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WANs use the OSI reference model, but focus
mainly on Layer 1 and Layer 2. WAN standards typically
describe both physical layer delivery methods and data link layer
requirements, including physical addressing, flow control, and encapsulation.
WAN standards are defined and managed by a number of recognized
authorities.
The physical layer protocols describe how
to provide electrical, mechanical, operational, and functional
connections to the services provided by a communications service
provider. Some of the common physical layer standards are listed in
Figure
 , and their
connectors illustrated in Figure
 .
The data link layer protocols define how
data is encapsulated for transmission to remote sites, and the
mechanisms for transferring the resulting frames. A variety of
different technologies are used, such as ISDN, Frame Relay or
Asynchronous Transfer Mode (ATM). These
protocols use the same basic framing mechanism, high-level data link
control (HDLC), an ISO standard, or one of its sub-sets or variants.
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Interactive Media Activity
Crossword Puzzle:
WAN Standards
Upon completing this activity, the student
will be able to identify various WAN standards.
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Web Links