and form open source consortium to expedite this process using a collaborative manner. Open source projects such as OpenStack and OpenDayLight (ODL) are formed. It will encourage greater collaboration among the industry participants. In such open source projects, the basic technologies can be shared across the industry via the upstream projects. Companies can focus on higher-value functions and system integration, which leveraging the nondifferential functions from open source effort from both the CSP and the NEP's perspectives. For the NEPs, they do not need to spend huge time and development resources on the undifferentiated hardware and infrastructure layer, which can be handled by standardized IT and open source software, but instead focusing on their specific network function. The CSPs can leverage the higher-quality code from open source for their infrastructure. Open source efforts is critical for NFV's growth because it can provide a solid code base for the basic functionalities SO that it enables rapid innovation of new services. Traditionally, open source Network Function Virtualization: Concepts and Applicability in 5G Networks, First Edition. Ying Zhang. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc. 6 Open Source and Research Activities has been widely used in the IT environment but not the telecom communication community. Thus, it will be disruptive to every party in the value chain. But on the other hand, it benefits all industry participants as it uses the collective intelligence of the ecosystem to solve the new NFV challenges, which is a critical step toward the NFV transformation. In this chapter, we introduce various open source initiatives and their focus. For each project, we will start with its goals and scopes, followed by their structure, drivers, and current status. Open Source Initiatives Open source frees the CSPs and NEPs from the development of baseline features that act as the platform upon which everyone can innovate. Many research and survey has shown tha