## 2 Background and Motivation  
There are several existing studies that focus on the general areas of SDN, NFV, and SFC, as summarised in Table 1. Each of the related surveys presented in our work explores different aspects such as NFV implementation problems, traffic steering in SFC, NFV deployment acceleration, optimal NFV and SFC concepts, design, and taxonomy of NFV platforms, the placement of network functions, and resource allocation. This section summarises the key contributions made by existing related surveys and provides the foundation for our research. As one of the most recent survey works in the NFV/SFC space, [PERSON] et al. [23] focused their work on the proposals that consider the acceleration of NFV deployments. A taxonomy of the surveyed approaches is presented and discussed, which mainly involves the hardware and software acceleration of NFV deployments. We take a different approach by considering the state-of-the-art NFV implementation frameworks, especially in scenarios where network functions are also chained, as in SFCs. In their work, [PERSON] et al. [21] presented NFV platform design choices. They presented three main open issues in NFV: (1) the use of artificial intelligence in NFV, (2) network slicing, that is, the management of network slices, the communication between slices and placement of network slices, and (3) the integration of NFV with IoT. The taxonomy of NFV platforms presented by [PERSON] et al. consists of prototyping, testing, deployment, management, execution, and integrated NFV platforms. We take a different approach in our work by first presenting the requirements that must be met for the chaining of vNFs and some useful use-cases. This is relevant in understanding the key components involved in creating service function chains in service provider network environments. Our work \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Survey Reference** & **Survey Focus** & **Open Challenges Presented** & **Year** \\ \hline [PERSON] et al. [20] & Network services anomalies in NFV & ✔ & 2022 \\ [PERSON] et al. [21] & NFV platforms, design and taxonomy & ✔ & 2021 \\ [PERSON] et al. [22] & Load balancing techniques in SDN & ✔ & 2021 \\ [PERSON] et al. [23] & NFV deployment acceleration & ✔ & 2020 \\ [PERSON] et al. [24] & vNF placement, availability, and load balancing & ✔ & 2020 \\ [PERSON] et al. [25] & Service function, 5G and next-generation networks & ✔ & 2020 \\ [PERSON] et al. [26] & NFV architectures; NFV/SDN design taxonomy & ✔ & 2019 \\ [PERSON] et al. [27] & Traffic steering in SFC; SDN-based chaining evaluation & ✔ & 2019 \\ [PERSON] et al. [4] & Service placement survey; WNF placement; existing virtual resource & Lessons learned & 2019 \\ [PERSON] et al. [28] & Optimal NFV and SFC concepts & ✔ & 2018 \\ [PERSON] et al. [29] & Next Generation Network SFC; SDN approaches in SFC; SFC implementations & Implementation limitations & 2017 \\ [PERSON] et al. [30] & SDN for IoT & ✔ & 2017 \\ [PERSON] et al. [31] & NFV survey; selected implementation problems and solutions & ✔ & 2017 \\ [PERSON] et al. [32] & Service function chaining NFV mobility & ✔ & 2016 \\ [PERSON] et al. [1] & NFV resource allocation & ✔ & 2016 \\ [PERSON] et al. [33] & Resource allocation in SFC; Existing NFV SFC RA solutions & Lessons learned & 2016 \\ [PERSON] et al. [7] & Network function placement; Selected framework comparison & ✔ & 2016 \\ [PERSON] et al. [34] & SDN/NFV for mobile and wireless networks & ✔ & 2015 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Existing NFV/SFC Surveys. focuses mainly on NFV frameworks that employ the chaining of network functions for effective service delivery. In addition to the taxonomy of the frameworks presented, we also discuss key open research challenges in these environments. In the survey presented by [PERSON] et al. [27], they discussed the traffic steering approaches used in SFC solutions with SDN. The current traffic steering approaches are classified into three methods: header-based, tag-based, and programmable switch-based methods.