Everything as a Service has become nearly a synonym for cloud computing. That’s unsurprising, as the benefits of cloud – from economy of scale to increased service velocity – are derived mainly from the abstraction of network, compute and storage resources into services that can be rapidly provisioned, elastically scaled and intelligently orchestrated. We’ve come to use «Everything as a Service» and «Software Defined Data Center» nearly interchangeably, because the goal of both is really to drive toward IT as a Service. A world in which end-users (application owners and administrators) can provision, scale and orchestrate the resources necessary to deliver applications from app dev through devops to the network.
This journey, in part, gave rise to SDN as a means to include the network in this new service-oriented data center. But SDN focused on only a subset of the network stack, leaving critical layer 4-7 services behind.