Welcome to Module 04 of the CISSP course! This module gets to the core of networking and data communications with an introduction to the OSI reference model. The OSI model is the foundation of networking protocols and governs the rules followed by all network devices. The protocols in the reference model are organized into layers and this is what is meant by "layered" protocols. These various layers correspond to the functions supported by network devices such as hubs, switches, routers, VLANs, and as it names implies, Layer-3 switches. We'll also have a look at wireless communications and the threats targeted against it. The various encryption protocols used in wireless communications will be discussed within this security context and these include WEP, WPA, and WPA-2. And don't think you can safely ignore WEP simply because it's outdated! Many devices that utilize it are still widely deployed. There's quite a bit of meat in this module and as such, is a very testable subject area on the CISSP exam!