Placement of dynamic service function chains in partially VNF-enabled networks

Network Function Virtualization (NFV) is an emerging approach to overcome the limitations of proprietary network hardware appliances. Under the paradigm of NFV, network functions may be implemented virtually-referred to as Virtual Network Functions (VNFs). A set of chained network functions compose an end-to-end network service called a Service Function Chain (SFC). The SFC placement problem on fully VNF-enabled networks has a reach body of work in the literature in recent years. However, before fully realizing NFV, we face hybrid networks in which only some network nodes support virtualization. In this paper, we study the problem of dynamic SFC placement considering such a hybrid network. First, we formulate the problem as an Integer Linear Programming (ILP) model. Then, we propose some heuristic algorithms for initial SFC placement and handling SFC scaling requests (i.e., network function insertion/deletion to/from the deployed SFC) reactively and proactively. Furthermore, we propose two placement strategies, i.e., sharing and grouping for placing SFCs on the substrate network. Using simulation, we compare the performance of the proposed model and algorithms on fully VNF-enabled and hybrid networks. Moreover, we show that sharing and grouping VNFs can provide higher performance in terms of request acceptance rate and efficiently and reduce the average delay and overall cost.