Summary

We have seen that the landscape of networking standards is littered with a figurative alphabet soup of standards bodies and their output. The Data Link layer is only one of the seven layers of the OSI-RM, an abstract model of a layered protocol stack. The TCP/IP protocol suite is much less formal than the OSI-RM, but layers similar functions in hierarchically similar ways.

The IEEE has developed numerous standards at the Data Link layer, and in doing so has created the logical partition of the Data Link layer into the Logical Link Control (LLC) and Medium Access Control (MAC) sub-layers.

Wireless LANs, which operate at the Data Link layer, are being standardized by the IEEE 802.11 working group, which has produced a fairly complex set of specifications which is laced with its own unique terminology, owing to the fact that operating a MAC sub-layer protocol over a wireless medium is much more challenging than over any wired medium.

The IEEE 802.11 MAC sub-layer protocol, which will be explored in depth in the subsequent chapters, relies on the IEEE 802.2 LLC sub-layer protocol (and optionally IEEE 802.2 SNAP, which may be layered over LLC) to encapsulate higher-layer protocols such as IPv4 over a wireless LAN.