Computer Networks 133 (2018) 212–262 Contents lists available at ScienceDirect Computer Networks journal homepage: www.elsevier.com/locate/comnet Review article A comprehensive survey of Network Function Virtualization ∗ Bo Yi a, Xingwei Wang b, , Keqin Li c, Sajal k. Das d, Min Huang e a College of Computer Science and Engineering, Northeastern University, Shenyang 110169, China b College of Software, Northeastern University, Shenyang 110169, China c Department of Computer Science, State University of New York, New York 12561, USA d Department of Computer Science, Missouri University of Science and Technology, Rolla, MO 65409, USA e College of Information Science and Engineering, State Key Laboratory of Synthetical Automation for Process Industries, Northeastern University, Shenyang 110819, China a r t i c l e i n f o a b s t r a c t Article history: Today’s networks are filled with a massive and ever-growing variety of network functions that coupled Received 13 April 2017 with proprietary devices, which leads to network ossification and difficulty in network management and Revised 15 January 2018 service provision. Network Function Virtualization (NFV) is a promising paradigm to change such situa- Accepted 17 January 2018 tion by decoupling network functions from the underlying dedicated hardware and realizing them in the form of software, which are referred to as Virtual Network Functions (VNFs). Such decoupling introduces Keywords: many benefits which include reduction of Capital Expenditure (CAPEX) and Operation Expense (OPEX), Network Function Virtualization improved flexibility of service provision, etc. In this paper, we intend to present a comprehensive survey Virtual network function on NFV, which starts from the introduction of NFV motivations. Then, we explain the main concepts of Software defined networking NFV in terms of terminology, standardization and history, and how NFV differs from traditional middle- Algorithm box based network. After that, the standard NFV architecture is introduced using a bottom up approach, Network softwarization based on which the corresponding use cases and solutions are also illustrated. In addition, due to the decoupling of network functionalities and hardware, people’s attention is gradually shifted to the VNFs. Next, we provide an extensive and in-depth discussion on state-of-the-art VNF algorithms including VNF placement, scheduling, migration, chaining and multicast. Finally, to accelerate the NFV deployment and avoid pitfalls as far as possible, we survey the challenges faced by NFV and the trend for future direc- tions. In particular, the challenges are discussed from bottom up, which include hardware design, VNF deployment, VNF life cycle control, service chaining, performance evaluation, policy enforcement, energy efficiency, reliability and security, and the future directions are discussed around the current trend to- wards network softwarization. ©2018 Elsevier B.V. All rights reserved. Contents 1. Introduction . 213 2. Network state Quo and NFV motivation . 215 3. What is Network Function Virtualization? . 218 3.1. Main terminologies . 218 3.2. Standardization activities . 218 3.2.1. European telecommunication standards institute. 219 3.2.2. Open networking foundation. 219 3.2.3. Internet research task force . 219 3.2.4. Internet engineering task force . 219 3.2.5. OPNFV . 219 3.2.6. Alliance for telecommunications industry solutions . 219 ∗ Corresponding author. E-mail addresses: [email protected] (B. Yi), [email protected] (X. Wang), [email protected] (K. Li), [email protected] (S.k. Das), [email protected] (M. Huang). https://doi.org/10.1016/j.comnet.2018.01.021 1389-1286/© 2018 Elsevier B.V. All rights reserved. B. Yi et al. / Computer Networks 133 (2018) 212–262 213 3.2.7. Broadband forum . 219 3.2.8. Open virtualization format. 220 3.2.9. The 3rd generation partnership project . 220 3.2.10. Summary . 220 3.3. History . 220 4. NFV review from bottom up . 221 4.1. Network Function Virtualization infrastructure layer . 221 4.1.1. Physical infrastructure layer . 221 4.1.2. Virtualization layer . 223 4.1.3. Virtual infrastructure layer . 224 4.1.4. Summary . 226 4.2. NFV management and orchestration layer . 226 4.3. Virtual network function layer . 227 4.4. Cross-field issues . 229 4.4.1. NFV use cases . 229 4.4.2. NFV solutions . 232 4.4.3. Coexistence with legacy systems. 233 5. VNF related algorithms . 234 5.1. VNF placement . 234 5.2. VNF scheduling . 236 5.3. VNF migration . 237 5.4. VNF chaining . 238 5.5. VNF multicast. 239 6. Ongoing researches and challenges. 240 6.1. Hardware design. 241 6.2. VNF deployment . 241 6.3. VNF life cycle control . ..