Tsawg DNS latency yog qhov tseem ceeb rau kev tshawb nrhiav hauv internet ceev. Yuav kom txo qis nws, nws yog ib qho tseem ceeb kom ua tib zoo xaiv DNS servers thiab
Qhov no yog vim li cas DNS yog thawj zaug tsim los ua tus txheej txheem cacheable heev. Cov thawj coj hauv cheeb tsam tau teem sijhawm nyob (TTL) rau tus kheej nkag, thiab cov neeg daws teeb meem siv cov ntaub ntawv no thaum khaws cov ntawv nkag hauv lub cim xeeb kom tsis txhob muaj tsheb khiav tsis tsim nyog.
Puas yog caching siv tau? Ob peb xyoos dhau los, kuv qhov kev tshawb fawb me me tau pom tias nws tsis zoo tag nrho. Cia wb mus saib lub xeev xwm txheej tam sim no.
Sau cov ntaub ntawv kuv patched
Π Π΅Π·ΡΠ»ΡΡΠΈΡΡΡΡΠΈΠΉ Π½Π°Π±ΠΎΡ Π΄Π°Π½Π½ΡΡ ΡΠΎΡΡΠΎΠΈΡ ΠΈΠ· 1 583 579 Π·Π°ΠΏΠΈΡΠ΅ΠΉ (name, qtype, TTL, timestamp). ΠΠΎΡ ΠΎΠ±ΡΠ΅Π΅ ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ TTL (ΠΎΡΡ X β ΡΡΠΎ TTL Π² ΡΠ΅ΠΊΡΠ½Π΄Π°Ρ ):
Ib cag los ntawm ib qho me me ntawm 86 (feem ntau rau SOA cov ntaub ntawv), nws yog qhov tseeb zoo nkauj tias TTLs nyob rau hauv qhov qis. Cia peb saib ze dua:
Okay, TTLs ntau dua 1 teev tsis yog qhov tseem ceeb. Tom qab ntawd cia peb tsom mus rau qhov ntau ntawm 0-3600:
Feem ntau TTLs yog los ntawm 0 mus rau 15 feeb:
Feem ntau yog los ntawm 0 mus rau 5 feeb:
Nws tsis zoo heev.
ΠΠ°ΠΊΠΎΠΏΠΈΡΠ΅Π»ΡΠ½ΠΎΠ΅ ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ Π΄Π΅Π»Π°Π΅Ρ ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ Π΅ΡΡ Π±ΠΎΠ»Π΅Π΅ ΠΎΡΠ΅Π²ΠΈΠ΄Π½ΠΎΠΉ:
Ib nrab ntawm cov lus teb DNS muaj TTL ntawm 1 feeb lossis tsawg dua, thiab peb lub hlis twg muaj TTL ntawm 5 feeb lossis tsawg dua.
Tab sis tos, nws yog qhov phem dua. Tom qab tag nrho, qhov no yog TTL los ntawm cov servers tso cai. Txawm li cas los xij, cov neeg daws teeb meem (xws li routers, hauv zos caches) tau txais TTL los ntawm cov neeg daws teeb meem, thiab nws txo qis txhua ob.
Yog li tus neeg siv khoom tuaj yeem siv txhua qhov nkag rau, qhov nruab nrab, ib nrab ntawm TTL thawj zaug ua ntej xa daim ntawv thov tshiab.
Tej zaum cov TTLs tsawg heev no tsuas yog siv rau cov kev thov txawv txawv thiab tsis yog cov vev xaib nrov thiab APIs? Cia peb saib:
X axis yog TTL, Y axis yog nug qhov chaw.
Hmoov tsis zoo, cov lus nug nrov tshaj plaws kuj yog qhov phem tshaj plaws rau cache.
Wb zoom in:
Kev txiav txim: nws phem heev. Nws twb phem ua ntej lawm, tab sis nws txawm phem dua. DNS caching tau dhau los ua tsis muaj txiaj ntsig. Raws li cov neeg tsawg dua siv lawv ISP's DNS daws teeb meem (rau qhov laj thawj zoo), qhov nce hauv latency yuav pom ntau dua.
DNS caching tau dhau los ua qhov tseem ceeb rau cov ntsiab lus uas tsis muaj leej twg tuaj xyuas.
Thov nco ntsoov tias lub software yuav
Vim licas?
Vim li cas DNS cov ntaub ntawv tau teeb tsa rau qhov qis TTL?
- Legacy load balancers tau sab laug nrog kev teeb tsa ua ntej.
- Π₯ΠΎΠ΄ΡΡ ΠΌΠΈΡΡ, ΡΡΠΎ Π±Π°Π»Π°Π½ΡΠΈΡΠΎΠ²ΠΊΠ° Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΏΠΎ DNS Π·Π°Π²ΠΈΡΠΈΡ ΠΎΡ TTL (ΡΡΠΎ Π½Π΅ ΡΠ°ΠΊ β ΡΠΎ Π²ΡΠ΅ΠΌΡΠ½ Netscape Navigator ΠΊΠ»ΠΈΠ΅Π½ΡΡ Π²ΡΠ±ΠΈΡΠ°ΡΡ ΡΠ»ΡΡΠ°ΠΉΠ½ΡΠΉ IP-Π°Π΄ΡΠ΅Ρ ΠΈΠ· Π½Π°Π±ΠΎΡΠ° RR ΠΈ ΠΏΡΠΎΠ·ΡΠ°ΡΠ½ΠΎ ΠΏΡΠΎΠ±ΡΡΡ Π΄ΡΡΠ³ΠΎΠΉ, Π΅ΡΠ»ΠΈ Π½Π΅ ΠΌΠΎΠ³ΡΡ ΠΏΠΎΠ΄ΠΊΠ»ΡΡΠΈΡΡΡΡ)
- Cov thawj coj xav thov kev hloov tam sim ntawd, yog li nws yooj yim dua rau kev npaj.
- Tus thawj tswj hwm ntawm DNS server lossis load balancer pom nws txoj haujlwm ua tau zoo siv cov kev teeb tsa uas cov neeg siv thov, thiab tsis ua kom cov chaw thiab cov kev pabcuam.
- Tsawg TTLs muab kev thaj yeeb nyab xeeb rau koj.
- ΠΡΠ΄ΠΈ ΠΏΠ΅ΡΠ²ΠΎΠ½Π°ΡΠ°Π»ΡΠ½ΠΎ ΡΡΠ°Π²ΡΡ Π½ΠΈΠ·ΠΊΠΈΠ΅ TTL Π΄Π»Ρ ΡΠ΅ΡΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΈ Π·Π°Π±ΡΠ²Π°ΡΡ ΠΏΠΎΡΠΎΠΌ ΠΈΡ ΠΈΠ·ΠΌΠ΅Π½ΠΈΡΡ.
Kuv tsis suav nrog "failover" hauv daim ntawv vim tias nws tau dhau los ua tsawg thiab tsis cuam tshuam. Yog tias koj xav tau hloov cov neeg siv mus rau lwm lub network tsuas yog los tso saib nplooj ntawv yuam kev thaum txhua yam puas lawm, ncua sijhawm ntau dua 1 feeb yog qhov ua tau.
Tsis tas li ntawd, ib-feeb TTL txhais tau hais tias yog kev tso cai DNS servers raug thaiv ntau tshaj 1 feeb, tsis muaj leej twg tuaj yeem nkag mus rau cov kev pabcuam nyob. Thiab redundancy yuav tsis pab yog tias qhov ua rau yog kev teeb tsa yuam kev lossis hack. Ntawm qhov tod tes, nrog TTL tsim nyog, ntau tus neeg siv khoom yuav txuas ntxiv siv cov kev teeb tsa yav dhau los thiab tsis pom dab tsi.
Π Π½ΠΈΠ·ΠΊΠΈΡ TTL Π² Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΡΠ΅ΠΏΠ΅Π½ΠΈ Π²ΠΈΠ½ΠΎΠ²Π°ΡΡ cΠ΅ΡΠ²ΠΈΡΡ CDN ΠΈ Π±Π°Π»Π°Π½ΡΠΈΡΠΎΠ²ΡΠΈΠΊΠΈ Π½Π°Π³ΡΡΠ·ΠΊΠΈ, ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎ ΠΊΠΎΠ³Π΄Π° ΠΎΠ½ΠΈ ΠΎΠ±ΡΠ΅Π΄ΠΈΠ½ΡΡΡ CNAME Ρ ΠΌΠ°Π»ΡΠΌΠΈ TTL ΠΈ Π·Π°ΠΏΠΈΡΠΈ Ρ ΡΠ°ΠΊΠΈΠΌΠΈ ΠΆΠ΅ ΠΌΠ°Π»ΡΠΌΠΈ (Π½ΠΎ Π½Π΅Π·Π°Π²ΠΈΡΠΈΠΌΡΠΌΠΈ) TTL:
$ drill raw.githubusercontent.com raw.githubusercontent.com. 9 IN CNAME github.map.fastly.net. github.map.fastly.net. 20 IN A 151.101.128.133 github.map.fastly.net. 20 IN A 151.101.192.133 github.map.fastly.net. 20 IN A 151.101.0.133 github.map.fastly.net. 20 IN A 151.101.64.133
Thaum twg CNAME lossis ib qho ntawm A cov ntaub ntawv tas sijhawm, yuav tsum xa daim ntawv thov tshiab. Ob leeg muaj 30 thib ob TTL, tab sis nws tsis zoo ib yam. Qhov tseeb nruab nrab TTL yuav yog 15 vib nas this.
Tab sis tos! Nws tseem phem dua. Qee tus neeg daws teeb meem coj tus cwj pwm phem heev hauv qhov xwm txheej no nrog ob qhov cuam tshuam qis TTLs:
$ drill raw.githubusercontent.com @4.2.2.2 raw.githubusercontent.com. 1 IN CNAME github.map.fastly.net. github.map.fastly.net. 1 IN A 151.101.16.133
The Level3 daws tej zaum yuav khiav ntawm BIND. Yog tias koj tseem xa daim ntawv thov no, TTL ntawm 1 yuav rov qab mus tas li. Qhov tseem ceeb, raw.githubusercontent.com
yeej tsis cached.
Nov yog lwm qhov piv txwv ntawm qhov xwm txheej zoo li no nrog lub npe nrov heev:
$ drill detectportal.firefox.com @1.1.1.1 detectportal.firefox.com. 25 IN CNAME detectportal.prod.mozaws.net. detectportal.prod.mozaws.net. 26 IN CNAME detectportal.firefox.com-v2.edgesuite.net. detectportal.firefox.com-v2.edgesuite.net. 10668 IN CNAME a1089.dscd.akamai.net. a1089.dscd.akamai.net. 10 IN A 104.123.50.106 a1089.dscd.akamai.net. 10 IN A 104.123.50.88
Yam tsawg kawg peb CNAME cov ntaub ntawv. Ay. Ib tus muaj TTL zoo, tab sis nws tsis muaj txiaj ntsig kiag li. Lwm CNAMEs muaj qhov pib TTL ntawm 60 vib nas this, tab sis rau cov thawj akamai.net
Qhov siab tshaj TTL yog 20 vib nas this thiab tsis muaj leej twg nyob rau theem.
Yuav ua li cas txog cov chaw uas niaj hnub soj ntsuam Apple cov khoom siv?
$ drill 1-courier.push.apple.com @4.2.2.2 1-courier.push.apple.com. 1253 IN CNAME 1.courier-push-apple.com.akadns.net. 1.courier-push-apple.com.akadns.net. 1 IN CNAME gb-courier-4.push-apple.com.akadns.net. gb-courier-4.push-apple.com.akadns.net. 1 IN A 17.57.146.84 gb-courier-4.push-apple.com.akadns.net. 1 IN A 17.57.146.85
Cov teeb meem tib yam li Firefox thiab TTL yuav raug daig ntawm 1 thib ob feem ntau thaum siv Level3 daws teeb meem.
Dropbox?
$ laum client.dropbox.com @8.8.8.8 client.dropbox.com. 7 Hauv CNAME client.dropbox-dns.com. client.dropbox-dns.com. 59 IN A 162.125.67.3 $ laum client.dropbox.com @4.2.2.2 client.dropbox.com. 1 hauv CNAME client.dropbox-dns.com. client.dropbox-dns.com. 1 IB 162.125.64.3
Π£ Π·Π°ΠΏΠΈΡΠΈ safebrowsing.googleapis.com
TTL tus nqi yog 60 vib nas this, zoo li Facebook domains. Thiab, dua, los ntawm tus neeg siv qhov kev xav, cov txiaj ntsig no yog halved.
ΠΠ°ΠΊ Π½Π°ΡΡΡΡ ΡΡΡΠ°Π½ΠΎΠ²ΠΊΠΈ ΠΌΠΈΠ½ΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ TTL?
Siv lub npe, hom kev thov, TTL, thiab lub sijhawm khaws cia thaum xub thawj, kuv tau sau ib tsab ntawv los simulate 1,5 lab qhov kev thov dhau los ntawm kev daws teeb meem caching los kwv yees qhov ntim ntawm cov ntawv thov tsis tsim nyog xa vim qhov kev nkag mus rau cache tas sij hawm.
47,4% ntawm kev thov tau ua tom qab cov ntaub ntawv uas twb muaj lawm tau tas sijhawm. Qhov no yog qhov tsis tsim nyog siab.
Dab tsi yuav cuam tshuam rau caching yog tias qhov tsawg kawg nkaus TTL raug teeb tsa?
ΠΡΡ X β ΡΡΠΎ ΠΌΠΈΠ½ΠΈΠΌΠ°Π»ΡΠ½ΡΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΡ TTL. ΠΠ°ΠΏΠΈΡΠΈ Ρ ΠΈΡΡ ΠΎΠ΄Π½ΡΠΌΠΈ TTL Π²ΡΡΠ΅ ΡΡΠΎΠ³ΠΎ Π·Π½Π°ΡΠ΅Π½ΠΈΡ Π½Π΅ Π·Π°ΡΡΠΎΠ½ΡΡΡ.
Y axis yog qhov feem pua ββββntawm kev thov los ntawm tus neeg siv khoom uas twb muaj qhov nkag mus hauv cached, tab sis nws tau tas sij hawm thiab tab tom ua qhov kev thov tshiab.
Qhov sib faib ntawm qhov kev thov "ntxiv" raug txo los ntawm 47% mus rau 36% los ntawm kev teeb tsa qhov tsawg kawg nkaus TTL rau 5 feeb. Los ntawm kev teeb tsa TTL yam tsawg kawg nkaus rau 15 feeb, tus lej ntawm cov kev thov no poob rau 29%. Qhov tsawg kawg nkaus TTL ntawm 1 teev txo lawv mus rau 17%. Qhov txawv tseem ceeb!
Yuav ua li cas tsis hloov ib yam dab tsi ntawm server sab, tab sis hloov qhov tsawg kawg nkaus TTL hauv cov neeg siv DNS caches (routers, cov neeg daws teeb meem hauv zos)?
Tus naj npawb ntawm kev thov yuav tsum poob los ntawm 47% mus rau 34% nrog qhov tsawg kawg nkaus TTL ntawm 5 feeb, mus rau 25% nrog tsawg kawg yog 15 feeb, thiab mus rau 13% nrog tsawg kawg yog 1 teev. Tej zaum 40 feeb yog qhov zoo.
Qhov cuam tshuam ntawm qhov kev hloov me me no loj heev.
Dab tsi yog qhov tshwm sim?
ΠΠΎΠ½Π΅ΡΠ½ΠΎ, ΡΠ΅ΡΠ²ΠΈΡ ΠΌΠΎΠΆΠ½ΠΎ ΠΏΠ΅ΡΠ΅Π²Π΅ΡΡΠΈ Π½Π° Π½ΠΎΠ²ΠΎΠ³ΠΎ ΠΎΠ±Π»Π°ΡΠ½ΠΎΠ³ΠΎ ΠΏΡΠΎΠ²Π°ΠΉΠ΄Π΅ΡΠ°, Π½ΠΎΠ²ΡΠΉ ΡΠ΅ΡΠ²Π΅Ρ, Π½ΠΎΠ²ΡΡ ΡΠ΅ΡΡ, ΡΡΠ΅Π±ΡΡ ΠΎΡ ΠΊΠ»ΠΈΠ΅Π½ΡΠΎΠ² ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡ ΠΏΠΎΡΠ»Π΅Π΄Π½ΠΈΠ΅ Π·Π°ΠΏΠΈΡΠΈ DNS. Π Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ ΠΌΠ°Π»ΡΠΉ TTL ΠΏΠΎΠΌΠΎΠ³Π°Π΅Ρ ΠΏΠ»Π°Π²Π½ΠΎ ΠΈ Π½Π΅Π·Π°ΠΌΠ΅ΡΠ½ΠΎ ΠΎΡΡΡΠ΅ΡΡΠ²ΠΈΡΡ ΡΠ°ΠΊΠΎΠΉ ΠΏΠ΅ΡΠ΅Ρ ΠΎΠ΄. ΠΠΎ Ρ ΠΏΠ΅ΡΠ΅Ρ ΠΎΠ΄ΠΎΠΌ Π½Π° Π½ΠΎΠ²ΡΡ ΠΈΠ½ΡΡΠ°ΡΡΡΡΠΊΡΡΡΡ Π½ΠΈΠΊΡΠΎ Π½Π΅ ΠΎΠΆΠΈΠ΄Π°Π΅Ρ, ΡΡΠΎ ΠΊΠ»ΠΈΠ΅Π½ΡΡ ΠΏΠ΅ΡΠ΅ΠΉΠ΄ΡΡ Π½Π° Π½ΠΎΠ²ΡΠ΅ Π·Π°ΠΏΠΈΡΠΈ DNS Π² ΡΠ΅ΡΠ΅Π½ΠΈΠ΅ 1 ΠΌΠΈΠ½ΡΡΡ, 5 ΠΌΠΈΠ½ΡΡ ΠΈΠ»ΠΈ 15 ΠΌΠΈΠ½ΡΡ. Π£ΡΡΠ°Π½ΠΎΠ²ΠΊΠ° ΠΌΠΈΠ½ΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΡΠΎΠΊΠ° ΠΆΠΈΠ·Π½ΠΈ Π² 40 ΠΌΠΈΠ½ΡΡ Π²ΠΌΠ΅ΡΡΠΎ 5 ΠΌΠΈΠ½ΡΡ Π½Π΅ ΠΏΠΎΠΌΠ΅ΡΠ°Π΅Ρ ΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΠ΅Π»ΡΠΌ ΠΏΠΎΠ»ΡΡΠΈΡΡ Π΄ΠΎΡΡΡΠΏ ΠΊ ΡΠ΅ΡΠ²ΠΈΡΡ.
ΠΠ΄Π½Π°ΠΊΠΎ ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΡ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎ ΡΠΎΠΊΡΠ°ΡΠΈΡΡ Π·Π°Π΄Π΅ΡΠΆΠΊΡ ΠΈ ΠΏΠΎΠ²ΡΡΠΈΡΡ ΠΊΠΎΠ½ΡΠΈΠ΄Π΅Π½ΡΠΈΠ°Π»ΡΠ½ΠΎΡΡΡ ΠΈ Π½Π°Π΄ΡΠΆΠ½ΠΎΡΡΡ, ΠΈΠ·Π±Π΅Π³Π°Ρ Π½Π΅Π½ΡΠΆΠ½ΡΡ Π·Π°ΠΏΡΠΎΡΠΎΠ².
Tau kawg, RFCs hais tias TTL yuav tsum tau ua raws li nruj me ntsis. Tab sis qhov tseeb yog tias DNS system tau dhau los ua tsis muaj txiaj ntsig.
Yog tias koj ua haujlwm nrog DNS servers tso cai, thov xyuas koj TTLs. Koj puas xav tau cov txiaj ntsig tsis zoo li no tiag?
Tau kawg, muaj cov laj thawj zoo los teeb tsa TTL me me rau cov ntaub ntawv DNS. Tab sis tsis yog rau 75% ntawm DNS tsheb uas tseem tsis tau hloov pauv.
Π Π΅ΡΠ»ΠΈ ΠΏΠΎ ΠΊΠ°ΠΊΠΈΠΌ-ΡΠΎ ΠΏΡΠΈΡΠΈΠ½Π°ΠΌ Π²Π°ΠΌ Π΄Π΅ΠΉΡΡΠ²ΠΈΡΠ΅Π»ΡΠ½ΠΎ Π½ΡΠΆΠ½ΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡ Π½ΠΈΠ·ΠΊΠΈΠ΅ TTL Π΄Π»Ρ DNS, Π·Π°ΠΎΠ΄Π½ΠΎ ΡΠ±Π΅Π΄ΠΈΡΠ΅ΡΡ, ΡΡΠΎ Π½Π° Π²Π°ΡΠ΅ΠΌ ΡΠ°ΠΉΡΠ΅ Π½Π΅ Π²ΠΊΠ»ΡΡΠ΅Π½ΠΎ ΠΊΡΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅. ΠΠΎ ΡΠ΅ΠΌ ΠΆΠ΅ ΠΏΡΠΈΡΠΈΠ½Π°ΠΌ.
ΠΡΠ»ΠΈ Ρ Π²Π°Ρ ΡΠ°Π±ΠΎΡΠ°Π΅Ρ Π»ΠΎΠΊΠ°Π»ΡΠ½ΡΠΉ DNS-ΠΊΡΡ, ΡΠ°ΠΊΠΎΠΉ ΠΊΠ°ΠΊ
Tau qhov twg los: www.hab.com