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The table 3-1 is the format of LLC PDU. It 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.
0xAAAA
0xE0E0
0xF0F0
0xFEFE
0xFFFF
0x4242
0x0606
0x9898
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
(SAP). Please refer to IEEE802.2 for more details.
Table 3-1 LLC Format
SNAP
Novell IPX
NetBios
IOS network layer PDU
Novell IPX 802.3 RAW packet
STP BPDU
IP
ARP
Table 3-2
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