{"id":52324,"date":"2019-11-06T00:00:00","date_gmt":"2019-11-05T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/hvatit-ispolzovat-smehotvorno-malyj-ttl-dlya-dns"},"modified":"2021-01-02T13:04:14","modified_gmt":"2021-01-02T11:04:14","slug":"hvatit-ispolzovat-smehotvorno-malyj-ttl-dlya-dns","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sv\/blog\/administrirovanie\/hvatit-ispolzovat-smehotvorno-malyj-ttl-dlya-dns","title":{"rendered":"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p>L\u00e5g DNS-f\u00f6rdr\u00f6jning \u00e4r en nyckelfaktor f\u00f6r snabb internetanv\u00e4ndning. F\u00f6r att minimera den \u00e4r det viktigt att noggrant v\u00e4lja DNS-servrar och <noindex><a rel=\"nofollow\" href=\"https:\/\/github.com\/DNSCrypt\/dnscrypt-resolvers\/blob\/master\/v2\/relays.md\">anonyma rel\u00e4er<\/a><\/noindex>. Men f\u00f6rst och fr\u00e4mst b\u00f6r man bli av med on\u00f6diga f\u00f6rfr\u00e5gningar.<\/p>\n<p>D\u00e4rf\u00f6r skapades DNS ursprungligen som en starkt cachad protokoll. Zonadministrat\u00f6rer s\u00e4tter livsl\u00e4ngd (TTL) f\u00f6r individuella poster, och resolverar anv\u00e4nder denna information n\u00e4r de lagrar poster i minnet f\u00f6r att undvika on\u00f6dig trafik.<\/p>\n<p>\u00c4r cachningen effektiv? F\u00f6r ett par \u00e5r sedan visade min lilla studie att den inte \u00e4r perfekt. L\u00e5t oss titta p\u00e5 den nuvarande situationen.<br \/>\n<noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><br \/>\nF\u00f6r att samla information har jag patchat <noindex><a rel=\"nofollow\" href=\"https:\/\/github.com\/jedisct1\/encrypted-dns-server\">Encrypted DNS Server<\/a><\/noindex> f\u00f6r att bevara TTL-v\u00e4rdet f\u00f6r svaret. Det definieras som den minimi TTL av dess poster f\u00f6r varje inkommande f\u00f6rfr\u00e5gan. Detta ger en bra \u00f6versikt av TTL-f\u00f6rdelningen f\u00f6r den verkliga trafiken och tar \u00e4ven h\u00e4nsyn till popul\u00e4riteten av individuella f\u00f6rfr\u00e5gningar. Den patchade versionen av servern k\u00f6rdes i flera timmar.<\/p>\n<p>\u0420\u0435\u0437\u0443\u043b\u044c\u0442\u0438\u0440\u0443\u044e\u0449\u0438\u0439 \u043d\u0430\u0431\u043e\u0440 \u0434\u0430\u043d\u043d\u044b\u0445 \u0441\u043e\u0441\u0442\u043e\u0438\u0442 \u0438\u0437 1&nbsp;583&nbsp;579 \u0437\u0430\u043f\u0438\u0441\u0435\u0439 (name, qtype, TTL, timestamp). \u0412\u043e\u0442 \u043e\u0431\u0449\u0435\u0435 \u0440\u0430\u0441\u043f\u0440\u0435\u0434\u0435\u043b\u0435\u043d\u0438\u0435 TTL (\u043e\u0441\u044c X \u2014 \u044d\u0442\u043e TTL \u0432 \u0441\u0435\u043a\u0443\u043d\u0434\u0430\u0445):<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/ce19a1ceb07e1fd2f3b2284f86271eac.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>\u0415\u0441\u043b\u0438 \u043d\u0435 \u0441\u0447\u0438\u0442\u0430\u0442\u044c \u043d\u0435\u0437\u043d\u0430\u0447\u0438\u0442\u0435\u043b\u044c\u043d\u043e\u0433\u043e \u0431\u0443\u0433\u0440\u0430 \u043d\u0430 86&nbsp;400 (\u0432 \u043e\u0441\u043d\u043e\u0432\u043d\u043e\u043c, \u0434\u043b\u044f \u0437\u0430\u043f\u0438\u0441\u0435\u0439 SOA), \u0434\u043e\u0432\u043e\u043b\u044c\u043d\u043e \u043e\u0447\u0435\u0432\u0438\u0434\u043d\u043e, \u0447\u0442\u043e TTL \u043d\u0430\u0445\u043e\u0434\u044f\u0442\u0441\u044f \u0432 \u043d\u0438\u0437\u043a\u043e\u043c \u0434\u0438\u0430\u043f\u0430\u0437\u043e\u043d\u0435. \u041f\u043e\u0441\u043c\u043e\u0442\u0440\u0438\u043c \u0431\u043b\u0438\u0436\u0435:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/abbe48952b616e1c5bdb18c2dc103dc7.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>Okej, TTL \u00f6ver 1 timme \u00e4r statistiskt ovidkommande. L\u00e5t oss fokusera p\u00e5 intervallet 0\u22123600:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/f8a88267e1868a55d9234f66ad8c5dee.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>De flesta TTL ligger mellan 0 och 15 minuter:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/aab650c806097513a5924e5262211ea5.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>Den \u00f6verv\u00e4ldigande majoriteten ligger mellan 0 och 5 minuter:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/736af4b33b745fb0d5070200fa511426.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>Detta \u00e4r inte bra.<\/p>\n<p>Den kumulativa f\u00f6rdelningen g\u00f6r problemet \u00e4nnu mer uppenbart:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/a3a4f03188dd6dbbf4558076b827f6a5.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>\u0412 \u043f\u043e\u043b\u043e\u0432\u0438\u043d\u0435 DNS-\u043e\u0442\u0432\u0435\u0442\u043e\u0432 TTL \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 1 \u043c\u0438\u043d\u0443\u0442\u0443 \u0438\u043b\u0438 \u043c\u0435\u043d\u044c\u0448\u0435, \u0430 \u0443 \u0442\u0440\u0451\u0445 \u0447\u0435\u0442\u0432\u0435\u0440\u0442\u0435\u0439&nbsp;\u2014 5 \u043c\u0438\u043d\u0443\u0442 \u0438\u043b\u0438 \u043c\u0435\u043d\u044c\u0448\u0435.<\/p>\n<p>Men v\u00e4nta, det \u00e4r faktiskt \u00e4nnu v\u00e4rre. Dessa \u00e4r TTL fr\u00e5n auktoritativa servrar. Men klientresolverare (t.ex. routrar, lokala cachar) f\u00e5r TTL fr\u00e5n \u00f6verordnade resolverare, och den minskar med varje sekund.<\/p>\n<p>D\u00e4rf\u00f6r kan klienten i genomsnitt anv\u00e4nda varje post under h\u00e4lften av den ursprungliga TTL, efter vilket ett nytt f\u00f6rfr\u00e5gan skickas.<\/p>\n<p>Kanske g\u00e4ller dessa mycket l\u00e5ga TTL bara ovanliga f\u00f6rfr\u00e5gningar, och inte popul\u00e4ra webbplatser och API:er? L\u00e5t oss se:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/2680f9669a90f449a593edcc84ca0dc8.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>\u041e\u0441\u044c X&nbsp;\u2014 \u044d\u0442\u043e TTL, \u043e\u0441\u044c Y&nbsp;\u2014 \u043f\u043e\u043f\u0443\u043b\u044f\u0440\u043d\u043e\u0441\u0442\u044c \u0437\u0430\u043f\u0440\u043e\u0441\u043e\u0432.<\/p>\n<p>Tyv\u00e4rr \u00e4r de mest popul\u00e4ra f\u00f6rfr\u00e5gningarna ocks\u00e5 de som cachas s\u00e4mst.<\/p>\n<p>L\u00e5t oss zooma in:<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/c670382b195169779743f43fd7b15827.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>Dom: det \u00e4r verkligen d\u00e5ligt. Det har alltid varit d\u00e5ligt, men nu har det blivit \u00e4nnu s\u00e4mre. DNS-caching har blivit praktiskt taget v\u00e4rdel\u00f6st. Eftersom f\u00e4rre och f\u00e4rre m\u00e4nniskor anv\u00e4nder sin leverant\u00f6rs DNS-resolver (av legitima sk\u00e4l) blir \u00f6kningen av latens mer m\u00e4rkbar.<\/p>\n<p>DNS-caching har blivit anv\u00e4ndbart endast f\u00f6r inneh\u00e5ll som ingen bes\u00f6ker.<\/p>\n<p>Observera ocks\u00e5 att programvaran kan <noindex><a rel=\"nofollow\" href=\"https:\/\/00f.net\/2011\/11\/17\/how-long-does-a-dns-ttl-last\/\">tolka p\u00e5 olika<\/a><\/noindex> s\u00e4tt l\u00e5ga TTL.<\/p>\n<h1>Varf\u00f6r s\u00e5?<\/h1>\n<p>Varf\u00f6r s\u00e4tts en s\u00e5 l\u00e5g TTL f\u00f6r DNS-poster?<\/p>\n<ul>\n<li>F\u00f6r\u00e5ldrade lastbalanserare har kvar standardinst\u00e4llningar.<\/li>\n<li>\u0425\u043e\u0434\u044f\u0442 \u043c\u0438\u0444\u044b, \u0447\u0442\u043e \u0431\u0430\u043b\u0430\u043d\u0441\u0438\u0440\u043e\u0432\u043a\u0430 \u043d\u0430\u0433\u0440\u0443\u0437\u043a\u0438 \u043f\u043e DNS \u0437\u0430\u0432\u0438\u0441\u0438\u0442 \u043e\u0442 TTL (\u044d\u0442\u043e \u043d\u0435 \u0442\u0430\u043a&nbsp;\u2014 \u0441\u043e \u0432\u0440\u0435\u043c\u0451\u043d Netscape Navigator \u043a\u043b\u0438\u0435\u043d\u0442\u044b \u0432\u044b\u0431\u0438\u0440\u0430\u044e\u0442 \u0441\u043b\u0443\u0447\u0430\u0439\u043d\u044b\u0439 IP-\u0430\u0434\u0440\u0435\u0441 \u0438\u0437 \u043d\u0430\u0431\u043e\u0440\u0430 RR \u0438 \u043f\u0440\u043e\u0437\u0440\u0430\u0447\u043d\u043e \u043f\u0440\u043e\u0431\u0443\u044e\u0442 \u0434\u0440\u0443\u0433\u043e\u0439, \u0435\u0441\u043b\u0438 \u043d\u0435 \u043c\u043e\u0433\u0443\u0442 \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0438\u0442\u044c\u0441\u044f)<\/li>\n<li>Administrat\u00f6rer vill till\u00e4mpa f\u00f6r\u00e4ndringar omedelbart, eftersom det \u00e4r mycket enklare att planera.<\/li>\n<li>DNS-serverns eller lastbalanserarens administrat\u00f6r ser det som sin uppgift att effektivt distribuera den konfiguration som anv\u00e4ndare beg\u00e4r, snarare \u00e4n att snabba upp webbplatser och tj\u00e4nster.<\/li>\n<li>L\u00e5ga TTL ger sinnesro.<\/li>\n<li>Folk s\u00e4tter initialt l\u00e5ga TTL f\u00f6r testning och gl\u00f6mmer sedan att \u00e4ndra dem.<\/li>\n<\/ul>\n<p>Jag inkluderade inte \"felhantering\" i listan, eftersom det blir mindre aktuellt. Om du beh\u00f6ver omdirigera anv\u00e4ndare till ett annat n\u00e4tverk bara f\u00f6r att visa en felmeddelandesida n\u00e4r allt annat \u00e4r trasigt, \u00e4r kanske en latens p\u00e5 \u00f6ver 1 minut acceptabel.<\/p>\n<p>Dessutom betyder en minut TTL att om de auktoritativa DNS-servrarna blockeras i mer \u00e4n 1 minut, kan ingen annan f\u00e5 tillg\u00e5ng till beroende tj\u00e4nster. Och redundans hj\u00e4lper inte om orsaken \u00e4r en konfigurationsfel eller hack. \u00c5 andra sidan, med rimliga TTL forts\u00e4tter m\u00e5nga klienter att anv\u00e4nda den tidigare konfigurationen och m\u00e4rker aldrig n\u00e5got.<\/p>\n<p>L\u00e5ga TTL ansvarar i h\u00f6g grad f\u00f6r CDN-tj\u00e4nster och lastbalanserare, s\u00e4rskilt n\u00e4r de kombinerar CNAME med l\u00e5ga TTL och poster med samma l\u00e5ga (men oberoende) TTL:<\/p>\n<pre>$ drill raw.githubusercontent.com\nraw.githubusercontent.com.\t9\tIN\tCNAME\tgithub.map.fastly.net.\ngithub.map.fastly.net.\t20\tIN\tA\t151.101.128.133\ngithub.map.fastly.net.\t20\tIN\tA\t151.101.192.133\ngithub.map.fastly.net.\t20\tIN\tA\t151.101.0.133\ngithub.map.fastly.net.\t20\tIN\tA\t151.101.64.133<\/pre>\n<p>Varje g\u00e5ng en CNAME- eller n\u00e5gon av A-posterna g\u00e5r ut, m\u00e5ste en ny f\u00f6rfr\u00e5gan skickas. De har b\u00e5da en TTL p\u00e5 30 sekunder, men de matchar inte. Den faktiska genomsnittliga TTL kommer att vara 15 sekunder.<\/p>\n<p>Men v\u00e4nta! Det \u00e4r fortfarande v\u00e4rre. Vissa resolverare beter sig v\u00e4ldigt d\u00e5ligt i en s\u00e5dan situation med tv\u00e5 relaterade l\u00e5ga TTL:<\/p>\n<pre>$ drill raw.githubusercontent.com @4.2.2.2\nraw.githubusercontent.com.\t1\tIN\tCNAME\tgithub.map.fastly.net.\ngithub.map.fastly.net.\t1\tIN\tA\t151.101.16.133<\/pre>\n<p>Level3-resolveraren arbetar sannolikt med BIND. Om du forts\u00e4tter att skicka denna f\u00f6rfr\u00e5gan, kommer TTL alltid att returneras som 1. I grund och botten, <code>raw.githubusercontent.com<\/code> kan aldrig cacheras.<\/p>\n<p>H\u00e4r \u00e4r ett annat exempel p\u00e5 en s\u00e5dan situation med en mycket popul\u00e4r dom\u00e4n:<\/p>\n<pre>$ drill detectportal.firefox.com @1.1.1.1\ndetectportal.firefox.com.\t25\tIN\tCNAME\tdetectportal.prod.mozaws.net.\ndetectportal.prod.mozaws.net.\t26\tIN\tCNAME\tdetectportal.firefox.com-v2.edgesuite.net.\ndetectportal.firefox.com-v2.edgesuite.net.\t10668\tIN\tCNAME\ta1089.dscd.akamai.net.\na1089.dscd.akamai.net.\t10\tIN\tA\t104.123.50.106\na1089.dscd.akamai.net.\t10\tIN\tA\t104.123.50.88<\/pre>\n<p>Minst tre CNAME-poster. Aj. En har en acceptabel TTL, men det \u00e4r helt v\u00e4rdel\u00f6st. I andra CNAME \u00e4r den ursprungliga TTL 60 sekunder, men f\u00f6r dom\u00e4nerna <code>akamai.net<\/code> \u00e4r den maximala TTL 20 sekunder, och ingen av dem \u00e4r synkroniserade.<\/p>\n<p>Hur \u00e4r det med dom\u00e4ner som st\u00e4ndigt queryar Apple-enheter?<\/p>\n<pre>$ drill 1-courier.push.apple.com @4.2.2.2\n1-courier.push.apple.com.\t1253\tIN\tCNAME\t1.courier-push-apple.com.akadns.net.\n1.courier-push-apple.com.akadns.net.\t1\tIN\tCNAME\tgb-courier-4.push-apple.com.akadns.net.\ngb-courier-4.push-apple.com.akadns.net.\t1\tIN\tA\t17.57.146.84\ngb-courier-4.push-apple.com.akadns.net.\t1\tIN\tA\t17.57.146.85<\/pre>\n<p>Samma problem som med Firefox, och TTL kommer f\u00f6r det mesta att fastna p\u00e5 1 sekund n\u00e4r man anv\u00e4nder Level3-resolveraren.<\/p>\n<p>Dropbox?<\/p>\n<pre>$ drill client.dropbox.com @8.8.8.8\nclient.dropbox.com.\t7\tIN\tCNAME\tclient.dropbox-dns.com.\nclient.dropbox-dns.com.\t59\tIN\tA\t162.125.67.3\n\n$ drill client.dropbox.com @4.2.2.2\nclient.dropbox.com.\t1\tIN\tCNAME\tclient.dropbox-dns.com.\nclient.dropbox-dns.com.\t1\tIN\tA\t162.125.64.3<\/pre>\n<p>I posten <code>safebrowsing.googleapis.com<\/code> \u00e4r TTL-v\u00e4rdet 60 sekunder, precis som f\u00f6r Facebook-dom\u00e4ner. Och \u00e5terigen, sett ur ett kundperspektiv, minskar dessa v\u00e4rden med h\u00e4lften.<\/p>\n<h1>Hur \u00e4r det med att st\u00e4lla in en minimal TTL?<\/h1>\n<p>Genom att anv\u00e4nda namnet, beg\u00e4rningstypen, TTL och den ursprungligen sparade tidsst\u00e4mpeln skrev jag ett skript f\u00f6r att simulera 1,5 miljoner f\u00f6rfr\u00e5gningar som passerade genom en cache-resolver f\u00f6r att bed\u00f6ma m\u00e4ngden on\u00f6diga f\u00f6rfr\u00e5gningar som skickades p\u00e5 grund av en utg\u00e5ngen cache-poster.<\/p>\n<p>47,4% av f\u00f6rfr\u00e5gningarna gjorde efter att den befintliga posten hade g\u00e5tt ut. Det \u00e4r orimligt h\u00f6gt.<\/p>\n<p>Vad kommer att bli effekten p\u00e5 caching om en minimal TTL s\u00e4tts?<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/3abd417d312450519b45f66865b23763.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>X-axeln representerar de minimi TTL-v\u00e4rden. Poster med ursprungliga TTL-v\u00e4rden \u00f6ver detta p\u00e5verkas inte.<\/p>\n<p>Y-axeln visar procentandelen f\u00f6rfr\u00e5gningar fr\u00e5n klienter som redan har en cachelagrad post, men vars giltighetstid har l\u00f6pt ut och som g\u00f6r en ny f\u00f6rfr\u00e5gan.<\/p>\n<p>Andelen \"\u00f6verskotts\" f\u00f6rfr\u00e5gningar minskar fr\u00e5n 47% till 36% genom att enkelt st\u00e4lla in en minimal TTL p\u00e5 5 minuter. Vid en minimal TTL p\u00e5 15 minuter minskar antalet dessa f\u00f6rfr\u00e5gningar till 29%. En minimal TTL p\u00e5 1 timme s\u00e4nker dem till 17%. En betydande skillnad!<\/p>\n<p>Vad s\u00e4gs om att inte f\u00f6r\u00e4ndra n\u00e5got p\u00e5 serversidan, utan ist\u00e4llet st\u00e4lla in minimala TTL-v\u00e4rden i klienternas DNS-cacher (routrar, lokala resolvers)?<\/p>\n<p><img decoding=\"async\" alt=\"Sluta anv\u00e4nda skrattretande kort TTL f\u00f6r DNS\" src=\"\/wp-content\/uploads\/2019\/11\/107a2bd53797d421d65ac7260bf78dfe.jpg\" style=\"display:block;margin: 0 auto;\"><\/p>\n<p>Antalet n\u00f6dv\u00e4ndiga f\u00f6rfr\u00e5gningar minskar fr\u00e5n 47% till 34% vid en minimal TTL p\u00e5 5 minuter, till 25% med ett minimum p\u00e5 15 minuter och till 13% med ett minimum p\u00e5 1 timme. Kanske \u00e4r det optimala v\u00e4rdet 40 minuter.<\/p>\n<p>Effekten av denna minimala f\u00f6r\u00e4ndring \u00e4r enorm.<\/p>\n<h1>Vad f\u00e5r detta f\u00f6r konsekvenser?<\/h1>\n<p>Sj\u00e4lvklart kan tj\u00e4nsten \u00f6verf\u00f6ras till en ny molnleverant\u00f6r, en ny server, ett nytt n\u00e4tverk, vilket kr\u00e4ver att kunderna anv\u00e4nder de senaste DNS-posterna. En tillr\u00e4ckligt l\u00e5g TTL hj\u00e4lper till att g\u00f6ra en s\u00e5dan \u00f6verg\u00e5ng smidig och osynlig. Men med \u00f6verg\u00e5ngen till en ny infrastruktur f\u00f6rv\u00e4ntar sig ingen att kunderna skal byta till nya DNS-poster inom 1 minut, 5 minuter eller 15 minuter. Att s\u00e4tta en minimal livsl\u00e4ngd p\u00e5 40 minuter ist\u00e4llet f\u00f6r 5 minuter hindrar inte anv\u00e4ndarna fr\u00e5n att f\u00e5 \u00e5tkomst till tj\u00e4nsten.<\/p>\n<p>Men detta kommer att kraftigt minska latensen och f\u00f6rb\u00e4ttra sekretessen och p\u00e5litligheten, genom att undvika on\u00f6diga f\u00f6rfr\u00e5gningar.<\/p>\n<p>Sj\u00e4lvklart s\u00e4ger RFC att man strikt ska f\u00f6lja TTL. Men verkligheten \u00e4r att DNS-systemet har blivit f\u00f6r ineffektivt.<\/p>\n<p>Om du arbetar med auktoritativa DNS-servrar, kontrollera v\u00e4nligen dina TTL-v\u00e4rden. Beh\u00f6ver du verkligen s\u00e5 l\u00f6jligt l\u00e5ga v\u00e4rden?<\/p>\n<p>Sj\u00e4lvklart finns det goda sk\u00e4l att st\u00e4lla in sm\u00e5 TTL-v\u00e4rden f\u00f6r DNS-poster. Men inte f\u00f6r 75% av DNS-trafiken som praktiskt taget inte f\u00f6r\u00e4ndras.<\/p>\n<p>Och om du av n\u00e5gon anledning verkligen beh\u00f6ver anv\u00e4nda l\u00e5ga TTL-v\u00e4rden f\u00f6r DNS, se ocks\u00e5 till att det inte finns n\u00e5got cachelagring aktiverat p\u00e5 din webbplats. Av samma sk\u00e4l.<\/p>\n<p>Om du har en lokal DNS-cache som fungerar, s\u00e5som <noindex><a rel=\"nofollow\" href=\"https:\/\/github.com\/dnscrypt\/dnscrypt-proxy\">dnscrypt-proxy<\/a><\/noindex>, som l\u00e5ter dig st\u00e4lla in en minimal TTL, anv\u00e4nd denna funktion. Det \u00e4r okej. Inget d\u00e5ligt kommer att h\u00e4nda. St\u00e4ll in en minimal TTL p\u00e5 ungef\u00e4r mellan 40 minuter (2400 sekunder) och 1 timme. En helt rimlig spann.<\/p>\n<p>K\u00e4lla: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/post\/474450\/\">habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u041d\u0438\u0437\u043a\u0430\u044f \u0437\u0430\u0434\u0435\u0440\u0436\u043a\u0430 DNS \u2014 \u043a\u043b\u044e\u0447\u0435\u0432\u043e\u0439 \u0444\u0430\u043a\u0442\u043e\u0440 \u0434\u043b\u044f \u0431\u044b\u0441\u0442\u0440\u043e\u0439 \u0440\u0430\u0431\u043e\u0442\u044b \u0432 \u0438\u043d\u0442\u0435\u0440\u043d\u0435\u0442\u0435. \u0427\u0442\u043e\u0431\u044b \u0435\u0451 \u043c\u0438\u043d\u0438\u043c\u0438\u0437\u0438\u0440\u043e\u0432\u0430\u0442\u044c, \u0432\u0430\u0436\u043d\u043e \u0442\u0449\u0430\u0442\u0435\u043b\u044c\u043d\u043e \u043f\u043e\u0434\u043e\u0431\u0440\u0430\u0442\u044c DNS-\u0441\u0435\u0440\u0432\u0435\u0440\u044b \u0438 \u0430\u043d\u043e\u043d\u0438\u043c\u043d\u044b\u0435 \u0440\u0438\u043b\u0435\u0438. \u041d\u043e \u043f\u0435\u0440\u0432\u044b\u043c \u0434\u0435\u043b\u043e\u043c \u0441\u043b\u0435\u0434\u0443\u0435\u0442 \u0438\u0437\u0431\u0430\u0432\u0438\u0442\u044c\u0441\u044f \u043e\u0442 \u0431\u0435\u0441\u043f\u043e\u043b\u0435\u0437\u043d\u044b\u0445 \u0437\u0430\u043f\u0440\u043e\u0441\u043e\u0432. \u0418\u043c\u0435\u043d\u043d\u043e \u043f\u043e\u044d\u0442\u043e\u043c\u0443 DNS \u0438\u0437\u043d\u0430\u0447\u0430\u043b\u044c\u043d\u043e \u0441\u043e\u0437\u0434\u0430\u0432\u0430\u043b\u0441\u044f \u043a\u0430\u043a \u0441\u0438\u043b\u044c\u043d\u043e \u043a\u044d\u0448\u0438\u0440\u0443\u0435\u043c\u044b\u0439 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b. \u0410\u0434\u043c\u0438\u043d\u0438\u0441\u0442\u0440\u0430\u0442\u043e\u0440\u044b \u0437\u043e\u043d \u0443\u0441\u0442\u0430\u043d\u0430\u0432\u043b\u0438\u0432\u0430\u044e\u0442 \u0432\u0440\u0435\u043c\u044f \u0436\u0438\u0437\u043d\u0438 (TTL) \u0434\u043b\u044f \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u044b\u0445 \u0437\u0430\u043f\u0438\u0441\u0435\u0439, \u0430 \u0440\u0435\u0437\u043e\u043b\u0432\u0435\u0440\u044b \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u044e\u0442 \u044d\u0442\u0443 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044e \u043f\u0440\u0438 \u0445\u0440\u0430\u043d\u0435\u043d\u0438\u0438 \u0437\u0430\u043f\u0438\u0441\u0435\u0439 [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-52324","post","type-post","status-publish","format-standard","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.4 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u041d\u0438\u0437\u043a\u0430\u044f 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