{"id":172,"date":"2021-02-12T13:02:53","date_gmt":"2021-02-12T13:02:53","guid":{"rendered":"https:\/\/homihost.com\/?p=172"},"modified":"2023-07-23T19:56:14","modified_gmt":"2023-07-23T12:56:14","slug":"dns-la-gi","status":"publish","type":"post","link":"https:\/\/kiencang.net\/dns-la-gi\/","title":{"rendered":"DNS l\u00e0 g\u00ec? N\u00f3 ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o?"},"content":{"rendered":"\n<p>H\u1ec7 th\u1ed1ng ph\u00e2n gi\u1ea3i t\u00ean mi\u1ec1n (Domain Name System \/ DNS) l\u00e0 danh b\u1ea1 kh\u1ed5ng l\u1ed3 d\u00e0nh ri\u00eang cho Internet.\u00a0Con ng\u01b0\u1eddi ch\u00fang ta truy c\u1eadp th\u00f4ng tin tr\u1ef1c tuy\u1ebfn th\u00f4ng qua c\u00e1c t\u00ean mi\u1ec1n d\u1ec5 hi\u1ec3u- d\u1ec5 nh\u1edb, ch\u1eb3ng h\u1ea1n nh\u01b0 <code>vnexpress.net<\/code> ho\u1eb7c <code>youtube.com<\/code>.\u00a0Tr\u00ecnh duy\u1ec7t web t\u01b0\u01a1ng t\u00e1c th\u00f4ng qua \u0111\u1ecba ch\u1ec9 giao th\u1ee9c Internet (Internet Protocol \/ IP).\u00a0DNS c\u00f3 nhi\u1ec7m v\u1ee5 d\u1ecbch t\u00ean mi\u1ec1n th\u00e0nh\u00a0\u0111\u1ecba ch\u1ec9 IP (IP address)\u00a0\u0111\u1ec3 tr\u00ecnh duy\u1ec7t c\u00f3 th\u1ec3 t\u1ea3i c\u00e1c t\u00e0i nguy\u00ean Internet v\u1ec1.<\/p>\n\n\n\n<p>M\u1ed7i thi\u1ebft b\u1ecb \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i v\u1edbi Internet c\u00f3 m\u1ed9t \u0111\u1ecba ch\u1ec9 IP duy nh\u1ea5t m\u00e0 c\u00e1c m\u00e1y kh\u00e1c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u00ecm \u0111\u1ebfn n\u00f3.&nbsp;M\u00e1y ch\u1ee7 DNS gi\u00fap con ng\u01b0\u1eddi lo\u1ea1i b\u1ecf nhi\u1ec7m v\u1ee5 c\u1ee7a vi\u1ec7c ph\u1ea3i ghi nh\u1edb c\u00e1c \u0111\u1ecba ch\u1ec9 IP nh\u01b0 <code>192.168.1.1<\/code> (trong IPv4) ho\u1eb7c c\u00e1c \u0111\u1ecba ch\u1ec9 IP g\u1ed3m ch\u1eef v\u00e0 s\u1ed1 ph\u1ee9c t\u1ea1p h\u01a1n nhi\u1ec1u nh\u01b0 <code>2400:cb00:2048:1::c629:d7a2<\/code> (trong IPv6).<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_60 counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title \" >M\u1ee5c l\u1ee5c<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\" role=\"button\"><label for=\"item-6577d74ac052c\" ><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input aria-label=\"Toggle\" aria-label=\"item-6577d74ac052c\"  type=\"checkbox\" id=\"item-6577d74ac052c\"><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#DNS_hoat_dong_nhu_the_nao\" title=\"DNS ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o?\">DNS ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#Su_khac_biet_giua_may_chu_DNS_co_tham_quyen_va_trinh_phan_giai_DNS_de_quy_la_gi\" title=\"S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa m\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n v\u00e0 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy l\u00e0 g\u00ec?\">S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa m\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n v\u00e0 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#Cac_buoc_trong_tra_cuu_DNS_la_gi\" title=\"C\u00e1c b\u01b0\u1edbc trong tra c\u1ee9u DNS l\u00e0 g\u00ec?\">C\u00e1c b\u01b0\u1edbc trong tra c\u1ee9u DNS l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#Trinh_phan_giai_DNS_la_gi\" title=\"Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS l\u00e0 g\u00ec?\">Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#Cac_loai_truy_van_DNS_la_gi\" title=\"C\u00e1c lo\u1ea1i truy v\u1ea5n DNS l\u00e0 g\u00ec?\">C\u00e1c lo\u1ea1i truy v\u1ea5n DNS l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/kiencang.net\/dns-la-gi\/#DNS_caching_la_gi_Bo_nho_dem_DNS_xay_ra_o_dau\" title=\"DNS caching l\u00e0 g\u00ec?&nbsp;B\u1ed9 nh\u1edb \u0111\u1ec7m DNS x\u1ea3y ra \u1edf \u0111\u00e2u?\">DNS caching l\u00e0 g\u00ec?&nbsp;B\u1ed9 nh\u1edb \u0111\u1ec7m DNS x\u1ea3y ra \u1edf \u0111\u00e2u?<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\" id=\"dns-ho\u1ea1t-d\u1ed9ng-nh\u01b0-th\u1ebf-nao\"><span class=\"ez-toc-section\" id=\"DNS_hoat_dong_nhu_the_nao\"><\/span>DNS ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Qu\u00e1 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS (DNS resolution) bao g\u1ed3m vi\u1ec7c chuy\u1ec3n \u0111\u1ed5i t\u00ean m\u00e1y ch\u1ee7 \/ hostname (ch\u1eb3ng h\u1ea1n nh\u01b0 <code>www.example.com<\/code>) th\u00e0nh \u0111\u1ecba ch\u1ec9 IP th\u00e2n thi\u1ec7n v\u1edbi m\u00e1y t\u00ednh (ch\u1eb3ng h\u1ea1n nh\u01b0 <code>192.168.1.1<\/code>).&nbsp;\u0110\u1ecba ch\u1ec9 IP \u0111\u01b0\u1ee3c c\u1ea5p cho m\u1ed7i thi\u1ebft b\u1ecb tr\u00ean Internet v\u00e0 \u0111\u1ecba ch\u1ec9 \u0111\u00f3 l\u00e0 c\u1ea7n thi\u1ebft \u0111\u1ec3 vi\u1ec7c t\u00ecm thi\u1ebft b\u1ecb Internet di\u1ec5n ra ch\u00ednh x\u00e1c &#8211; gi\u1ed1ng nh\u01b0 \u0111\u1ecba ch\u1ec9 \u0111\u01b0\u1eddng ph\u1ed1 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u00ecm m\u1ed9t ng\u00f4i nh\u00e0 c\u1ee5 th\u1ec3 v\u1eady.&nbsp;<\/p>\n\n\n\n<p>Khi ng\u01b0\u1eddi d\u00f9ng mu\u1ed1n t\u1ea3i m\u1ed9t trang web, s\u1ef1 chuy\u1ec3n \u0111\u1ed5i ph\u1ea3i x\u1ea3y ra gi\u1eefa th\u00f4ng tin ng\u01b0\u1eddi d\u00f9ng nh\u1eadp v\u00e0o tr\u00ecnh duy\u1ec7t web c\u1ee7a h\u1ecd (vd: example.com) v\u00e0 \u0111\u1ecba ch\u1ec9 th\u00e2n thi\u1ec7n v\u1edbi m\u00e1y (\u0111\u1ecba ch\u1ec9 IP) c\u1ea7n thi\u1ebft \u0111\u1ec3 \u0111\u1ecbnh v\u1ecb website example.com \u0111ang n\u1eb1m tr\u00ean m\u00e1y ch\u1ee7 web n\u00e0o.<\/p>\n\n\n\n<p>\u0110\u1ec3 hi\u1ec3u \u0111\u01b0\u1ee3c quy tr\u00ecnh \u0111\u1eb1ng sau qu\u00e1 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS, \u0111i\u1ec1u quan tr\u1ecdng l\u00e0 ch\u00fang ta ph\u1ea3i t\u00ecm hi\u1ec3u v\u1ec1 c\u00e1c th\u00e0nh ph\u1ea7n ph\u1ea7n c\u1ee9ng kh\u00e1c nhau m\u00e0 truy v\u1ea5n DNS ph\u1ea3i di chuy\u1ec3n qua.&nbsp;\u0110\u1ed1i v\u1edbi tr\u00ecnh duy\u1ec7t web, vi\u1ec7c tra c\u1ee9u DNS x\u1ea3y ra \u1edf ch\u1ebf \u0111\u1ed9 &#8220;\u1ea9n \/ sau c\u00e1nh g\u00e0&#8221; v\u00e0 kh\u00f4ng y\u00eau c\u1ea7u t\u01b0\u01a1ng t\u00e1c t\u1eeb m\u00e1y t\u00ednh c\u1ee7a ng\u01b0\u1eddi d\u00f9ng ngo\u00e0i y\u00eau c\u1ea7u ban \u0111\u1ea7u.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<p>C\u00f3 4 m\u00e1y ch\u1ee7 DNS tham gia v\u00e0o vi\u1ec7c t\u1ea3i trang web:<\/p>\n\n\n\n<ul>\n<li><strong>Tr\u00ecnh \u0111\u1ec7 quy DNS<\/strong>&nbsp;&#8211; \u0110\u1ec7 quy (recursor) c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c coi nh\u01b0 ng\u01b0\u1eddi th\u1ee7 th\u01b0, ng\u01b0\u1eddi \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u \u0111i t\u00ecm m\u1ed9t cu\u1ed1n s\u00e1ch c\u1ee5 th\u1ec3 \u1edf \u0111\u00e2u \u0111\u00f3 trong th\u01b0 vi\u1ec7n.&nbsp;\u0110\u1ec7 quy DNS l\u00e0 m\u1ed9t m\u00e1y ch\u1ee7 \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 nh\u1eadn c\u00e1c truy v\u1ea5n t\u1eeb c\u00e1c m\u00e1y kh\u00e1ch th\u00f4ng qua c\u00e1c \u1ee9ng d\u1ee5ng nh\u01b0 tr\u00ecnh duy\u1ec7t web.&nbsp;Th\u00f4ng th\u01b0\u1eddng, tr\u00ecnh \u0111\u1ec7 quy sau \u0111\u00f3 ch\u1ecbu tr\u00e1ch nhi\u1ec7m th\u1ef1c hi\u1ec7n c\u00e1c y\u00eau c\u1ea7u b\u1ed5 sung \u0111\u1ec3 \u0111\u00e1p \u1ee9ng truy v\u1ea5n DNS c\u1ee7a m\u00e1y kh\u00e1ch.<\/li>\n\n\n\n<li><strong>M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh g\u1ed1c<\/strong>&nbsp;(root nameserver) &#8211; M\u00e1y&nbsp;ch\u1ee7 root&nbsp;l\u00e0 b\u01b0\u1edbc \u0111\u1ea7u ti\u00ean trong vi\u1ec7c d\u1ecbch (ph\u00e2n gi\u1ea3i) c\u00e1c t\u00ean m\u00e1y ch\u1ee7 c\u00f3 th\u1ec3 \u0111\u1ecdc \u0111\u01b0\u1ee3c c\u1ee7a con ng\u01b0\u1eddi th\u00e0nh \u0111\u1ecba ch\u1ec9 IP.&nbsp;N\u00f3 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c coi nh\u01b0 m\u1ed9t ch\u1ec9 m\u1ee5c trong th\u01b0 vi\u1ec7n tr\u1ecf \u0111\u1ebfn c\u00e1c gi\u00e1 s\u00e1ch kh\u00e1c nhau &#8211; th\u01b0\u1eddng n\u00f3 d\u00f9ng nh\u01b0 m\u1ed9t tham chi\u1ebfu \u0111\u1ebfn c\u00e1c v\u1ecb tr\u00ed c\u1ee5 th\u1ec3 h\u01a1n.<\/li>\n\n\n\n<li><strong>M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh TLD<\/strong>&nbsp;&#8211; M\u00e1y ch\u1ee7 mi\u1ec1n c\u1ea5p cao nh\u1ea5t (TLD) c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c coi nh\u01b0 m\u1ed9t gi\u00e1 s\u00e1ch c\u1ee5 th\u1ec3 trong th\u01b0 vi\u1ec7n.&nbsp;M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh n\u00e0y l\u00e0 b\u01b0\u1edbc ti\u1ebfp theo trong vi\u1ec7c t\u00ecm ki\u1ebfm m\u1ed9t \u0111\u1ecba ch\u1ec9 IP c\u1ee5 th\u1ec3 v\u00e0 n\u00f3 l\u01b0u tr\u1eef ph\u1ea7n cu\u1ed1i c\u00f9ng c\u1ee7a t\u00ean m\u00e1y ch\u1ee7 (trong v\u00ed d\u1ee5 example.com, m\u00e1y ch\u1ee7 TLD l\u00e0 \u201ccom\u201d).<\/li>\n\n\n\n<li><strong>M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n<\/strong>&nbsp;(authoritative nameserver) &#8211; M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh cu\u1ed1i c\u00f9ng n\u00e0y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c coi nh\u01b0 m\u1ed9t cu\u1ed1n t\u1eeb \u0111i\u1ec3n tr\u00ean gi\u00e1 s\u00e1ch, trong \u0111\u00f3 m\u1ed9t t\u00ean c\u1ee5 th\u1ec3 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c d\u1ecbch theo \u0111\u1ecbnh ngh\u0129a c\u1ee7a n\u00f3.&nbsp;M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n l\u00e0 \u0111i\u1ec3m d\u1eebng cu\u1ed1i c\u00f9ng trong truy v\u1ea5n m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh (nameserver query).&nbsp;N\u1ebfu m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n c\u00f3 quy\u1ec1n truy c\u1eadp v\u00e0o b\u1ea3n ghi \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u, n\u00f3 s\u1ebd tr\u1ea3 l\u1ea1i \u0111\u1ecba ch\u1ec9 IP cho t\u00ean m\u00e1y ch\u1ee7 (hostname \/ t\u00ean mi\u1ec1n) \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u tr\u1edf l\u1ea1i DNS Recursor (th\u1ee7 th\u01b0) \u0111\u00e3 th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u l\u00fac ban \u0111\u1ea7u.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"s\u1ef1-khac-bi\u1ec7t-gi\u1eefa-may-ch\u1ee7-dns-co-th\u1ea9m-quy\u1ec1n-va-trinh-phan-gi\u1ea3i-dns-d\u1ec7-quy-la-gi\"><span class=\"ez-toc-section\" id=\"Su_khac_biet_giua_may_chu_DNS_co_tham_quyen_va_trinh_phan_giai_DNS_de_quy_la_gi\"><\/span>S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa m\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n v\u00e0 tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>C\u1ea3 hai kh\u00e1i ni\u1ec7m \u0111\u1ec1u \u0111\u1ec1 c\u1eadp \u0111\u1ebfn c\u00e1c m\u00e1y ch\u1ee7 (nh\u00f3m m\u00e1y ch\u1ee7) kh\u00f4ng th\u1ec3 t\u00e1ch r\u1eddi v\u1edbi c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng DNS, nh\u01b0ng m\u1ed7i m\u00e1y th\u1ef1c hi\u1ec7n m\u1ed9t vai tr\u00f2 kh\u00e1c nhau v\u00e0 ho\u1ea1t \u0111\u1ed9ng \u1edf c\u00e1c v\u1ecb tr\u00ed kh\u00e1c nhau b\u00ean trong \u0111\u01b0\u1eddng d\u1eabn truy v\u1ea5n DNS.&nbsp;<\/p>\n\n\n\n<p>M\u1ed9t c\u00e1ch \u0111\u1ec3 suy ngh\u0129 v\u1ec1 s\u1ef1 kh\u00e1c bi\u1ec7t l\u00e0&nbsp;tr\u00ecnh ph\u00e2n gi\u1ea3i&nbsp;\u0111\u1ec7 quy&nbsp;\u1edf \u0111\u1ea7u truy v\u1ea5n DNS v\u00e0 m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n \u1edf cu\u1ed1i.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<p><strong>Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy<\/strong><\/p>\n\n\n\n<p>Tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy (recursive resolver) l\u00e0 m\u00e1y t\u00ednh ph\u1ea3n h\u1ed3i y\u00eau c\u1ea7u \u0111\u1ec7 quy t\u1eeb m\u00e1y kh\u00e1ch v\u00e0 d\u00e0nh th\u1eddi gian \u0111\u1ec3 theo d\u00f5i&nbsp;b\u1ea3n ghi DNS.&nbsp;<\/p>\n\n\n\n<p>N\u00f3 th\u1ef1c hi\u1ec7n \u0111i\u1ec1u n\u00e0y b\u1eb1ng c\u00e1ch th\u1ef1c hi\u1ec7n m\u1ed9t lo\u1ea1t c\u00e1c y\u00eau c\u1ea7u cho \u0111\u1ebfn khi n\u00f3 nh\u1eadn \u0111\u01b0\u1ee3c t\u1eeb m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh DNS c\u00f3 th\u1ea9m quy\u1ec1n (authoritative DNS nameserver) cho b\u1ea3n ghi \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u (ho\u1eb7c h\u1ebft th\u1eddi gian ch\u1edd ho\u1eb7c tr\u1ea3 v\u1ec1 l\u1ed7i n\u1ebfu kh\u00f4ng t\u00ecm th\u1ea5y b\u1ea3n ghi).&nbsp;<\/p>\n\n\n\n<p>May m\u1eafn l\u00e0, c\u00e1c tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng c\u1ea7n th\u1ef1c hi\u1ec7n nhi\u1ec1u y\u00eau c\u1ea7u \u0111\u1ebfn v\u1eady \u0111\u1ec3 theo d\u00f5i c\u00e1c b\u1ea3n ghi c\u1ea7n thi\u1ebft nh\u1eb1m ph\u1ea3n h\u1ed3i cho m\u1ed9t m\u00e1y kh\u00e1ch;&nbsp;b\u1ed9 nh\u1edb \u0111\u1ec7m cache&nbsp;l\u00e0 m\u1ed9t qu\u00e1 tr\u00ecnh l\u01b0u tr\u1eef d\u1eef li\u1ec7u gi\u00fap r\u00fat ng\u1eafn c\u00e1c y\u00eau c\u1ea7u c\u1ea7n thi\u1ebft b\u1eb1ng c\u00e1ch cung c\u1ea5p b\u1ea3n ghi t\u00e0i nguy\u00ean \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u tr\u01b0\u1edbc \u0111\u00f3 trong tra c\u1ee9u DNS (DNS lookup).<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/02\/dns-record-request-sequence-1-1024x255.png\" alt=\"quy tr\u00ecnh ph\u00e2n gi\u1ea3i DNS\" class=\"wp-image-188\"\/><\/figure><\/div>\n\n\n<p><strong>M\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n<\/strong><\/p>\n\n\n\n<p>N\u00f3i m\u1ed9t c\u00e1ch \u0111\u01a1n gi\u1ea3n, m\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n l\u00e0 m\u1ed9t m\u00e1y ch\u1ee7 th\u1ef1c s\u1ef1 l\u01b0u gi\u1eef v\u00e0 ch\u1ecbu tr\u00e1ch nhi\u1ec7m v\u1ec1 c\u00e1c b\u1ea3n ghi t\u00e0i nguy\u00ean DNS.&nbsp;\u0110\u00e2y l\u00e0 m\u00e1y ch\u1ee7 \u1edf cu\u1ed1i chu\u1ed7i tra c\u1ee9u DNS s\u1ebd ph\u1ea3n h\u1ed3i v\u1edbi b\u1ea3n ghi t\u00e0i nguy\u00ean \u0111\u01b0\u1ee3c truy v\u1ea5n, cu\u1ed1i c\u00f9ng n\u00f3 cho ph\u00e9p tr\u00ecnh duy\u1ec7t web th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u c\u00f3 \u0111\u01b0\u1ee3c \u0111\u1ecba ch\u1ec9 IP c\u1ea7n thi\u1ebft \u0111\u1ec3 truy c\u1eadp trang web ho\u1eb7c c\u00e1c t\u00e0i nguy\u00ean web kh\u00e1c.&nbsp;<\/p>\n\n\n\n<p>M\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n c\u00f3 th\u1ec3 \u0111\u00e1p \u1ee9ng c\u00e1c truy v\u1ea5n t\u1eeb d\u1eef li\u1ec7u c\u1ee7a ch\u00ednh n\u00f3 m\u00e0 kh\u00f4ng c\u1ea7n truy v\u1ea5n ngu\u1ed3n kh\u00e1c, v\u00ec n\u00f3 l\u00e0 <strong>ngu\u1ed3n trung th\u1ef1c cu\u1ed1i c\u00f9ng<\/strong> cho c\u00e1c b\u1ea3n ghi DNS nh\u1ea5t \u0111\u1ecbnh.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/02\/dns-record-request-sequence-2-1024x259.png\" alt=\"m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n\" class=\"wp-image-189\"\/><\/figure><\/div>\n\n\n<p>\u0110i\u1ec1u \u0111\u00e1ng n\u00f3i l\u00e0 trong c\u00e1c tr\u01b0\u1eddng h\u1ee3p truy v\u1ea5n d\u00e0nh cho mi\u1ec1n ph\u1ee5 (subdomain) nh\u01b0 foo.example.com ho\u1eb7c&nbsp;blog.cloudflare.com, m\u1ed9t m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh b\u1ed5 sung s\u1ebd \u0111\u01b0\u1ee3c th\u00eam v\u00e0o ngay sau m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n, ch\u1ecbu tr\u00e1ch nhi\u1ec7m l\u01b0u tr\u1eef&nbsp;b\u1ea3n ghi CNAME&nbsp;c\u1ee7a mi\u1ec1n ph\u1ee5.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/02\/dns-record-request-sequence-3-1024x496.png\" alt=\"m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u1ee7a mi\u1ec1n ph\u1ee5\" class=\"wp-image-190\"\/><\/figure><\/div>\n\n\n<p>C\u00f3 m\u1ed9t s\u1ef1 kh\u00e1c bi\u1ec7t ch\u00ednh gi\u1eefa nhi\u1ec1u d\u1ecbch v\u1ee5 DNS v\u00e0 d\u1ecbch v\u1ee5 m\u00e0 Cloudflare cung c\u1ea5p.&nbsp;C\u00e1c tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS kh\u00e1c nhau nh\u01b0 Google DNS, OpenDNS v\u00e0 c\u00e1c nh\u00e0 cung c\u1ea5p nh\u01b0 Comcast \u0111\u1ec1u duy tr\u00ec c\u00e0i \u0111\u1eb7t trung t\u00e2m d\u1eef li\u1ec7u c\u1ee7a tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS.&nbsp;C\u00e1c tr\u00ecnh ph\u00e2n gi\u1ea3i n\u00e0y cho ph\u00e9p th\u1ef1c hi\u1ec7n c\u00e1c truy v\u1ea5n nhanh ch\u00f3ng v\u00e0 d\u1ec5 d\u00e0ng th\u00f4ng qua c\u00e1c c\u1ee5m h\u1ec7 th\u1ed1ng m\u00e1y t\u00ednh \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a DNS, nh\u01b0ng v\u1ec1 c\u01a1 b\u1ea3n ch\u00fang kh\u00e1c v\u1edbi c\u00e1c m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh do Cloudflare l\u01b0u tr\u1eef.<\/p>\n\n\n\n<p>Cloudflare duy tr\u00ec c\u00e1c m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u1ea5p c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng kh\u00f4ng th\u1ec3 thi\u1ebfu \u0111\u1ed1i v\u1edbi c\u00e1c ho\u1ea1t \u0111\u1ed9ng c\u1ee7a Internet.&nbsp;M\u1ed9t v\u00ed d\u1ee5 ch\u00ednh l\u00e0&nbsp;<em>m\u1ea1ng m\u00e1y ch\u1ee7 f-root<\/em>&nbsp;m\u00e0 Cloudflare ch\u1ecbu tr\u00e1ch nhi\u1ec7m l\u01b0u tr\u1eef m\u1ed9t ph\u1ea7n.&nbsp;F-root l\u00e0 m\u1ed9t trong nh\u1eefng th\u00e0nh ph\u1ea7n c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh DNS c\u1ea5p c\u01a1 s\u1edf ch\u1ecbu tr\u00e1ch nhi\u1ec7m v\u1ec1 h\u00e0ng t\u1ef7 y\u00eau c\u1ea7u Internet m\u1ed7i ng\u00e0y.&nbsp;<\/p>\n\n\n\n<p>M\u1ea1ng Anycast&nbsp;c\u1ee7a ch\u00fang t\u00f4i&nbsp;\u0111\u1eb7t ch\u00fang t\u00f4i v\u00e0o v\u1ecb tr\u00ed \u0111\u1ed9c nh\u1ea5t \u0111\u1ec3 x\u1eed l\u00fd kh\u1ed1i l\u01b0\u1ee3ng l\u1edbn l\u01b0u l\u01b0\u1ee3ng DNS m\u00e0 kh\u00f4ng b\u1ecb gi\u00e1n \u0111o\u1ea1n d\u1ecbch v\u1ee5.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"cac-b\u01b0\u1edbc-trong-tra-c\u1ee9u-dns-la-gi\"><span class=\"ez-toc-section\" id=\"Cac_buoc_trong_tra_cuu_DNS_la_gi\"><\/span>C\u00e1c b\u01b0\u1edbc trong tra c\u1ee9u DNS l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u0110\u1ed1i v\u1edbi h\u1ea7u h\u1ebft c\u00e1c t\u00ecnh hu\u1ed1ng, DNS li\u00ean quan \u0111\u1ebfn vi\u1ec7c: m\u1ed9t t\u00ean mi\u1ec1n \u0111\u01b0\u1ee3c d\u1ecbch sang \u0111\u1ecba ch\u1ec9 IP chu\u1ea9n x\u00e1c.&nbsp;<\/p>\n\n\n\n<p>\u0110\u1ec3 t\u00ecm hi\u1ec3u c\u00e1ch th\u1ee9c ho\u1ea1t \u0111\u1ed9ng c\u1ee7a qu\u00e1 tr\u00ecnh n\u00e0y, h\u00e3y th\u1ef1c hi\u1ec7n theo \u0111\u01b0\u1eddng d\u1eabn tra c\u1ee9u DNS khi n\u00f3 di chuy\u1ec3n t\u1eeb tr\u00ecnh duy\u1ec7t web c\u1ee7a ng\u01b0\u1eddi d\u00f9ng, xuy\u00ean qua quy tr\u00ecnh tra c\u1ee9u DNS v\u00e0 quay l\u1ea1i l\u1ea7n n\u1eefa.&nbsp;Ch\u00fang ta h\u00e3y xem x\u00e9t l\u1ea7n l\u01b0\u1ee3t c\u00e1c b\u01b0\u1edbc.<\/p>\n\n\n\n<p>L\u01b0u \u00fd: Th\u00f4ng th\u01b0\u1eddng th\u00f4ng tin tra c\u1ee9u DNS s\u1ebd \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef c\u1ee5c b\u1ed9, c\u1ea3 b\u00ean trong m\u00e1y t\u00ednh truy v\u1ea5n ho\u1eb7c t\u1eeb xa trong c\u01a1 s\u1edf h\u1ea1 t\u1ea7ng DNS.&nbsp;Th\u01b0\u1eddng c\u00f3 8 b\u01b0\u1edbc trong tra c\u1ee9u DNS.&nbsp;Khi th\u00f4ng tin DNS \u0111\u01b0\u1ee3c l\u01b0u v\u00e0o b\u1ed9 nh\u1edb cache, c\u00e1c b\u01b0\u1edbc s\u1ebd \u0111\u01b0\u1ee3c b\u1ecf qua kh\u1ecfi quy tr\u00ecnh tra c\u1ee9u DNS, gi\u00fap qu\u00e1 tr\u00ecnh n\u00e0y di\u1ec5n ra nhanh h\u01a1n.&nbsp;V\u00ed d\u1ee5 d\u01b0\u1edbi \u0111\u00e2y ph\u00e1c th\u1ea3o t\u1ea5t c\u1ea3 8 b\u01b0\u1edbc khi kh\u00f4ng c\u00f3 g\u00ec \u0111\u01b0\u1ee3c l\u01b0u v\u00e0o b\u1ed9 nh\u1edb cache.<\/p>\n\n\n\n<p><strong>8 b\u01b0\u1edbc trong tra c\u1ee9u DNS<\/strong>:<\/p>\n\n\n\n<ol>\n<li>Ng\u01b0\u1eddi d\u00f9ng nh\u1eadp &#8216;example.com&#8217; v\u00e0o tr\u00ecnh duy\u1ec7t web v\u00e0 truy v\u1ea5n s\u1ebd \u0111\u01b0\u1ee3c chuy\u1ec3n t\u1edbi Internet v\u00e0 \u0111\u01b0\u1ee3c nh\u1eadn b\u1edfi tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS (DNS recursive resolver).<\/li>\n\n\n\n<li>Sau \u0111\u00f3, tr\u00ecnh ph\u00e2n gi\u1ea3i s\u1ebd truy v\u1ea5n m\u1ed9t m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh g\u1ed1c DNS (DNS root namesever).<\/li>\n\n\n\n<li>Sau \u0111\u00f3, m\u00e1y ch\u1ee7 root s\u1ebd ph\u1ea3n h\u1ed3i tr\u00ecnh ph\u00e2n gi\u1ea3i b\u1eb1ng \u0111\u1ecba ch\u1ec9 c\u1ee7a m\u00e1y ch\u1ee7 DNS c\u1ee7a Mi\u1ec1n c\u1ea5p cao nh\u1ea5t (Top Level Domain \/ TLD) (ch\u1eb3ng h\u1ea1n nh\u01b0 .com ho\u1eb7c .net), n\u01a1i l\u01b0u tr\u1eef th\u00f4ng tin cho c\u00e1c mi\u1ec1n c\u1ee7a n\u00f3.&nbsp;Khi t\u00ecm ki\u1ebfm example.com, y\u00eau c\u1ea7u c\u1ee7a ch\u00fang ta \u0111\u01b0\u1ee3c h\u01b0\u1edbng t\u1edbi TLD .com.<\/li>\n\n\n\n<li>Sau \u0111\u00f3, tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u01b0a ra y\u00eau c\u1ea7u t\u1edbi .com TLD.<\/li>\n\n\n\n<li>Sau \u0111\u00f3, m\u00e1y ch\u1ee7 TLD s\u1ebd ph\u1ea3n h\u1ed3i b\u1eb1ng \u0111\u1ecba ch\u1ec9 IP c\u1ee7a m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u1ee7a mi\u1ec1n, example.com.<\/li>\n\n\n\n<li>Cu\u1ed1i c\u00f9ng, tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy g\u1eedi m\u1ed9t truy v\u1ea5n \u0111\u1ebfn m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u1ee7a mi\u1ec1n.<\/li>\n\n\n\n<li>\u0110\u1ecba ch\u1ec9 IP cho example.com sau \u0111\u00f3 \u0111\u01b0\u1ee3c tr\u1ea3 v\u1ec1 tr\u00ecnh ph\u00e2n gi\u1ea3i t\u1eeb m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh.<\/li>\n\n\n\n<li>Sau \u0111\u00f3, tr\u00ecnh ph\u00e2n gi\u1ea3i DNS s\u1ebd ph\u1ea3n h\u1ed3i l\u1ea1i tr\u00ecnh duy\u1ec7t web b\u1eb1ng \u0111\u1ecba ch\u1ec9 IP c\u1ee7a mi\u1ec1n \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u l\u00fac ban \u0111\u1ea7u.<\/li>\n<\/ol>\n\n\n\n<p>Sau khi 8 b\u01b0\u1edbc c\u1ee7a qu\u00e1 tr\u00ecnh t\u00ecm ki\u1ebfm DNS tr\u1ea3 v\u1ec1 \u0111\u01b0\u1ee3c \u0111\u1ecba ch\u1ec9 IP cho t\u00ean mi\u1ec1n example.com, tr\u00ecnh duy\u1ec7t c\u00f3 kh\u1ea3 n\u0103ng th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u t\u1edbi trang web:<\/p>\n\n\n\n<p>9. Tr\u00ecnh duy\u1ec7t th\u1ef1c hi\u1ec7n m\u1ed9t&nbsp;y\u00eau c\u1ea7u&nbsp;HTTP&nbsp;\u0111\u1ebfn \u0111\u1ecba ch\u1ec9 IP.<\/p>\n\n\n\n<p>10. M\u00e1y ch\u1ee7 t\u1ea1i IP \u0111\u00f3 tr\u1ea3 v\u1ec1 trang web- c\u00e1i s\u1ebd \u0111\u01b0\u1ee3c hi\u1ec3n th\u1ecb trong tr\u00ecnh duy\u1ec7t (b\u01b0\u1edbc 10).<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/02\/dns-lookup-diagram-4-1024x682.png\" alt=\"quy tr\u00ecnh t\u00ecm ki\u1ebfm DNS di\u1ec5n ra trong th\u1ef1c t\u1ebf\" class=\"wp-image-187\"\/><\/figure><\/div>\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"trinh-phan-gi\u1ea3i-dns-la-gi\"><span class=\"ez-toc-section\" id=\"Trinh_phan_giai_DNS_la_gi\"><\/span>Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS (DNS resolver) l\u00e0 \u0111i\u1ec3m d\u1eebng \u0111\u1ea7u ti\u00ean trong qu\u00e1 tr\u00ecnh tra c\u1ee9u DNS, v\u00e0 n\u00f3 ch\u1ecbu tr\u00e1ch nhi\u1ec7m x\u1eed l\u00fd m\u00e1y kh\u00e1ch \u0111\u00e3 \u0111\u01b0a ra y\u00eau c\u1ea7u ban \u0111\u1ea7u.&nbsp;Tr\u00ecnh ph\u00e2n gi\u1ea3i b\u1eaft \u0111\u1ea7u chu\u1ed7i truy v\u1ea5n cu\u1ed1i c\u00f9ng d\u1eabn \u0111\u1ebfn m\u1ed9t URL \u0111\u01b0\u1ee3c d\u1ecbch th\u00e0nh \u0111\u1ecba ch\u1ec9 IP c\u1ea7n thi\u1ebft.<\/p>\n\n\n\n<p>L\u01b0u \u00fd: Tra c\u1ee9u DNS th\u00f4ng th\u01b0\u1eddng ch\u01b0a \u0111\u01b0\u1ee3c cache s\u1ebd li\u00ean quan \u0111\u1ebfn c\u1ea3 truy v\u1ea5n \u0111\u1ec7 quy v\u00e0 l\u1eb7p l\u1ea1i.<\/p>\n\n\n\n<p>\u0110i\u1ec1u quan tr\u1ecdng l\u00e0 ch\u00fang ta ph\u1ea3i ph\u00e2n bi\u1ec7t \u0111\u01b0\u1ee3c gi\u1eefa&nbsp;<em>truy v\u1ea5n&nbsp;DNS \u0111\u1ec7 quy (recursive DNS)<\/em>&nbsp;v\u00e0 <em>tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy (recursive DNS resolver)<\/em>.&nbsp;<\/p>\n\n\n\n<p>Truy v\u1ea5n \u0111\u1ec1 c\u1eadp \u0111\u1ebfn y\u00eau c\u1ea7u t\u1edbi tr\u00ecnh ph\u00e2n gi\u1ea3i DNS, y\u00eau c\u1ea7u gi\u1ea3i quy\u1ebft truy v\u1ea5n.&nbsp;<\/p>\n\n\n\n<p>Tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS l\u00e0 m\u00e1y t\u00ednh ch\u1ea5p nh\u1eadn truy v\u1ea5n \u0111\u1ec7 quy v\u00e0 x\u1eed l\u00fd ph\u1ea3n h\u1ed3i b\u1eb1ng c\u00e1ch \u0111\u01b0a ra c\u00e1c y\u00eau c\u1ea7u c\u1ea7n thi\u1ebft.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" src=\"https:\/\/kiencang.net\/wp-content\/uploads\/2021\/02\/dns-recursive-query-5-1024x157.png\" alt=\"tr\u00ecnh ph\u00e2n gi\u1ea3i DNS \u0111\u1ec7 quy\" class=\"wp-image-191\"\/><\/figure><\/div>\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"cac-lo\u1ea1i-truy-v\u1ea5n-dns-la-gi\"><span class=\"ez-toc-section\" id=\"Cac_loai_truy_van_DNS_la_gi\"><\/span>C\u00e1c lo\u1ea1i truy v\u1ea5n DNS l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Trong m\u1ed9t tra c\u1ee9u DNS \u0111i\u1ec3n h\u00ecnh, c\u00f3 ba lo\u1ea1i truy v\u1ea5n x\u1ea3y ra.&nbsp;B\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng k\u1ebft h\u1ee3p c\u00e1c truy v\u1ea5n n\u00e0y, m\u1ed9t quy tr\u00ecnh \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a \u0111\u1ec3 ph\u00e2n gi\u1ea3i DNS c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn vi\u1ec7c gi\u1ea3m kho\u1ea3ng c\u00e1ch di chuy\u1ec3n.&nbsp;Trong t\u00ecnh hu\u1ed1ng l\u00fd t\u01b0\u1edfng, d\u1eef li\u1ec7u b\u1ea3n ghi \u0111\u00e3 l\u01b0u trong b\u1ed9 nh\u1edb cache s\u1ebd c\u00f3 s\u1eb5n, cho ph\u00e9p m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh DNS tr\u1ea3 v\u1ec1 m\u1ed9t truy v\u1ea5n kh\u00f4ng \u0111\u1ec7 quy (non-recursive query).<\/p>\n\n\n\n<p><strong>3 lo\u1ea1i truy v\u1ea5n DNS<\/strong>:<\/p>\n\n\n\n<ol>\n<li><strong>Truy v\u1ea5n \u0111\u1ec7 quy<\/strong>&nbsp;&#8211; Trong truy v\u1ea5n \u0111\u1ec7 quy, m\u00e1y kh\u00e1ch DNS y\u00eau c\u1ea7u m\u00e1y ch\u1ee7 DNS (th\u01b0\u1eddng l\u00e0 tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS) s\u1ebd tr\u1ea3 l\u1eddi m\u00e1y kh\u00e1ch b\u1eb1ng b\u1ea3n ghi t\u00e0i nguy\u00ean \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u ho\u1eb7c th\u00f4ng b\u00e1o l\u1ed7i n\u1ebfu tr\u00ecnh ph\u00e2n gi\u1ea3i kh\u00f4ng th\u1ec3 t\u00ecm th\u1ea5y b\u1ea3n ghi.<\/li>\n\n\n\n<li><strong>Truy v\u1ea5n l\u1eb7p l\u1ea1i<\/strong>&nbsp;&#8211; trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y, m\u00e1y kh\u00e1ch DNS s\u1ebd cho ph\u00e9p m\u00e1y ch\u1ee7 DNS tr\u1ea3 v\u1ec1 c\u00e2u tr\u1ea3 l\u1eddi t\u1ed1t nh\u1ea5t c\u00f3 th\u1ec3.&nbsp;N\u1ebfu m\u00e1y ch\u1ee7 DNS \u0111\u01b0\u1ee3c truy v\u1ea5n kh\u00f4ng kh\u1edbp v\u1edbi t\u00ean truy v\u1ea5n, n\u00f3 s\u1ebd tr\u1ea3 v\u1ec1 th\u00f4ng tin gi\u1edbi thi\u1ec7u \u0111\u1ebfn m\u00e1y ch\u1ee7 DNS c\u00f3 th\u1ea9m quy\u1ec1n cho c\u1ea5p th\u1ea5p h\u01a1n c\u1ee7a kh\u00f4ng gian t\u00ean mi\u1ec1n.&nbsp;M\u00e1y kh\u00e1ch DNS sau \u0111\u00f3 s\u1ebd th\u1ef1c hi\u1ec7n truy v\u1ea5n \u0111\u1ebfn \u0111\u1ecba ch\u1ec9 gi\u1edbi thi\u1ec7u.&nbsp;Qu\u00e1 tr\u00ecnh n\u00e0y ti\u1ebfp t\u1ee5c v\u1edbi c\u00e1c m\u00e1y ch\u1ee7 DNS b\u1ed5 sung trong chu\u1ed7i truy v\u1ea5n cho \u0111\u1ebfn khi x\u1ea3y ra l\u1ed7i ho\u1eb7c h\u1ebft th\u1eddi gian.<\/li>\n\n\n\n<li><strong>Truy v\u1ea5n kh\u00f4ng \u0111\u1ec7 quy<\/strong>&nbsp;&#8211; th\u01b0\u1eddng \u0111i\u1ec1u n\u00e0y s\u1ebd x\u1ea3y ra khi m\u00e1y kh\u00e1ch ph\u00e2n gi\u1ea3i DNS (DNS resolver client) truy v\u1ea5n m\u00e1y ch\u1ee7 DNS (DNS server) v\u1ec1 b\u1ea3n ghi m\u00e0 n\u00f3 c\u00f3 quy\u1ec1n truy c\u1eadp, v\u00ec n\u00f3 c\u00f3 th\u1ea9m quy\u1ec1n cho b\u1ea3n ghi ho\u1eb7c b\u1ea3n ghi t\u1ed3n t\u1ea1i b\u00ean trong b\u1ed9 nh\u1edb cache c\u1ee7a n\u00f3.&nbsp;Th\u00f4ng th\u01b0\u1eddng, m\u1ed9t m\u00e1y ch\u1ee7 DNS s\u1ebd l\u01b0u tr\u1eef c\u00e1c b\u1ea3n ghi DNS \u0111\u1ec3 ng\u0103n ch\u1eb7n vi\u1ec7c ti\u00eau th\u1ee5 th\u00eam b\u0103ng th\u00f4ng v\u00e0 t\u1ea3i tr\u00ean c\u00e1c m\u00e1y ch\u1ee7 \u0111\u1ea7u ngu\u1ed3n (upstream servers).<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"dns-caching-la-gi-b\u1ed9-nh\u1edb-d\u1ec7m-dns-x\u1ea3y-ra-\u1edf-dau\"><span class=\"ez-toc-section\" id=\"DNS_caching_la_gi_Bo_nho_dem_DNS_xay_ra_o_dau\"><\/span>DNS caching l\u00e0 g\u00ec?&nbsp;B\u1ed9 nh\u1edb \u0111\u1ec7m DNS x\u1ea3y ra \u1edf \u0111\u00e2u?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>M\u1ee5c \u0111\u00edch c\u1ee7a b\u1ed9 nh\u1edb \u0111\u1ec7m l\u00e0 \u0111\u1ec3 d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef t\u1ea1m th\u1eddi \u1edf m\u1ed9t v\u1ecb tr\u00ed d\u1eabn \u0111\u1ebfn c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t v\u00e0 \u0111\u1ed9 tin c\u1eady cho c\u00e1c y\u00eau c\u1ea7u d\u1eef li\u1ec7u.&nbsp;<\/p>\n\n\n\n<p>B\u1ed9 nh\u1edb \u0111\u1ec7m DNS li\u00ean quan \u0111\u1ebfn vi\u1ec7c l\u01b0u tr\u1eef d\u1eef li\u1ec7u g\u1ea7n h\u01a1n v\u1edbi m\u00e1y kh\u00e1ch y\u00eau c\u1ea7u, \u0111\u1ec3 truy v\u1ea5n DNS c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c gi\u1ea3i quy\u1ebft s\u1edbm h\u01a1n v\u00e0 c\u00f3 th\u1ec3 tr\u00e1nh \u0111\u01b0\u1ee3c c\u00e1c truy v\u1ea5n b\u1ed5 sung b\u00ean d\u01b0\u1edbi chu\u1ed7i tra c\u1ee9u DNS, do \u0111\u00f3 c\u1ea3i thi\u1ec7n th\u1eddi gian t\u1ea3i v\u00e0 gi\u1ea3m ti\u00eau th\u1ee5 b\u0103ng th\u00f4ng \/ CPU.&nbsp;<\/p>\n\n\n\n<p>D\u1eef li\u1ec7u DNS c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c l\u01b0u v\u00e0o b\u1ed9 nh\u1edb cache \u1edf nhi\u1ec1u v\u1ecb tr\u00ed kh\u00e1c nhau, m\u1ed7i v\u1ecb tr\u00ed s\u1ebd l\u01b0u tr\u1eef c\u00e1c b\u1ea3n ghi DNS trong m\u1ed9t kho\u1ea3ng th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh theo&nbsp;th\u1eddi gian t\u1ed3n t\u1ea1i (time-to-live \/ TTL)&nbsp;.<\/p>\n\n\n\n<p><strong>B\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ee7a tr\u00ecnh duy\u1ec7t<\/strong><\/p>\n\n\n\n<p>C\u00e1c tr\u00ecnh duy\u1ec7t web hi\u1ec7n \u0111\u1ea1i \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf (theo m\u1eb7c \u0111\u1ecbnh) \u0111\u1ec3 l\u01b0u c\u00e1c b\u1ea3n ghi DNS v\u00e0o b\u1ed9 nh\u1edb cache trong m\u1ed9t kho\u1ea3ng th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh.&nbsp;M\u1ee5c \u0111\u00edch \u1edf \u0111\u00e2y l\u00e0 r\u00f5 r\u00e0ng;&nbsp;b\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u00e0ng \u1edf g\u1ea7n v\u1edbi tr\u00ecnh duy\u1ec7t web, th\u00ec c\u00e0ng ph\u1ea3i th\u1ef1c hi\u1ec7n \u00edt b\u01b0\u1edbc x\u1eed l\u00fd h\u01a1n \u0111\u1ec3 ki\u1ec3m tra b\u1ed9 nh\u1edb cache v\u00e0 th\u1ef1c hi\u1ec7n c\u00e1c y\u00eau c\u1ea7u ch\u00ednh x\u00e1c \u0111\u1ed1i v\u1edbi \u0111\u1ecba ch\u1ec9 IP.&nbsp;Khi y\u00eau c\u1ea7u b\u1ea3n ghi DNS \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n, b\u1ed9 nh\u1edb cache c\u1ee7a tr\u00ecnh duy\u1ec7t l\u00e0 v\u1ecb tr\u00ed \u0111\u1ea7u ti\u00ean \u0111\u01b0\u1ee3c ki\u1ec3m tra cho b\u1ea3n ghi \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u.<\/p>\n\n\n\n<p>Trong tr\u00ecnh duy\u1ec7t chrome, b\u1ea1n c\u00f3 th\u1ec3 xem tr\u1ea1ng th\u00e1i b\u1ed9 nh\u1edb cache DNS c\u1ee7a m\u00ecnh b\u1eb1ng c\u00e1ch truy c\u1eadp chrome:\/\/net-internals\/#dns.<\/p>\n\n\n\n<p><strong>B\u1ed9 nh\u1edb \u0111\u1ec7m DNS c\u1ea5p h\u1ec7 \u0111i\u1ec1u h\u00e0nh (OS)<\/strong><\/p>\n\n\n\n<p>Tr\u00ecnh ph\u00e2n gi\u1ea3i DNS c\u1ea5p h\u1ec7 \u0111i\u1ec1u h\u00e0nh l\u00e0 \u0111i\u1ec3m d\u1eebng c\u1ee5c b\u1ed9 th\u1ee9 hai v\u00e0 cu\u1ed1i c\u00f9ng tr\u01b0\u1edbc khi truy v\u1ea5n DNS r\u1eddi m\u00e1y t\u00ednh c\u1ee7a b\u1ea1n.&nbsp;Qu\u00e1 tr\u00ecnh b\u00ean trong h\u1ec7 \u0111i\u1ec1u h\u00e0nh c\u1ee7a b\u1ea1n \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 x\u1eed l\u00fd truy v\u1ea5n n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 &#8220;tr\u00ecnh ph\u00e2n gi\u1ea3i s\u01a1 khai \/ stub resolver&#8221; ho\u1eb7c m\u00e1y kh\u00e1ch DNS.&nbsp;<\/p>\n\n\n\n<p>Khi &#8220;stub resolver&#8221; nh\u1eadn \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u t\u1eeb m\u1ed9t \u1ee9ng d\u1ee5ng, tr\u01b0\u1edbc ti\u00ean n\u00f3 s\u1ebd ki\u1ec3m tra b\u1ed9 nh\u1edb cache c\u1ee7a ch\u00ednh n\u00f3 xem li\u1ec7u n\u00f3 c\u00f3 b\u1ea3n ghi hay kh\u00f4ng.&nbsp;N\u1ebfu kh\u00f4ng, n\u00f3 s\u1ebd g\u1eedi m\u1ed9t truy v\u1ea5n DNS (v\u1edbi c\u1edd \u0111\u1ec7 quy \u0111\u01b0\u1ee3c \u0111\u1eb7t), b\u00ean ngo\u00e0i m\u1ea1ng c\u1ee5c b\u1ed9 t\u1edbi tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy DNS b\u00ean trong nh\u00e0 cung c\u1ea5p d\u1ecbch v\u1ee5 Internet (ISP).<\/p>\n\n\n\n<p><strong>B\u1ed9 nh\u1edb \u0111\u1ec7m c\u1ee7a tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy<\/strong><\/p>\n\n\n\n<p>Khi tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy b\u00ean trong ISP nh\u1eadn \u0111\u01b0\u1ee3c truy v\u1ea5n DNS, gi\u1ed1ng nh\u01b0 t\u1ea5t c\u1ea3 c\u00e1c b\u01b0\u1edbc tr\u01b0\u1edbc \u0111\u00f3, n\u00f3 c\u0169ng s\u1ebd ki\u1ec3m tra xem b\u1ea3n d\u1ecbch \u0111\u1ecba ch\u1ec9 m\u00e1y ch\u1ee7 sang IP \u0111\u01b0\u1ee3c y\u00eau c\u1ea7u \u0111\u00e3 \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef b\u00ean trong l\u1edbp l\u01b0u tr\u1eef c\u1ee5c b\u1ed9 l\u00e2u d\u00e0i hay ch\u01b0a.<\/p>\n\n\n\n<p>Tr\u00ecnh ph\u00e2n gi\u1ea3i \u0111\u1ec7 quy c\u0169ng c\u00f3 ch\u1ee9c n\u0103ng b\u1ed5 sung t\u00f9y thu\u1ed9c v\u00e0o c\u00e1c lo\u1ea1i b\u1ea3n ghi m\u00e0 n\u00f3 c\u00f3 trong b\u1ed9 nh\u1edb cache:<\/p>\n\n\n\n<ol>\n<li>N\u1ebfu tr\u00ecnh ph\u00e2n gi\u1ea3i kh\u00f4ng c\u00f3&nbsp;b\u1ea3n ghi A, nh\u01b0ng c\u00f3&nbsp;b\u1ea3n ghi NS&nbsp;cho m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh c\u00f3 th\u1ea9m quy\u1ec1n, n\u00f3 s\u1ebd truy v\u1ea5n tr\u1ef1c ti\u1ebfp c\u00e1c m\u00e1y ch\u1ee7 \u0111\u1ecbnh danh \u0111\u00f3, b\u1ecf qua m\u1ed9t s\u1ed1 b\u01b0\u1edbc trong truy v\u1ea5n DNS.&nbsp;L\u1ed1i t\u1eaft n\u00e0y ng\u0103n ch\u1eb7n vi\u1ec7c tra c\u1ee9u t\u1eeb m\u00e1y ch\u1ee7 t\u00ean g\u1ed1c v\u00e0 .com (trong v\u00ed d\u1ee5 t\u00ecm ki\u1ebfm DNS cho tr\u00ean mi\u1ec1n example.com) v\u00e0 gi\u00fap vi\u1ec7c gi\u1ea3i quy\u1ebft truy v\u1ea5n DNS di\u1ec5n ra nhanh h\u01a1n.<\/li>\n\n\n\n<li>N\u1ebfu tr\u00ecnh ph\u00e2n gi\u1ea3i kh\u00f4ng c\u00f3 b\u1ea3n ghi NS, n\u00f3 s\u1ebd g\u1eedi m\u1ed9t truy v\u1ea5n \u0111\u1ebfn m\u00e1y ch\u1ee7 TLD (.com trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y), b\u1ecf qua m\u00e1y ch\u1ee7 root.<\/li>\n\n\n\n<li>Trong tr\u01b0\u1eddng h\u1ee3p kh\u00f4ng ch\u1eafc ch\u1eafn r\u1eb1ng tr\u00ecnh ph\u00e2n gi\u1ea3i kh\u00f4ng c\u00f3 b\u1ea3n ghi tr\u1ecf \u0111\u1ebfn m\u00e1y ch\u1ee7 TLD, th\u00ec n\u00f3 s\u1ebd truy v\u1ea5n m\u00e1y ch\u1ee7 root.&nbsp;S\u1ef1 ki\u1ec7n n\u00e0y th\u01b0\u1eddng x\u1ea3y ra sau khi b\u1ed9 nh\u1edb cache DNS \u0111\u00e3 \u0111\u01b0\u1ee3c x\u00f3a.<\/li>\n<\/ol>\n\n\n\n<p><em>(Bi\u00ean t\u1eadp t\u1eeb b\u00e0i vi\u1ebft <a href=\"https:\/\/www.cloudflare.com\/learning\/dns\/what-is-dns\/\" target=\"_blank\" rel=\"noreferrer noopener nofollow\">What Is DNS? | How DNS Works<\/a> c\u1ee7a Cloudflare)<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>H\u1ec7 th\u1ed1ng ph\u00e2n gi\u1ea3i t\u00ean mi\u1ec1n (Domain Name System \/ DNS) l\u00e0 danh b\u1ea1 kh\u1ed5ng l\u1ed3 d\u00e0nh ri\u00eang cho Internet.\u00a0Con ng\u01b0\u1eddi ch\u00fang ta truy c\u1eadp th\u00f4ng tin tr\u1ef1c tuy\u1ebfn th\u00f4ng qua c\u00e1c t\u00ean mi\u1ec1n d\u1ec5 hi\u1ec3u- d\u1ec5 nh\u1edb, ch\u1eb3ng h\u1ea1n nh\u01b0 vnexpress.net ho\u1eb7c youtube.com.\u00a0Tr\u00ecnh duy\u1ec7t web t\u01b0\u01a1ng t\u00e1c th\u00f4ng qua \u0111\u1ecba ch\u1ec9 giao th\u1ee9c Internet &hellip;<\/p>\n","protected":false},"author":1,"featured_media":19731,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[97],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>DNS l\u00e0 g\u00ec? N\u00f3 ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o? &#8226; Ki\u1ebfn c\u00e0ng<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/kiencang.net\/dns-la-gi\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"DNS l\u00e0 g\u00ec? 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