REST API Design Patterns for SDN Northbound API

REST architectural style gains increasing popularity in the networking protocol design, and it has become a prevalent choice for northbound API of Software-Defined Networking (SDN). This paper addresses many critical issues in RESTful networking protocol design, and presents a framework on how a networking protocol can be designed in a truly RESTful manner, making it towards a service oriented data networking. In particular, we introduce the HTTP content negotiation mechanism which allows clients to select different representation formats from the same resource URI. Most importantly, we present a hypertext-driven approach, so that hypertext links are defined between REST resources for the networking protocol to guide clients to identify the right resources rather than relying on fixed resource URIs. The advantages of our approach are verified in two folds. First, we show how to apply our approach to fix REST design problems in some existing northbound networking APIs, and then we show how to design a RESTful northbound API of SDN in the context of OpenStack. We implemented our proposed approach in the northbound REST API of SOX, a generalized SDN controller, and the benefits of the proposed approach are experimentally verified.