  The Network Function Virtualization (NFV) is very promising for efficient
provisioning of network services and is attracting a lot of attention. NFV can
be implemented in commercial off-the-shelf servers or Physical Machines (PMs),
and many network services can be offered as a sequence of Virtual Network
Functions (VNFs), known as VNF chains. Furthermore, many existing network
devices (e.g., switches) and collocated PMs are underutilized or
over-provisioned, resulting in low power-efficiency. In order to achieve more
energy efficient systems, this work aims at designing the placement of VNFs
such that the total power consumption in network nodes and PMs is minimized,
while meeting the delay and capacity requirements of the foreseen demands.
Based on existing switch and PM power models, we propose a Integer Linear
Programming (ILP) formulation to find the optimal solution. We also propose a
heuristic based on the concept of Blocking Islands (BI), and a baseline
heuristic based on the Betweenness Centrality (BC) property of the graph. Both
heuristics and the ILP solutions have been compared in terms of total power
consumption, delay, demands acceptance rate, and computation time. Our
simulation results suggest that BI-based heuristic is superior compared with
the BC-based heuristic, and very close to the optimal solution obtained from
the ILP in terms of total power consumption and demands acceptance rate.
Compared to the ILP, the proposed BI-based heuristic is significantly faster
and results in 22% lower end-to-end delay, with a penalty of consuming 6% more
power in average.
