Point-to-Point Communications Links

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. The following figure illustrates these concepts.

Figure 21-1 Basic Point-to-Point Link

Dial-out Operations and Outbound Communications

When an endpoint system wants to communicate with the endpoint 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 endpoint A starts and information it passes are considered outbound communications.

Dial-ins and Inbound 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.