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By separating network functionalities from the dedicated hardware and implementing them in the form of Virtual Network Function (VNF), Network Function Virtualization (NFV) provides a new service paradigm called Service Function Chain (SFC). It is unrealistic to replace the running VNFs due to the stateful information accumulated, which makes the current VNF re-deployment or replacement approaches no longer effective enough. Such a situation is even worse when VNFs are shared. Instead of replacing VNFs, this paper proposes a VNF migration approach to maintain the network balance and performance by migrating VNFs from poor-state nodes to good-state nodes. In particular, two situations are considered, which are node-aware and link-aware VNF migrations respectively. Via migrating the VNFs that are related to the nodes or links causing Quality of Service (QoS) issues, the network and service performance can be optimized. In addition, the migration impact is also minimized by perceiving the global network states. The experimental results indicate that the service performance is improved and the load balance is achieved after the VNF migration.

Most existing broadcast protocols for wireless ad hoc networks use a minimal virtual backbone subnet to broadcast messages, which can minimize the total broadcast transmission number. However, since the unreliability of wireless link is not considered, the broadcast efficiencies of these protocols are not high in real networks. This paper proposes an efficient network-wide reliable broadcast protocol (ENWRB), which adopts network coding scheme to reduce the retransmissions in single-hop broadcast and a link-aware virtual backbone election algorithm to generate the more efficient broadcast backbone. Simulation results show that, under the same premise of ensuring all nodes to receive broadcast message successfully, the efficiency of ENWRB is higher than that of Hierarchical CDS-based Algorithm (HCA) greatly. [ABSTRACT FROM AUTHOR]