Heterogeneous network architectures: a layered approach for modeling key building blocks for continuing network evolution

Future networks will be heterogeneous! Due to the sheer size of networks (e.g., the Internet) upgrades cannot be instantaneous and thus heterogeneity appears. This means that instead of trying to find the olution, networks hould be designed as being heterogeneous. One of the key equirements here is flexibility. This thesis investigates such heterogeneous network architectures and how to make them flexible. A survey of algorithms for network design is presented, and it is described how using heuristics can increase the speed. A hierarchical, MPLS based network architecture is described and it is discussed that it is advantageous to heterogeneous networks and illustrated by a number of examples. Modeling and simulation is a well-known way of doing performance evaluation. An approach to event-driven simulation of communication networks is presented and mixed complexity modeling, which can simplify models, is introduced. Modeling and simulation is then used to evaluate the behavior of adaptation devices in the context of heterogeneous networks - devices that can interconnect network domains employing diverse technologies. The simulation shows how queuing disciplines impact delay profiles. TCP and application behavior on top of such adaptation devices are also investigated by simulation. Finally, a new concept for packet forwarding is introduced and modeling of this scheme is presented. The simulation results show that the scheme is feasible to use in future networks. All in all these issues investigated is part of what is needed for getting the required flexibility into future, heterogeneous networks.