One of the most common types of WAN connections, especially in long-distance communications, is a point-to-point connection, also called a serial or leased line connection. Because these connections are typically provided by a carrier, such as a telephone company, boundaries between what is managed by the carrier and what is managed by the customer must be clearly established.
This chapter covers the terms, technology, and protocols used in serial connections. The High-Level Data Link Control (HDLC) and Point-to-Point Protocol (PPP) are introduced. PPP is a protocol that is able to handle authentication, compression, error detection, monitor link quality, and logically bundles multiple serial connections together to share the load.