TCP/IP and DNS

SEMINAR ON TCP/IP AND DNS
By Biswadip Dey (Roll No. – 11G5MMS136)

1/1/2013 6:33 AM

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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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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OSI MODEL
Application
TELNE
T
Session


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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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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 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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 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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OSI MODEL
Application
TELN
ET
Session


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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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



R1 R3

R2
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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n


Transport Layer 2,58,53 H Mes 3,58,53 sage Transport Layer
Connec
Internet Layer 1,2 1,58,53
t Internet Layer


R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n



Connec
Data-link Layer 41,45 1,2 1,58,53
t
T Data-link Layer

R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n




Connec
Physical Layer H 41,45 1,2 1,58,53
t
T Physical Layer
R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n




Connec
Physical Layer H 46,47 1,2 1,58,53
t
T Physical Layer
R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n




Connec
Physical Layer 46,47 1,2 1,58,53
t
T Physical Layer
R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n



Connec
Data-link Layer 1,2 1,58,53
t Data-link Layer

R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n


Connec
Internet Layer 1,58,53
t Internet Layer


R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n


Transport Layer 2,58,53 H Mes 3,58,53 sage 2,53,58 Ack Transport Layer



R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n





R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n


Transport Layer 2,58,53 H Mes 3,58,53
2,58,53sage Mes
H 3,58,53 sage Transport Layer



R1 R3

R2
14

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P2 P3 P1 P1 P5 P6
99 66 58 53 46 23

Source Destinatio
n


Transport Layer 4,58,53 Close 2,58,53 H Mes 3,58,53 sage Transport Layer



R1 R3

R2
14

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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



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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INVERSE DOMAIN

 The inverse domain is used to map an
address to a name.

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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
36

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