LLC
802.2 LLC . LLC HDLC (High-level Data Link Control Procedure), .
LLC
802.2 LLC :
- LLC1 - ;
- LLC2 - ;
- LLC3 - , .
, 802.3-802.5.
LLC1 . , , , LLC.
LLC2 , , . LLC2 HDLC (LAP-B, LAP-D, LAP-M), .
(, , ), , , . , , LLC3.
? . , TCP/IP LLC LLC1. . LLC IPX/SPX.
Microsoft/IBM, NetBIOS/NetBEUI, LLC2. , NetBIOS/NetBEUI . LLC2. NetBIOS/NetBEUI , LLC LLC1.
, LLC1. , . , LLC2 . , LLC2 . , SNA , IBM Token Ring. LLC2 Hewlett-Packard , Ethernet , .
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LLC
LLC ( 802.2 - Protocol Data Unit, PDU) - , :
- . .
- , .
- , , LLC-, - , .
LLC (. 10.1). :
- (Destination Service Access Point, DSAP),
- (Source Service Access Point, SSAP),
- (Control)
- (Data)
10.1. LLC- 802.2
LLC "", 01111110. MAC- .
LLC - IP, IPX, AppleTalk, DECnet, - , , . .
( ) - , . , , LLC LLC2 . LAP-B.
DSAP SSAP , . , , , .
DSAP - , . , , . , , LLC , , , , DSAP, .
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SSAP - , LLC.
, DSAP SSAP , .
DSAP SSAP 1 .
SAP 802.2. , IP SAP 06, NetBIOS -0*F0.
, SAP, , . , LLC DSAP SSAP IPX, IPX-, . DSAP SSAP , LLC .
LLC ( Control):
- (Unnumbered) Control 1 , 11,
- (Information) Control 2 , 0,
- (Supervisory) Control 2 , 10.
Control .10.2.
10.2. Control LLC
LLC1 ( ). Ethernet , Control LLC1, Ethernet, 0x03.
LLC2 . . P/F Poll () , , F (Final) .
, M , , . , , . N(S) , N(R) , -. N(S) N(R) , 0 127. , , (, 56 58, 57), S N(R). , .
, (Reject, REJ), : (Receiver Not Ready, RNR) (Receiver Ready, RR), . , RNR, RR.
, , LLC1 . LLC1 .
. / - P/F (Poll/Final).
P/F : Poll. - , Final, - .
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P/F LLC1.
. .
- LLC2. , : , (), .
. LLC2 , LLC2.
LLC2 , . :
(SABME). . HDLC.
, .
(UA). .
(REST). .
, , . LLC2 . . - 0 - , P/F.
N(S) N(R). ? LLC2 . 127 . 0 127. , - N(S). N(R) - , .
, , . , . , V(R).
, V(R) N(R) , .
, . N(S) , m, N(R) m+1.
, V(R) m. , N(S) V(R), (, , ), .
m, N(S) m+1, V(R), - , .
. 10. :
(REJ) ( V(R)).
V(R), , , , 127 .
(Receiver Not Ready, RNR);
RNR , . , , . RNR , RR.
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