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CONTENTS
WHAT IS TCP/IP
ARCHITECTURE OF TCP/IP
HOW TCP/IP WORKS
DIFFERENCE BETWEEN TCP/IP AND OSI
WHAT IS DNS
DOMAIN NAME SPACE
DNS SERVERS AND DIFFERENT TYPES OF DNS
SERVERS
TYPES OF DNS
RESOLVER AND RESOLUTION TECHINQUES
REFERENCES
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WHAT IS TCP/IP?
TCP/IP is named after its two primary
protocol TCP and IP.
TCP/IP stands for Transmission Control
Protocol / Internet Protocol.
TCP/IP defines how electronic devices (like
computers) should be connected to each
other, and how data should be transmitted
between them.
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ARCHITECTURE OF TCP/IP
OSI MODEL
Application
TELNE
Presentation DNS SMTP FTP HTTP … Application
T
Session
Transport SCTP TCP UDP Transport
ICMP IGMP
Network IP Internet
RARP ARP
Data Link
Physical
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PHYSICAL LAYER
The physical layer is responsible for moving
individual bits between two hops or node.
It defines Transmission Rate (the number of
bits sent each second).
It is responsible for synchronization of bits.
The physical layer is also concerned with the
physical topology.
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ARCHITECTURE OF TCP/IP
OSI MODEL
Application
TELNE
Presentation DNS SMTP FTP HTTP … Application
T
Session
Transport SCTP TCP UDP Transport
ICMP IGMP
Network IP Internet
RARP ARP
Data Link
Physical
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DATA LINK LAYER
The data link layer is responsible for error
control and flow control.
Here the unit of communication is a frame.
The header of frame contains source
address and destination address along with
other information.
The trailer of frame is used to achieve error
control mechanism.
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ARCHITECTURE OF TCP/IP
OSI MODEL
Application
TELNE
Presentation DNS SMTP FTP HTTP … Application
T
Session
Transport SCTP TCP UDP Transport
ICMP IGMP
Network IP RAR Internet
ARP
P
Data Link
Physical
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INTERNET LAYER
At the Internet layer, TCP/IP supports the
Internet Protocol (IP).
IP transports data in packets called
datagrams.
Datagrams can travel along different routes.
IP does not keep track of the routes and has
no facility for reordering datagrams once they
arrive at their destination.
Communication at the internet layer is end-
to-end.
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INTERNET LAYER (CONTINUES…)
ARP (Address Resolution Protocol) is used to
associate a logical address to its corresponding
physical address.
RARP (Reverse Address Resolution Protocol) allows
a host to discover its logical address when it knows
only its physical address.
ICMP (Internet Control Message Protocol) is used by
hosts and gateways to send notification of datagram
problems, back to the sender.
IGMP (Internet Group Message Protocol) is used to
facilitate the simultaneous transmission of message
to a group of recipients.
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ARCHITECTURE OF TCP/IP
OSI MODEL
Application
TELNE
Presentation DNS SMTP FTP HTTP … Application
T
Session
Transport SCTP TCP UDP Transport
ICMP IGMP
Network IP Internet
RARP ARP
Data Link
Physical
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TRANSPORT LAYER
The transport layer is responsible for delivering
the whole message (also called user datagram
or segment) from source process to destination
process.
The communication at this layer is process-to-
process.
Transport layer defines three protocol namely
UDP (User Datagram Protocol), TCP
(Transmission Control Protocol) & SCTP
(Stream Control Transmission Protocol)
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TRANSPORT LAYER (CONTINUES…)
UDP does not create any virtual connection between
the source and destination processes, so it is a
connectionless protocol.
UDP does not support acknowledgement , so it is a
unreliable protocol.
UDP uses port numbers to create a process-to-
process communication.
UDP does provide error control to some extent.
If UDP detects an error in the received packet, it
silently drops it.
UDP packets are called user datagrams.
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TRANSPORT LAYER (CONTINUES…)
TCP creates a virtual connection before
sending packet, so it is connection oriented
protocol.
TCP supports acknowledgement, so it is a
reliable protocol.
TCP uses port numbers to provides process-
to-process communication.
TCP is a stream-oriented protocol.
A packet in TCP is called a segment.
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TRANSPORT LAYER (CONTINUES…)
SCTP combines the best features of UDP
and TCP.
SCTP is a reliable message oriented
protocol.
It preserves the message boundaries and at
the same time detects lost data, duplicate
data, and out-of-order data.
It also has congestion control and flow
control mechanisms.
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16. 1/1/2013 6:33 AM
ARCHITECTURE OF TCP/IP
OSI MODEL
Application
TELN
Presentation DNS SMTP FTP HTTP … Application
ET
Session
Transport SCTP TCP UDP Transport
ICMP IGMP
Network IP Internet
RARP ARP
Data Link
Physical
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APPLICATION LAYER
The application layer in TCP/IP is equivalent to
the combined session, presentation, and
application layers in the OSI model.
The application layer allows a user to access
the services of our private internet or the global
Internet.
Many protocols are defined at this layer to
provide services such as electronic mail, file
transfer, accessing the World Wide Web, and so
on.
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PUTTING ALL TOGETHER
P2 P3 P1 Message P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer H Message Application Layer
Connec
Transport Layer 1,58,53
t
2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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20. 1/1/2013 6:33 AM
PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Connec
Internet Layer 1,2 1,58,53
t Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Connec
Data-link Layer 41,45 1,2 1,58,53
t
T Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Connec
Physical Layer H 41,45 1,2 1,58,53
t
T Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Connec
Physical Layer H 46,47 1,2 1,58,53
t
T Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Connec
Physical Layer 46,47 1,2 1,58,53
t
T Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Connec
Data-link Layer 1,2 1,58,53
t Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Connec
Internet Layer 1,58,53
t Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage 2,53,58 Ack Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 2,58,53 H Mes 3,58,53
2,58,53sage Mes
H 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
14
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Application Layer
Transport Layer 4,58,53 Close 2,58,53 H Mes 3,58,53 sage Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
14
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PUTTING ALL TOGETHER
P2 P3 P1 P1 P5 P6
99 66 58 53 46 23
Source Destinatio
n
Application Layer Message Application Layer
Transport Layer H Message Transport Layer
Internet Layer Internet Layer
Data-link Layer Data-link Layer
Physical Layer Physical Layer
R1 R3
R2
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COMPARISONS BETWEEN TCP/IP AND OSI
When we compare the two models, we find
that two layers, session and presentation,
are missing from the TCP/IP protocol suite.
The OSI Model specifies which function
belongs to each of its layers. Whereas
TCP/IP defines protocols for each layer
which provides a specific functionality, the
protocols are not necessarily interdependent.
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WHAT IS DNS?
Domain Name System (DNS) is a
hierarchical distributed database system that
translates a computer's fully qualified domain
name into an IP address or vise versa.
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DOMAIN NAME SPACE
It is a hierarchical name space.
It is an inverted-tree structure with root at the
top.
Each node in the tree has a label, which is a
string with a maximum of 63 characters.
The root is labeled by null string (.).
Children of each node have unique labels.
A domain name is a sequence of labels
separated by dots (.).
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DOMAIN NAME SPACE (CONTINUES…)
If a sequence of labels is terminated by a null string
(.), it is called a fully qualified domain name
(FQDN).
If a sequence of labels is not terminated by a null
string, it is called a partially qualified domain name
(PQDN). 18
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DOMAIN NAME SPACE (CONTINUES…)
A domain is a subtree of the domain name
space.
The name of the domain is the name of the
node at the top of the subtree.
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DNS SERVERS
This are the servers which stores the
information about its domain and
subdomains.
Each server is responsible for keeping the
information about its domain and
subdomains. The undertaking domain and
subdomains forms a zone.
Each DNS servers maintains a database
known as zone file to keep the information
about its zone.
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DIFFERENT TYPES OF DNS SERVERS
Root Server
Primary DNS Server
Secondary DNS Server
Cache Only DNS Server
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ROOT SERVER
A root server is a server whose zone
consists of all the other DNS servers.
The root server does not keep information
about its undertaking DNS servers.
It rather keeps a reference to the those DNS
servers.
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PRIMARY DNS SERVER
A Primary DNS Server is a server that
stores a file about the zone for which it is an
authority.
It is responsible for creating, maintaining,
and updating the zone file.
It stores the zone file on a local disk.
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SECONDARY DNS SERVER
A Secondary DNS Server is a server that
gathers the complete information (zone file)
about a zone from another server (primary or
secondary) and stores the file on its local
disk.
The secondary server neither creates nor
updates the zone files.
If updating is required, it must be done by the
Primary DNS Server, which sends the
updated version to the Secondary DNS
server. 24
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PURPOSE OF PRIMARY & SECONDARY DNS SERVER
Zone Zone
File File
Secondary
Primary DNS Server
DNS Server
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CACHE ONLY DNS SERVER
To speed up the resolution this server is
used.
It caches the mapping information before
sending the response to the client.
If the same or another client ask for the same
mapping then it resolve the problem by itself
rather going to the authoritative source.
It uses a TTL (Time-To-Live) to validate the
mapping.
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WORKING PRINCIPAL OF CACHE ONLY DNS SERVER
Authoritative
DNS Server
Cache Only INFORMATIO INFORMATIO
DNS Server N N
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TYPES OF DNS
In the Internet, the domain name space (tree)
is divided into three different sections:
generic domains, country domains, and the
inverse domain.
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GENERIC DOMAIN
The generic domains define registered
hosts according to their generic behavior.
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COUNTRY DOMAIN
The country domains section uses two-
character country abbreviations.
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WHAT IS RESOLVER
Resolver is a DNS client.
It gets the request from its host’s processes
and searches its nearest DNS server.
After getting the response from server it
transfers the result to the host’s process that
requested it.
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RESOLUTION
Mapping a name to an address or an
address to a name is called name-address
resolution.
There are two types of resolutions
techniques, Recursive Resolution and
Iterative Resolution.
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RECURSIVE RESOLUTION
root server
edu
com
exam.ed
u
yahoo.com
Client
Requests: yahoo.com
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ITERATIVE RESOLUTION
root server
edu
com
exam.ed
u
yahoo.com
Client
Requests: yahoo.com
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REFERENCES
Data Communications and Networking
(Fourth Edition) By Behrouz A Forouzan,
Published by McGraw-Hill
Computer Networks (Fourth Edition) By
Andrew S. Tanenbaum, Published by
Pearson Education
TCP/IP Protocol Suite (Fourth Edition) By
Behrouz A Forouzan, Published by McGraw-
Hill
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