Cloud services are fundamentally supported by data center networks (DCNs). With the fast growth of cloud services, the scale of DCNs is increasing rapidly, leading to great concern about system scalability due to multiple constraints. This paper proposes a scalable DCN architecture based on optical switching and transmission, with the distributed placement of optical switches and server racks at different nodes in a given optical network. This solves the scalability issue by relaxing power and cooling constraints and by reducing the number of (electronic) switches using high-capacity optical switches, as well as by simplifying DCN internal connections using wavelengths in the optical network. Moreover, the distributed optical switches provide service access interfaces to meet demand within areas, and thus reduce the transmission cost of the external traffic. The major concern is the additional delay and cost for remote transmissions of the DCN internal traffic. To this end, we study the component placement problem in DCNs under a given set of external demands and internal traffic patterns. By leveraging among multiple conflicting factors such as scalability and internal overhead of the DCN as well as the transmission cost of external traffic, we propose both an integer linear program and a heuristic to minimize the system cost of a DCN while satisfying all service demands in the network. This addresses both scalability and cost minimization issues from a network point of view.
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