The most common use of Solaris PPP is to set up a point-to-point communications link. A generic point-to-point communications configuration consists of two endpoints connected by a communications link. In a generic configuration, an endpoint system could be a computer or terminal, either in an isolated location or physically connected to a network. The term communications link refers to the hardware and software connecting these endpoint systems. Figure 7-1 illustrates these concepts.
When an endpoint system wants to communicate with the end point on the other side of the communications link, it begins a dial-out operation. For example, to communicate with endpoint B, a user at its peer host, endpoint A, types rlogin end-point-B. This causes endpoint A to dial out over the communications link. In this instance, endpoint A functions as a dial-out machine. The rlogin command causes its modem to dial the phone number of endpoint B. The action it starts and information it passes are considered outbound communications.
When the data travels over the link to endpoint B, this system receives incoming data and sends an acknowledgment signal to endpoint A to establish communications. In this instance, endpoint B functions as a dial-in machine, since it permits other systems to dial in to it. The information passed to the communications recipient and the actions the recipient takes are considered inbound communications.