As network service providers seek to take advantage of the scale, flexible deployment, and cost reductions first realized in cloud computing, they have begun to define new architectures for their infrastructure in order to realize network function virtualization (NFV). At the same time, measurement functions will be implemented for deployment as virtual functions. This document makes recommendations in key areas such as On-Demand Deployment and Accuracy Considerations. Development of virtualized measurement systems in areas highly relevant to SG 12 work are in the early stages, so this Recommendation is timely.