Protection Strategies for Dynamic VNF Placement and Service Chaining

Network Function Virtualization (NFV) provides a major shift in the provisioning of telecommunication services by decoupling network functions from dedicated hardware devices. Such decoupling enables operational expenditure (OpEx) and capital expenditure (CapEx) reduction and allows to increase service agility. NFV relies on Virtualized Network Functions (VNFs) and, by placing VNFs on NFV-capable network nodes, and by chaining them in a specific order while guaranteeing a given end to end latency, Service Chains (SCs) are formed to provide a specific service. To achieve great flexibility in resource assignment in the network and decrease further OpEx, it is important to consider provisioning of SCs in a dynamic scenario in which traffic evolves in the network. In this study we observe that, when deploying a SC in a situation where SC requests arrive dynamically in the network, it is important to consider protection techniques to withstand failures of the network components supporting the SC. Different protection approaches can be followed to protect the SC against failures. We consider three different protection strategies, namely, Virtual-Node protection, Virtual-Link protection and End-to-End protection, which provide protection against single virtual node (hosting a VNF), single virtual link (connecting two consequent VNF of SC together) and single virtual node/virtual link failure for dynamic VNF placement. For each of them, we provide a heuristic approach for dynamic provisioning of the SC with protection. In our simulative numerical results over realistic network and SC settings, we compare the three strategies and show that End-to-End protection and Virtual-Node protection have both high blocking, however, End-to-End is able to satisfy the latency requirement of more SCs with respect to virtual node protection. Of the three protection strategies, Virtual-Link protection requires less network and computational resources and achieves lower SC latency violation.