The blockchain technology enables entities to query and alter information without trusting a middle party while providing a secure data storage in a decentralized manner. In this paper, we focus on an IT data supply chain scenario, where multiple actors negotiate a tenancy agreement for virtualized network resources. This process consists of service providers (SPs) requesting the embedding of specified virtual networks across multiple infrastructure providers (InPs). Since InPs are typically not willing to disclose detailed internal network information, this is a major deal breaker that hampers the efficiency of the service negotiation process. After reviewing the related work on centralized and decentralized virtual network embedding (VNE) approaches, we briefly discuss the reasons for a blockchain approach for this problem. Our approach comprises of a brokerless blockchain based system, that uses smart contracts and a VN partitioning algorithm based on the Vickrey auction model. Finally, we investigate the feasibility of our approach, by first analyzing the behavior of the introduced auction model in adverse conditions and by secondly evaluating the blockchain performance given different consensus protocols.

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A wide variety of virtual worlds exists today. They embed the user into a virtual reality allowing interaction with the virtual environment and, in case of multiplayer worlds, other users. Our goal is to support these interactions. Therefore we are using virtual parameters to describe the user's virtual context and provide additional services depending on this context. These services can either be included into the virtual world or can be realized using a community portal. In this paper we will introduce the concept of virtual context based services and its fundamentals like the classification of interaction in virtual worlds, a generic interaction model and an extended model including additional services.

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