PPP Encapsulation Configuration

We can configure PPP on the following types of physical interfaces:

1. Asynchronous serial
2. Synchronous serial
3. High-Speed Serial Interface (HSSI)
4. ISDN

PPP uses its Network Control Program (NCP) component to encapsulate and negotiate options for multiple network layer protocols. PPP uses another of its major components, the link control protocol (LCP), to negotiate and set up control options on the WAN data link.

Cisco routers that use PPP encapsulation may include these LCP configuration options, as shown in the figure:

1. Authentication: Requires the calling side of the link to enter information to help ensure that the caller has network administrator permission to make the call. Peer routers exchange authentication messages. Two alternatives are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).
2. Compression: Increases the effective throughput on PPP connections by reducing the amount of data in the original frame that must travel across the link. The protocol decompresses the frame at its destination. Two compression protocols available in Cisco routers are Stacker and predictor.
3. Error-detection: Along with PPP, enables a compression process to identify fault conditions. The Quality and Magic Number options help ensure a reliable, loop-free data link.
4. Multilink PPP (MLP): Provides load balancing over the router interfaces that PPP uses. This feature is sometimes referred to as Multilink Protocol. Cisco IOS Release 11.1 (and later releases) support MLP.

Tagged as: link control protocol, Network control program, PPP Encapsulation Configuration