Components
Ethernet and wired LANs

A WLAN topology can be an extension to an existing scalable LAN. The best-built and managed scalable internetworks are typically designed in layers, following a hierarchical model. By using hierarchical layers, the user can break a large network into smaller pieces, which can each be dealt with separately. To understand the importance of layering, consider the OSI Reference Model. The OSI Reference Model is a layered model for understanding and implementing computer communications. By dividing up the total network functionality into smaller pieces, or layers, the OSI model simplifies the tasks required for two computers to communicate. Activity 4.1.6a shows many of the devices that exist in a typical enterprise environment. The devices are shown at the highest layer of the OSI Model, on which they operate.

Hierarchical models for internetwork design also use layers, to simplify the task required for internetworking. Each layer can be focused on specific functions, thereby allowing the user to choose the right systems and features for the layer. As a result, a hierarchical model simplifies the management of the internetwork and allows the user to control the growth, without overlooking the network requirements. The Cisco three-layer hierarchical model is shown in Figure .

The traditional wired devices that are utilized include routers, switches, servers, and printers. These devices are shown in Figures through , along with their graphical icons. Developing technologies, such as voice over IP (VoIP), can add additional capabilities to both wired and wireless LANs. IP phones and the graphical icon are shown in Figure . Finally, network security devices such as firewalls, VPN devices, and intrusion detection systems are becoming requirements for a secure LAN/WAN. A Cisco PIX Security Appliance and its icon are pictured in Figure .

All of these devices must be considered when implementing a WLAN solution. This is because the WLAN must seamlessly interoperate with the existing wired network. WLAN security configuration will be covered later in the course. The wired LAN will continue as a predominant portion of the complete and modern network system.


Interactive Media Activity

Interactive Activity: Layer Launch

In this activity players use a spring board to launch devices into the right layer hole.

Interactive Media Activity

Interactive Activity: OSI Layer Devices

This animation classifies networking devices by the OSI layer upon which they operate.