The Price of Specificity in the Age of Network Virtualization

The virtualization trend in today's Internet decouples services from the constraints of the underlying physical infrastructure. This decoupling has the potential to facilitate more flexible and efficient resource allocations: the service can be realized at any place in the substrate network which fulfills the service specification requirements. This paper studies such flexibilities in the context of virtual network (VNet) embeddings. The network virtualization paradigm envisions an Internet where users can request arbitrary VNets from a substrate provider (e.g., an ISP). A VNet describes a set of virtual nodes which are connected by virtual links, both nodes and links provide certain resource guarantees. While some parts of the VNet may be fully specified (e.g., the node and link locations or technologies), other parts may be flexible or left open entirely. For example, it may be irrelevant for some users on which vendor hardware the VNet is realized, or a user only requests that the VNet runs in some European cloud provider. We study how flexible specifications can be exploited to improve the embedding of virtual networks. We introduce the notion of the Price of Specificity which captures the resource cost of the embedding under a given specification. We analyze on which parameters the Price of Specificity depends, and evaluate its magnitude in different scenarios.