comprises four fields, DSAP, SSAP, Control and Information. The DSAP address
field identifies the one or more service access points, in which the I/G bit indicates it
is individual or group address. If all bit of DSAP is 1s, it’s a global address. The
SSAP address field identifies the specific services indicated by C/R bit (command or
response). The DSAP and SSAP pair with some reserved values indicates some
well-known services listed in the table below.
Table 3-2
LLC type 1 connectionless service, LLC type 2 connection-oriented service
and LLC type 3 acknowledge connectionless service are three types of LLC frame
for all classes of service. In Fig 3-2, it shows the format of Service Access Point
Fig. 3-3 SAP Format
(SAP). Please refer to IEEE802.2 for more details.
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