{"id":354,"date":"2020-04-06T08:11:16","date_gmt":"2020-04-06T06:11:16","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=354"},"modified":"2020-04-06T22:43:03","modified_gmt":"2020-04-06T20:43:03","slug":"4-6-hierarchicke-smerovanie","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/06\/4-6-hierarchicke-smerovanie\/","title":{"rendered":"4.11. Hierarchick\u00e9 smerovanie"},"content":{"rendered":"

Ani jeden z algoritmov LSA a DVA nie je vhodn\u00fd na glob\u00e1lne pou\u017eitie pre cel\u00fd internet. Ke\u010f\u017ee na svete s\u00fa mili\u00f3ny routrov, ka\u017ed\u00fd z nich by si musel uchov\u00e1va\u0165 a po\u010d\u00edta\u0165 vzdialenosti ku v\u0161etk\u00fdm ostatn\u00fdm. Tento syst\u00e9m by sa nikdy neust\u00e1lil a v\u00fdmenn\u00e9 spr\u00e1vy by zahltili internet tak, \u017ee by u\u017e mo\u017eno ani neostalo prenosov\u00e9 p\u00e1smo pre re\u00e1lnu komunik\u00e1ciu koncov\u00fdch zariaden\u00ed.<\/p>\n

Podobne ako napr\u00edklad pri DNS m\u00e1 aj hierarchick\u00e9 smerovanie ve\u013ea v\u00fdhod oproti centralizovan\u00e9mu rie\u0161eniu. Je to hlavne nez\u00e1vislos\u0165 administr\u00e1cie lok\u00e1lnych skup\u00edn siet\u00ed a routrov.<\/p>\n

Routre v tom istom AS komunikuj\u00fa spolo\u010dn\u00fdm smerovac\u00edm protokolom\u00a0vn\u00fatri-AS<\/strong>\u00a0(napr. RIP alebo OSPF). Ka\u017ed\u00fd AS m\u00f4\u017ee pou\u017e\u00edva\u0165 vo vn\u00fatri \u013eubovo\u013en\u00fd smerovac\u00ed protokol. Ka\u017ed\u00fd AS komunikuje s ostatn\u00fdmi AS cez routre na hranici AS, ktor\u00e9 naz\u00fdvame\u00a0br\u00e1ny<\/strong>, alebo\u00a0gateway routre<\/strong>, ktor\u00e9 s\u00fa napojen\u00e9 na jeden alebo viac routrov in\u00fdch AS. Jednotliv\u00e9 AS medzi sebou komunikuj\u00fa nejak\u00fdm smerovac\u00edm protokolom\u00a0medzi-AS<\/strong>. Spr\u00e1vy protokolu medzi-AS v\u0161ak prich\u00e1dzaj\u00fa aj na routre vo vn\u00fatri AS. Smerovacie tabu\u013eky routrov tak m\u00f4\u017eu by\u0165 ovplyv\u0148ovan\u00e9 ako smerovac\u00edm protokolom vn\u00fatri-AS tak aj medzi-AS.<\/p>\n

Majme nasledovn\u00e9 3 auton\u00f3mne syst\u00e9my.<\/p>\n

\"\"<\/p>\n

Predpokladajme, \u017ee k routru 1d pr\u00edde datagram, ur\u010den\u00fd pre sie\u0165 mimo AS1. Router 1d vie, \u017ee na to, aby datagram odi\u0161iel, mus\u00ed ho nasmerova\u0165 ku br\u00e1ne, ale ku ktorej? V AS1 s\u00fa dve br\u00e1ny 1c a 1b. Cestu k nim vieme zisti\u0165 na z\u00e1klade nejak\u00e9ho smerovacieho protokolu vn\u00fatri-AS. Na ur\u010denie toho, cez ktor\u00fd z t\u00fdchto dvoch routrov m\u00e1 datagram odosla\u0165, u\u017e sl\u00fa\u017ei smerovac\u00ed protokol medzi-AS.<\/p>\n

Protokol medzi-AS mus\u00ed distribuova\u0165 inform\u00e1cie, na z\u00e1klade ktor\u00fdch vie ka\u017ed\u00fd AS, ktor\u00e9 adresy s\u00fa dostupn\u00e9 cez ktor\u00e9 susedn\u00e9 AS, a teda aj cez ktor\u00e9 br\u00e1ny. T\u00e1to dostupnos\u0165 sa mus\u00ed premietnu\u0165 do v\u0161etk\u00fdch routrov v AS.<\/p>\n

Predpokladajme, \u017ee AS1 sa nau\u010d\u00ed cez medzi-AS protokol, \u017ee sie\u0165\u00a0X<\/strong>\u00a0je dostupn\u00e1 cez AS3 (t.j. cez br\u00e1nu 1c), ale nie cez AS2 (t.j. cez br\u00e1nu 1b). Medzi-AS protokol o tom informuje v\u0161etky routre vo vn\u00fatri AS1. Ke\u010f router 1d zist\u00ed, \u017ee\u00a0X<\/strong>\u00a0je dostupn\u00e1 cez br\u00e1nu 1c, pou\u017eije znalosti z\u00edskan\u00e9 z protokolu vn\u00fatri-AS. Zist\u00ed, cez ak\u00e9 rozhranie posiela datagramy smerom k 1c a zap\u00ed\u0161e si, \u017ee aj datagramy pre sie\u0165 X maj\u00fa \u00eds\u0165 cez toto rozhranie.<\/p>\n

Teraz predpokladajme, \u017ee AS1 sa nau\u010dilo cez medzi-AS protokol, \u017ee sie\u0165\u00a0X<\/strong>\u00a0je dostupn\u00e1 cez AS2 aj cez AS3. To, \u010di bude datagramy pre sie\u0165\u00a0X<\/strong>\u00a0posiela\u0165 cez 1b alebo 1c, je u\u017e \u00faloha pre protokol vn\u00fatri-AS. Cez takzvan\u00e9\u00a0smerovanie hor\u00faceho zemiaku<\/strong>\u00a0(hot potato routing), mus\u00ed protokol vn\u00fatri-AS pre ka\u017ed\u00fd router zisti\u0165 cenu ciest ku 1b a 1c, vybra\u0165 t\u00fa lacnej\u0161iu a doplni\u0165 riadok v smerovac\u00edch tabu\u013ek\u00e1ch routrov vo vn\u00fatri AS pre cie\u013eov\u00fa sie\u0165\u00a0X<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Ani jeden z algoritmov LSA a DVA nie je vhodn\u00fd na glob\u00e1lne pou\u017eitie pre cel\u00fd internet. Ke\u010f\u017ee na svete s\u00fa mili\u00f3ny routrov, ka\u017ed\u00fd z nich…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"_links":{"self":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/354"}],"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=354"}],"version-history":[{"count":2,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/354\/revisions"}],"predecessor-version":[{"id":535,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/354\/revisions\/535"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=354"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=354"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=354"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}