SDNPS: A Load-Balanced Topic-Based Publish/Subscribe System in Software-Defined Networking

Yali Wang, Yang Zhang, Junliang Chen
2016 Applied Sciences  
Publish/subscribe systems on the traditional Internet suffer from poor scalability and high delay in the face of the Internet of Things (IoT) environment. Being customizable, the paradigm of software-defined networking (SDN) provides a chance to establish an IoT-specific network. In this paper, we propose an SDN-based publish/subscribe system named SDNPS, which can construct and fine-tune topic-connected overlays for the sake of disseminating events efficiently and non-redundantly based on a
more » ... bal topology overview. It organizes topics as a Huffman-like topic tree and codes them into binary strings so that filtering and forwarding events can be operated directly on SDN-configurable switches, which helps to reduce end-to-end latency. This hierarchical organization form of topic tree makes it possible to incrementally construct and store overlays, which contribute to reducing the time and space complexity of routing computation. More specifically, it achieves a better tradeoff between load-balancing of the overall optimization objective and the minimal forwarding cost of per-topic overlay. However, under the traditional network architecture, due to the lack of global traffic information, publish/subscribe systems suffer from insufficient utilization of the physical network infrastructure, such as traffic imbalance on different links. In such a largely distributed IoT environment, the emerging mass data mega-trends also worsen the traffic imbalance phenomenon. To address this concern, some methods, including static load balancing (preplanned allocation bandwidth) and dynamic load balancing (dynamic allocation bandwidth during run-time), were proposed [6-8]. However, this problem is not solved, essentially owing to the global knowledge insufficiency under the distributed management of the traditional Internet. On the one hand, the filtering operation, which mainly saves bandwidth in a publish/subscribe system, is performed by specific components called brokers. This imposes a significant delay by lengthening the end-to-end path with a detour to the brokers and a processing delay for matching events against filters' rules. On the other hand, the best-effort service provided by the traditional Internet cannot meet delay-sensitive requirements. Recently, software-defined networking (SDN) [9,10] emerged as a new-style network architecture that decouples the control plane from the forwarding plane. Maintaining a network-wide view of up-to-date datapath elements and link state information, SDN makes it possible to enable on-demand resource allocation, self-service provisioning and network virtualization. OpenFlow as the actual standard for SDN enables many filtering operations to match received packets efficiently through specifying the interface to install and modify flows directly on SDN-configurable switches. Therefore, it is possible to flexibly control the forwarding plane, which is conducive to outperforming the traditional Internet in the overall performance of the network, as well as assuring the desired performance for diverse applications, by adopting a traffic management mechanism [11] . In this paper, we propose and construct a topic-based publish/subscribe system in an SDN environment named SDNPS. The implemented prototype deploys traffic engineering by making full use of the centralized control nature under SDN. Firstly, we obtain the global overview of the topology by abstracting and aggregating the network link state. Then, we predict the traffic distribution for some time to come in terms of the predictability of the mass data from IoT. Finally, we calculate minimum overlay networks per topic and extract multicast routing paths in light of the well-known shortest path algorithm. Our design makes a better tradeoff between global load balancing of links and the minimum cost forwarding for per-topic events. The contributions of this paper are summed up in the following.
doi:10.3390/app6040091 fatcat:6hbnrtxuavexpnypog4bn7dvlu