Key to the economic viability of clouds and datacenters is their elastic scalability. Therefore most active related research areas focus on the datacenter fabric scalability, efficiency, performance, virtualization, optimal virtual machine (VM) allocation and migration. Here we ask the questions: Given a set of tenant workloads running on generic servers interconnected by a 10-100G Ethernet fabric with modern network virtualization and transport protocols, how can the datacenter operator reach the optimal operation region? How is this optimum traded between operator and tenants, and measured with what metrics? In this paper we propose an evaluation methodology and a set of simple, but descriptive, metrics as a first attempt to answer the questions raised above. As proof of concept, we investigate a multitenant virtualized datacenter network running a 3-tier workload. Our proposal enables a quantitative comparison between competing datacenter fabrics and virtualization architectures. Copyright 2013 ACM.