WAN technologies are considered to exist and function at the three lower layers of the OSI model – Physical, Data Link, and Network. While not all WAN technologies have elements that function at the Network Layer, some (like X.25 and ISDN) do. The figure below provides an overview of how the WAN technologies that you’ll look at in this chapter map to the OSI model.
Figure: A high-level overview of how various WAN technologies map to the Physical, Data Link, and Network layers of the OSI model.
Author: Dan DiNicolo
Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of 2000Trainers.com. He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.
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