An APPC Application Example

Figure 1 depicts a typical APPC application. The application consists of two transaction programs, TPA and TPB, which hold a conversation between different systems in an SNA network. Their conversation occurs across a session between their logical units, LU01 and LU02, which represent points of entry into the network from their systems. This example is repeated and adapted throughout the chapter to illustrate the different mechanisms for LU and conversation security.

In the example, TPA is the outbound TP, which starts (allocates) the conversation. The conversation is considered outbound from TPA. TPB is the inbound TP; it receives and processes the conversation request from TPA. From TPB's point of view, the conversation is inbound.

Most of the APPC/MVS security mechanisms protect inbound TPs and LUs on MVS, such as TPB and LU02, from unauthorized inbound requests.