HDLC-. HDLC (Higher-level Data Link Control) ISO. , SDLC (Synchronous Data Link Control) IBM. :
, . . -;
;
; , - ;
point-to-point, multipoint, ;
;
, ;
;
.
. , . - , , . - , . , . . multipoint- , , , .
. . , .
( ). , . , . .
01111110. . , , , .
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bit staffing. 32 , .
, . , , .
, , (1111111). , 15 , . , . , , (1111111101111110). , .
. HDLC- ( ) 3- 3- , . : . . :
1: , . 01111110.
2:8 , . 00000000 - . , , 11111111. - , . . 8 256 . , ( ) , . , , , . , 128 .
3: 8 , , . : . (8 16 ) - Ns, Mr, 3 7 . :
1 2: 16- . 3: , .
HDLC (. 5.111):
l-: ;
S-: ,
( , , , ).
U-: ,
;
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1- S-. .
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0- . 1 0 . P/F : (polling), , , . = 1 , . , F = 1, . , P/F . , .
, , . , , . . -: 1) , 2) . -, HDLC, .
. 3- 8 0 7, 0. 16 , , 7- 128. Ns . , Mr , . , Mr . , l- : Ns - Nr - , Nr-1- .
1-, S-, Nr-1.
. HDLC :
NRM (normal response mode);
ARM (asynchronous response mode);
ABM (asynchronous balanse response).
NRM. . , . . (polling) . P/F (poll/final) . , - (S- , ), 1- , = 1. . , , S- ( ), l-, F = 1. , l-, . , l-, S- 1-. , . , :
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-;
- ;
,
ARM. , , . , ( ). - . , .. - , .
. . . -, -. .
. , . 1- S-. , , ARM- --, .
:
NDM (Normal Disconnect Mode);
ADM (Asynchronous Disconnected Mode);
() 1 (Initialization Mode).
, . :
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.
NDM. I- S-. , U- = 1 , . :
; -
;
; -
, U- ;
; ,
U-, -.
ADM. ADM NDM , , . , , - .
() IM. , , . , . U-. , , . , -. (U-). , -.
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. , 3 7 .
NRME (Normal Response Mode Extended) - ( NRM).
ARME (Asynchronous Response Mode Extended) - ( ARM).
(Asynchronous Balanced Mode Extended) - ( ).
. S- . 6 . . , S- (. 5.75).
5.75
S-
3, 4 | ||
RR (Receive Ready) | . Nr-, Nr . | |
REJ (Reject) | . l- . Mr . | |
RNR (Receive Not Ready) | . l-. Nr, Nr . | |
SREJ (Selective reject) | . Nr-. Nr . |
. :
,
;
, , -
, ;
-
, , .
, U- 5 . 32 , (. 5.76).
DISC (Disconnect) - .
SIM (Set Initialization Mode) - .
RSET (Reset) - , , .
UP (Unnumbered Poll). , , . .
DM (Disconnect Mode) , .
RIM-(Request Initialization Mode) - , , .
UA (Unnumbered Acknowledgement) , U-.
RD (Request Disconnection) - , .
U-, RIM, UA, RD, .
FRMR (Frame Reject) - , , . . , :
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1) , ; 2) , , ; 3) , , ; 4) Ns Nr; 5) , , .
XID, TEST, U1 .
XID (Exchange Identification) - , . , . TEST . , , , . , . .
U1 (Unnumbered Information) - .