## 4 Policy/Intent-Based Security in SDN and NFV Networks
### Transition to Intent-Based Networking  
After delving into the literature on the current state of networking paradigms, it was easy to notice a shift toward what is referred to as intent-based networking. This relatively recent concept adds another level of abstraction to what has been seen in policy-based networks, and in this new paradigm of networking, which is much more user-centric than previous ones; the objective is to give the user the possibility of asking what it wants from the network without worrying how this is achieved in a way that is as user-friendly as possible. To better understand this concept, studying the works of [106; 107] shows how and why this transition from policy-based networking to intent-based networking happened. Their works discuss the limitations of policy-based networking, which is a more rigid, less scalable network methodology, and this causes it to struggle with the current rise of network complexity leveraged by technologies such as cloud computing, IoT, and the ever-present NS into which these technologies can be integrated. This means that the issue lies in scalability and flexibility, and even though policy-based networks are considerably more autonomous than previous network paradigms, they still require manual intervention for changes and updates, which also introduces the possibility of human error in network configuration. This is the gap that intent-based networking (IBN) tries to bridge; by granting a higher level of abstraction in the network configuration, it introduces more flexibility, which was not possible when using policy-based methods that required the network to follow static configurations that do not easily accommodate changes in business requirements or network conditions. This flexibility will be demonstrated further in this section, but first, the process that is required to deploy intent-based networks must be known, and therefore we look at some of the things that remained from policy-based networking and what has changed in this new methodology. For that purpose, insights from the work of [108] can also be drawn, which showcases how IBNs translate users' business intent(s) into network strategies, thereby moving beyond policy-driven approaches. This work also demonstrates how AI, which was already discussed previously in the context of NS, can be integrated into this paradigm for real-time network fault identification, network optimization, and the integral process of intent translation, which is the key to IBNs. Therefore, it is safe to say that AI will undoubtedly help propel this paradigm shift once it has matured enough in these applications. Nonetheless, the whole process can be illustrated as follows. Summing up, the illustrated process (Figure 4) can be described in a few steps:  
* **Intent Profiling:** This first step involves defining the intent, which should be in an easily understandable, declarative statement of what is expected from the network. This contrasts with policy-based networking, where specific rules and configurations are detailed. * **Intent Translation:** After being defined, the high-level intent must be translated into actionable network policies and configurations. Unlike policy-based systems that apply rules directly, IBN systems interpret intents and determine the best methods to achieve the desired outcomes. * **Intent Resolution and Activation:** Before being activated, potential conflicts among different intents must be addressed, ensuring that new intents do not disrupt existing network functions. This dynamic adjustment capability is a significant advancement over static policy-based systems. * **Intent Assurance:** Much like in policy-based systems, the process of continuously monitoring network performance to ensure that it aligns with the defined policies, and in this case, the intent, is critical to maintaining a reliable service. However, in the case of intent-based networking, its inherent flexibility allows it to adapt faster to changes in network conditions or business objectives over time.