etwork owned by an enterprise, a commercial organization, or a residential user. The purpose of a LAN is to allow employees and residential users to share resources. For example, without a local area network, each person would need his or her own printer, router, switch, and applications. The LAN enables employees to share high-speed printers, routers, modems, Wi-Fi equipment, and broadband services to reach the Internet, and to receive incoming and make outgoing calls. Without a LAN, each user would additionally require her own connection to the Internet. In short, costs would be sky-high and staff would be burdened with arranging all their own access to services. www.TechnicalPDF.com Table 2-1 is a partial list of devices connected to LANs. Growing numbers of "connected" devices is adding tremendous traffic to LANs. It is additionally increasing the criticality of LANs. Each device on a LAN is referred to as a node. The size of a LAN is often described as the number of nodes on that LAN. Table 2-1 Devices (Nodes) on LANs Routers Security cameras Printers Wi-Fi equipment Switches Telephones Personal computers Cable modems Thermostats Video conferencing equipment Electronic white boards for Security alarms meetings Lights Equipment to manage lighting Fire alarms Factory automation systems Shared applications Projectors Wireless devices connected to Bar code scanners in retail Wi-Fi locations Cash registers LAN monitoring software Storage networks Databases Televisions Set-top boxes including Apple TV and Roku SWITCHES, MEDIA, AND PROTOCOLS IN LANS www.TechnicalPDF.com Switches have been described as "goes into, goes out of." Requests for access to applications including e-mail go "into" switches and the responses to these requests are transmitted "out of" switches. LANs are made up of Layer 3 (also referred to as core or backbone) switches and Layer 2 switches. Layer 3 core or backbone switches Transmit messages between buildings on a campus. Are connected to other Layer 2 and to Layer 3 switches. . Are not conne