i‐WABA: An efficient wavelengths arrangement and bandwidth allocationWDMAprotocol for passive optical intra‐rack data center networks

Abstract

In this article, we effectively handle the continuously growing traffic within data centers (DCs) and we focus on the intra-rack communication. We propose a passive optical intra-rack DC network (DCN) that uses a set of wavelengths for the data intra-rack communication and a separate control wavelength for pre-transmission coordination. We introduce a distributed access control scheme, named intra-rack wavelengths arrangement and bandwidth allocation (i-WABA) protocol, to effectively arrange the data wavelengths into groups and efficiently allocate them among the servers for transmission, avoiding synchronization complexity. The proposed i-WABA protocol ensures the collisions-free transmission over the data wavelengths and at destination achieving high performance, scalability, and reliability. In opposition to the majority of the state-of-the-art intra-rack MAC protocols that adopt synchronous transmission requiring strict time compliance, the proposed i-WABA protocol is unslotted providing simple and reliable access control even under high data rates. Moreover, unlike other studies that assume that the control communication is performed over an Ethernet link, the proposed intra-rack DCN considers that it is performed in the optical domain, ensuring its effective parallel operation to the data communication. The throughput improvement is extensively studied and it is proven to be an increasing function of the number of data wavelengths groups.Finally, the proposed intra-rack DCN along with the proposed i-WABA protocol is compared with other state-of-the-art intra-rack DCNs in terms of throughput, power consumption, and cost, while it is proven to be a performance, energy, and cost efficient DCN solution.