The packet forwarding behaviour of a network relies on the forwarding rules residing in the networking element (e.g. switches and routers) to forward packets. This applies to both traditional networking and software-defined networking (SDN). These forwarding rules vary in their structures and sizes, but they represent the same fundamental functionality: to match incoming packets against rules and determine its forwarding behaviour. All these rules in a network device constitute a packet forwarding pipeline. This survey paper presents a new taxonomy for the representation of the forwarding pipeline in SDN based on core networking functionality. The new taxonomy uses a typology and attributes of the forwarding behaviour to establish a cohesive vocabulary and a classification system to study and characterise the interactions of FTE along an end-to-end path in SDN. The survey also shows that Boolean algebra is most widely used for the low-level representation of FTEs and facilitates the assessment of “equivalence” between FTEs and has practical uses in traffic monitoring and packet classification within SDN, among others.

网络的数据包转发行为依赖于网络元素（例如，交换机和路由器）中的转发规则来转发数据包。这适用于传统网络和软件定义网络（SDN）。这些转发规则的结构和大小各不相同，但是它们表示相同的基本功能：根据规则匹配传入的数据包并确定其转发行为。网络设备中的所有这些规则构成了数据包转发管道。这份调查报告提出了一种新的分类法，用于基于核心网络功能的SDN中转发管道的表示。新的分类法使用转发行为的类型和属性来建立衔接词汇，并使用分类系统来研究和表征SDN中沿端到端路径的FTE交互。调查还显示，布尔代数最广泛地用于FTE的低级表示，并且有助于评估FTE之间的“等效性”，并且在SDN中的流量监控和数据包分类中具有实际用途。