Abstract — The advance on data transmission in optical networks has allowed data forwarding decisions to be taken at multiple levels in the protocol stack (e.g., at network and optical levels). With such capability, big IP flows can be moved from the network level and switched completely at the optical level over lambda-connections, where they get better Quality of Service (QoS). Meanwhile, the regular IP routing level is offloaded and can serve smaller flows better. With the continuous growing of traffic on the Internet, the selection of big IP flows can become difficult to be done by using current management approaches (conventional management and Generalized Multiprotocol Label Switching (GMPLS) signaling). The University of Twente (UT) is researching the use of self-management as an alternative to overcome this issue. In order to properly identify IP flows eligible to be moved to the optical level, the characteristics of these flows must be known, though. In this context, this paper analyses some of the characteristics of IP flows eligible to the optical level by observing their size, duration, throughput, and recurrence. In this analysis, we observe those characteristics while using various definitions for an IP flow as well as using different time intervals. The main contribution of this paper is to show the behavior of IP flows eligible for lambda-connections. Not in the least, we also show how this knowledge can be used in our self-management of optical networks approach.