Placing Traffic-Changing and Partially-Ordered NFV Middleboxes via SDN

Network Function Virtualization (NFV) enables flexible implementation of network functions, also called middleboxes, as virtual machines running on standard servers. However, the flexibility also makes it a challenge to optimally place middleboxes, because a middlebox may be hosted by different servers at different locations. The middlebox placement challenge is further complicated by additional constraints, including the capability of middleboxes to change traffic volumes and dependency between them. In this paper, we address the optimal placement challenge of NFV middleboxes for the data plane using a software-defined networking (SDN) approach. First, we formulate the optimization problem to place traffic-changing and interdependent middleboxes. When the flow path is predetermined, we design optimal algorithms to place a non-ordered or totally-ordered middlebox set, and propose a low-complexity solution for the general scenario of a partially-ordered middlebox set after proving its NP-hardness. When the flow path is not predetermined, we show that the problem is NP-hard even for a non-ordered or totally-ordered middlebox set, and propose an efficient traffic and space aware routing algorithm. We have evaluated the proposed algorithms using large scale simulations and a real application based SDN prototype, and present extensive evaluation results to demonstrate the superiority of our design over benchmark solutions.