Abstract-Recently network virtualization has been proposed as a promising way to overcome the current ossification of the Internet by allowing multiple heterogeneous virtual networks (VNs) to coexist on a shared infrastructure. A major challenge in this respect is the VN embedding problem that deals with efficient mapping of virtual nodes and virtual links onto the substrate network resources. Since this problem is known to be N P-hard, previous research focused on designing heuristic-based algorithms which had clear separation between the node mapping and the link mapping phases. This paper proposes VN embedding algorithms with better coordination between the two phases. We formulate the VN embedding problem as a mixed integer program through substrate network augmentation. We then relax the integer constraints to obtain a linear program, and devise two VN embedding algorithms D-ViNE and R-ViNE using deterministic and randomized rounding techniques, respectively. Simulation experiments show that the proposed algorithms increase the acceptance ratio and the revenue while decreasing the cost incurred by the substrate network in the long run.

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Abstract-Recently network virtualization has been pushed forward by its proponents as a long term solution to the gradual ossification problem faced by the existing Internet and proposed to be an integral part of the next-generation networking paradigm. By allowing multiple heterogeneous network architectures to cohabit on a shared physical substrate, network virtualization provides flexibility, promotes diversity, and promises security and increased manageability. However, many technical issues stand in the way toward its successful realization. This article investigates the past and the state of the art in network virtualization along with the future challenges that must be addressed to realize a viable network virtualization environment.

Abstract-In recent years, network virtualization has beenpropounded as an open and flexible future internetworking paradigm that allows multiple virtual networks (VNs) to coexist on a shared physical substrate. Each VN in a network virtualization environment (NVE) is free to implement its own naming, addressing, routing, and transport mechanisms. While such flexibility allows fast and easy deployment of diversified applications and services, ensuring end-to-end communication and universal connectivity poses a daunting challenge. This paper advocates that effective and efficient management of heterogeneous identifier spaces is the key to solving the problem of end-to-end connectivity in an NVE. We propose iMark, an identity management framework based on a global identity space, which enables end hosts to communicate with each other within and outside of their own networks through a set of controllers, adapters, and well-placed mappings without sacrificing the autonomy of the concerned VNs. We describe the procedures that manipulate these mappings between different identifier spaces and provide performance evaluation of the proposed framework.

Grid-synchronization may be the most significant task in order to integrate renewable energy sources (RESs) and electric vehicles (EVs) into the power grid. The popular technique for grid synchronization is the power based phase locked loop (PLL). The major challenges that one encounters to design a robust power based PLL is the filter design inside the power based PLL control loop, and estimating the grid voltage parameters under frequency drift conditions. A wide bandwidth should be considered during filter design if a wide range of frequency variations are predicted in the grid voltage. The traditional filters cause a large phase delay if a wide bandwidth is considered during filter design. As a result, it degrades the transient performance of the power based PLL. In order to improve the transient performance of the PLL, this paper adopted a Fourier linear combiner (FLC) filter inside the PLL control loop. Moreover, a feedback loop is used to make the FLC frequency adaptive in order to estimate the grid voltage parameter when grid frequency drift occurs. Simulation and experimental results are provided to verify the proposed technique.