Transcript Domain Name System

BZUPAGES.COM
Presented to:
Sir. Muizuddin sb
Presented by:
M.Sheraz Anjum
Atif Aneaq
Khurram Shehzad
Wasif Laeq
Taha Khan
Bukhtyar Ali
Hafiz Shahrukh
Muhammad Arqum
Roll NO.07-16
Roll NO. 07-15
Roll NO. 07-32
Roll NO. 07-01
Roll NO. 07-06
Roll NO. 07-18
Roll NO. 07-22
Roll NO. 06-24
Bs(IT) 6th
Department Of Information Technology
(Institute of Computing)
B-Z-U
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Domain Name
• A domain name is an identification label
that defines a scope of administrative
autonomy, authority, or control in the
Internet, based on the Domain Name
System (DNS).
• Simply it is a user friendly name.
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Domain Name System
Definition:
It is a hierarchical naming system for
computers, services, or any resource
connected to the Internet or a private
network.
• Associates various information with
domain names assigned to each of the
participants.
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Explanation
• It translates domain names meaningful to
humans into the numerical identifiers associated
with networking equipment for the purpose of
locating and addressing these devices
worldwide.
• It serves as the "phone book" for the Internet by
translating human-friendly computer hostnames
into IP addresses.
For example: www.bzupages.com translates to
69.162.70.115.
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Characteristics
• Domain names are assigned to groups of
Internet users.
• It is independent of each user's physical
location.
• Is easier to remember than IP addresses
such as 208.77.188.166.
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An Intro To basic Authorities
• The Domain Name System distributes the
responsibility of assigning domain names and
mapping those names to IP addresses by
designating authoritative name servers for
each domain.
• Authoritative name servers are assigned to be
responsible for their particular domains, and in
turn can assign other authoritative name servers
for their sub-domains.
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Domain name space
• Consists of a tree of domain names.
• Zone(Domain) consists of a collection of
connected nodes, served by an
authoritative name server.
• Single name server can host several
zones.
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Domain name space (Cont.)
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Domain name space (Cont.)
• Administrative responsibility over any
zone may be divided, thereby creating
additional zones.
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Domain name formulation
• A domain name consists of one or more
parts called labels .
• Labels are conventionally concatenated,
by dots, such as IFhosting.com.
• The right-most label conveys the top-level
domain
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Domain name formulation (Cont)
• Descends from right to left .
• Each label to the left specifies a
subdivision, or sub domain of the domain
to the right .
• E.g in www.ifhsoting.com
• Label ifhosting is sub domain of .com and
www is the sub domain of ifhosting.com
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Domain name formulation (Cont)
• This tree of subdivisions may consist of
127 levels .
• Each label may contain up to 63
characters
• The full domain name may not exceed a
total length of 253 characters.
thelongestlistofthelongeststuffatthelongest
domainnameatlonglast.com/
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Domain name formulation (Cont)
• The characters allowed in a label are a
subset of the ASCII character set, and
includes
–
–
–
–
a through z
A through Z
digits 0 through 9
Hyphen
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Domain name formulation (Cont)
• Hostname:
It is a domain name that has at least one IP
address associated .
For example:
The domain names www.example.com and
sheikho.com are hostnames.
Whereas .com is not a hostname.
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Types of Domains
• Generic Top Level Domain (GTLD)
– E.g .com .org .net
• Country Code Top Level Domain
(CCTLD)
– E.g .pk .in .un
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Internationalized domain names
• Permitted character set of the DNS prevented the
representation of names and words of many languages
in their native alphabets.
• ICANN has approved the Punycode-based
internationalized domain name (IDNA)
• system.
– e.g ‫محمد‬.com
• In 2009 ICANN approved the installation of IDN country
code top-level domains.
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Name servers
• The Domain Name System is maintained
by a distributed database system.
• The nodes of this database are the name
servers.
• Each domain has at least one
authoritative DNS server.
• The top of the hierarchy is served by the
root name servers.
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Name servers (Cont.)
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Primary and Secondary NS
• Primary name server and secondary name servers are
required.
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Recursive and caching name server
• Every DNS query must start with recursive queries at the
root zone of the Domain Name System.
• The Domain Name System supports DNS cache
servers which store DNS query results for a period of
time.
• Many home networking routers implement DNS caches
and improve efficiency in the local network.
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DNS resolvers
• The client-side of the DNS is called a DNS resolver.
• Initiates and sequences queries.
• A DNS query may be either a non-recursive query or a
recursive query.
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Operation
•
•
•
•
Address resolution mechanism
Record caching
Client lookup
Other applications
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Address Resolution Mechanism
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Record Caching
• A mechanism to reduce the load on individual DNS
servers.
• Records are cached for a period of time after an answer.
• Time to live (TTL) time for which a resolver caches a
DNS response.
• Changes to DNS records do not propagate throughout
the network immediately
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Client lookup
•
Users generally do not communicate directly with a DNS
resolver.
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Other applications
• Hostnames and IP addresses do not necessarily match
on a one-to-one basis.
• There are many uses of DNS besides translating names
to IP addresses.
•
E-mail Blacklists
• Software Updates ( e.g an AntiVirus)
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Other applications (Cont.)
• Multiple DNS servers are usually provided for coverage
of all domains.
• Thirteen very powerful root servers exist to provide
flexibility in case of computer failure.
• Dynamic DNS (also referred to as DDNS) provides
clients the ability to update their IP address in the DNS.
– As in case of DHCP, dynamically IP addresses are
assigned to users from pool of IP addresses.
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Domain name registration
• The right to use a domain name is given by domain
name registrars.
– e.g dotcomgenie.com
• It is credited by the Internet Corporation for Assigned
Names and Numbers (ICANN).
• A registry is responsible for maintaining the database of
names registered within the Top Level Domain (TLD) it
administers.
• The registry receives registration information from each
domain name registrar authorized to assign names in
the corresponding TLD.
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Domain name registration (Cont)
• The registry publishes this information using a special
service, the WHOIS protocol.
• Some domain name registries, often called network
information centers (NIC), also function as registrars to
end-users.
• The registrants (users of a domain name) are
customers of the registrar
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Domain Tools
www.whois.domaintools.com/
Store all NS and registration information about
each WWW.
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