. That is why the overlay routing has been considered. End users of overlay networks greedily choose better routes to optimize their own performance without considering the performance with regards to the network-wide criteria. Such selfish behaviors of end users cause unexpected increase of traffic volumes and traffic distributions on the underlay network. Since the underlay network cannot directly control the behaviors of the end users of overlay networks, it is important for network operators of underlay networks to appropriately design the networks by taking into account the selfish behavior of the overlay routing. In this thesis, we first evaluate the impact of the overlay routing’s selfish behavior on realistic router-level topologies from the perspective of maximum link load and average latency in the case that the fixed shortest path routing is adopted for the underlay networks. The results of our evaluation show that the overlay routing achieves near optimal latency but concentrates traffic on certain links, when the overlay routing is at equilibrium. In addition, our results show that the maximum link load and the average latency in realistic router-level topologies which have the power-law attribute are more affected by the overlay routing than those in POP level topologies. We next consider the case that the routes in underlay networks are dynamically updated against the change of link load. In such cases, the routing in overlay networks and that in the underlay networks interfere with each other. We then evaluate the impact of the interaction between the 1 overlay routing and the routing in the underlay networks in realistic router-level topologies. The results indicate that the interaction makes the maximum link load be over 1.0. We then investigate the impact of the interaction in cases that the number of nodes dynamically updating the routes in underlay networks is limited. We examine where we should allocate the nodes that dynamically update the routes. The results shows that the maximum link load is decreased to 0.65 from 1.0 when only the nodes classified as “provincial hubs” dynamically update the routes in the underlay networks against the change of link load. Based on this observation, we finally investigate the network design of ISP networks with consideration to overlay routing behaviors. We then introduce overlay-optimal capacity design and compare the design to two conventional capacity designs in order to clear up which links we should enhance in ISP topologies. The results show that we need to enhance the capacities of some links more than that of the conventional design if we consider the overlay routing behaviors. It also indicates that there exist nodes that have important roles for reducing the impact of the overlay routing behavior.