Design and Implementation of an OpenFlow-based Orchestration protocol for multiple SDN controllers

Abstract

Software-defined networking (SDN) decouples the control plane from the data plane. It enables programmability in control of data flow through the logically centralized controller. However, the centralized controller has a serious problem in scalability as nodes and links are increased. In order to achieve scalability of increasing nodes and links, and confidentiality of network information for the deployment of different network operators, it is common to segment networks into multiple domains. Segmenting a network into multiple SDN domains can bring about each domain being provided by a different SDN controller. As a network comprises multiple SDN domains, SDN requires coordination control among multiple SDN controllers for orchestration in order to support intra-domain and inter-domain topology discovery, fault monitoring, and seamless end-to-end service across multiple domains. Many protocols have been suggested in SDN orchestration and most of them are based on Representational State Transfer (REST). Although REST is becoming a good candidate for SDN orchestration, the REST still has several remaining works on data modeling and real-time event notification mechanism. Unfortunately, REST is not interoperable until now. In order to avoid these shortcomings of REST, some other protocols are proposed using path computation element communication protocol (PCEP) with some proprietary extensions. However, these protocols are not standardized yet. In this thesis, we propose a standard-based unified orchestration protocol: OpenFlow-based orchestration protocol, instead of designing a new orchestration protocol. By using the standard OpenFlow protocol as an orchestration protocol, the proposed orchestration protocol can be implemented without making a new standardization of data modeling and protocol. Moreover, the proposed protocol can support real-time event notification mechanism. In addition, the proposed protocol can reuse SDN controllers. Reusing SDN controllers can omit network administrator overhead to design and implement extra orchestrators. In order to validate the effectiveness and efficiency of the OpenFlow-based orchestration protocol, we implement an OpenFlow-based orchestration testbed. By implementing a testbed in real SDN orchestration environment, we show the effectiveness of the OpenFlow-based orchestration protocol through some experiments and compare the performance with the results of other orchestration protocols. Moreover, we find out the OpenFlow-based orchestration protocol has better performance in provisioning and provides real-time event notification mechanism compared with the other mechanisms, even though it increases a little traffic in topology discovery. In addition, if the orchestration protocol enables the topology abstraction with implicit approaches, the proposed approach further improves the scalability and confidentiality of multiple SDN domains and reduces the traffic burden of the OpenFlow-based orchestration protocol. These results prove that the OpenFlow-based orchestration protocol is a good candidate for the unified orchestration protocol and improves the scalability and confidentiality of multiple SDN domains. Besides, it can further improve the reliability using secure TCP session compared with the REST-based approaches.