{"id":269,"date":"2020-04-05T23:01:37","date_gmt":"2020-04-05T21:01:37","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=269"},"modified":"2020-04-06T16:27:43","modified_gmt":"2020-04-06T14:27:43","slug":"1-7-straty-a-zdrzania-paketov","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/05\/1-7-straty-a-zdrzania-paketov\/","title":{"rendered":"1.7.\u2002Straty a zdr\u017eania paketov"},"content":{"rendered":"<p>Paket na svojej ceste do cie\u013ea stret\u00e1va cel\u00fd rad routrov. Na ka\u017edom z t\u00fdchto routrov sa nejak\u00fd \u010das zdr\u017e\u00ed, pokia\u013e nie je odoslan\u00fd \u010falej. \u010casu potrebn\u00e9mu na spracovanie paketu routrom a jeho dopraveniu k \u010fal\u0161iemu uzlu hovor\u00edme\u00a0<strong>celkov\u00e9 zdr\u017eanie<\/strong>\u00a0medzi uzlami. Celkov\u00e9 zdr\u017eanie medzi uzlami rozde\u013eujeme na 4 za sebou nasleduj\u00face zdr\u017eania<\/p>\n<ul>\n<li><strong>spracovanie<\/strong>\n<ul>\n<li>Po tom, ako router prijme cel\u00fd paket a rozhoduje sa, kam ho prepo\u0161le, umiestni ho do radu paketov v\u00fdstupn\u00e9ho buffra toho portu (z\u00e1suvky), kam m\u00e1 by\u0165 preposlan\u00fd.<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u010dakanie v rade na odoslanie<\/strong>\n<ul>\n<li>Paket \u010dak\u00e1, k\u00fdm cez dan\u00fd port routra nie s\u00fa odoslan\u00e9 v\u0161etky predch\u00e1dzaj\u00face pakety, ktor\u00e9 maj\u00fa by\u0165 cez tento port odoslan\u00e9. Toto \u010dakanie je t\u00fdm dlh\u0161ie, \u010d\u00edm viac paketov za sekundu \u010dak\u00e1 na odoslanie dan\u00fdm smerom. Pokia\u013e je rad zaplnen\u00fd na cel\u00fa svoju kapacitu, v\u0161etky nov\u00e9 pakety preposlan\u00e9 t\u00fdmto smerom s\u00fa\u00a0<strong>zahoden\u00e9<\/strong>, doch\u00e1dza teda k strate paketov. Na druhej strane, ke\u010f je rad pr\u00e1zdny, k \u017eiadnemu \u010dakaniu v rade nedoch\u00e1dza.<\/li>\n<\/ul>\n<\/li>\n<li><strong>odosielanie<\/strong>\n<ul>\n<li>Ka\u017ed\u00e9 pripojenie m\u00e1 dan\u00fa svoju prenosov\u00fa r\u00fdchlos\u0165, t. j. po\u010det bitov za sekundu, ktor\u00e9 sa m\u00f4\u017eu cez neho odosla\u0165. Prenosov\u00e1 r\u00fdchlos\u0165 sa m\u00f4\u017ee nazva\u0165 aj ako r\u00fdchlos\u0165 pripojenia \u010di r\u00fdchlos\u0165 uploadu (odosielania). Ak je prenosov\u00e1 r\u00fdchlos\u0165 R bitov za sekundu a d\u013a\u017eka paketu L bitov, tak toto zdr\u017eanie je presne L\/R sek\u00fand. Ide teda o \u010das, odkedy sa odo\u0161le prv\u00fd bit paketu, a\u017e pokia\u013e sa po\u0161le posledn\u00fd bit paketu. Je d\u00f4le\u017eit\u00e9 poznamena\u0165, \u017ee tento \u010das sa nepripo\u010d\u00edtava s \u010dasom potrebn\u00fdm na prijatie paketu na \u010fal\u0161om uzle. \u010casto sa st\u00e1va, \u017ee v \u010dase odosielania posledn\u00e9ho bitu paketu s\u00fa u\u017e prv\u00e9 bity toho ist\u00e9ho paketu prijat\u00e9 na druhom uzle.<\/li>\n<\/ul>\n<\/li>\n<li><strong>prenos<\/strong>\n<ul>\n<li>Toto zdr\u017eanie predstavuje \u010das, za ktor\u00fd sa jeden bit prenesie k druh\u00e9mu uzlu. Tento \u010das z\u00e1vis\u00ed od vzdialenosti a prenosovej r\u00fdchlosti sign\u00e1lu v spoji (t\u00e1 je obvykle bl\u00edzka r\u00fdchlosti svetla). Toto zdr\u017eanie nem\u00e1 s prenosovou r\u00fdchlos\u0165ou ni\u010d spolo\u010dn\u00e9 \u2013 je jedno \u010di je prenosov\u00e1 r\u00fdchlos\u0165 10 Gb\/s alebo 10 kb\/s !<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Celkov\u00e9 zdr\u017eanie sa d\u00e1 odmera\u0165 programom\u00a0<em>ping\u00a0<\/em>alebo\u00a0<em>traceroute<\/em>. Ak d\u00f4jde k strate paketu z d\u00f4vodu zahltenia routra (v\u00fdstupn\u00fd buffer\/rad je pln\u00fd), m\u00f4\u017ee by\u0165 tento paket znova poslan\u00fd odosielaj\u00facim koncov\u00fdm zariaden\u00edm, ale aj nemus\u00ed \u2013 to z\u00e1vis\u00ed od zvolen\u00e9ho transportn\u00e9ho protokolu.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Paket na svojej ceste do cie\u013ea stret\u00e1va cel\u00fd rad routrov. Na ka\u017edom z t\u00fdchto routrov sa nejak\u00fd \u010das zdr\u017e\u00ed, pokia\u013e nie je odoslan\u00fd \u010falej. \u010casu&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"_links":{"self":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/269"}],"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=269"}],"version-history":[{"count":1,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/269\/revisions"}],"predecessor-version":[{"id":270,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/269\/revisions\/270"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=269"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}