On Adapting SNMP as Communication Protocol in Distributed Control Loops for Self-adaptive Systems

Self-adaptive Systems (SASs) are one way to address the ever-growing complexity of software systems by allowing the system to react on changes in its operating environment. In today's systems, self-adaptation is typically realized with a control loop, for which the MAPE-K feedback loop is a prominent example. Research uses the notion of patterns to describe the distribution and decentralization of individual control loop components or control loops and their underlying managed subsystems. While there are some well-accepted standards about which components a managed subsystem has to implement so that it can interact with the control loop, research still lacks detailed investigation of control mechanisms, protocols, message formats and trade-offs for communication within and across control loops. This paper examines the idea of using the Simple Network Management Protocol (SNMP) for the communication in centralized, decentralized and distributed control loops. For this, a mapping of the SNMP function pool on the component communication of the MAPE-K control loop based on interfaces will be presented. Then, the SNMP approach is assessed with respect to its support for self-adaptive capabilities and limitations are discussed. The evaluation is based on a prototype that implements the prior presented mapping for the well-accepted Znn.com benchmark. The evaluation shows that the presented infrastructure can handle a sudden increase or decrease in resource demand by using self-adaptivity, which otherwise would lead to partial or complete loss of functionality by using SNMP as its communication protocol.