The assumption of routing symmetry is often embedded into traffic analysis and classification tools. This paper uses passively captured network data to estimate the amount of traffic actually routed symmetrically on a specific link. We propose a Flow-Based Symmetry Estimator (FSE) – a set of metrics to assess symmetry in terms of flows, packets and bytes, which disregards inherently asymmetrical traffic such as UDP, ICMP and TCP background radiation. This normalized metric allows fair comparison of symmetry across different links. We evaluate our method on a large heterogeneous dataset, and confirm anecdotal reports that routing symmetry typically does not hold for non-edge Internet links, and decreases as one moves toward core backbone links, due to routing policy complexity. Our proposed metric for traffic asymmetry induced by routing policies will help the community improve traffic characterization techniques and formats, but also support quantitative formalization of routing policy effects on links in the wild.

By increasing popularity of SOC, using Web services in applications has increased too. SOC creates a loosely coupled environment in which the actual execution environment might differ significantly from the one with the presupposed conditions during application design. Therefore, although an appropriate Web service might have been selected, by passing time, the Web service may not be efficient enough or may not be applicable under specific conditions. For service-oriented systems to be flexible and self-adaptive, it is necessary to automatically select and use a similar service instead of the one which causes the above mentioned problems. Finding a similar service means specifying the proper services which fulfill the same requirements as those fulfilled by the problematic service. In most of the previous works, a number of the best services (k) are selected and ordered based on functional similarity. The user must select one of these services based on his/her preferences. One important metric in selecting a similar service is considering QoS properties and user preferences about QoS. Because of the importance of this issue, in the present paper, an architecture is proposed in which, in addition to functional similarity, QoS properties and user preferences are also considered in selecting a similar service.

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