Lokal'naya set': Ethernet, Token ring, FDDI
Carrier Sense Multiple Access Collision Detect (CSMA/CD)
Kontrol' nesushchej s mnozhestvennym dostupom i razresheniem
kollizij.
Standart Ethernet/2 i IEEE 802.3 pohozhi, no imeyut razlichnyj
format frejma
Ethernet'ov sushchestvuet 3 tipa:
10baseT Neekranirovannaya vitaya para, raz®em RJ45
Twisted pair (Dlinna odnoj pary do 100m).
V lyuboj cepochke dolzhno byt' ne bolee 4-h habov.
10base5 Tolstyj Ethernet. ZHeltyj 2sm kabel', 15 pinovyj AUI
Thick ethernet konnektor u hosta. "Krab" - dlya podklyucheniya k osnovnomu
kabelyu. Na koncah - N-terminatory.(L<= 500m)
10base2 Tonkij Ethernet s koaksial'nym 50-omnym kabelem
Thin ethernet i BNC konnektorami.
Oficial'naya dlina kabelya 185 m (<=300m)
30 hostov na odnom segmente
+-----+
|Host o------------------. "Zvezda"
+-----+ \
\ ___
+-----+ \o | Hub
|Host o----------------------o | 10-base-T
+-----+ o___|
/
+-----+ /
|Host o------------------'
+-----+
+-----+ +-----+ +-----+ "Obshchaya shina"
|Host | |Host | |Host |
+--+--+ +--+--+ +--+--+ Thin
z-+---------------+---------------+-z
+-----+ +-----+ +-----+
|Host | |Host | |Host |
+--sh--+ +--sh--+ +--sh--+ Tolstyj ethernet
n n n ^
n n n |do 50m
"krab" n n v
n==M===============M===============M=======n
Standart Token ring razrabotan dlya setej IBM, i prakticheski
sovpadaet s IEEE 802.5
Apparatno - zvezda (8 sht) na vitoj shielded ili unshielded
pare, podklyuchennaya k MultiStationAccessUnit (MSAU) Neskol'ko
MSAU mozhno soedinyat' drug s drugom, oni pri etom organizuyut
logicheskoe obshchee kol'co.
Logicheski - kol'co po kotoromu idet marker-telezhka. Prinyavshij
marker s soobshcheniem schityvaet esli ono emu, mozhet polozhit' svoe
esli marker "pust", ishch v lyubom sluchaet peredaet marker dal'she.
Projdya krug marker unichtozhaetsya stanciej, ego zapustivshej, i
zapuskaetsya novyj. Dopustim rovno odin marker. Marker vezet ne
bolee odnogo paketa s dannymi. Naznachaetsya stanciya-Monitor,
kotoraya sledit, chtob markery ne shli vtoroj krug, esli stanciya
ego porodivshaya ne smogla ego udalit'.
Apparatno - dvojnoe optovolokonnoe kol'co. V bazovom rezhime
odno iz kol'ec ne ispol'zuetsya. V kol'ce est' nekotoroe
kolichestvo Dual Attachment stancij. Esli takaya stanciya
zamechaet, chto proshedshij skvoz' nee paket ne vernulsya po krugu
(kol'co porvano), ona avtomaticheski aktiviziruet vtoroe kol'co.
(To zhe dolzhna sdelat' DAS na drugoj storone ot obryva)
___0 DAS ___0 DAS
/___o /___|
// \\ //
|| |* --> || *
|| o| || o*
\\___/o DAS \\___/| DAS
\___/ \___/
Logicheski - kak i Token ring. Marker mozhet vezti pakety srazu
ot neskol'kih stancij. Funkcii Monitor'a vypolnyayut vse
uchastniki kol'ca.
Raspaj Unshielded twisted pair.
1 oranzh Tx+ | +-1---8-+ | Rx+ 3
2 ORANZH Tx- | | | | Rx- 6
3 zelen Rx+ | |_____| | Tx+ 1
4 SINIJ | |
5 sinij | |
6 ZELEN Rx- |___________| Tx- 2
7 korich (provod na nas)
8 KORICH
-----------------------------------------------------------------
Dlya soedineniya dvuh adapterov napryamuyu, bez HUB'a (point-to-point)
ispol'zuetsya "perevernutyj" provod. Tx+<-->Rx+, Tx-<-->Rx-,...
Mnogie sovremennye ethernet-kontrollery imeyut avtomaticheskoe
opredelenie kabelya, i ih mozhno vyazat' napryamuyu standartnym
"pryamym" kabelem - ne perevorachivaya.
Last-modified: Fri, 10 Jul 1998 05:17:05 GMT