DNS
Domain Name Server
Group: 4
Group Members Names
Bilal Virk
Sehrish Javed
Maryam Azhar
Rehan Ali
DNS
introduction
DNS (Domain Name Server)
BriefPresentation.
We could spend all Day.
Unsure about level of technical
expertise.
Stop me at any point if you have a
query.
What This Talk Is About!
What Is DNS?
Why DNS Is Needed?
History of DNS.
Hierarchy of DNS.
How Dose It Works?
What Are Zones?
What is DNS?
Computers use IP addresses for Internet
Traffic.
IP Addresses Are hard To remember
So, We use Names Instead.
What is DNS? (Cont…)
The domain name system is usually used to
translate a host name into an IP address .
Domain names comprise a hierarchy so that
names are unique, yet easy to remember.
So , We Can Say
DNS is used for name to IP resolution
&
IP to name resolution.
History of DNS
Host File System
Old Solution (host.txt)
Back in the early 80’s when the internet was called
ARPANET, consisted of few hundred computers,
servers on MIT university Campus.
Held A file that listed the names and IP address of
those few computers.
That File was Named As HOST.TXT.
When a new host was attached to ARPANET it
needed the NAMES and IPs of others computers
over ARPANET for that reason it would just contact
MIT server and download the latest Host file.
Old Solution (host.txt)
A centrally-maintained file, distributed to all
hosts on the Internet
This feature still exists
/etc/hosts[Linux]
c:\windows\system32\drivers\etc\hosts
[Windows]
128.4.13.9 SPARKY
4.98.133.7 UCB-MAILHOST
200.10.194.33 FTPHOST
Hosts.txt Doesn't Scale
✗Huge file
✗Needs frequent copying to ALL hosts
✗Consistency
✗Always out-of-date
✗Name uniqueness
✗Single point of administration
Hierarchy of DNS
Domain Levels
Hierarchy of DNS
We Offten Forget This Little Root Domain
Thing which has a huge role level Domain
TOP
in DNS
2nd Level Domain
Host ,PC
www .Yahoo .Com .
www.Yahoo.Com.
Hierarchy of DNS
. (root)
uk com net org
co.uk Yahoo.com Iso.net isoc.org nsrc.org
tiscali.co.uk www.Yahoo.com ftp.Iso.net www.isoc.org
Hierarchy of DNS
. (root)
uk com net org
co.uk Yahoo.com Iso.net isoc.org nsrc.org
tiscali.co.uk www.Yahoo.com ftp.Iso.net www.isoc.org
Example : www.yahoo.com
www.yahoo.com root
server
referral to ‘.com' DNS
Servers
www.yahoo.com .com
server
referral to ‘yahoo.com’
DNS Server
www.yahoo.com ww.yahoo.com
server
Answer:
212.74.101.10
Point To Ponder
Root Address
Root Address
In the Previous Slide We saw
Root Provided the Address for Com
Com Provided the Address for Yahoo
Yahoo Provided the Address for www.yahoo.com
But What or Who Provided The
Address For .Root Server?
Answer
There is a Term called
“ROOT HINTS”
Root Hint: On the DNS server there is a file
which contains the ROOT SERVER ADDRESS
which Holds the address for the root servers.
Thus, It Comes For the Root Server Address
File
Amazing Fact:
There Are Only 13 Root Servers on the Whole
Planet.
Non-Authoritative DNS.
Application
e.g. web Request For IP Address
browser
Caching ISP Authoritative
Resolver IP Address Found
/ DNS DNS
Authoritative DNS.
Application
e.g. web Request For IP Address
browser
Caching ISP
Resolver Found Authoritative
IP Address Not IP Address DNS
/ DNS Found
What is a resource record?
A domain contains resource records
Resource records are analogous to
files
Classified into types
Some of the important types are,
A,CNAME and MX
The “A” Record
• The “Address” record
• One or more normally defines a host
• Contains an IPv4 Address (the address computers
use to uniquely identify each other on the internet)
• Eg. The record:
www A 203.18.56.31
In the yahoo.com domain, defines the host uniquely
identifiable as “www.yahoo.com.” to be reachable
at the IPv4 Address 203.18.56.31
The “CNAME” Record
• A CNAME defines an alias
• Assign multiple names against single IP Adress
• Eg. The record:
search CNAME www.yahoo.com.
In the yahoo.com domain, defines the name
uniquely identifiable as “search.yahoo.com” to be
and alias to “www.yahoo.com”
The “MX” Record
• An MX record defines the mail servers for a
particular domain
• Mail eXchange records hold the name of hosts, and
their priorities, able to deliver mail for the domain.
• Eg. The record:
ausregistry.com.au MX 10 mail
In the ausregistry.com.au domain, defines the host
mail to be the priority 10 mail server for the
“ausregistry.com.au” domain