The growth of e-commerce is creating demand for services with financial incentives for service providers. Such services are specified by service level agreements (SLAs) in which revenue accrues with the number of completed transactions, and costs are incurred if response times go above a specified threshold. In this paper we propose a profit-oriented feedback control system that automates the admission control decisions in a way that balances the loss of revenue due to rejected work against the penalties incurred if admitted work has excessive response times. One approach to making these trade-offs is to employ classical control theory (e.g., proportional integral controllers); however, doing so requires a labor-intensive design process that tailors the controller to a specific workload and profit model. Instead, we develop a fuzzy control algorithm that implements hill climbing logic to maximize profits and handle the stochastics that make profits quite "bumpy." Our studies of a Lotus Notes ® e-mail server reveal that the fuzzy controller requires little human intervention and is robust to changes in workloads and values of SLA parameters. Further, we prove that our design of the fuzzy controller leads to a value of the admission control parameter that maximizes steady state profits. The advent of e-commerce has created a business need for high-quality information technology (IT) services. For example, a "buy" transaction that takes more than a few seconds may cause the customer to abandon the purchase. As a result, businesses are seeking quality-of-service (QoS) guarantees from their service providers (SPs). These guarantees are expressed as part of service level agreements (SLAs), often with financial incentives. For example, provider revenues may be determined by the number of completed transactions, and providers may incur financial penalties for SLA violations (e.g., exceeding response time guarantees). Since demand for services is often unpredictable, providers must sometimes make trade-offs between losing revenue (e.g., as a result of admission control that denies access to some customers) and incurring penalties (e.g., because admitted work cannot be completed within the SLA-dictated response time). Making such choices is skill-intensive and time-consuming, and the decisions must be made in real time. In this paper we focus on QoS at the application layer, as opposed to the network-level QoS considered in the work on DIFFSERV and RSVP. 1 A variety of SLAs have been published. Reference 2 describes a template for frame relay SLAs. Reference 3 provides guidelines for the state of Texas, including considerations for response time, availability, and downtime. Reference 4 does the same for the University of Michigan IT. We generalize these examples and consider a simple profit model in which: (A) the service provider receives revenues for each completed interaction (hereafter, transaction)
Similarly, the authors in REF propose a profit-oriented feedback control system that automates the admission control decisions in a way that balances the loss of revenue due to rejected work against the penalties incurred if admitted work has excessive response times.
Using Fuzzy Control to Maximize Profits in Service Level Management
IBM Syst. J.
IBM Syst. J.
Computer Science