APM is the most common tool for optimizing applications but often requires deep application integration to get the best optimization results. However, application performance can also use "black box" models and external characteristics from network transactions to capture a set of metrics that can also optimize your applications. In understanding a metrics value, we'll first investigate the business goals of application optimization. We'll follow up with a review of the advantages and disadvantages of using network metrics, and the systems changes required for both APM and network-derived metrics collection.