(NDM), . (ADM), .
(IS Initialization State)
.
(ITS Information Transfer State)
. NRM, ARM, ABM.
HDLC , :
(Normal Response Mode, NRM) . ( ), . . -.
(Asynchronous Response Mode, ARM) . , . (token). , . , .
(Asynchronous Balanced Mode, ABM) . , . ABM , - -.
, (), HDLC 3 :
(UN Unbalanced Normal) 1 () , .
(UA Unbalanced Asynchronous) . 1 , . .
(BA Balanced Asynchronous) 2 . () , . .
|
|
|
HDLC , . , (FD Frame Delimiter) '01111110'(0x7E ), . . , 0 5 1. ( ) . , , ( ). 01111110 . . , . escape-, '01111101'(0x7D ), FD(0x7E) (0x7D, 0x5E), (0x7D) (0x7D, 0x5D).
0x7E ('01111110') . 0 0 . ́ .
HDLC, FD:
| FD | FCS | FD | |||
| 8 | 8 | 8 16 | 0 , 8 | 16 | 8 |
FD , 01111110, HDLC-, . HDLC- . ( ) .
-. HDLC (10000000) (11000000).
1 2 . . : 0 , 10 , 11 . P/F, - - -. , - - - P -, F.
IP, IPX, AppleTalk, DECnet, , . .
|
|
|
FCS (Frame Check Sequence) , . Ÿ X16+X12+X5+1 (CRC-16) CCITT V.41. CRC . 16 , 99,9984 % . FCS , , . . FCS . -.
I- ( , )
. . . HDLC , , , . , . HDLC 7 ( 1 ) 127 ( 2 ). - 2 :
N(S) ;
N(R) , .
, NA(S) NA(R). , NB(S) NA(R), . -, NB(S) NA(R), REJ () NA(R). , NA(R), , , .
I- / P/F (poll/final). NRM P , F I- . ARM ABM P/F .
| / | . 87654321.. | |
| C/R | .-N(R)- P/F..-N(S)-..0 |
S- (
. , :
(RR)
( N(r)-1).
, P.
F , .
(RNR)
I- RR.
P / .
/ P .
(REJ)
|
|
|
( N(r))
(SREJ)
( )
PPP (. Point-to-Point Protocol) (Data Link) OSI. , , ( ECP, RFC 1968) . : - , , . .
PPP, Point-to-Point Protocol over Ethernet (PPPoE), Ethernet, DSL; Point-to-Point Protocol over ATM (PPPoA), ATM Adaptation Layer 5 (AAL5), PPPoE DSL.
PPP : (LCP), (NCP), (PAP,CHAP), PPP (MLPPP).
PPP HDLC , .
Link Control Protocol (LCP) (, ) . LCP PPP, PPP LCP.
RFC 1994 Challenge-handshake authentication protocol (CHAP), . Password authentication protocol (PAP) .
PPP Extensible Authentication Protocol (EAP).[1]
, , . Internet Protocol Control Protocol (IPCP), Internetwork Packet Exchange Control Protocol (IPXCP) AppleTalk Control Protocol (ATCP) - . Internet Protocol Version 6 Control Protocol(IPv6CP) , IPv6 IPv4 .
PPP . , PPP- (IP, Novell IPX . .), . Network Control Protocol (NCP) ( ).
PPP , , magic numbers. PPP LCP , . , LCP .
