reduced cost, widespread expertise in Ethernetrelated protocols, and simplicity of using a single fabric. However, the transition to a unified Ethernet fabric requires resolving several major challenges, including efficient implementation of the dominant protocol layers-for example, iSCSI, TCP, RDMA, and SSL-at high data rates; advanced quality of service to ensure that a unified fabric works almost as well as multiple isolated fabrics; sophisticated high-availability mechanisms; and security

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... chanisms to address the exposure of storage/IPC traffic on the Ethernet. Satisfying these and other demands of future data center applications could require examining new protocols, adding enhancements to existing protocols, and introducing new platform features. Developments in wireless and optical networking technologies provide another dimension for data center fabric research. SCALE-UP VERSUS SCALE-OUT The evolving economics of hardware technology has forced a rethinking of how to implement data center applications. In particular, with the availability of inexpensive but high-performance clustering solutions, using clustered application deployment instead of expensive multiway symmetric multiprocessors (SMPs) becomes more attractive. A clustered solution offers many advantages over SMPs, including incremental upgradability, more flexibility, and the potential for higher fault toler-Several ongoing developments necessitate a study of architectural and operational concerns in modern data centers, including data center fabric research, scale-up versus scale-out, resource consolidation, infrastructure management, and operational cost reduction.