Dynamic Overlay Routing Based On Active Probing Measurements

As a new network architecture, overlay network has become the research focus in the network area recently. Overlay routing, the key problem in overlay network, has aroused even more attention from network researchers. Compared with traditional IP infrastructure providing single defaule path, topology diversity of the overlay network provides multi choices during the path selection process. We research the overlay routing problem in light of the following considerations. First, routing in the overlay often uses metrics such as hops and reference bandwidth, while the end-to-end performance metrics such as end-to-end delay and available bandwidth which may largely influence the user experience are rarely taken into account. Second, previous dynamic overlay routing based on active probing basically use a single metric, which can not reflect the end-to-end performance of the network comprehensively. Third, there are different kinds of business flow on the enterprise overlay network, the overlay routing mechanism should adjust accordingly to provide appropriate Quality of Service. In this paper, we first present a detailed comparison between overlay network infrastructure and traditional IP network infrastructure and summarize an approach to classify the overlay routing mechanism based on the TCP/IP hierarchy model. Then taking the above-mentiond considerations as the start point, we present a dynamic overlay routing mechanism based on active probing measurements. This mechanism uses a composite metric which is composed of delay, jitter and available bandwidth information. To implement differentiated service, we present an approach to dynamically adjust the composite metric to fullfil the specific service demand of the business flow carried by overlay network. In addition, we discuss possible optimization measures of the active probing mechanism, including the choice of probing packet type, metric, probing frequency and sample point, etc, with the purpose in mind that we should impose less interference to the network while at the same time gurantee the measurement accuracy to the greatest extent.As for the experiment, we first validate the mechanism's applicability in the virtual network testbed constructed using VMware. More importantly, we construct an emulation testbed using network performance data collected from an enterprise overlay network. We did comprehensive emulation experiment on this testbed, experiment results demonstrate the routing mechanism proposed runs well and the path chosen by our mechanism provides beter end-to-end performance than the default path in a significant way.