When we adopt a connection-oriented approach to networking, we gain determinism and control at the expense of scalability and availability. By contrast, a connectionless approach gives us broad accessibility and self-healing connectivity at the expense of granular control and sequencing. Service-based networks defy this conventional wisdom, marrying the predictability of deterministic models with the scalability of routed models. Network services combine the determinism, richness, and predictability of a connection-oriented approach with the pervasiveness, compelling economics, and inherent flexibility of connectionless networks. Rather than dealing with discrete chunks of data, service-based networks deal with content and users.
Network services are location-independent.
Services are provisioned by network administrators, but negotiated at demand-time. DNS, for example, is a form of service provisioning. The service is made available through a central directory that is broadly available, and a simple set of protocols allows an application to establish the sessions it needs. Perhaps most importantly, services rely on the exchange of information about how to locate the optimal fulfillment point for a given application, how to deliver it economically, and so on. The determinism and scalability of these approaches is described in Figure 3, below.