The traffic growth as well as the diversity in Quality of Service (QoS) requirements are drastically increasing the challenges in achieving effective network management. The need to handle dynamic QoS requests exacerbates such challenges and dictates novel solutions able to make network management more flexible and adaptable to traffic changes. To this aim, in this paper we propose a novel approach aiming at dynamically managing the QoS within the Software-defined Networks through flow initialization and termination requests from the end-client. This approach allows management and control planes to be informed as soon as possible about the changes in the traffic requirements of the network, thus introducing a more flexible (re)configuration of the network according to the actual traffic demands. Such flexibility is particularly interesting within the next generation networks that aim to serve a diverse set of vertical industries. While the full picture of the network architecture is depicted in this paper, we also present the prototype implementation of this novel approach. The latency and overhead as introduced by the proposed approach in this paper are studied using the prototype implementation.