Quorum: Flexible quality of service for Internet services

In this paper we describe Quorum, a non-invasive approach to scalable quality-of-service provisioning that uses traffic shaping, admission control, and response monitoring at the border of an Internet site to ensure throughput and response time guarantees. We experimentally compare an implementation of Quorum both to hardware over-provisioning and to leading software approaches using real world workloads. Our results show that Quorum can enforce the same QoS guarantees as either of the compared approaches, while achieving better resource utilization than over-provisioning and without the application rewriting overhead required by intrusive software approaches. We also demonstrate that our implementation can successfully handle extreme situations such as sudden traffic surges, application misbehavior and node failures. Furthermore, we demonstrate the flexibility of Quorum by providing QoS guarantees for a complex and heterogeneous Internet service that cannot be implemented by other current software approaches.