Abstract-Bandwidth-hungry applications such as Cloud computing, video sharing and social networking drive the creation of more powerful Data Centers (DCs) to manage the large amount of packetized traffic. Data center network (DCN) topologies rely on thousands of servers that exchange data via the switching backbone. Cluster switches and routers are employed to provide interconnectivity between elements of the same DC and inter DCs and must be able to handle the continuously variable loads. Hence, robust and scalable switching modules are needed. Conventional DCN switches adopt crossbars or/and blocks of memories in multistage interconnection architectures (commonly 2-Tiers or 3-Tiers). However, current multistage packet switch architectures, with their space-memory variants, are either too complex to implement, have poor performance, or not cost effective. In this paper, we propose a novel and highly scalable multistage packet-switch design based on Networks-on-Chip (NoC) fabrics for DCNs. In particular, we describe a novel three-stage packet-switch fabric with a Round-Robin packets dispatching scheme where each central stage module is based on a Unidirectional NoC (UDN), instead of a conventional singlehop crossbar fabric. The proposed design, referred to as Clos-UDN, overcomes all the shortcomings of conventional multistage architectures. In particular, as we shall demonstrate, the proposed Clos-UDN architecture: (i) Obviates the need for a complex and costly input modules, by means of few, yet simple, input FIFO queues. (ii) Avoids the need for a complex and synchronized scheduling process over a high number of input-output modules and/or port pairs. (iii) Provides speedup, load balancing and path-diversity thanks to a dynamic dispatching scheme as well as the NoC based fabric nature. Extensive simulation studies are conducted to compare the proposed Clos-UDN switch to conventional multistage switches. Simulation results show that the Clos-UDN outperforms conventional design under a wide range of input traffic scenarios, making it highly appealing for ultra-high capacity DC networks.

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Abstract-The switch fabric in a Data-Center Network (DCN) handles constantly variable loads. This is stressing the need for high-performance packet switches able to keep pace with climbing throughput while maintaining resiliency and scalability. Conventional multistage switches with their space-memory variants proved to be performance limited as they do not scale well with the proliferating DC requirements. Most proposals are either too complex to implement or not cost effective. In this paper, we present a highly scalable multistage switching architecture for DC switching fabrics. We describe a three-stage Clos packet-switch fabric with Output-Queued Unidirectional NoC (OQ-UDN) modules and Round-Robin packets dispatching scheme. The proposed OQ Clos-UDN architecture avoids the need for complex and costly input modules and simplifies the scheduling process. Thanks to a dynamic packets dispatching and the multi-hop nature of the UDN modules, the switch provides load balancing and path-diversity. We compared our proposed architecture to state-of-the art previous architectures under extensive uniform and non-uniform DC traffic types. Simulations of various switch settings have shown that the proposed OQ Clos-UDN outperforms previous proposals and maintains high throughput and latency performance.

Abstract-Scaling-up Data Center Networks (DCNs) should be done at the network level as well as the switching elements level. The glaring reason for this, is that switches/routers deployed in the DCN can bound the network capacity and affect its performance if improperly chosen. Many multistage switching architectures have been proposed to fit for the next-generation networking needs. However all of them are either performance limited or too complex to be implemented. Targeting scalability and performance, we propose the design of a large-capacity switch in which we affiliate a multistage design with a Networkson-Chip (NoC) design. The proposal falls into the category of buffered multistage switches. Still, it has a different architectural aspect and scheduling process. Dissimilar to common point-topoint crossbars, NoCs used at the heart of the three-stage Closnetwork allow multiple packets simultaneously in the modules where they can be adaptively transported using a pipelined scheduling scheme. Our simulations show that the switch scales well with the load and size variation. It outperforms a variety of architectures under a range of traffic arrivals.

The growing trends of data centers over last decades including social networking, cloud-based applications and storage technologies enabled many advances to take place in the networking area. Recent changes imply continuous demand for bandwidth to manage the large amount of packetized traffic. Cluster switches and routers make the switching fabric in a Data Center Network (DCN) environment and provide interconnectivity between elements of the same DC and inter DCs. To handle the constantly variable loads, switches need deliver outstanding throughput along with resiliency and scalability for DCN requirements. Conventional DCN switches adopt crossbars or/and blocks of memories mounted in a multistage fashion (commonly 2-Tiers or 3-Tiers). However, current multistage switches, with their space-memory variants, are either too complex to implement, have poor performance, or not cost effective. We propose a novel and highly scalable multistage switch based on Networkson-Chip (NoC) fabrics for DCNs. In particular, we describe a three-stage Clos packet-switch with a Round Robin packets dispatching scheme where each central stage module is based on a Unidirectional NoC (UDN), instead of the conventional singlehop crossbar. The design, referred to as Clos-UDN, overcomes shortcomings of traditional multistage architectures as it (i) Obviates the need for a complex and costly input modules, by means of few, yet simple, input FIFO queues. (ii) Avoids the need for a complex and synchronized scheduling process over a high number of input-output modules and/or port pairs. (iii) Provides speedup, load balancing and path-diversity thanks to a dynamic dispatching scheme as well as the NoC based fabric nature. Simulations show that the Clos-UDN outperforms some common multistage switches under a range of input traffics, making it highly appealing for ultra-high capacity DC networks.