Design of Multi-layer Telecommunication Networks: Fairness, Resilience, and Load Balancing

Migration to Next Generation Internet architectures poses new challenges for network operators in planning core networks and calls for efficient network planning and optimization tools. Optimization models underlying such tools are developed in this thesis. We study a number of single and two-layer core network design problems defined as mathematical programmes, focusing on fair bandwidth allocation among demands, recovery mechanisms, and load balancing on network links. Assuming elastic traffic, fair allocation of network bandwidth among the users is not trivial since different users may have different preferences and requirements for minimum bandwidth. We study single and two layer network dimensioning tasks where elastic and non-elastic demands are combined, and investigate different fairness principles, with special attention devoted to proportional fairness. The models are developed for designing the networks for the normal state of network operation, as well as for failure states. For the two-layer problems it is not at all clear in which layer the recovery should be performed, and what recovery mechanisms to use. Therefore, recovery aspects in different layers are studied and models are provided for different recovery mechanisms. Furthermore, a generic resolution framework and heuristic algorithms for the selected dimensioning and allocation problems in two-layer networks are developed. Balancing of load on network links decreases probability of rejection of future requests due to shortage of resources in some parts of the network. In the thesis different load balancing options are discussed, and an integrated routing, recovery, and load balancing strategy is developed. It combines failure dependent backup path protection, shortest path routing, and load balancing according to proportional fairness principle. The thesis presents both theoretical findings, models, and resolution algorithms for the studied problems. Efficiency of the algorithms is illustrated by numerical examples. The thesis also gives a systematic view and classification of different aspects related to network architecture, recovery, fairness, and flow/congestion control

An IP/MPLS over WDM network design problem

to be adde

Two design problems for the IP/MPLS over WDM networks

Design problems related to the next generation Internet core networks can be difficult to solve in an exact way. Hence, for large networks they may require approximate algorithms. The paper considers two optimization problems for off-line design of robust NGI core networks carrying elastic traffic with a two-layer IP/MPLS over WDM architecture. The problems are NP-hard and are formulated as mixed-integer programs. An efficient approximate iterative method based on separate design of the two layers is proposed for solving the problems; the method is illustrated with numerical example

Design models for robust multi-layer next generation Internet core networks carrying elastic traffic

The paper presents three optimization models for designing robust two-layer networks carrying elastic traffic. The formulations correspond to different restoration mechanisms against failures. An original iterative algorithms to solve the models is given and illustrated with numerical examples. The models can be applied for designing NGI IP over DWDM core networks

Design models for robust multilayer next generation Internet core networks, carrying elastic traffic

This paper presents three mathematical formulations for designing robust two-layer networks carrying elastic traffic. The formulations differ by the way flow reconfiguration is performed in the case of link failures. An iterative algorithm to solve the problems is given and an extensive numerical study is provided comparing the effectiveness of the three reconfiguration approaches. The formulations can be applied for designing next generation Internet (NGI) core networks with two-layer IP-over-WDM structur

Robust dimensioning of proportionally fair networks

The notion of proportional fairness has recently gained considerable interest as a potential means for a fair allocation of bandwidth between the end nodes of demands in the networks carrying elastic traffic. The issue of proportionally fair allocation of bandwidth for the nominal state of the network has been studied before, both in the capacitated (link capacities given) and the uncapacitated (link capacities are also subject to optimisation) cases. In the presented paper, we address a more complicated uncapacitated problem - optimisation of link capacities for a proportionally fair network robust to failures. We formulate a relevant optimisation problem and propose efficient solution algorithms. Efficiency of the algorithms is illustrated with numerical examples including large networks. The design approach is applicable to IP/MPLS networks based on leased transmission capacity

Recovery, routing and load balancing strategy for an IP/MPLS network

The paper considers a problem of routing, protection and load balancing in the IP/MPLS network. A network design problem combining all these aspects is presented. Proportionally fair distribution of residual bandwidths on links is used for load balancing, and protection is achieved with failure-dependent backup paths. The efficiency of the proposed approach is tested by combining optimization and simulation tools. Numerical experiments show that using the proposed load balancing and protection mechanisms decreases the number of disrupted LSPs in case of failures, as compared to other recovery options considered