A two-level method of fast re-routing with load balancing in a software-defined network (SDN) is proposed. The novelty of the method consists, firstly, in the introduction of a two-level hierarchy of calculating the routing variables responsible for the formation of the primary and backup paths, and secondly, in ensuring a balanced load of the communication links of the network, which meets the requirements of the traffic engineering concept. The method provides implementation of link, node, path, and bandwidth protection schemes for fast re-routing in SDN. The separation in accordance with the interaction prediction principle along two hierarchical levels of the calculation functions of the primary (lower level) and backup (upper level) routes allowed to abandon the initial sufficiently large and nonlinear optimization problem by transiting to the iterative solution of linear optimization problems of half the dimension. The analysis of the proposed method confirmed its efficiency and effectiveness in terms of obtaining optimal solutions for ensuring balanced load of communication links and implementing the required network element protection schemes for fast re-routing in SDN.

The dynamics analysis of multipath QoS-routing tensor model with support of different flows classes is presented. The novelty of the tensor model is a representation of its covariant and contravariant components and metric of the introduced geometrical space as a function of time. The QoS-routing guarantees for different flows classes with different metrics such as average packet rate and average end-to-end delay were proposed. The research results demonstrated that it is especially important to take into account the dynamics of network state changes in the conditions of high utilization of its interfaces, when the average packet end-to-end delay along the network paths behaves nonstationary, changing quite widely during the router update timer.

SD-WAN is currently considered as a technology that has the potential to revolutionize the use of WAN services. It supports a new concept known as Application-driven networking, where the network is expected to meet the needs of applications, services and customers. In short, SD-WAN is a centralized management of WAN networks, usually with a close connection to Cloud computing and security. This way, customers can easily manage their networks regardless of the connectivity provider. SD-WAN is currently one of the most current topics with a real impact on CC services and WAN environments. SD-WAN influences thinking about how we have used network services so far. More importantly, it has great potential to change the way we use communication services in the future. There are several industries that are interesting in terms of SD-WAN deployment. Based on our analyzes, we can include the education sector among them.

An optimization model of MPLS Traffic Engineering Fast ReRoute is proposed. The novelty of the model is that the optimization problem of load balancing at Fast ReRoute with bandwidth protection is presented in the linear form. Such a solution, in practice, reduces the computational complexity of the calculation the routing variables responsible for the formation of the primary and backup paths and ensuring a balanced load of the network links, which meets the requirements of the Traffic Engineering concept. The model provides the implementation of the link, node, and bandwidth protection schemes for MPLS Traffic Engineering Fast ReRoute. The analysis of the proposed model confirmed its functionality and efficiency from the point of view of obtaining optimal solutions for ensuring balanced load of network links and implementing the required network elements (link, node) and bandwidth protection schemes.

Flow-based model for traffic management in communication network were proposed, which provides a consistent solution of the following network tasks: multipath routing; traffic policing; and dynamic allocation of network throughput among the users flows. Obtained solutions provide the required values of the key indicators of Quality of Service such as packet rate, average delay and packet loss probability.

In this paper, the consistent solution for default gateway protection within fault-tolerant routing in an IP network is presented, and it is based on development of the appropriate flow-based mathematical model. Within the framework of the proposed model, a fault-tolerant routing problem has been reduced to the solution of the optimization problem of nonlinear programming. Fault-tolerance functions are implemented by introducing additional routing variables responsible for the calculation of a backup default gateway and the corresponding path (multipath) in the transport network. Several examples have demonstrated features of the application of the proposed model in solving default gateway protection within fault-tolerant routing for the case of realization of single path and multipath routing. The results have confirmed the efficiency of the proposed model and adequacy of the calculation results obtained