21Q: 2 (00,01,10,11) 4 . , , .
4.
(, )
5. .
5. : MAC LLC
. . , . , , , , ( , , ). , (, , , -), . .
LLC (Logical Link Control) , , ( ).
LLC
() = 0111 1110
DSAP, SSAP (Destination Service Access point, Source SAP) /
DSAP :
SSAP :
Control () ( ):
( )
( REJ, R eceiver N ot R eady, RR LLC2)
(/ , )
( , LLC2)
Data
MAC (Media Access Control) , LLC MAC, . LLC. , .. (Ethernet, Talking Ring, FDDI).
Ethernet:
()
10101010 10101010 10101011
DA, SA (Destination Address, Source Address) MAC /
EtherType ( ) () ( DSAP/SSAP)
Data
FCS (Frame check sequence) CRC32
6 CSMA\CD
, , . , . , .. 2 , , . CSMA 3 : , ; , ; p , p .
|
|
2 , ( ). , , .
Ethernet 9,6 . .
, jam- , . 32 47 .
. ( 0 2^N)*512 , N- . 10 52,4 .
(collision domain) Ethernet, ,
,