{"id":383,"date":"2020-04-06T08:39:45","date_gmt":"2020-04-06T06:39:45","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=383"},"modified":"2020-04-06T17:00:23","modified_gmt":"2020-04-06T15:00:23","slug":"5-6-topologie-lan-sieti","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/06\/5-6-topologie-lan-sieti\/","title":{"rendered":"5.6.\u2002Topol\u00f3gie LAN siet\u00ed"},"content":{"rendered":"

Ethernet je p\u00f4vodne navrhnut\u00fd pre\u00a0zbernicov\u00fa topol\u00f3giu<\/strong>. To znamen\u00e1, \u017ee stanice s\u00fa napojen\u00e9 na ten ist\u00fd spoj (dr\u00f4t). T\u00e1to topol\u00f3gia vy\u017eaduje ma\u0165 pr\u00edstupov\u00fa met\u00f3du pre zdie\u013ean\u00fd spoj (napr. CSMA\/CD).<\/p>\n

V polovici 90-tych rokov sa za\u010dala presadzova\u0165\u00a0topol\u00f3gia hviezdy<\/strong>. V tejto topol\u00f3gii s\u00fa stanice napojen\u00e9 samostatn\u00fdm k\u00e1blom na centr\u00e1lne zariadenie. V pr\u00edpade LAN siet\u00ed je centr\u00e1lnym zariaden\u00edm hub alebo switch.<\/p>\n

Niektor\u00e9 technol\u00f3gie, ako napr. IBM Token Ring, predpokladaj\u00fa\u00a0kruhov\u00fa topol\u00f3giu<\/strong>. V takomto pr\u00edpade je stanica napojen\u00e1 iba na svojich susedov na kru\u017enici zapojenia, mo\u017enosti okrem komunik\u00e1cie so susedmi, sl\u00fa\u017ei aj na preposielanie komunik\u00e1cie z jednej strany na druh\u00fa, ak chc\u00fa komunikova\u0165 zariadenia, ktor\u00e9 nie s\u00fa susedmi na kru\u017enici. Poznamenajme, \u017ee aj v pr\u00edpade Token Ringu, podobne ako v Ethernete, sa za\u010dala presadzova\u0165 topol\u00f3gia hviezdy a samotn\u00e9 kruhov\u00e9 zapojenie sa realizuje u\u017e iba skryte, vo vn\u00fatri centr\u00e1lneho zariadenia.<\/p>\n

5.6.1.\u2002 Hub (rozbo\u010dova\u010d), Repeater (opakova\u010d)<\/h3>\n

Hub funguje ve\u013emi jednoducho. Ak cez niektor\u00fa z\u00e1suvku pr\u00edde sign\u00e1l, tento sign\u00e1l hub zosiln\u00ed a po\u0161le ho do v\u0161etk\u00fdch ostatn\u00fdch z\u00e1suviek, okrem tej, cez ktor\u00fa sign\u00e1l pri\u0161iel. Hub je zariadenie, ktor\u00e9 pracuje iba na fyzickej vrstve. V\u00f4bec netu\u0161\u00ed ak\u00e9 d\u00e1ta preposiela, od koho a kam id\u00fa. Pre\u0148ho s\u00fa to iba jednotky a nuly. Tejto bitovej inform\u00e1cii v\u0161ak rozumie, preto\u017ee rekon\u0161truuje sign\u00e1l. Ak pr\u00edde sign\u00e1l, ktor\u00fd je mierne za\u0161umen\u00fd, ale pre hub zrozumite\u013en\u00fd, posiela tento sign\u00e1l do ostatn\u00fdch z\u00e1suviek bez tohto \u0161umu. Ak dve \u013eubovo\u013en\u00e9 zariadenia napojen\u00e9 cez hub za\u010dn\u00fa naraz vysiela\u0165 sp\u00f4sobia kol\u00edziu. Hovor\u00edme tomu, \u017ee s\u00fa v spolo\u010dnej\u00a0kol\u00edznej dom\u00e9ne<\/strong>. Hub je z tohto d\u00f4vodu zariadenie, ktor\u00e9 sa u\u017e v s\u00fa\u010dasnosti v obchodoch nepred\u00e1va (sn\u00e1\u010f v nejak\u00fdch baz\u00e1roch).<\/p>\n

Repeater je hub, ktor\u00fd m\u00e1 iba dve z\u00e1suvky.<\/p>\n

5.6.2.\u2002 Switch (prep\u00edna\u010d), Bridge (most)<\/h3>\n

Switch je u\u017e zariadenie, ktor\u00e9 pracuje na fyzickej aj spojovej vrstve. To znamen\u00e1, \u017ee u\u017e, na rozdiel od hubu, rozumie hlavi\u010dke r\u00e1mca a teda pozn\u00e1 MAC adresu odosielate\u013ea aj pr\u00edjemcu r\u00e1mca. To vyu\u017e\u00edva tak, \u017ee ak vie, cez ktor\u00fa z\u00e1suvku je dostupn\u00fd pr\u00edjemca r\u00e1mca, po\u0161le tento r\u00e1mec iba cez t\u00fato z\u00e1suvku. Ostatn\u00e9 stanice v takomto pr\u00edpade nedostan\u00fa cudzie r\u00e1mce. To m\u00e1 hne\u010f nieko\u013eko v\u00fdhod.<\/p>\n

Prvou v\u00fdhodou je \u201ebezpe\u010dnos\u0165\u201c a od\u013eah\u010denie spojov. Stanice, aj ke\u010f s\u00fa v jednej sieti, navz\u00e1jom si nesleduj\u00fa komunik\u00e1ciu (aj ke\u010f existuje nieko\u013eko \u00fatokov, ktor\u00e9 s\u00fa schopn\u00e9 tento princ\u00edp ob\u00eds\u0165 alebo zablokova\u0165 napr. ARP poisoning).<\/p>\n

Druhou v\u00fdhodou je to, \u017ee stanice u\u017e nie s\u00fa v rovnakej kol\u00edznej dom\u00e9ne, teda, ak \u013eubovo\u013en\u00e9 dve stanice vysielaj\u00fa v rovnakom \u010dase, kol\u00edzia nevznikne. Na spolo\u010dnej kol\u00edznej dom\u00e9ne s\u00fa u\u017e iba switch a dan\u00e1 stanica. Dokonca aj to u\u017e v s\u00fa\u010dasnosti neplat\u00ed, ke\u010f\u017ee ethernetov\u00e9 k\u00e1ble umo\u017e\u0148uj\u00fa\u00a0\u00fapln\u00fd duplex<\/strong>\u00a0(full duplex), t.j. stanica vysiela a prij\u00edma nez\u00e1visle cez in\u00e9 zv\u00e4zky k\u00e1blov. Sign\u00e1ly zo switch-a a zo stanice sa tak nikdy nestretn\u00fa. Switch je teda zariadenie, ktor\u00e9 \u00faplne odstra\u0148uje kol\u00edzie v sieti a umo\u017e\u0148uje tak efekt\u00edvne vyu\u017eitie celej \u0161\u00edrky p\u00e1sma spojov a nez\u00e1visl\u00fa komunik\u00e1ciu zariaden\u00ed. Dokonca, ak ide o switch typu store-and-forward (je ich v\u00e4\u010d\u0161ina), t.j. \u017ee neza\u010dne vysiela\u0165 r\u00e1mec sk\u00f4r, ako ho cel\u00fd nedostane, umo\u017e\u0148uje aj prepojenie r\u00f4zne r\u00fdchlych spojov (napr. 100Mbit\/s a 1Gb\/s).<\/p>\n

Switch, podobne ako hub, je\u00a0transparentn\u00e9 zariadenie<\/strong>, to znamen\u00e1, \u017ee o jeho existencii uzly nevedia. Uzly komunikuj\u00fa s cie\u013eov\u00fdmi uzlami tak, \u017ee zap\u00ed\u0161u do hlavi\u010dky r\u00e1mca cie\u013eov\u00fa MAC adresu a r\u00e1mec vy\u0161l\u00fa do spoja v\u017edy rovnako, bez oh\u013eadu na to, \u010di s\u00fa uzly napojen\u00e9 priamo alebo cez jeden \u010di viac switchov. Switch pod\u013ea z\u00e1kladnej charakteristiky ani nem\u00e1 svoju MAC adresu. To v\u0161ak neplat\u00ed pre drah\u0161ie mana\u017eovate\u013en\u00e9 switche, ktor\u00e9 poskytuj\u00fa (obvykle webov\u00e9) rozhranie na ich \u010fal\u0161ie nastavenie (napr\u00edklad nastavenie VLANu).<\/p>\n

Switch, ktor\u00fd m\u00e1 iba dve z\u00e1suvky sa naz\u00fdva Bridge.<\/p>\n

Prep\u00ednacia tabu\u013eka<\/h3>\n

Predpokladom toho, aby r\u00e1mce putovali iba k uzlu (stanici alebo routru), ktor\u00e9mu s\u00fa ur\u010den\u00e9, je to, \u017ee switch vie, cez ktor\u00fa z\u00e1suvku je napojen\u00fd dan\u00fd uzol. T\u00fato inform\u00e1ciu m\u00e1 ulo\u017een\u00fa v prep\u00ednacej tabu\u013eke. Konkr\u00e9tne v niektorom riadku prep\u00ednacej tabu\u013eky, kde m\u00e1 ulo\u017een\u00e9 3 inform\u00e1cie: MAC adresu uzla, \u010d\u00edslo z\u00e1suvky, cez ktor\u00fa je tento uzol dostupn\u00fd a \u010dasov\u00fa pe\u010diatku o tom, kedy bol tento z\u00e1znam pridan\u00fd\/aktualizovan\u00fd.<\/p>\n

Prep\u00ednaciu tabu\u013eku nie je potrebn\u00e9 ru\u010dne aktualizova\u0165, preto\u017ee\u00a0switch je samou\u010diaci<\/strong>\u00a0a dop\u013a\u0148a a aktualizuje si ju s\u00e1m cez nasledovn\u00fd algoritmus:<\/p>\n

Ke\u010f pr\u00edde r\u00e1mec na niektor\u00fa zo z\u00e1suviek:<\/p>\n

    \n
  1. Pre\u010d\u00edtaj si z r\u00e1mca adresu odosielate\u013ea a ulo\u017e si ju do prep\u00ednacej tabu\u013eky spolu s \u010d\u00edslom z\u00e1suvky, cez ktor\u00fa r\u00e1mec pri\u0161iel. Ak z\u00e1znam s danou adresou u\u017e existoval, iba ho aktualizuj.<\/li>\n
  2. Pre\u010d\u00edtaj si adresu pr\u00edjemcu a sk\u00fas ju n\u00e1js\u0165 v prep\u00ednacej tabu\u013eke.<\/li>\n
  3. Ak si na\u0161iel z\u00e1znam s touto adresou potom:\n
      \n
    • ak je pr\u00edjemca dostupn\u00fd cez t\u00fa ist\u00fa z\u00e1suvku, ako odosielate\u013e, zaho\u010f r\u00e1mec;<\/li>\n
    • inak po\u0161li r\u00e1mec pr\u00edjemcovi cez z\u00e1suvku, zisten\u00fa z prep\u00ednacej tabu\u013eky.<\/li>\n<\/ul>\n<\/li>\n
    • Ak si nena\u0161iel z\u00e1znam s touto adresou, potom po\u0161li r\u00e1mec do v\u0161etk\u00fdch z\u00e1suviek okrem tej, cez ktor\u00fa tento r\u00e1mec pri\u0161iel (chovaj sa ako hub).<\/li>\n<\/ol>\n

      Je potrebn\u00e9 poznamena\u0165, \u017ee aj ke\u010f switch odde\u013euje kol\u00edzne dom\u00e9ny, nerozde\u013euje\u00a0broadcastov\u00fa dom\u00e9nu<\/strong>. Ak niekto odo\u0161le broadcastov\u00fd r\u00e1mec (s cie\u013eovou adresou FF:FF:FF:FF:FF:FF), switch odosiela tak\u00fdto r\u00e1mec do v\u0161etk\u00fdch z\u00e1suviek okrem tej, z ktorej r\u00e1mec pri\u0161iel.<\/p>\n","protected":false},"excerpt":{"rendered":"

      Ethernet je p\u00f4vodne navrhnut\u00fd pre\u00a0zbernicov\u00fa topol\u00f3giu. To znamen\u00e1, \u017ee stanice s\u00fa napojen\u00e9 na ten ist\u00fd spoj (dr\u00f4t). T\u00e1to topol\u00f3gia vy\u017eaduje ma\u0165 pr\u00edstupov\u00fa met\u00f3du pre zdie\u013ean\u00fd…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[],"_links":{"self":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/383"}],"collection":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/comments?post=383"}],"version-history":[{"count":2,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/383\/revisions"}],"predecessor-version":[{"id":478,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/383\/revisions\/478"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=383"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}