Modelling And Analyzing Behaviors Of Tunnelled Virtual Networks

Virtual networks are those network systems which depend upon the delivery capability provided by the Internet infrastructure but are independent of the Internet in both topology and information forwarding rules. Virtual networks are of parts of today's Internet structure and functionality. Tunnels play the role of virtual links for packet-switched virtual networks, which make the end-to-end concept of applications different from that of networks and, accordingly, make the services that the final users perceive are different from what the physical infrastructure carries. Therefore, the capacity of the infrastructure carrymg user communications is an essentially important issue about the virtual network behavior as well as its architecture. The thesis studies on the issues and applies the results to the practice of designing scaleable virtual network architectures.Theoretical analysis is combined with modelling and simulations in the thesis. On one hand, the definition of packet-switched network model, introduced by previous works over 2-dimensional von Neumann lattice, are expended to a generic Cellular Queueing Network model with any dimensionality and any neighborhood. Further, a new Dual-layer Cellular Queueing Network model is defined to describe interactions between virtual and physical networks. Simulations on the models explain the meanings of the analysis in the Mean-Field Theory, and present how seriously the carrying capacity of the physical network is degraded by large detours of tunnelling.On the other hand, based on approximately describing packet-switched networks with open Jackson queueing network model, a Mean-Field Theory is developed for the critical traffic behavior, which represents the capacity of a network carrying user traffics. It is shown that the decisive factor of the carrying capacity is the rate that traffic leaves the networks, and it is proved that the mean value of the critical traffic is negatively proportional to the free delay of an arbitrary packet without being queued. On the interactions of virtual and physical networks, it is discovered that delivering virtual network traffic with detours among the physical network is the major reason which degrades the leaving rate of traffic greatly. Therefore, it is proposed that the configuration of tunnels should be optimized with a "Minimum-Detour" criterion. Algorithms for this optimization problem is studied with implementations.Three engineering solutions for interconnecting IPv4 and IPv6 by virtual networks are investigated for case study. The Tunnel Broker and Dynamic Tunnel Peers are not conforming to the requirement of improving the carrying capacity as high as possible, though they have introduced useful mechanisms such as broker and arbiter. Under the Minimum-Detour criterion, a new architecture with an arbiter for the core part and brokers for the subscriber networks is designed for the circumstances of Wide-Area Networks where the structure is hierarchized. This design can play the role of the blue-print for the systems interconnecting customers to traditional IPv4 resources over the native IPv6 infrastructure of the next generation Internet.