Networking and software design principles converge currently under the notions of Software-Defined Networking (SDN) and Network Function Virtualization (NFV). This means that network services are not anymore static and manually configured, but they become flexible and in the end virtualized components. This convergence enables to dynamically orchestrate the network, to move network functions to the cloud and to direct and prioritize traffic intelligently. Applying cloud principles to network services, configuration and management requires mechanisms for automation, virtualization and elasticity. Ultimately, network services may improve the customer experience for the end users requiring on-demand network resources. The Cross-Layer Orchestrator (CLO) presented in this paper, establishes a tie between the Application and the Network Layers. Through the proposed Cross Layer API, the CLO provides an interface for client and server side applications to reserve, alter and release network resources. Our solution makes the network more dynamic by extending the orchestration functionalities not only to provide on-demand provisioning of network services, but also network flows. In this way the network should be able to adapt accordingly to the requirements of the applications

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IEEE802.11 wireless LAN systems are being widely used and multiple wireless LAN coexistence systems like 802.11b/g are available at the same time. However, in such environments, network performance is likely to degrade because the CAMA/CA mechanism does not always work well. Especially in the 802.11b/g systems, issues on performance degradation caused by the CTSprotection mechanism come to surface. To manage and maintain the QoS in such environments, it is required to detect and estimate the QoS degradation effectively. We found that the so-called retry ratio (i.e., the retry ratio of the numbers of transmitted packets to retransmitted ones) is strongly correlated with IPpacket quality metrics through our IP packet experiments. It is thus considered that retry ratio is applicable to managing the quality of some applications over wireless LAN.