ABSTRACT
As we saw in Chapter 1, the physical network layer is the lowest layer in the Transmission Control Protocol/Internet Protocol (TCP/IP) stack and is used to provide connection to the network. The services provided by this layer are simple and consist of sending and receiving packets. The TCP/IP protocols are designed to operate on any type of network, and therefore assume a minimal level of service provided by the layer. Even though the physical network layer provides a minimal set of services, the implementation can be complex and subject to attack. We can group the physical network protocols into categories based on the physical medium used to interconnect the devices. The two broad categories are wired and wireless. At the heart of the physical network layer is a network access controller, which is implemented in hardware and used to connect the device to the network medium [1-3]. Figure 5.1 shows a block diagram of a typical physical network layer.
