Université Catholique de Louvain: Olivier Bonaventure's "Computer Networking: Principles, Protocols, and Practice"
Read the beginning of section 6.3, "Datalink Layer Technologies," on page 229. Stop at section 6.3.1 "The Point-to-Point Protocol," which you will read below.
It would take a library full of volumes to discuss all of the technologies used on the Internet. Your textbook has condensed this information into a discussion of six major categories. The following subunits address the datalink services of these technologies.