Domain Name System Fundamentals( Computer Industry)- A lecture delivered at USTTI

7/27/2019 Domain Name System Fundamentals( Computer Industry)- A lecture delivered at USTTI

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DNS 101

A Domain Name System Primer


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What is DNS? Domain Name System Converts domain names (easy to remember

words) to IP Addresses Is a hierarchal flat database that can be

spread out and managed by multiple entities


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DNS is a tree DNS is a hierarchal structure that allows

separate entities to manage zones of data.

The DNS tree points downward, so if youknow the top (the root), it will refer you until

you find the answer youre looking for


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The DNS TreeDNS Hierarchy

www.nike.com

Host

nike.com

Domain

.com

gTLD

www.bentley.co.uk

Host

bentley.co.uk

Domain

.co.uk

Sub-Domain

.uk

ccTLD

.pro

sTLD

.

(root)


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Resolutionhttp://www.nike.com


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Resolutionhttp://www.nike.com ISPs DNS


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Resolutionhttp://www.nike.com ISPs DNS Root Server

www.nike.com?


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www.nike.com?

IP Addresses of .comDNS servers


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www.nike.com?


.COM Servers

www.nike.com?


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www.nike.com?


.COM Servers

www.nike.com?

IP Addresses ofnike.com

DNS servers


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www.nike.com?


.COM DNS Servers

www.nike.com?


DNS servers

nike.com DNS Servers

www.nike.com?


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www.nike.com?


.COM DNS Servers

www.nike.com?


DNS servers


www.nike.com?

IP Address ofwww.nike.com

(72.246.44.212)


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www.nike.com?


.COM DNS Servers

www.nike.com?


DNS servers


www.nike.com?


(72.246.44.212)

72.246.44.212


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www.nike.com?


.COM DNS Servers

www.nike.com?


DNS servers


www.nike.com?


(72.246.44.212)

72.246.44.212

www.nike.com


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Resolution Average response time is in the milliseconds DNS servers cache results so it doesnt have to

ask unnecessary queries

Cached results hold the answers that the DNSserver has asked for the TTL (time to live) of thedomain so further queries can go directly to thedestination. (ie, once a DNS server queries,the .com servers, that is cached and all future

queries to a .com domain will bypass the root serverqueries)

Once TTL expires, DNS will go back up the treewhen querying.


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g/sTLDs (Top Level Domain)aero, biz, cat, com, coop, info,

jobs, mobi, museum, name, net,

org, pro, tel, travel, gov, mil, int


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ccTLDs (Country Code TLD)ac, ad, ae, af, ag, ai, al, am, an, ao, aq, ar, as, at, au, aw, ax, az, ba, bb,

bd, be, bf, bg, bh, bi, bj, bm, bn, bo, br, bs, bt, bv, bw, by, bz, ca, cc, cd,

cf, cg, ch, ci, ck, cl, cm, cn, co, cr, cu, cv, cx, cy, cz, de, dj, dk, dm, do,dz, ec, ee, eg, eh, er, es, et, eu, fi, fj, fk, fm, fo, fr, ga, gb, gd, ge, gf, gg,

gh, gi, gl, gm, gn, gp, gq, gr, gs, gt, gu, gw, gy, hk, hm, hn, hr, ht, hu, id,ie, il, im, in, io, iq, ir, is, it, je, jm, jo, jp, ke, kg, kh, ki, km, kn, kp, kr, kw,

ky, kz, la, lb, lc, li, lk, lr, ls, lt, lu, lv, ly, ma, mc, md, me, mg, mh, mk, ml,

mm, mn, mo, mp, mq, mr, ms, mt, mu, mv, mw, mx, my, mz, na, nc, ne,nf, ng, ni, nl, no, np, nr, nu, nz, om, pa, pe, pf, pg, ph, pk, pl, pm, pn, pr,

ps, pt, pw, py, qa, re, ro, rs, ru, rw, sa, sb, sc, sd, se, sg, sh, si, sj, sk, sl,

sm, sn, so, sr, st, su, sv, sy, sz, tc, td, tf, tg, th, tj, tk, tl, tm, tn, to, tp, tr,tt, tv, tw, tz, ua, ug, uk, um, us, uy, uz, va, vc, ve, vg, vi, vn, vu, wf, ws,

ye, yt, yu, za, zm, zw


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Resource Record Types DNS zone files hold many types of resource

records

MX - Mail ServersA / AAAA - IP address (v4 / v6) of hosts NS - Name Server


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Resources http://www.icann.org http://www.iana.org http://en.wikipedia.org/wiki/Dns


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Questions?

Domain Name System Fundamentals( Computer Industry)- A lecture delivered at USTTI

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