On efficient virtual network function chaining in NFV-based telecommunications networks

Network function virtualization enables the softwarization of network functions on standardized commodity hardware, which is promising to help the network carriers to achieve a lower investment cost, a shorter time to deployment, as well as a more flexible and dynamic way of network configuration and management. One of the key challenges is how to efficiently place and chain the software-based virtual network functions in the physical substrate to provision the requested network service while minimizing the physical network cost. In this paper, we mathematically formulate the virtual network function chaining problem using Integer Linear Programming (ILP), in order to facilitate an optimal solution. We propose a set of centralized algorithms to efficiently minimize the physical network cost. The proposed Close To Destination (CTD) algorithm can achieve a near-optimal physical network cost that is close to the optimal result obtained from the ILP solution, but with a very low computational complexity. In addition, we propose a distributed algorithm, called Look Ahead (LA), which plans ahead and jointly considers multiple next-hops VNF requirements to facilitate an efficient VNF chain forwarding decision. Comprehensive simulations are conducted to evaluate the proposed approaches, and the results demonstrate the effectiveness of the proposed CTD algorithm and the distributed LA algorithm.