  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
Networks-on-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 single-hop 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.
