Hierarchical virtual networking: Architecture and resource management

Virtual networks are autonomous logical networking environments overlaid on top of a shared physical networking infrastructure. As a network cluster management tool for user and/or application groups, virtual networking can facilitate various logical overlay networks such as virtual private networks and virtual network operators. Being logical, virtual networks are highly Such flexibility of virtual networks is further extended in this thesis via hierarchical superimposition of virtual networks. In the interest of provisioning hierarchically organized virtual networks with service quality assurance, the focus of this thesis is laid on the issues of hierarchical connectivity and resource management. Hierarchical connectivity amongst virtual networks is captured through the notions of ‘virtual nodes’ and ‘virtual links’, which are logical subsets of the underlying physical nodes and links. For ‘hierarchically-fair’ sharing of link bandwidths, we develop a novel hierarchical fair queuing algorithm. Our approach for hierarchical packet scheduling is to approximate the hierarchical link sharing rule, dictated by the hierarchical generalized processor sharing model, in a single step. The advantage of our single-step approach, as opposed to the multi-step approach taken in H-PFQ, is the delay characteristics that do not depend on the relative positions of scheduling classes in the scheduling hierarchy. The two potentially conflicting goals of hierarchical bandwidth distribution and layer-independent delay performance are accomplished in harmony via the notions of ‘distributed virtual times’ and ‘service credits’.