On the Use of Anycast in DNS Sa nde e p Sa ra t Jo hns Ho pkins - PowerPoint PPT Presentation

On the Use of Anycast in DNS Sa nde e p Sa ra t Jo hns Ho pkins Unive rsity Va sile io s Pa ppa s UCL A Andre a s T e rzis Jo hns Ho pkins Unive rsity http:/ / hinrg .c s.jhu.e du/

Background • Wha t is Anyc a st? – Clie nt tra nspa re nt me c ha nism to ro ute pa c ke t to o ne o f multiple se rve rs in a nyc a st g ro up – I mple me nte d via a nno unc e me nts o f the sa me a ddre ss pre fix fro m multiple o rig ins (I GP+E GP) – De plo ye d in to p-le ve l DNS na me se rve rs • Re duc tio n in q ue ry la te nc y • Sc a la b ility • Ava ila b ility • Re sista nc e to DDo S a tta c ks 2

Goal • Me a sure the impa c t o f a nyc a st o n DNS – Re spo nse time s – Ava ila b ility in te rms o f numb e r a nd dura tio n o f o uta g e s – Co nsta nc y o f se rve r se le c tio n – E ffe c tive ne ss o f lo c a liza tio n 3

What we tested • Ba se Ca se : Unic a st se rve r – T e st-c a se : B-Ro o t (lo c a l lo a d b a la nc ing ) • Anyc a st Co nfig ura tio ns – Hie ra rc hic a l • T e st-Ca se s: F -Ro o t (26 se rve rs), K -Ro o t (7 se rve rs) – E xplo re the e ffe c t o f numb e r a nd lo c a tio ns o f se rve rs – F la t • T e st-Ca se : Ultra DNS (8 se rve rs *) 4

Measurement Methodology • Me a sure me nts using Pla ne tL a b • Spe c ia l DNS q ue rie s to the a nyc a st a ddre ss fro m e a c h PL site e ve ry [25-35] se c o nds • Pe rio d o f study: 3 we e ks fro m Se pt 19, 2004 to Oc t 8, 2004 • De finitio ns – Outa g e : Pe rio d o f time whe n q ue rie s a re una nswe re d (multiple o f me a s. pe rio d) – F lip: Clie nt switc he s fro m o ne se rve r to a no the r 5

Response Times • Anyc a st se rve rs ha ve Std. dev Server Mean Median (ms) (ms) (ms) lo we r re spo nse time s Hypo. Unicast* Flat vs. Hierarchical 45 35 13 • Ultra DNS T L D1 ha s the min{TLD1.TLD2}* 69 51 173 lo we st q ue ry la te nc y TLD1 96 54 207 F-Root 75 70 85 • Amo ng the re st, F - TLD2 104 85 237 Ro o t is the b e st B-Root 115 95 121 K-Root 140 121 104 – Re a so n: hig h g e o g ra phic dive rsity * Hypo the tic a l c a se s pure ly fo r Effect of server • Re spo nse time s ha ve c o mpa riso n location hig h de via tio ns – Due to insta b ility a s we will se e la te r 6

Availability • Pe rc e nta g e o f una nswe re d q ue rie s < 0.9% • T L D1,T L D2 ha ve the la rg e st numb e r o f o uta g e s • F -Ro o t ha s the le a st – Re a so ns (spe c ula tio n) • Ultra DNS is sing le -ho me d • L o ng e r I nte rne t pa ths • Ave ra g e inte r-o uta g e time fo r sa me c lie nt is in the o rde r o f da ys 7

8 All sc he me s sho w ro ug hly sa me b e ha vio r Outage Duration

Constancy • Co nsta nc y me a sure d b y fre q ue nc y o f flips b e twe e n se rve rs • T L D1, T L D2 ha ve mo st flips • F -Ro o t, K -Ro o t ha ve hig he r pe rc e nta g e o f flips a fte r a n o uta g e 5 o rde rs o f ma g nitude • Ma jo rity o f flips fo r F - Ro o t a nd K -Ro o t a re b e twe e n the g lo b a l no de s 9

Effectiveness of Localization 60% to 80% o f c lie nts • Que stio n: Do e s g o to the c lo se st a nyc a st le a d c lie nts to a nyc a st se rve r the c lo se st se rve r? • Dire c t c o mpa riso n fla we d due to diffe re nt ro uting pa ths fo r unic a st a nd a nyc a st a ddre sse s • So lutio n: – Co mpa re pa th use d b y a nyc a st to pa ths to a ll la st ho p ro ute rs 10

Comparison of Strategies • Hie ra rc hic a l sc he me s ha ve hig he r sta b ility a nd a va ila b ility • F la t sc he me s a re mo re e ffe c tive in dire c ting q ue rie s to the “c lo se st” a nyc a st insta nc e • Po ssib le ide a : – T une pa ra me te r to a da ptive ly c ha ng e pro pe rtie s a nyc a st sc he me – Ra dius o f a nno unc e me nt a t e a c h a nyc a st no de 11

Summary • Anyc a st impro ve s a va ila b ility • Othe r pro pe rtie s de pe nd o n the sc he me use d • T ra de -o ff b e twe e n a va ila b ility, sta b ility a nd e ffe c tive ne ss o f lo c a liza tio n • Ca ve a ts: – Re sults a pply to Pla ne t L a b e nviro nme nt – Suppo rt a rg ume nts using BGP da ta – Ske w due to lo a d o n the a nyc a st se rve r • F o r mo re : – http:/ / www.c s.jhu.e du/ ~sa ra t/ Anyc a st-T R.pdf 12