V.42 .
) MNP3 V.42 MNP2, , 20% .
) - , DLE, 100%. , , ( 0FFh), 20% - 0 .
) I V.42, , 6 . LT, , MNP3 8 , MNP2 - 12 .
) MNP , "" , , , .. 11 MNP3 15 MNP2 ( LA). I V.42 , .
) LAPM .
MNP LR - . MNP3 LA (, , ), LR. LR 31 , LA - 15 . , 31 , 31 , , 15 . , LAPM 4 - 2 ODP/ADP, . , 4 1.5 . 10 . , ( ) 10 , 31 , , 46 .
, ODP/ADP 10 , .. 5 . , LR - , - ( - ). , LAPM MNP.
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- , LAPM MNP. . ( ) , . "" , . , MNP2, . , , , . , -. , , , - .
. . . , . , " " , - . V.42 MNP. -, V.42, MNP, . , , , . -, SREJ LAPM , .
LAPM MNP. . , , .
) . , . , , . , . , , . MNP , .
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) XID LAPM, , , "ID () ". ( ) .
) (CRC-32) , . .
) .
) . ( SREJ) .
) U- TEST , , . .
) . , XID, , . , , , , : , , CRC-32. MNP , .
) LAPM . , .
CRC ( )
/ , . . CRC (cyclic redundancy check) , . CRC : ( ) q(x) = x16 + + 1 . . 216, .. 16- L(x), : F(x) * 216 + L(x). (, 2) , ( ) - , ( CRC):
F(x) * 216 + L(x) = Int(x) * q(x) + O(x)
O(x) = Int(x) * q(x) F(x) * 216 L(x) .
.. F(x) * 216 + O(x). ( 2) (). L(x). , . , , .
, L(x) . 10-12.
. : F(x) = 10011101 (8 ), (5 ): q(x) = 11001 ( 1). , 4- (L(x) = 0000): F(x) = 10011101 0000. F(x) q(x). 2 .
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0010 (CRC).
CRC . .. F(x) O(x) CRC. F(x) O(x): F(x) = 10011101 0010. 2 q(x):
0000 , L(x), . LAP M q(x) = x16 + x12 + x5 + 1, + - 2. :
: , .
32- LAP M: q(x) = x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 +1, + - 2. . , , .
