3, CSMA /CD (Carrier - Sense Multiple Access with Collision Detection ) (, ) . Ethernet, (Fast Ethernet, Gigabit Ethernet). , .
. Alohanet, 1970 . , ( "" ), CSMA ( ). Ethernet Fast Ethernet , "" , . ( ) ( -II) ( 86, Fast Ethernet 100BaseT4 ). CSMA CSMA /CD () , .
Ethernet Fast Ethernet, () :
- IPG (interpacket gap, ) (9,6 Ethernet / 0,96 Fast Ethernet). .
- (Bit Time, ) (100 Ethernet / 10 Fast Ethernet).
- PDV (Path Delay Value, ) (, ). , , .
- Collision window ( ) PDV .
- Collision domain ( , ) , , .
- Slot time ( ) (512 ).
- Minimum frame size (512 ).
- Maximum frame size (1518 ).
- Maximum network diameter ( ) - , slot time, .
- Truncated binary exponential back off ( ) ( 16 ). :
RAND(0,2min(N,10)) x 512 x
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N , RAND(a, b) ...b, . (PDV).
. 10.1 CSMA /CD , () .
, , () . , CSMA /CD, "" "" , , .
, () . , IPG ( 1 ). IPG ( 2 ).
() . , ( 4 ). , .
- , . () , 32- (JAM) ( 3 ). , , .
, , ( ). 16, , . , , . , .
16, , . , , , . . , , .
. 10.1. CSMA/CD
( ) , , ( 5 ). IPG . , ( - ).
, , CSMA /CD , , , . , , . , . "" " ", 512- . 512- .
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480 , , 512 (64 ) . () (runt frames). 512- ( 480 ), ( ). . , 32 , . , , ( 1 4,2 ).
( ) . , FCS, CRC (Cyclic Redundancy Check), .
, , , . , Ethernet / Fast Ethernet 64 1518 , .
. , - :
- 64 (512 );
- FCS (, );
- .
, Ethernet -II , .
3. . , () .