Research On Test Of RESTful Northbound Interface Of SDN

SDN(Software Defined Networking)is an emerging network architecture and technology,featured by decoupling control plane and data plane to enable centralized network control.In the typical SDN architecture proposed by ONF(Open Network Foundation),the network of next generation should be constituted of three hierarchical planes--the uppermost application plane populated by various network services and applications,the control plane in the middle responsible for management of data plane resources,and the underlying data plane which fulfills the tasks of handling and forwarding data.The northbound and southbound interface which respectively communicates the central control plane with the upper-layer application plane and the underlying data plane,are two important components in the SDN architecture.The southbound interface is well standardized by OpenFlow protocol defined by ONF.As for the northbound interface,there is not yet any specification.As a consequence of which it becomes the focus of competition among the industry.Various implementations have been introduced by different vendors with accordance to their specific needs of services and applications.Though lacks of a uniform specification,the idea that it should be REST flavored has reached a consensus within the industry.Most of the northbound interfaces are now implemented in compliance with REST rules,which were adopted by the under-progress standardization of northbound interface within ONF as well.Since REST is not a specification but merely a designing style,northbound interfaces implemented in this style still vary with great diversity.To test these diverse interfaces,very specific code must be written or test systems be developed for each of them.Existing test technologies for RESTful northbound interface are all one-to-one solutions which develop different systems for each different implementation,and must change code every time the specification is modified.To solve this problem,this paper introduces a YANG-model-based test methodology of RESTful northbound interface of SDN,which enables a test system to be developed once and applicable for all implementations of SDN northbound interface that is REST flavored.The test system doesn't rely on any specification but a data model file as the input,describing the structuralized data model of the interface under test.For the test of interfaces with different specifications,only the model file needs to be replaced while the code of the test system remains unchanged,thus eliminating the negative impact of interfaces diversity to the development of test system.This methodology takes advantage of the YANG model defined in most current SDN controllers to save some of the data modeling work,leaving only simple and basic interface modeling to testers' concern.Based on this methodology,a testing platform for RESTful northbound interface of SDN was designed and implemented,and used to test the northbound interfaces of two different domestic vendors'controllers,proving the YANG-model-based test methodology and the corresponding test platform introduced and implemented in this paper highly effective to the test of SDN's RESTful northbound interface.