ETHERNET
Ethernet .
Ethernet, . Ethernet , Ethernet Network, Xerox 1975 . : 60- , Aloha. 1980 DEC, Intel Xerox Ethernet II , , Ethernet. Ethernet Ethernet DIX Ethernet .
Ethernet DIX IEEE 802.3, , . IEEE 802.3 MAC LLC, Ethernet . Ethernet DIX (Ethernet Configuration Test Protocol), IEEE 802.3. , . , Ethernet, IEEE, Ethernet DIX, 802.3, Ethernet .
IEEE 802.3 - 10Base-5, 10Base-2, 10Base-T, 10Base-FL, 10Base-FB.
1995 Fast Ethernet, , , 802.3 802.3u. , 1998 Gigabit Ethernet 802.3z .
Ethernet, 10 /, .
Ethernet ( Fast Ethernet Gigabit Ethernet) CSMA/CD.
Ethernet
Ethernet 6- MAC.
MAC Ethernet , , .
Ethernet :
- (Vendor codes)
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6 | 5 | 4 | 3 | 2 | 1 |
IEEE - . MAC . , -:
E0-14-00-00-00
Ethernet IEEE 802.3 :
- Unicast ;
- Multicast ;
- Broadcast .
(Unicast) , - .
Multicast 1 .
C-CC-CC-CC
, DA Multicast, , Vendor Code Cisco. Multicast - Cisco Discovery Protocol (CDP).
Ethernet IEEE 802.3 Broadcast. Broadcast :
FF-FF-FF-FF-FF-FF
, .
CSMA/CD
Ethernet , (carrier-sense-multiply-access with collision detection, CSMA/CD) ( ).
CSMA/CD . . , . . , . , ( , Token Ring FDDI), - , ( Arcnet, 100VG AnyLAN).
, , - , , . , , . , , Ethernet, . ( , Base(band), Ethernet (, 10Base-2,10Base-T . .). Baseband network , , .)
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Ethernet. , , . , - , , , . .
, , (collision domain) .
- , ( , > 20-25) (> 2 ).
, , , . : , 1- - (.11.2).
11.2. (CSMA) (collision back off)
(nonpersistent) . , , .
1. , (.. ) , - - 2;
2. , ( c ) 1.
. , , , , . ( , ), , , , . , . . , , , , , , , . , , .
1- (1-persistent) . , , 1- . , , .
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1. , , 2;
2. , , .
1- , , 1- "". , ( ), , , . , .
- (p-persistent) . :
1. , p (1- p) T. T ;
2. , , , 1;
3. T, 1.
p. , . , n , . , , np. np > 1, , . , , 1, . , , n, , . np . , , p. , p , (1- p)/ p T, . p=0,1 , , 9T.
CSMA/CD - . , , () . , . . CSMA/CD (.11.3):
1. , , . , . (.. ) 2. - , ( 1);
2. , , , ;
3. , , , - jam-, , ;
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4. jam- 1.
, , . , (carrier-sense, CS). , 5-10 , , .
(Inter Packet Gap) 9,6 (96 bt). , , , .
11.3. CSMA/CD ( MAC):
Jam- (jamming - ). jam- , , , , jam-, . Jam- , , SF (safety margin) . jam- , CRC (802.3), 62 1 0 1.
11.4. CSMA/CD
.11.5 ( ( 10Base5 10Base2 ).
A (DTE A) , . , B (DTE B), , , , . , B ( ). B jam- . A, A jam- .
11.5. CSMA/CD
IEEE 802.3 , . , , 64 . ST (slot time)- , , . , . - . , , A B . , A B . A . B . A . , , A, , , A , , , A , , . . , A - PDV (Path Delay Value, PDV). PDV , - , , . : bt (bit time). 1 bt , , .. 0,1 10 /.
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Ethernet. - , , . - , (, - ). , - , , . ( ) , Ethernet. Ethernet, .
:
Tmin>=PVD,
Tmin , a PDV , . ( , ), (Path Delay Value, PDV).
, , , .
, , , , , ( ).
Ethernet , . , , , .
Ethernet , 46 ( 64 , 72 576 ).
, 1500 , , , , 64 ( , , , "" , ). jam- , CSMA/CD , . . , , , . ( ) U PDV/ST:
- . . ( PDV=ST) 37%, ( PDV , ST) 1. , , , , , , , , 15.
(truncated binary exponential backoff). CSMA/CD, IEEE 802.3, 1- , - . , . , MAC- . .
:
= L( ),
( ) = 512 (51,2 );
L , , N : 1,2,..., 10.
10- , , . , 0 52,4 .
16 , .
CSMA/CD , . . -, 1, ( ), 2, , . 2 . , , . -, . , 25 2 . , .
(.11.6)
11.6. CSMA/CD ( MAC):
, , ( ). .
MAC , . , , SDF FCS , FCS ( CRC-32). , . . , , , , . .
, , , . 70- , 10 / , . , , , Ethernet. . Ethernet , . , , , , , Fast Ethernet.
, CSMA/CD , - . , , , 1, . , Ethernet . Token Ring FDDI, Demand Priority 100VG-AnyLAN .
, . .
, , CSMA/CD, Fast Ethernet, . Fast Ethernet 210 , Gigabit Ethernet 25 , .
. 11.1 802.3, . , Ethernet , , .
11.1. MAC Ethernet
10 / | |
512 bt | |
(IPG) | 9,6 |
jam- | 32 |
( ) | 1518 |
( ) | 64 (512 ) |
64 | |
0 bt | |
524000 bt | |
2500 | |
Ethernet
Ethernet, IEEE 802.3, MAC. MAC LLC, IEEE 802.2, IEEE Ethernet , MAC LLC .
, Ethernet 4- (). Ethernet, IEEE 802, LLC , , LLC .
Digital, Intel Xerox 1980 802.3 Ethernet ( , , ) , 802.3 , DIX. , Ethernet.
Novell Ethernet.
, , 802:2 .
, Ethernet. , , / Ethernet, .
Ethernet ( , , MAC LLC ). , :
- 802.3/LLC ( 802.3/802.2 Novell 802.2);
- Raw 802.3 ( Novell 802.3);
- Ethernet DIX ( Ethernet II);
- Ethernet SNAP.
Ethernet . 11.7.
802.3/LLC
802.3/LLC , IEEE 802.3 802.2.
802.3 (. 11.7; ).
- (Preamble) 10101010. 5 .
- (Start-of-frame-delimiter, SFD) 10101011. , .
- (Destination Address, DA) 2 6 . 6 . , . 0, (unicast), a 1, (multicast). , 0xFFFFFFFFFFFF, (broadcast).
IEEE Ethernet , - . Ethernet. , RFC IETF, ITU-T, ISO, , , - . . , , , , Ethernet , IEEE. , , IEEE 1000 0000 0000 0000 1010 0111 1111 0000 0000 0000 0000 0000 80-00-A7-FO-00-00, , , 01-00-5E-0F-00-00.
- (Source Address, SA) 2- 6- , - . 0.
- (Length, L) 2- , .
- (Data) 0 1500 . 46 , , 46 .
- (Padding) , 46 . . , .
- (Frame Check Sequence, PCS) 4 , . CRC-32. , , , , .
802.3 -, 802.2 LLC . LLC . LLC 3 ( LLC1) 4 ( LLC2), 1497 1496 .
11.7. Ethernet