Optical networks are fast and reliable networks that enable, amongst others, dedicated light paths to be established for elephant IP flows. Elephant IP flows are characterized by being small in number, but long in time and high in traffic volume. Moving these flows from the general IP network to dedicated light paths can be beneficial for both the elephant flows as well as the general IP network. Elephant flows over light paths would benefit from receiving better Quality of Service (at the optical level there is no jitter and far more bandwidth) and, at the same time, IP networks would be off-loaded and therefore offer better Quality of Service to the remaining, smaller IP flows. Identifying elephant flows in large scale IP networks is therefore an important task in order to effectively manage the network. In practice such flows are generally characterized using 5-tuple flow definition (source/destination address/port and protocol), which may be too restrictive for the purpose of establishing optical light paths. In this paper we evaluate different flow definitions at different levels of granularity. Using measurements at a large national research network, we compare our alternative flow definitions to the traditional 5-tuple definition. We show that the discovery of elephant flows eligible to be transferred over light paths can better be reached using less restrictive flow definitions.
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