Most network engineers consider the 'network' to be routers, switches, NICs, and wires. But, is this enough? Consider what application developers believes to be the network: they believe it to be the path between one API to another API some distance away; this network includes NIC drivers, CPU, memory, busses, and operating systems. Now consider an end user who believes that everything is the network, including the application and computer. Delivery monitoring is designed to view the network from the perspective of the application, API-to-API, and refers to this network as the 'apparent network'.
Applications connect to a network via the network’s Application Program Interfaces (API). Within Delivery monitoring, the network API-to-API path that an application uses is measured, and is referred to as an “apparent network”. This can include effects that are experienced by the application such as systematic delays originating at the host operating system or within the NIC hardware.
An apparent network reaches further than the traditional view of a network. The traditional “the network is this big and this full” approach is often insufficient. We must consider operating systems, packet drivers, API interfaces, network protocols, which API is used and how an application uses the networks.