Networking author Howard C. Berkowitz provides tips on avoiding and fixing data link network failures in Part 3 of his series.

What is a network switch? A network switch is a physical device that operates at the Data Link layer of the Open Systems Interconnection (OSI) model — Layer 2.

The third layer of the OSI Model, the network layer, is where most network engineers focus their time and expertise. As Darragh commented in my post on the data link layer, Layer 2 is cool but ...

Data Link Layer The data link layer is responsible for transmitting packets of information across the link between hosts. If the link is shared by many hosts (for example, a LAN) this layer also ...

In networking and communications, the formats, codes and procedures for transmitting a unit of data (frame, packet) from one node to another. Known as a "layer 2 protocol," the data link protocol ...

Anyway some datalink layers used by ISPs: Ethernet, PPP, VPLS. It's mostly Ethernet- although cable companies use a different layer 2- Docsis. Wireless ISP might use 802.11 and other wireless L2.