Design and Implementation of Common YANG Gateway for Heterogeneous SDN Domains in RESTful Orchestration Architecture

Abstract

Most network infrastructures have the limitations of programmability and flexibility due to the tightly coupled architecture of control plane and data plane. Software Defined Networking (SDN) is proposed for a new networking architecture through the decoupling control plane from the data plane. The decoupled SDN architecture enables the “programmable” capability of the data plane and increases the flexibility of simple forwarding devices by using a logically centralized control plane. However, the logically centralized control plane has a serious problem in scalability as the number of nodes is increased. In order to solve the scalability problem of increasing nodes and links, and confidentiality of network information for the deployment of different network operators in the SDN environment, the need for scalable and flexible SDN orchestration framework for multi-domains is becoming the paramount topic in SDN research. In multi-domain SDN infrastructure, the SDN orchestration framework coordinately controls multiple interconnected domains by using controllers’ northbound interface. In SDN orchestration framework, many controllers utilize their own northbound interface. Most of these are based on Representational State Transfer (REST) architecture. Although REST architecture is becoming a good candidate for SDN orchestrations, it still has several differences on uniform resource locators (URLs) for identifying the path of the resources, data modeling for describing the structure of the data like node, links, topology, and so on, and event notification service mechanism for fault monitoring and provisioning in heterogeneous environment. However, REST application program interfaces (APIs) have not been standardized until now. Many variations of the REST APIs are flooding. Thus, the interoperability between the heterogeneous SDN controllers can be a big issue when implementing an SDN orchestration framework. In this thesis, we proposed a Common Yang Gateway between orchestrator and SDN controllers using the REST APIs. Our gateway offers common data structures based on the standard Yang data models for translating information of SDN controllers and enables orchestrator to provide common service mechanisms to support inter-domain and intra-domain topology discovery, event-driven fault monitoring and end-to-end provisioning services across multiple heterogeneous SDN controllers. IETF already specified the YANG data modeling language in RFC 6020, and steadily standardizes other data models. Based on the standard YANG models, we build common data structures for the SDN domain. The proposed gateway translates REST APIs and common data structures including topology information such as explicit topology and abstract topology, and explicit route objects (EROs) for providing end-to-end provisioning service. Therefore, the gateway can specify the topology information of heterogeneous domains into a common data structure and translate EROs to different flows using in SDN controllers. Thus, the gateway enables coordination control for different controllers through their own APIs, which allows the interoperability among heterogeneous SDN controllers. In addition, the gateway provides various real-time event notification mechanisms for fault monitoring like RabbitMQ or the controller service API in a heterogeneous environment. Besides, the proposed gateway can also reduce the burden of orchestrator and improve the confidentiality of the orchestration by using an abstraction. In order to validate the effectiveness and efficiency of the proposed gateway architecture, we implement a gateway based on the Java framework. The gateway has the following three key functions; topology discovery, fault monitoring and an end-to-end provisioning service. By implementing a testbed using our gateway in a real SDN orchestration environment, we can make a clear proof-of-concept for the architecture. Next, we can show the performance and effectiveness of the gateway through some experiments and compare the results to those of the same orchestration framework without the gateway. Lastly, we show the enhancement of the SDN orchestration framework by using an abstraction in the proposed gateway. Although the Common Yang Gateway architecture can cause a little bit of performance reduction due to the additional data translation and transferring, it remains a viable candidate of the SDN orchestration framework. It effectively provides interoperability among heterogeneous SDN controllers, which use different types of the REST APIs, as well as improves the scalability and confidentiality of multi-domain SDN network infrastructures.