A decisive advantage of software-defined networking (SDN) is its support for flexible network reconfigurations. Considering that, software-defined networks require accurate and timely data-plane state information. Network monitoring mechanisms usually require considerable resources on SDN controllers as well as on the data-plane elements. In this paper, we propose an optimization of the statistic transmission to reduce costs on both control- and data-plane regardless of the used monitoring application and statistic provisioning tool. To this end, we intercept the statistic message exchange and 1) aggregate multiple requests coming from different monitoring applications/controllers, 2) filter irrelevant statistic messages with respect to their information gain before delivering them to the control applications, and 3) deploy statistic caching. The proposed system, denoted STATISTIC REQUEST RELAY, forms a logically centralized statistic relay between controllers and the managed data-plane network. Our evaluation shows that the number of statistics processed on controllers as well as statistic requests on switches is reduced significantly while the performance penalty is negligible when using statistic aggregation and filtering as proposed here.