# Layered Approach

The JunosE CLI enables you to configure your network based on the hierarchy of the OSI model. Therefore, the JunosE configuration guides use a bottom-up approach to describe the configuration process. Figure 3 shows the relationship of layers, protocols, and interfaces to the configuration process. Software functions are layered on top of physical (copper or optical) interfaces. The router supports a number of access protocols (PPP/POS, Frame Relay, ATM) that allow service providers to offer a number of access methods and line speeds to their subscribers. The router is optimized to handle IP connections regardless of the access protocol used. The router also supports a number of protocols that are specific to the B-RAS application. These are shown in Figure 3, and include IP/PPP/ATM and IP/PPP/Ethernet/ATM.

Figure 3: Network Configuration Using a Bottom-Up Approach

Layer 2 (data link) defines how the data is packaged and sent to an IP data connection point in layer 3 (IP interfaces). In layer 3, you define the global attributes for IP services that serve as a platform from which you add routing information.