SUMMARY
The subject of research in the article is the processes of inter-domain routing with ensuring the end-to-end quality of service. The aim of the work is to develop a method of hierarchical inter-domain routing with ensuring the end-to-end quality of service in terms of average end-to-end packet delay in a multi-domain software-defined telecommunications network. The following tasks are solved in the article: development and research the hierarchical inter-domain routing method with ensuring the end-to-end quality of service. The following methods are used: graph theory, tensor theory, theory of hierarchical multi-level systems, queuing theory, and mathematical programming methods. The following results were obtained: the method of hierarchical inter-domain routing in a software-defined telecommunications network with the provision of end-to-end quality of service has been developed and investigated, which allows, based on load balancing in the telecommunication network domains, to provide a specified level of QoS in terms of performance and average end-to-end packet delay. Conclusions: The paper proposes a method of hierarchical inter-domain routing in a software- defined telecommunications network with ensuring the quality of service in terms of bandwidth and average packet end-to-end delay. The novelty of the method is that the implementation of QoS requirements for the average end-to-end packet delay is carried out not on the basis of preliminary normalization of its values by domain, but through the introduction and implementation of two-level coordination of route solutions in accordance with the principle of target coordination. The proposed method is based on a decomposition flow-based model of inter-domain routing, and to obtain in an analytical form the conditions for ensuring the end-to-end quality of service, a tensor description of each of the network domains is used. Using the hierarchical inter-domain routing method allows to reassign the channel resource, but only on the basis of load balancing in the telecommunication network domains, to provide the specified level of QoS in terms of performance and average end-to-end packet delay. Decentralization of route computations in each of the network domains based on the use of local information about their state makes it possible to increase the scalability of route decisions, and the introduction of coordination procedures ensures consistency in the work of telecommunication domain controllers in terms of QoS. The investigation of the proposed method on a number of computational examples confirmed its convergence to optimal solutions with a finite number of iterations of the coordination procedure.