This chapter starts your exploration of WAN technologies by introducing point-to-point communications and the Point-to-Point Protocol (PPP).
One of the most common types of WAN connection is the point-to-point connection. Point-to-point connections are used to connect LANs to service provider WANs, and to connect LAN segments within an Enterprise network. A LAN-to-WAN point-to-point connection is also referred to as a serial connection or leased-line connection, because the lines are leased from a carrier (usually a telephone company) and are dedicated for use by the company leasing the lines. Companies pay for a continuous connection between two remote sites, and the line is continuously active and available. Understanding how point-to-point communication links function to provide access to a WAN is important to an overall understanding of how WANs function.
Point-to-Point Protocol (PPP) provides multiprotocol LAN-to-WAN connections handling TCP/IP, IPX, and AppleTalk simultaneously. It can be used over twisted pair, fiber-optic lines, and satellite transmission. PPP provides transport over ATM, Frame Relay, ISDN and optical links. In modern networks, security is a key concern. PPP allows you to authenticate connections using either Password Authentication Protocol (PAP) or the more effective Challenge Handshake Authentication Protocol (CHAP). These are taught in the fourth section.
In this chapter you will also learn the key concepts of serial communications, and how to configure and troubleshoot a PPP serial connection on a Cisco router.