Figure 1 illustrates the logical view of a sample network. It consists of three communication resource managers(3) (CRMs): CRM X, CRM Y, and CRM Z. Each CRM has two logical connections with two other CRMs; the logical connections are shown as the gray portions of Figure 1 and enable communication between the CRMs. The network shown in Figure 1 is a simple one. In a real network, the number of CRMs and logical connections between the CRMs can be in the tens of thousands or higher.
Figure 1. Programs Using CPI Communications to Converse through a Network
The CRMs and the logical connections shown in Figure 1 are generic representations of real networks. If this were an SNA network, the CRMs would be referred to as logical units of type 6.2 and the logical connections would be sessions. In an OSI network, CRMs are called application-entities and the logical connections are associations. The physical network, which consists of nodes (processors) and data links between nodes, is not shown in Figure 1 because a program using CPI Communications does not "see" these resources. A program uses the logical network of CRMs, which in turn communicates with and uses the physical network. This manual discusses CRMs of type LU 6.2 and type OSI TP.
(3) Communication resource managers can provide many functions in a network. In this manual, the term communication resource manager refers only to resource managers that provide conversation services to CPI Communications programs. Other CRMs might, for example, provide services for remote procedure calls or message-queuing interfaces.