In the Point-to-Point Protocol (PPP), the Link ControlProtocol (LCP) establishes, configures, and tests data-link Internet connections. Before establishing communications over a point-to-point link, each end of the PPP link must send out LCP packets. The LCP packet either accepts or rejects the identity of its linked peer, agrees upon packet size limits, and looks for common misconfiguration errors. Basically, the LCP packet checks the telephone line connection to see whether the connection is good enough to sustain data transmission at the intended rate. Once the LCP packet accepts the link, traffic can be transported on the network; if the LCP packet determines the link is not functioning properly, it terminates the link.
LCP packets are divided into three classes:
- Link configuration packets used to establish and configurea link
- Link termination packets used to terminate a link
- Link maintenance packets used to manage and debug a link