, , . , :
Local Talk (230 /), Ethernet 10 /), Token Ring (16 /) ARC net (2,5 /).
( , ) .
: FDDI (100 /), (155 /) , 100 1000 Ethernet, 20- ARC net Plus.
, .
(FDDI ATM) - , , , .
Ethernet
() Ethernet DEC, Intel Xerox 1980 IEEE 802.3. DIX, . Ether () . Ethernet v1.0 Ethernet v2.0 , IEEE 802.3 . Ethernet IEEE 802.3 ( 10 /). 1995 IEEE 802.3u Fast Ethernet 100 /, 1997 I 802.3z -Gigabit Ethernet (1000 /). 1999 IEEE 802.3ab Gigabit Ethernet 5. Ethernet 10Base2, 100BaseTX . , /. : Base () , Broad . : (10Base2 185 , 10Base5 500 , 1Base5 250) (, , 2, 4 , FX, FL, FB, SX LX , Gigabit Ethernet). , 1se5 10Broad36 75- , .
Ethernet CSMA/CD. Ethernet (10 / ) .
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1.2.1. CSMA/CD
, CSMA/CD ( ) . , () , . , ( ), , (). (frame, ), , () . , , . , . ( ), . - - . - , . , , , . , : . , . , , , ( ) . , ( 16 ), . ( 64 , ) .
, Ethernet. CSMA/CD ( ) 30 %. , Ethernet. , Ethernet ( ) , , ( ), . .
bt (bit time). , , 10 / 0,1 . 8- , .
. : -V +V , +V -V . , . 40 , . , , 100 . 50 , 50- . - . 25 , 30 ( , ). 40 1 . ( 1,5 ) , . . (, 75 ) ( 50 ) - . (1,5-1,6 ) , , , . , ( ), , , ( ). , . : . (transmit mode collision detection) , ( ) , . ( ) . (receive mode collision detection) ( ) , . 802.3 , , . , ( 300 1000 ) ( 100 ). (. 1.2.6.1) , .
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Ethernet (vl.0) 0 1 B (full step signal), . (halt step signal), .
(preamble) 7 10101010, 1- SFD (Start Frame Delimiter) 10101011. 6- , 6- , , 4- CRC-, . -, 48 a 1502 . , (Pad), . , ( CRC-) 64 1518 . ( ):
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(long, oversized) 1518 CRC-. .
(runt, undersized) 64 CRC-. .
(jabber) 1518 CRC-. ().
(alignment error) , . , , .
(CRC-error) , CRC-. , .
, . , ( 64 CRC-), , .
IPG (Inter Packet Gap) 9,6 , IPG . 0,6 1,4- SQE window. , , SQE (Signal Quality Error), heartbit, . SQE , . 2.0, 802.3 v2.0 v1.0, jam-, .
, , ( ) . ( ), , . .
, , 64 , . , (32-48-) (jam), . , , . , . , 64- (collision window), (later collision) Ethernet.
tRT TS t, or n:
tRT= TS t.
TS - (time slot) 512 bt. t , 0 2 n n = 1, 2,...10 0 210 n > 10. 16 , . 210 TS = 524 288 bt 52,4 , 0 ( ).
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, , . . 2 , . t 0 A, . t 0 t 1 . , . t 1 A . , , t TRAmax = tAB + tBA (round trip time). , , , , . , . , 45 . , . , , ( ), . 25,6 , 1 5 . . Fast Ethernet Gigabil Etherner , - (bt = 10 c Fast bt = 1 c Gigabit Ethernet) . Gigabit Ethernet .
. 1.
,
Ethernet 4 :
Ethernet II;
Ethernet 802.3;
Ethernet 802.2;
Ethernet SNAP
, ( ) . 3, .
(Preamble) SFD (Start of Frame Delimiter) ( ).
DA (Destination Address) :
- (unicast address).
(broadcast address), , .
(multicast address), , .
. 2. Ethernet
(. 3):
00h , . , ( ) (Manufactorr Id) 2-3 ( , ). 4-6 ( ). , . ( ) - , . (02-----).
FF-FF-FF-FF-FF-FF .
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01----- . 2 6.
SA (Source Address) - , . , . 3.
Data (LLC) .
FCS (Frame Check Sequence) CRC-, DA Data . ; CRC, , , , .
. 3. Ethernet: ,
, ,
(. 2) .
Ethernet II e Type , Type 1500 ( ) . Ethernet II .
Ethernet 802.3, rw (, ), . (, IPX IP) . 802.3 Novell IPX/SPX, (NetWare 3.12+, 4., 5.) 802.2. Length .
Ethernet 802.2 LLC-. Length LLC ( DSAP Data ). DSAP (Destination Service Access Point ) SSAP (Sour Service Access Point ) . Control LLC-.
Ethernet SNAP (Sub-Network Access Protocol) 5- Protocol Id, , Ethernet II 802.2 . 802.2 OSAP SSAP AAh, Control 03h. Length LLC ( DSAP Data ). SNAP Ethernet Token Ring.
, 802.3, . IPX 802.3 , FFFFh DSAP SSAP ( IPX, , FFFFh). , IPX/SPX 802.2 802.3 , . ( !) ( NetWare, IPX ).
Ethernet Data, . 64 + 8 = 72 = 576 bt = 57,6 . 9,6 1/(57,6 + 9,6) = 14881 / (fps frame per second, ). (1526 = 12 208 bt) 813 /.
( 802.2 SNAP) 14 881 37 8 = 4 404 776 / (4,4 /), Ethernet II 802.3 5476208 / (5,48 /). 813 1500 8 = 9 756 000 / (9,76 /), (10 M/). , . , . , .
1.2.3. Ethernet 10 /: