Managing Network Reservation for Tenants in Oversubscribed Clouds

As businesses move their critical IT operations to multi-tenant cloud data centers, it is becoming increasingly important to provide network performance guarantees to individual tenants. Due to the impact of network congestion on the performance of many common cloud applications, recent work has focused on enabling network reservation for individual tenants. Current network reservation methods, however, do not gracefully degrade in the presence of network over subscriptions that may frequently occur in a cloud environment. In this context, for a shared data center network, we introduce Network Satisfaction Ratio (NSR) as a measure of the satisfaction derived by a tenant from a given network reservation. NSR is defined as the ratio of the actual reserved bandwidth to the desired bandwidth of the tenant. Based on NSR, we present a novel network reservation mechanism that can admit time-varying tenant requests and can fairly distribute any degradation in the NSR among the tenants in presence of network over subscription. We evaluate the proposed method using both synthetic network traffic trace and representative data center traffic trace generated by running a reduced data center job trace in a small test bed. The evaluation shows that our method adapts to changes in network reservations, and it provides significant and fair improvement in NSR when the data center network is oversubscribed.