Chapter 3. Fundamentals of WANs
Most Layer 1 and 2 networking technology falls into one of two primary categories: wide-area networks (WAN) and LANs. Because both WANs and LANs match OSI Layers 1 and 2, they have many similarities: Both define cabling details, transmission speeds, encoding, and how to send data over physical links, as well as data link frames and forwarding logic.
Of course, WANs and LANs have many differences as well, most notably the distances between nodes and the business model for paying for the network. First, in terms of the distance, the terms local and wide give us a small hint: LANs typically include nearby devices, while WANs connect devices that can be far apart, potentially hundreds or thousands of miles apart.