  Network Functions Virtualization (NFV) and Software-Defined Networking (SDN)
are new paradigms in the move towards open software and network hardware. While
NFV aims to virtualize network functions and deploy them into general purpose
hardware, SDN makes networks programmable by separating the control and data
planes. NFV and SDN are complementary technologies capable of providing one
network solution. SDN can provide connectivity between Virtual Network
Functions (VNFs) in a flexible and automated way, whereas NFV can use SDN as
part of a service function chain. There are many studies designing NFV/SDN
architectures in different environments. Researchers have been trying to
address reliability, performance, and scalability problems using different
architectural designs. This Systematic Literature Review (SLR) focuses on
integrated NFV/SDN architectures, with the following goals: i) to investigate
and provide an in-depth review of the state-of-the-art of NFV/SDN
architectures, ii) to synthesize their architectural designs, and iii) to
identify areas for further improvements. Broadly, this SLR will encourage
researchers to advance the current stage of development (i.e., the
state-of-the-practice) of integrated NFV/SDN architectures, and shed some light
on future research efforts and the challenges faced.
