ls who have the capability to contribute to open source software platform components; and committing to the use and continuous improvement of an open source platform in collaboration with other community members. Chapter 17 covers many examples of successful operations in a software world and contrasts them with where a telecom provider may be coming from. REFERENCES 1. https://tools.ietf.org/html/rfc6020 2. http://www.etsi.org/technologies-clusters/technologies/nfv 3. http://www.etsi.org/deliver/etsi_es/282000_282099/282007/02.00.00_50/es_282007v020000m.pdf. Network Functions Virtualization John Medamana and Tom Siracusa CONTENTS Virtualization 3.1.1 Network Virtualization 3.1.2 Compute Virtualization 3.1.3 Virtualization of Network Functions 3.1.4 Benefits of NFV NFV and Software-Defined Networking 3.2.1 Relationship between NFV and SDN Decomposition of VNFs 3.3.1 Decoupling Virtual Functions 3.3.1.1 Data Plane 3.3.1.2 Control Plane 3.3.1.3 Management Plane 3.3.2 Service Chaining 3.3.3 Overlay, Underlay, and vSs/vRs 3.3.4 Reusability 3.3.5 Multi and Single Tenancy NFV Resiliency and Scaling 3.4.1 Multipath and Distributed VNF Designs 3.4.2 vPE Example for VNF-Specific Resiliency Design NFV Economics 3.5.1 Hardware Costs 3.5.2 Software Costs 3.5.3 Operational Costs 3.6 NFV Best Practices Acknowledgment References Network functions virtualization (NFV) is a set of software capabilities created by developments in two separate disciplines: networking and operating systems (OSs). In the early days, both networks and computers were very expensive. Hence, sharing a networked computer became a necessity- while the cost per user reduced considerably, every time a new user was added to the network, the "value" of the network increased in proportion to the number of users (Metcalfe's Law). As the number of computers increased, the design of the network became more complicated, with switches and routers being used to direct traffic from source to destination, and networking technologies that facilitated traffic flow in loc