802.1
, ISO/OSI
802.1D - .
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802.2
LLC
802.3 802.5
MAC Ethernet[CSMA/CD] TokenRing
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"" 10BASE-5
(STP)
4 / 16 /
"" 10BASE-2
10BASE-T
(UDP)
10BASE-F
, 100BASE-T
IEEE 802. OSI - , .
:
(Media Access Control) - . , . , . .
LLC (Logical Link Control) - . , . LLC . LLC , .
LLC - LLC .
LLC (802.2)
LLC - ( IP, IPX, NetBEUI), , , LLC . LLC , . LLC MAC, LLC (, Ethernet).
LLC HDLC (High-level Data Link Control), ISO , .
|
|
802.2 LLC :
LLC1 - ( ). , .
LLC2 - .
LLC3 - , .
. TCP/IP LLC1, - IP, ARP, RARP. IPX/SPX. Microsoft/IBM, NetBIOS/NetBEU LLC2.
LLC ( 802.2 Protocol Data Unit, PDU) :
n (Information) LLC2 . .
n (Supervisory) LLC2, .
n (Unnumbered) , , . LLC2 - , .
LLC :
(DSAP) | (SSAP) | (Control) | (Data) |
LLC, LLC MAC: Ethernet, Token Ring, FDDI ..
LLC IP, IPX .. , .
DSAP (Destination Service Access Point) SSAP (Source Service Access Point) 1 . , . , , . Service Access Point, SAP. SAP 802.2. , IP SAP 06, NetBIOS 0F0. , SAP , DSAP SSAP.
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|
(1 2 )
(Information) | N(S) | P/F | N(R) | ||||||||||||||
(Supervisory) | S | - | - | - | N(R) | ||||||||||||
(Unnumbered) | M | P/F | M |
LLC1 , . 0, , . , Ethernet , LLC1, Ethernet 003.
LLC2 , .
P/F (Poll/Final) :
- Poll , ;
- Final , .
LLC2. , .
. LLC2 . , . , .
N(S) , N(R) , . LLC2 127 0 127.
, , , V(R). N(R) , . , N(S) V(R), (REJ) V(R). , , .
:
- (REJect)
- (Receiver Not Ready, RNR)
- (Receiver, RR)
Ethernet (802.3)
CSMA/CD
(carrier-sense-multiply-access with collision detection, CSMA/CD)
:
1. , , .
2. , , . ( , 5-10 , ).
3. , , . , 7 10101010 8- 10101011.
4. , , , , , , . .
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5. (Inter Packet Gap) 9,6 . .
( ), , , - . - Ethernet .
. , . , , 32 - jam-, . , , .
= L x ( ),
512 ( , 10 / 0,1 ). L , [0, 2N], N - : 1, 2,.... 10. 10- , , - 0 52,4 . 16 , .
Ethernet. - , , .
:
Tmin >= PDV,
Tmin - , PDV - , . , (Path Delay Value).
, .
Ethernet , 46 , - 64 , - 72 576 .
10- Ethernet 575 , 57,5 . , 13280 . 6635 . - , , , . 500 . , . , , , 2500 . , .
|
|
, . Fast Ethernet 210 , Gigabit Ethernet 25 , .
Ethernet, .
10 / | |
512 | |
(IPG) | 9,6 |
jam- | 32 |
( ) | 1518 |
( ) | 64 (512 ) |
64 | |
0 | |
524000 | |
2500 | |
Ethernet
Ethernet , , , .
72 576 . 57,5 . 9,6 , 67,1 . Ethernet 14880 /c. , .
1526 12208 . Ethernet - 813 /.
, .
- , . -:
*
*
* .
: = 14880 46 8 = 5,48 /c.
: = 813 1500 8 = 9,76 /.
512 9,29 /c.