Chapter 11 began with an introduction to WAN technologies, including how they map to the lowest three layers of the OSI model. Different WAN concepts and connectivity techniques were also introduced, including point-to-point, circuit-switched, and packet-switched connections. A look at different carrier lines and speeds compared the differences between the T and E carrier systems used in North America and Europe, respectively.
Point-to-point or leased-line connections were looked at next, including concepts and the configuration of both HDLC and PPP on Cisco routers. While HDLC is the default encapsulation used on synchronous serial interfaces on Cisco routers, PPP provides a standard method of encapsulating data over point-to-point links, and includes the ability to configure additional features like mutual authentication using CHAP or PAP.
ISDN was introduced next as a circuit-switching technology that uses all-digital links between locations. The configuration of both dedicated and demand-dial ISDN connections were explored, as was a breakdown of ISDN services, protocols, equipment, reference points, and standards.
This was followed by a detailed overview of Frame Relay, a popular packet-switching technology used to interconnect locations using virtual circuits. This included a look at not only the Frame Relay communication process, but also the ways in which virtual circuits are identified, provisioned, and configured on Cisco routers. The configuration of Frame Relay for both production and lab environments was also discussed.