The network interface layer, also commonly referred to as the datalink layer or link layer, is the lowest layer in the TCP/IP model. This particular layer has several unique security vulnerabilities that can be exploited by a determined adversary.
It defines how data packets are to be formatted for transmission and routings. Some common link layer protocols include IEEE 802.2 and X.25. The data link layer and its associated protocols govern the physical interface between the hostcomputer and the network hardware.
Example of usage – “The application–interface layer involves a variety of applications and interfaces from RFID tag tracking to smart home, which are implemented by standard protocols as well as service-composition technologies.”