Service function chaining (SFC) is one way of providing end-to-end network connectivity while maintaining different Service Level Agreements promised by Cloud Service Providers (CSPs). This chapter discusses different SFC objectives, design and deployment considerations and challenges faced by CSPs in SFC provisioning. It also discusses the SFC architecture, core concepts, and challenges introduced in SFC by topological dependencies, resource availability and configuration complexity. The chapter describes the SFC on top of Software-Defined Networking/Network Functions Virtualization framework with different applications such as segment routing. It introduces different SFC research project-based testbed and their architectures, such as T-Nova and Tacker. The chapter examines the research works in the field of secured service function chaining such as Secure In Cloud Chaining and Network Security Defense Pattern. Middleboxes are the devices used by network operators to perform network functions along the packet's datapath from source to destination, e.g., Web Proxy, Firewall, and Intrusion Detection System.