DNS Terminology

8/13/2019 DNS Terminology

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dyn.com @dyninc THE MASTER LIST OF DNS TERMINOLOGYFirs Ediion



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DNS can be hard o undersand and if

you’re unfamiliar wih he erminology,

learning more abou DNS can seem as

dauning as learning a new language.

To help people who are new o he

world of DNS, hose looking o learn

more, or even seasoned veerans who

wan a refresher, we’ve compiled a lis

of he need-o-know DNS erms along

wih heir definiions.

Who We Are

Dyn is he worldwide Inerne Infrasrucure as a Service (IaaS) leader,

powering Managed DNS,Traffic Managemen, Email Delivery & Email

Reporing for more han four million enerprise, small business and

personal users. Wih nearly 20 daa ceners around he world and

indusry-leading upime for over 10 years, Dyn’s commimen o cus-

omer relaionships and engineering excellence shines every day.

A Dyn, we do no discriminae beween he hobbyis, he Forune 500

company, or op sies on Alexa. We believe our users deserve premier

performance, reliabiliy, suppor and securiy – no mater wha sage

of he game hey are a. We hold ourselves o he highes sandards

and have pu a focus on engineering excellence and world-class

cusomer suppor since day one.

We are passionae abou wha we do and we love our cusomers. We

specialize in DNS and Email Delivery so hey are free o specialize in

heir own areas of experise o keep he Inerne awesome.

THE MASTER LIST OF DNS TERMINOLOGY / 1



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Table of Contents

/ 3 A Record through Cache

/ 4 CDN through DNS

/ 5 DNS Clien through GSLB

/ 6 gTLD through Namesever

/ 7 Node through Round Robin

/ 8 RTTM through Upime/Downime

Who Should

Read This?

NoviceBeginner conen is for readers who are new o

email delivery. This conen will ypically walk

you hrough he basics and give generalized

overviews of various subjecs.

Inermediae

Inermediae conen is for readers wih someexperience in email delivery. This conen will

focus on echniques and sraegies o ake your

delivery o he nex level.

ExperExper conen is for readers who are seasoned

in email delivery. This conen will focus on ad-

vanced echniques wih a heavier ech focus.




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A RecordPoins a hosname o an IPv4 address.

AAAA RecordsPoins a hosname o an IPv6 address.

Acive FailoverAcive Failover enables your websie o say up and running – all while

making he experience a seamless one for your visiors. When an ou-

age is deeced, your raffic is auomaically re-roued o an alernae

endpoin ha you have pre-configured.

AnycasDNS nework opology ha uses BGP o roue DNS queries o he

fases nameserver on he nework.

Auh CodeThe “auh code” (someimes called an “EPP code” or a “ransfer code”)

is a sring, usually beween 8 and 16 characers long and randomly cre-

aed a he ime of a domain’s regisraion, used o auhorize ransfers

in cerain Top Level Domains. The auh code provides an exra layer of

securiy over he normal ransfer reques procedures.

Auhoriaive NameserverA nameserver which has been configured o provide answers for a

specific domain, raher han simply geting and caching daa abou

domains from oher nameservers.

CacheCaching refers o a process where Recursive DNS servers remember

he resuls of a DNS Query for he ime specified in he TTL (Time

o Live). This reduces DNS query raffic as he Recursive DNS server

already knows he answer. Once he TTL expires, he answer is

removed from he cache.




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We have wo whiepapers on DDoS:Everyhing You Need To Know Abou A DDoS Atack

Defending Agains DDoS Atacks ToManaged DNS Sysems

CDNA Conen Delivery Nework is a nework of servers ha serves

conen o end users from he closes node for he fases load ime.

CNAMEA CNAME is a special ype of DNS record used o creae an alias from

one hosname o anoher. For example:

www.dyn.com is a CNAME to dyn.com

This means ha someone accessing www.dyn.com will be poined o

he same IP address ha dyn.com poins o.

This is useful so ha when your IP address changes, you only have

o updae dyn.com’s enry and hen www.dyn.com will auomaically

poin o he righ place.

Cu NodeCu nodes allow you o keep he DNS for your zone wih your curren

DNS provider, bu poin or cu a specific node over o Dyn’s nameserv-

ers, allowing you o use one of our advanced feaures.

Daa CenerDaa ceners house servers, compuer sysems, and oher elecom-

municaion componens, usually wih redundan power and specialsecuriy measures. They are designed o wihsand major naural and

man-made disasers.

DDoSDisribued Denial of Service is an atack when muliple sysems are

used o flood servers wih raffic in an atemp o overwhelm is avail-

able resources (bandwidh, memory, processing power, ec), making i

unavailable o respond o legiimae users.

Delegae

To specify in DNS which nameservers handle a specific domain or sub-domain. See delegaion.

DelegaionDelegaion, as a verb (see delegae), is he process of designaing he

nameservers for a domain. As a noun, i is used o refer o he curren

se of nameservers o which a domain has been delegaed.

DNSDNS (the Domain Name System) provides mapping of

hostnames to IP addresses and back again.


http://dyn.com/dns/whitepapers-technical-documents/








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DNS ClienAlso known as a DNS resolver, a DNS clien is he sysem ha makes a

DNS reques (e.g. your compuer, smar phone, an ATM).

DNS QueryA reques a clien sends o a DNS server o resolve he IP address for a

domain name or hosname.

DNS ZoneA porion of he DNS namespace ha has been divided up for more

granular adminisraion of DNS. Zones hold DNS records ha conain

mapping informaion.

DNSSECDNSSEC is he ac of adding special signaures o he roo, TLD, and

auhoriaive nameservers for your zone o esablish a chain of rus.

DNSSEC enabled zones ensure ha he answer o a DNS query has no

been ampered wih.

DoS

A Denial of Service is an atack on a URL ha is coming from one source.

EndpoinEnd locaion ha a clien is geting o - IP address or CNAME.

FailoverWhen your primary server goes down, failover is he ac of rerouing

raffic o a redundan server. (Also see Acive Failover.)

Forward LookupA forward lookup is when you use a hos name (domain name) o find

an IP address. Find ou your IP address: htp://checkip.dyn.com/

Fully Qualified Domain NameA fully qualified domain name is a complee hosname, like ha which

you would use when connecing o a server on he Inerne. Fully

qualified hosnames mus be used when updaing wih a clien, e.g., if

your hosname is “myhos.dnsalias.ne”, you mus provide ha enire

hosname o he clien, no simply “myhos”.

GSLBGlobal Server Load Balancing responds o DNS requess by direcing

raffic wih he bes performing server in a geographic region.


http://checkip.dyn.com/

http://checkip.dyn.com/



dyn.com @dyninc

gTLDGlobal TLDs are TLDs ha are no counry specific and can be used by

he enire Inerne communiy. Examples of gTLDs are .com, .ne, and

.org.

IP AddressAn IP address is how compuers all

over he Inerne find each oher.

I is similar o your sree address,

excep i is for compuers. IPv4

addresses look like 207.127.235.88.

IPv6 addresses look somehing

like fe80::216:3eff:fe1e:c440. They

are ofen hard o remember num-

bers, and hey cerainly don’ ell

you very much abou a compuer.Tha is why we provide aliasing

services. IP addresses can be saic

or dynamic.

ISPInerne Service Providers are hose providing heir cusomers access

o he Inerne. They are also commonly mailbox providers (e.g. AOL).

Ieraive QueryAn ieraive query commonly akes place when a name server gives

anoher name server he bes answer i has for an IP query. An example

of which is when a server asks roo he locaion of example.com, he

roo responds wih he bes answer i can o he .com name server.

LaencyLaency is he lengh of a delay ha end users experience when rying

o access conen.

Load BalancingLoad Balancing is used o disribue your raffic over several servers,

resuling in increased reliabiliy and efficiency.

MX RecordA Mail Exchanger record ells wha mail server is responsible for ac-

ceping mail for a given domain. Someimes, here can be more han

one mail server so he server wih he lowes prioriy (ha is available)

will receive he mail.

NameserverA nameserver is a server which has been se up o answer DNS queries,

and provide informaion abou a cerain se of domains.


Internet Protocol Version 4

(IPv4) was the first publicly

used version of the Internet

Protocol in 1981. Due to

IPv4 address exhaustion, the

IPv6 system was created & isslowly being integrated.



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NodeA Node in our conex is a DNS label. The pars of a domain beween

he dos. A Node can also refer o a Subdomain.

PoPA Poin of Presence is he physical locaion of a server, daa cener, ec.

Primary DNSThe DNS provider wih conrol of zone file modificaion.

PTR RecordsPTR records are a reverse lookup for an A record. Due o he naure

of DNS and he way reverse lookups work, PTR records can only be

conrolled by your ISP.

QPSQueries per Second is he measuremen used in DNS o record how

many queries a DNS server is receiving.

Recursive QueryA recursive query akes place when a DNS clien makes a reques o he

recursive server for he IP address of a hos name. The recursive server

will eiher reurn he answer or an error message ha he domain does

no exis.

Recursive ResolverThe recursive server is ypically supplied by your ISP and is he server

ha a DNS clien makes is iniial query o. Once he recursive server

receives he correc informaion abou an IP address from oher name

servers, he recursive server will cache he informaion.

RedundancyRedundancy is having more han one server available. In he siuaion

of a failure, a redundan server can be used as a backup.

Reverse lookupLooking up an IP address o rerieve a hos name.

RooThe roo servers are nameservers ha all oher nameservers on he

Inerne know abou, and conain very basic informaion abou he

DNS sysem, which will lead oher servers along he pah o finding

ou specific informaion abou a hos.

B

L

E

F

I

ACJ

K

MD

HG

Global RootServer Locations




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Round RobinDisribue server load evenly across muliple servers.

RTTMReal Time Traffic Managemen moniors all of your endpoins o

deec he bes-performing one and provides you wih he loweslaency possible. RTTM collecs real-ime daa o rack he load ime

of each of your endpoins, raher han jus rouing your raffic o he

closes geographical daa cener.

Secondary DNSSecondary DNS provides backup DNS servers ha download informa-

ion from your primary DNS server and share is load. Secondary DNS

servers essenially have a read-only copy of he zone ha says in sync

wih he maser or primary DNS server.

SoA RecordSar of Auhoriy record indicaes he DNS server wih he bes source

of informaion in a zone along wih some basic zone configuraionsetings. I has he mos auhoriy o make changes in he domain or

answer quesions.

Traffic ManagemenTraffic Managemen is an advanced feaure ha allows for he weigh-

ed disribuion of applicaion load beween global daa ceners, cloud

providers, or your exising CDNs based on seven geographic regions.

This gives cusomers he flexibiliy o roue raffic in each region o he

opimal endpoins in heir infrasrucure.

TLDTop Level Domain - .com, .ne, .org, ec.

TTLTTL is he amoun of ime in seconds ha a DNS record will be cached

by an ouside DNS server.

TXT RecordsTXT records are used o sore informaion. Common uses include SPF,

DKIM, ec.

UnicasIn a Unicas nework, here is only one responding server.

Upime/DownimeUpime and Downime refer o if a server is currenly acive or is

unavailable, respecively.

Learn how Dyn does RTTM and Traffic Managemen

© 2013 Dyn. All rights reserved. DynECT is a trademark or registered trademark of Dyn and such marks are protected by law.THE MASTER LIST OF DNS TERMINOLOGY / 8

Questions in regards to your Managed DNS infrastructure? +1 888 840 3258 [email protected] htp://dyn.com

http://dyn.com/dns/dynect-managed-dns/real-time-traffic-management-rttm/

http://dyn.com/dns/dynect-managed-dns/traffic-management-load-balancing-round-robin-cdn-manager/

http://dyn.com/dns/dynect-managed-dns/traffic-management-load-balancing-round-robin-cdn-manager/

http://dyn.com/dns/dynect-managed-dns/real-time-traffic-management-rttm/

DNS Terminology

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