Section: New Results

Efficient Orchestration Mechanisms for Congestion Mitigation in Network Functions Virtualization: Models and Algorithms

Nowadays, telecommunication infrastructures are composed of property hardware operated by a single entity to offer communication services to their final users. While this architecture simplifies the design and optimization of the network equipment for specific tasks, its low degree of flexibility represents the main limitation for the evolution of the network infrastructure. For this reason, network operators and equipment manufacturers have started the standardization process of a plethora of virtualization solutions that have been individually developed in recent years for enabling the sharing of general-purpose resources and increasing the flexibility of their network architectures. Such a process has led to the specification of the Network Functions Virtualization (NFV) technology, which promises to bring about several benefits, such as reduced CAPEX and OPEX (CAPital and OPerational EXpenditure), low time-tomarket for new network services, higher flexibility to scale up and down the services according to users' demand, simple and cheap testing of new services. Nevertheless, the consolidation of the virtualization technology represents one of the main challenging problems for its success and widespread utilization in telecommunication infrastructures, which still consist of a huge set of property hardware appliances and software systems. Indeed, the sharing of the physical infrastructure among multiple virtual operators as well as the simple configuration of network services require the design of complex management mechanisms for the orchestration of the network equipment, with the final goal of dynamically adapting the infrastructure to the resource utilization.

In particular, spatio-temporal correlation of traffic demands and computational loads can result in high congestion and low network performance for virtual operators, thus leading to service level agreement breaches. In [10], we propose novel orchestration mechanisms to optimally control and mitigate the resource congestion of a physical infrastructure based on the NFV paradigm. More specifically, we analyze the congestion resulting from the sharing of the physical infrastructure and propose innovative orchestration mechanisms based on both centralized and distributed approaches, aimed at unleashing the potential of the NFV technology. In particular, we first formulate the network functions composition problem as a non-linear optimization model to accurately capture the congestion of physical resources. To further simplify the network management, we also propose a dynamic pricing strategy of network resources, proving that the resulting system achieves a stable equilibrium in a completely distributed fashion, even when all virtual operators independently select their best network configuration. Numerical results show that the proposed approaches consistently reduce resource congestion. Furthermore, the distributed solution well approaches the performance that can be achieved using a centralized network orchestration system.