RESEARCH ARTICLE Hardware implementation of contention aware optical switching node for data center networks Vikas Yadav | Vijayan Nithin | Shivam Mishra | Chandran Hemanth | Rengachary Gopalan Sangeetha School of Electronics Engineering, VIT, Chennai, India Correspondence Rengachary Gopalan Sangeetha, School of Electronics Engineering, VIT, Chennai, India. Email: sangeetha.rg@vit.ac.in Abstract In the multistage bidirectional networks, the same node is accessed multiple times in the same time slot resulting in contention. In this article, we experimentally demonstrate the contention resolution with minimum electronics. This is verified in the experimental testbed and the data is switched from one node to other node without contention. The results are verified in terms of eye diagram in both the directions. KEYWORDS bidirectional networks, contention resolution, testbed implementation 1 | INTRODUCTION Highly scalable optical packet switched networks with large number of port counts are deployed in data center networks to obtain high throughput while achieving the low latency. 1 Multistage bidirectional optical network is a suitable candidate to sustain the huge internet traffic. The multistage network includes more than 10 000 port counts in which every source and destination node may have multiple paths. 2 The data are transferred from source node to destination node by crossing multiple node and paths. It is obvious that the same node is accessed multiple times in the same time slot. 2 Therefore, the contention should be resolved so that only one packet is processed in a time slot at any node. This can be achieved with a suitable signal processing module. In the all optical networks, the contention is handled by wavelength routing. 3,4 But the bidirectional data traffic needs multiple wavelengths for con- tention resolution and increases the complexity. Therefore, we propose the suitable control logic to resolve the contention with minimum electronics. The bit level processing in the elec- tronics domain resolves contention and aids simple routing of data from source to destination node. We have demonstrated the bidirectional communication with electronics signal processing in Reference 5. In many multistage interconnection networks like Benes, Butterfly, Shuffle net, there are more than one path available from any source node to any destination node. Since, every packet has to reach the desired destination node from a source node, by selecting the path via the interme- diate nodes, there is a possibility of choosing the same interme- diate node while selecting the path from different input ports. Therefore, there is a possibility of contention and has to be resolved to achieve better throughput otherwise the contented packet may go into an indefinite loop wherever the default path is available and may not allow the new packet to enter into the network. In this article, we choose a multistage interconnection network to explain and demonstrate the contention resolution with minimum electronics. The rest of the article is organized as follows: section 2 discusses the contention in a multistage network. Section 3 gives the proposed hardware model to resolve contention. In section 4, implementation of contention resolution in a testbed is demonstrated. Section 5 gives observed results and discussions. Section 6 gives the concluding remarks. 2 | CONTENTION IN MULTISTAGE NETWORK Optical multistage networks with multiple port counts have become important for next-generation networks. Many dif- ferent technologies are available to realize optical multistage networks. The first generation optical network architectures consist of point to point WDM links. Such networks are comprised of several point to point links at which all traffic arriving to a node is converted from optics to electronics, processed electronically, and converted from electronics to optics before departing from the node. This conversion at every node in the network involves significant overhead in terms of switch complexity and electronic processing cost. Alternative approach is to have a packet with header and Received: 25 February 2019 DOI: 10.1002/mop.31899 Microw Opt Technol Lett. 2019;1–7. wileyonlinelibrary.com/journal/mop © 2019 Wiley Periodicals, Inc. 1