3.2 PPP Link Control Protocol Options
3.2.1 Configuration features
Earlier, you learned about the PPP architecture and how the LCP is used for establishing, configuring, authenticating, and testing the data-link connection. This section presents the following configuration features that are negotiated through the LCP:

Authentication, with PAP or CHAP, is used as a security measure with PPP and PPP callback. Authentication allows the dialup target to identify that any given dialup client is a valid client with a preassigned username and password.

Callback is a PPP option used to provide call and dialup billing consolidation. PPP callback was first supported in Cisco IOS Release 11.0(3).

Compression is used to improve throughput across existing lines. PPP compression was first supported in Cisco IOS Release 10.3. As you will see later, Cisco routers support Stacker, Predictor, and Microsoft Point to Point Compression (MPPC).

Multilink PPP (MLP) takes advantage of multiple bearer channels to improve throughput. Datagrams are split, sequenced, transmitted across multiple links, and then recombined at the destination. The multiple links together are called a bundle. Multilink is especially useful with ISDN, in which both B channels can be used to achieve 128-Kbps throughput. MLP also works with modems to provide additional bandwidth. This protocol was first supported in Cisco IOS Release 11.0(3).

The following sections provide detailed explanations of LCP options.