Specifying and placing chains of virtual network functions

TLDR

Network appliances perform distinct functions on traffic, and chaining them is standard, but virtualization of these functions is now a key research area. The authors propose a formal model using a context‑free language to describe the chaining of virtual network functions. Deployment requests are translated into virtual network function graphs, which are then mapped onto the network by solving a mixed‑integer quadratically constrained program that optimizes placement and chaining under resource constraints. A Pareto‑set analysis reveals the trade‑offs among competing optimization objectives for VNF placement and chaining.

Abstract

Network appliances perform different functions on network flows and constitute an important part of an operator's network. Normally, a set of chained network functions process network flows. Following the trend of virtualization of networks, virtualization of the network functions has also become a topic of interest. We define a model for formalizing the chaining of network functions using a context-free language. We process deployment requests and construct virtual network function graphs that can be mapped to the network. We describe the mapping as a Mixed Integer Quadratically Constrained Program (MIQCP) for finding the placement of the network functions and chaining them together considering the limited network resources and requirements of the functions. We have performed a Pareto set analysis to investigate the possible trade-offs between different optimization objectives.