The Service Function Chaining (SFC) is an architecture to orchestrate network services by creating and deploying the rule-based service function chains and steering network traffic through them. One of the main tasks in SFC is the optimal composition of the service functions and checking the validation of the composed service chain based on the predefined rules. As the problem of optimal chain composition is NP hard, in this paper a Finite Automaton (FA) model is proposed to limit the solution space by considering the practical scenarios. Since the chaining rules depend on the substrate physical platform, the proposed FA is based on the data centre, mobile, and security scenarios introduced by Internet Engineering Task Force (IETF). Subsequently, Finite Automaton Matcher (FAM) shows that the proposed FA is an acceptable tool for validating the correctness of the composed service chain. Experimental results and complexity analysis show that this method reduces the number of service chain compositions and therefore the time complexity significantly.

服务功能链（SFC）是一种架构，可通过创建和部署基于规则的服务功能链并控制通过它们的网络流量来协调网络服务。SFC中的主要任务之一是优化服务功能，并根据预定义规则检查组成的服务链的有效性。由于最优链组成问题是NP难题，因此本文提出了一种有限自动机（FA）模型，通过考虑实际情况来限制求解空间。由于链接规则取决于基板物理平台，因此建议的FA基于Internet工程任务组（IETF）引入的数据中心，移动和安全方案。后来，有限自动机匹配器（FAM）表明，建议的FA是用于验证组成的服务链的正确性的可接受工具。实验结果和复杂度分析表明，该方法减少了服务链组成的数量，从而大大减少了时间复杂度。