{"id":376,"date":"2020-04-06T08:32:05","date_gmt":"2020-04-06T06:32:05","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=376"},"modified":"2020-04-06T22:48:25","modified_gmt":"2020-04-06T20:48:25","slug":"5-3-adresacia-na-spojovej-vrstve","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/06\/5-3-adresacia-na-spojovej-vrstve\/","title":{"rendered":"5.3.\u2002Adres\u00e1cia na spojovej vrstve"},"content":{"rendered":"

Na adres\u00e1ciu na spojovej vrstve sa pou\u017e\u00edvaj\u00fa MAC adresy. Niekedy sa naz\u00fdvaj\u00fa aj ako fyzick\u00e9 adresy, hardv\u00e9rov\u00e9 adresy alebo Ethernetov\u00e9 adresy. MAC adresa sl\u00fa\u017ei na identifik\u00e1ciu sie\u0165ov\u00e9ho adapt\u00e9ra (sie\u0165ovej karty) v r\u00e1mci tej istej siete. MAC adresy s\u00fa pride\u013eovan\u00e9 v\u00fdrobcom sie\u0165ovej karty a s\u00fa nez\u00e1visl\u00e9 od siete, v ktorej sa nach\u00e1dzaj\u00fa. MAC adresy pride\u013eovan\u00e9 v\u00fdrobcami s\u00fa jedine\u010dn\u00e9. O jedine\u010dnos\u0165 MAC adries sa star\u00e1 organiz\u00e1cia IEEE. Ka\u017ed\u00fd v\u00fdrobca si mus\u00ed pred t\u00fdm, ako chce sie\u0165ov\u00e9 karty vyr\u00e1ba\u0165, k\u00fapi\u0165 od organiz\u00e1cie IEEE nejak\u00fd rozsah MAC adries a tie potom postupne pride\u013euje jednotliv\u00fdm v\u00fdrobkom (sie\u0165ov\u00fdm kart\u00e1m). Na z\u00e1klade MAC adresy sa d\u00e1 teda\u00a0ur\u010di\u0165<\/a>\u00a0v\u00fdrobca danej sie\u0165ovej karty.<\/p>\n

MAC adresa m\u00e1 6 bajtov. Obvykle sa p\u00ed\u0161e hexadecim\u00e1lne po jednotliv\u00fdch bajtoch oddelen\u00fdch dvojbodkou. Napr\u00edklad AA:BB:CC:DD:EE:FF.<\/p>\n

D\u00f4le\u017eit\u00e9 si je uvedomi\u0165 in\u00fd charakter inform\u00e1cie dan\u00fd IP adresou a MAC adresou. IP adresa je z\u00e1visl\u00e1 od siete, v ktorej sa zariadenie nach\u00e1dza a ur\u010duje tak polohu zariadenia na internete a MAC adresa od siete z\u00e1visl\u00e1 nie je \u2013 nemen\u00ed sa prenesen\u00edm zariadenia (napr. notebooku) do inej siete. Ako anal\u00f3giu si m\u00f4\u017eeme zobra\u0165 to, \u017ee IP adresa je nie\u010do ako po\u0161tov\u00e1 adresa, na ktorej sa \u010dlovek nach\u00e1dza a MAC adresa je nie\u010do ako rodn\u00e9 \u010d\u00edslo, ktor\u00e9 nez\u00e1le\u017e\u00ed od poz\u00edcie dan\u00e9ho \u010dloveka. MAC adresa tak jednozna\u010dne ur\u010duje, s ktor\u00fdm konkr\u00e9tnym zariaden\u00edm v r\u00e1mci siete chceme komunikova\u0165.<\/p>\n

5.3.1\u2002 R\u00e1mec Ethernetu<\/h3>\n

IEEE 802.3<\/a><\/p>\n

Ethernet je jednou z mnoh\u00fdch technol\u00f3gi\u00ed najni\u017e\u0161ej vrstvy referen\u010dn\u00e9ho modelu TCP\/IP \u2013 vrstvy sie\u0165ov\u00e9ho rozhrania. Popri mno\u017estve technol\u00f3gi\u00ed patr\u00ed Ethernet 802.3 medzi tie najroz\u0161\u00edrenej\u0161ie v dr\u00f4tov\u00fdch LAN sie\u0165ach. Na spojovej vrstve vyu\u017e\u00edva pr\u00edstupov\u00fa met\u00f3du CSMA\/CD. Datagramy sie\u0165ovej vrstvy s\u00fa oba\u013eovan\u00e9 do r\u00e1mcov, ktor\u00e9 s\u00fa prostredn\u00edctvom CSMA\/CD vysielan\u00e9 do zdie\u013ean\u00e9ho spoja.<\/p>\n

Hlavi\u010dka ethernetov\u00e9ho r\u00e1mca je ve\u013emi jednoduch\u00e1. Prv\u00fdch 8 bajtov hlavi\u010dky, zvan\u00fdch preambula, obsahuje len synchroniza\u010dn\u00e9 bity, ktor\u00e9 tvoria postupnos\u0165 so striedaj\u00facimi hodnotami 1 a 0, ukon\u010denej dvoma jednotkami (101010\u202610101011). Potom nasleduj\u00fa cie\u013eov\u00e1 a zdrojov\u00e1 MAC adresa a ozna\u010denie typu obsahu (datagramu), ktor\u00fd je pren\u00e1\u0161an\u00fd v tele r\u00e1mca. Po tejto hlavi\u010dke u\u017e nasleduje samotn\u00e9 telo r\u00e1mca, teda obvykle IP datagram, ktor\u00fd m\u00f4\u017ee ma\u0165 ve\u013ekos\u0165 maxim\u00e1lne MTU (maximal transfer unit), \u010do je v pr\u00edpade dr\u00f4tov\u00e9ho Ethernetu 1500 bajtov. Doln\u00e1 hranica ve\u013ekosti r\u00e1mca je 46 bajtov pre 100Mb\/s Ethernet, pre r\u00fdchlej\u0161\u00ed ako 100 Mb\/s Ethernet m\u00f4\u017ee by\u0165 doln\u00e1 hranica v\u00e4\u010d\u0161ia (vi\u010f vy\u0161\u0161ie). Po tele r\u00e1mca u\u017e nasleduj\u00fa iba kontroln\u00e9 bity met\u00f3dy CRC.<\/p>\n

\n\n\n\n\n
8 bajtov<\/td>\n6 bajtov<\/td>\n6 bajtov<\/td>\n2 bajty<\/td>\n46 \u2013 1500 bajtov<\/td>\n4 bajty<\/td>\n<\/tr>\n
preambula<\/td>\ncie\u013eov\u00e1 MAC adresa<\/td>\nzdrojov\u00e1 MAC adresa<\/td>\ntyp protokolu vy\u0161\u0161ej vrstvy<\/td>\ntelo r\u00e1mca<\/td>\nCRC<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/figure>\n","protected":false},"excerpt":{"rendered":"

Na adres\u00e1ciu na spojovej vrstve sa pou\u017e\u00edvaj\u00fa MAC adresy. Niekedy sa naz\u00fdvaj\u00fa aj ako fyzick\u00e9 adresy, hardv\u00e9rov\u00e9 adresy alebo Ethernetov\u00e9 adresy. MAC adresa sl\u00fa\u017ei na…<\/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\/376"}],"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=376"}],"version-history":[{"count":4,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/376\/revisions"}],"predecessor-version":[{"id":543,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/376\/revisions\/543"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=376"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=376"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=376"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}