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WAN and VPN TechnologiesDay 4CCNA 640-802 Exam Topics■■Describe different methods for connecting to a WAN.Describe VPN technology (importance, benefits, role, impact, components).Key TopicsToday is a whirlwind review of WAN technologies, WAN connection options, and VPN. Becausethese exam topics are conceptual in nature, requiring no configuration skills, read this review severaltimes. If necessary, refer to your study resources for more in-depth review.WAN Technology ConceptsWAN access standards typically describe both physical layer delivery methods and data link layerrequirements, including physical addressing, flow control, and encapsulation. The physical layer protocolsdescribe how to provide electrical, mechanical, operational, and functional connections to aservice provider. The data link layer protocols define how data is encapsulated and the mechanismsfor transferring the resulting frames. A variety of technologies are used, such as Frame Relay andAsynchronous Transfer Mode (ATM). Some of these protocols use the same basic framing mechanismas High-Level Data Link Control (HDLC), an ISO standard, or one of its subsets or variants.WAN Components and DevicesFigure 4-1 illustrates the terminology commonly used to describe physical WAN connections.The WAN components shown in Figure 4-1 are described in further detail in the following list:■■■■■■Customer Premises Equipment (CPE): The devices located at the premises of the WANsubscriber. The subscriber either owns or leases the CPE.Data Communications Equipment (DCE): Consists of devices that put data on the localloop. The DCE primarily provides an interface to connect subscribers to the WAN cloud.Data Terminal Equipment (DTE): The customer devices that pass the data from a customernetwork to the DCE for transmission over the WAN.Local loop: The copper or fiber cable that connects the CPE the central office (CO) of theservice provider. The local loop is sometimes called the “last mile.”Demarcation point: A point where customer equipment is separated from service providerequipment. It is the place where the responsibility for the connection changes from the customerto the service provider.Central office (CO): A local service provider facility or building where local cables link tolong-haul, all-digital, fiber-optic communications lines through a system of switches andother equipment.