Ethernet - . , Ethernet, 5 , , Ethernet - 50 .
Ethernet, . , Ethernet - , Ethernet Network, Xerox 1975 ( ). : 60- , Aloha. 1980 DEC, Intel Xerox Ethernet II , . Ethernet DIX .
Ethernet DIX IEEE 802.3, , . , IEEE 802.3 MAC LLC, Ethernet . Ethernet (Ethernet Configuration Test Protocol), IEEE 802.3. , .
IEEE 802.3 - 10Base-5, 10Base-2, 10Base-T, 10Base-F.
Ethernet .
Ethernet - CSMA/CD.
4.2. CSMA/CD
Ethernet , (carrier-sense-multiply-access with collision detection, CSMA/CD).
( , ). , . - , Ethernet. , , , (multiply-access,MA).
, , . . , , , , , , -. - , - , .
|
|
, (. 3). ( ), , . (carrier-sense, CS), , . , , . , , , .
, . , (collision detection, CD). , , , , jam-.
, .
, , , . , 10 / , . , , , . Ethernet' .
CSMA/CD , :
- 9.6 ; , .
- ( ) 32- (jam-), .
- , , . 16 , . , . .
|
|
. 1. CSMA/CD (tp - A B)
Ethernet. - , , , - , ( - ). , - , , , . ( ) , Ethernet. , Ethernet, .
Ethernet , . 46 ( 72 576 ). , . 10 /, Ethernet, 2500 .
, , CSMA/CD, , Fast Ethernet, . Fast Ethernet 210 , Ethernet 25 .
, Ethernet , :
- 2500 ,
- 1024 .
, , .
Ethernet, .
, , MAC- . , MAC- 10 . , (interframe gap), , .
- , . , , MAC- LLC-.
, MAC- jam-, . jam- MAC- .
|
|
(attempt limit), 16. , .
, , MAC- . (truncated binary exponential backoff). .
(slot time) - , , . - (collision window). - , , . :
= +
802.3 , 10 / 0.1 .
802.3 512 , 2.5 . 512 64 , - , . .
N- L , L - , [0, 2N]. 10 (, 16), [0, 210], [0, 1024]. 802.3 1.
1.
10 /c | |
512 | |
9.6 | |
jam- | 32 |
( ) | 1518 |
( ) | 64 (512 ) |
64 |
, Ethernet , (packets-per-second, pps). Ethernet , . Ethernet , , .
64+8 = 72 576 , 57.6 . 9.6 , , 67.2 . Ethernet 14880 /.