t CSPs are willing to deploy open source solutions and engage in the open source projects. In the IT industry, there is a long tradition on open source projects, such as Linux and Kernel-based Virtual Machine (KVM). In NFV, several open source projects are developed, each of which has a different focus. They use the same open source model, that is, having a single upstream code base. Contributors include CSPs, NEPs, and NF vendors, each of whom contribute to the common code base in the areas of their specific expertise. Together, they can provide a wide spectrum of the projects. Usually by employing this model, the open source project can leverage a large set of great developers and thus has better quality of code. In this section, we present five different open source activities in the area of Software-defined networking (SDN), NFV, and their usage in telecom networks. 6.1.1 OpenStack OpenStack is open source cloud computing software that provides infrastructure as a service cloud deployment for public and private cloud [111]. It was started in 2010, when rooted from the NASA's Nebula platform and Rackspace's Cloud Files platform. It is written in python and all of the code for OpenStack is freely available under the Apache 2.0 license. Currently, the projects are managed by OpenStack foundation. The OpenStack architecture is shown in Figure 6.1. It is organized to cover the three main components in cloud computing: compute, 6.1 Open Source Initiatives Openstack dashboard (Horizon) Compute Storage Networking (Nova) (Swift) (Neutron) Openstack shared services Cinder Keystone Celometer Figure 6.1 OpenStack architecture. storage, and networking. Besides, dashboard projects are important as they provide administrative interfaces. Their compute component provisions VMs to provide scalable computation resources. The storage component uses objects storage for storing VM images and instances. The networking component provides network services for inter-VM and external network connectivities. Each component and managemen