Virtual-network-function placement for dynamic service chaining in metro-area networks

Abstract

The advent of new services with stringent requirements on bandwidth and latency has led to a downward curve in per-user revenues of telecom operators. This has stimulated a significant shift in the way operators provision their services, moving from the utilization of dedicated and static hardware to support network functions (as NATs, firewalls, etc.), to the deployment of Virtual Network Functions (VNFs) in the form of dynamically-reconfigurable virtual machines on low-cost servers and switches. These VNFs must be chained together and should be placed optimally to meet the Quality of Service requirements of the supported services. This problem consists in placing the VNFs and routing traffic sequentially among them and is known as Service Chaining (SC). Solving this problem dynamically based on how traffic evolves allows to achieve great flexibility in resource assignment in the existing infrastructure and to save operational expenditures. An effective algorithm for dynamic SC must promote consolidation in VNF placement (it is desirable to consolidate VNFs in the fewer possible number of network nodes), while maintaining low blocking probability and guaranteeing latency targets to the supported services. In this paper we propose an algorithm which performs dynamic SC in a metro-area network, while minimizing average number of nodes required to host VNF instances as well as the blocking probability. This algorithm can help telecom operators reduce their operational expenditures up to 50% by activating less nodes to host VNFs in the network, while maintaining an acceptable level of blocking probability.