As economic globalization and digital transformation accelerate, enterprises keep expanding their scales. More and more branches locate in different regions, with each branch network being considered as a local area network (LAN). The headquarters and branches need to cross geographical locations to communicate with each other. To better carry out services, an enterprise needs to connect these geographically dispersed branches through a wide area network (WAN). The development of the WAN technologies is accompanied by the continuously increased bandwidth.In the early stage, X.25 provided only the bandwidth of 64 kbit/s. Later, the digital data network (DDN) and Frame Relay (FR) increased the bandwidth to 2 Mbit/s. Synchronous digital hierarchy (SDH) and asynchronous transfer mode (ATM) further increased the bandwidth to 10 Gbit/s. Now, the current IP-based WANs provide 10 Gbit/s or even higher bandwidth. This course describes the development history of WAN technologies, especially the implementations and configurations of Point-to-Point Protocol (PPP) and Point-to-Point Protocol over Ethernet (PPPoE).