BCA

COMPUTER NETWORKS
2 MARKS

1.What is a computer network?

A computer network is a system that connects numerous independent computers in
order to share information (data) and resources. The integration of computers and other
different devices allows users to communicate more easily.
A computer network is a collection of two or more computer systems that are linked
together. A network connection can be established using either cable or wireless media.
Hardware and software are used to connect computers and tools in any network.

2.What are the different types of area networks?

There are four types of computer network. they are:
i)LAN
ii)WAN
iii)MAN
iv)PAN

3.Define network protocol?

Network Protocols are a set of guidelines governing the exchange of
information in a simple, dependable and secure way. Network protocols are
formal standards and policies comprised of rules, methodology, and
configurations that define communication between two or more devices over a
network.

4.What are the components of transmission medium?

The five components are:
1. Message - It is the information to be communicated. Popular
forms of information include text, pictures, audio, video etc.
2. Sender - It is the device which sends the data messages. It can be
a computer, workstation, telephone handset etc.
3. Receiver - It is the device which receives the data messages. It
can be a computer, workstation, telephone handset etc.
4. Transmission Medium - It is the physical path by which a
message travels from sender to receiver. Some examples include
twisted-pair wire, coaxial cable, radiowaves etc.
5. Protocol - It is a set of rules that governs the data
communications. It represents an agreement between the
communicating devices. Without a protocol, two devices may be
connected but not communicating.

4.What are the key elements of protocol?

 KEY ELEMENTS OF PROTOCOL
 Syntax: Refers to the structure or format of the data, meaning the
order in which they are presented.
 Semantics: Refers to the meaning of each section of bits.
 Timing: Refers to two characteristics. (1). When data should be
sent and (2). How fast they can be sent.

5.What is ARPANET?
ARPANET stands for Advanced Research Projects Agency NET.
ARPANET was first network which consisted of distributed control. It was first to
implement TCP/IP protocols. It was basically beginning of Internet with use of
these technologies. It was designed with a basic idea in mind that was to
communicate with scientific users among an institute or university.

ARPANET was introduced in the year 1969 by Advanced Research Projects

Agency (ARPA) of US Department of Defense. It was established using a bunch of
PCs at various colleges and sharing of information and messages was done. It was
for playing as long separation diversions and individuals were asked to share their
perspectives. In the year 1980, ARPANET was handed over to different military
network, Defense Data Network.

6 .What is OSI model and its types?

OSI stands for Open Systems Interconnection. It was developed by ISO –
‘International Organization for Standardization’, in the year 1984. It is a 7-layer
architecture with each layer having specific functionality to perform. OSI model
divides the whole task into seven smaller and manageable tasks. Each layer is
assigned a particular task.Each layer is self-contained, so that task assigned to each
layer can be performed independently.

There are the seven OSI layers. Each layer has different functions. A list of seven layers
are given below:

1. Physical Layer
2. Data-Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

7.What is meant by internetworking and it types?

 Internetworking started as a way to connect disparate types
of computer networking technology. Computer network term is used to describe
two or more computers that are linked to each other. When two or more
computer LANs or WANs or computer network segments are connected using
devices such as a router and configure by logical addressing scheme with
a protocol such as IP, then it is called as computer internetworking.

Extranet, Intranet, and Internet are three types of internetwork. Extranet refers to a
controlled and secure extension of an organization's internal network that allows
authorized external parties to access certain resources, services, and information.

8.Define Internet?
Internet is a global network that connects billions of computers
across the world with each other and to the World Wide Web. It uses standard
internet protocol suite (TCP/IP) to connect billions of computer users
worldwide. It is set up by using cables such as optical fibers and other wireless
and networking technologies. At present, internet is the fastest mean of sending
or exchanging information and data between computers across the world. It is
believed that the internet was developed by "Defense Advanced Projects
Agency" (DARPA) department of the United States. And, it was first connected
in 1969.

9.Define jitter?
Jitter is a problem that if different packets of data encounter different delays
and the application using the data at the receiver site is time-sensitive
(audio and video data, for example).If the delay for the first packet is 20 ms,
for the second is 45 ms, and for the third is 40 ms, then the real-time
application that uses the packets endures jitter.
10.Define IP address?

IP addresses are reserved by the Internet Assigned Numbers Authority (IANA).

These are typically reserved for networks that carry a specific purpose on
the Transmission Control Protocol/Internet Protocol (TCP/IP), which is used to
interconnect devices. Four of these IP address classes include:

1. 0.0.0.0: This IP address in IPv4 is also known as the default network. It is the non-
routeable meta address that designates an invalid, non-applicable, or unknown
network target.
2. 127.0.0.1: This IP address is known as the loopback address, which a computer uses
to identify itself regardless of whether it has been assigned an IP address.
3. 169.254.0.1 to 169.254.254.254: A range of addresses that are automatically
assigned if a computer is unsuccessful in an attempt to receive an address from the
DHCP.
 4. 255.255.255.255: An address dedicated to messages that need to be sent to every
computer on a network or broadcasted across a network.

Further reserved IP addresses are for what is known as subnet classes. Subnetworks are
small computer networks that connect to a bigger network via a router. The subnet can be
assigned its own IP address system, so that all devices connecting to it can communicate
with each other without having to send data via the wider network.

10 MARKS

1.Explain in detail about the types of computer network?

A computer network is a group of computers linked to each other that enables

the computer to communicate with another computer and share their resources,
data, and applications.

A computer network can be categorized by their size. A computer network is

mainly of four types:
o LAN(Local Area Network)
o PAN(Personal Area Network)
o MAN(Metropolitan Area Network)
o WAN(Wide Area Network)

LAN(Local Area Network)

o Local Area Network is a group of computers connected to each other in a small

area such as building, office.
o LAN is used for connecting two or more personal computers through a
communication medium such as twisted pair, coaxial cable, etc.
o It is less costly as it is built with inexpensive hardware such as hubs, network
adapters, and ethernet cables.
o The data is transferred at an extremely faster rate in Local Area Network.
o Local Area Network provides higher security.

PAN(Personal Area Network)

o Personal Area Network is a network arranged within an individual person,

typically within a range of 10 meters.
o Personal Area Network is used for connecting the computer devices of personal
use is known as Personal Area Network.
o Thomas Zimmerman was the first research scientist to bring the idea of the
Personal Area Network.
o Personal Area Network covers an area of 30 feet.
o Personal computer devices that are used to develop the personal area network
are the laptop, mobile phones, media player and play stations.
 There are two types of Personal Area Network:

MAN(Metropolitan Area Network)

o A metropolitan area network is a network that covers a larger geographic area

by interconnecting a different LAN to form a larger network.
o Government agencies use MAN to connect to the citizens and private industries.
o In MAN, various LANs are connected to each other through a telephone
exchange line.
o The most widely used protocols in MAN are RS-232, Frame Relay, ATM,
ISDN, OC-3, ADSL, etc.
o It has a higher range than Local Area Network(LAN).

Uses Of Metropolitan Area Network:

o MAN is used in communication between the banks in a city.
o It can be used in an Airline Reservation.
o It can be used in a college within a city.
o It can also be used for communication in the military.
 WAN(Wide Area Network)

o A Wide Area Network is a network that extends over a large geographical area
such as states or countries.
o A Wide Area Network is quite bigger network than the LAN.
o A Wide Area Network is not limited to a single location, but it spans over a
large geographical area through a telephone line, fibre optic cable or satellite
links.
o The internet is one of the biggest WAN in the world.
o A Wide Area Network is widely used in the field of Business, government, and
education.

Examples Of Wide Area Network:

o Mobile Broadband: A 4G network is widely used across a region or country.
o Last mile: A telecom company is used to provide the internet services to the
customers in hundreds of cities by connecting their home with fiber.
o Private network: A bank provides a private network that connects the 44 offices.
This network is made by using the telephone leased line provided by the telecom
company.
o

2.Explain topologies of network?

Two or more devices connect to a link. Two or more links form a

topology.Topology is defined as
(1) The way in which a network is laid out physically.
(2) The geometric representation of the relationship of all the links and nodes to
one-another.
The various types of topologies are : Bus, Ring, Tree, Star, Mesh and Hybrid.

BUS TOPOLOGY

 Bus topology is a network type in which every computer and network device
is connected to single cable.
 The long single cable acts as a backbone to link all the devices in a network.
 When it has exactly two endpoints, then it is called Linear Bus topology.
 It transmits data only in one direction.

Advantages of Bus Topology Disadvantages of Bus Topology

1. It is cost effective. 1. Cables fails then whole network fails.
2. Cable required is least compared to 2. If network traffic is heavy or nodes are
other network topology. more, the performance of the network
3. Used in small networks. decreases.
4. It is easy to understand. 3. Cable has a limited length.
5. Easy to expand joining two cables 4. It is slower than the ring topology.
together
 RING TOPOLOGY

 In a ring topology, each device has a dedicated point-to-point connection

with only the two devices on either side of it.
 A signal is passed along the ring in one direction, from device to device, until
it reaches its destination.
 Each device in the ring incorporates a repeater.
 When a device receives a signal intended for another device, its repeater
regenerates the bits and passes them along.

Advantages of Ring Topology Disadvantages of Ring Topology

1. Transmitting network is not affected by 1. Troubleshooting is difficult in ring
high traffic or by adding more nodes, topology.
as only the nodes having tokens can 2. Adding or deleting the computers
transmit data. disturbs the network activity.
2. Cheap to install and expand 3. Failure of one computer disturbs the
whole network

TREE TOPOLOGY

 It has a root node and all other nodes are connected to it forming a hierarchy.
 It is also called hierarchical topology.
 It should at least have three levels to the hierarchy.
 Tree topology is ideal if workstations are located in groups.
 They are used in Wide Area Network.

Advantages of Tree Topology Disadvantages of Tree Topology

1. Extension of bus and star topologies. 1. Heavily cabled.
2. Expansion of nodes is possible and easy. 2. Costly.
3. Easily managed and maintained. 3. If more nodes are added maintenance is
4. Error detection is easily done. difficult.
4. Central hub fails, network fails.
 STAR TOPOLOGY

 In a star topology, each device has a dedicated point-to-point link only to

a central controller, usually called a hub.
 The devices are not directly linked to one another.
 The controller acts as an exchange.
 If one device wants to send data to another, it sends the data to the
controller, which then relays the data to the other connected device.
Advantages of Star Topology

1. Fast performance with few nodes and low network traffic.

2. Hub can be upgraded easily.
3. Easy to troubleshoot.
4. Easy to setup and modify.
5. Only that node is affected which has failed, rest of the nodes can work smoothly
Disadvantages of Star Topology
1. Cost of installation is high.
2. Expensive to use.
3. If the hub fails, then the whole network is stopped.
4. Performance is based on the hub that is it depends on its capacity

MESH TOPOLOGY

 In a mesh topology, every device has a dedicated point-to-point link to

every other device.
 The term dedicated means that the link carries traffic only between the
two devices it connects.
 The number of physical links in a fully connected mesh network with n nodes
is given by n (n – 1) / 2.
 Advantages of Mesh Topology
1. Each connection can carry its own data load.
2. It is robust.
3. Fault is diagnosed easily.
4. Provides security and privacy.

Disadvantages of Mesh Topology

1. Installation and configuration is difficult.
2. Cabling cost is more.
3. Bulk wiring is required.

HYBRID TOPOLOGY

 Hybrid Topology is a combination of one or more basic topologies.

 For example if one department in an office uses ring topology, the other
departments uses star and bus topology, then connecting these topologies will
result in Hybrid Topology.
 Hybrid Topology inherits the advantages and disadvantages of the topologies
included.

Advantages of Hybrid Topology Disadvantages of Hybrid Topology

1. Reliable as Error detecting and trouble 1. Complex in design.
shooting is easy. 2. Costly
2. Effective.
3. Scalable as size can be increased easily.
4. Flexible.
3.Explain in detail about TRANSMISSION MODES?

o The way in which data is transmitted from one device to another

device is known as transmission mode.
o The transmission mode is also known as the communication mode.
o Each communication channel has a direction associated with it,
and transmission media provide the direction. Therefore, the
transmission mode is also known as a directional mode.
o The transmission mode is defined in the physical layer.

Types of Transmission mode

The Transmission mode is divided into three categories:

o Simplex Mode
o Half-duplex Mode
o Full-duplex mode (Duplex Mode)

SIMPLEX MODE

o In Simplex mode, the communication is unidirectional, i.e., the

data flow in one direction.
o A device can only send the data but cannot receive it or it can
receive the data but cannot send the data.
o This transmission mode is not very popular as mainly
communications require the two-way exchange of data. The
simplex mode is used in the business field as in sales that do not
require any corresponding reply.
o The radio station is a simplex channel as it transmits the signal to
the listeners but never allows them to transmit back.
o Keyboard and Monitor are the examples of the simplex mode as
a keyboard can only accept the data from the user and monitor can
 only be used to display the data on the screen.
o The main advantage of the simplex mode is that the full
capacity of the communication channel can be utilized
during transmission.

Advantage of Simplex mode:

o In simplex mode, the station can utilize the entire
bandwidth of the communication channel, so that more
data can be transmitted at a time.

Disadvantage of Simplex mode:

o Communication is unidirectional, so it has no inter-
communication between devices.

HALF-DUPLEX MODE

o In a Half-duplex channel, direction can be reversed, i.e., the

station can transmit and receive the data as well.
o Messages flow in both the directions, but not at the same time.
o The entire bandwidth of the communication channel is utilized in
one direction at a time.
o In half-duplex mode, it is possible to perform the error detection,
and if any error occurs, then the receiver requests the sender to
retransmit the data.
o A Walkie-talkie is an example of the Half-duplex mode.
o In Walkie-talkie, one party speaks, and another party listens. After
a pause, the other speaks and first party listens. Speaking
simultaneously will create the distorted sound which cannot be
understood.
Advantage of Half-duplex mode:
o In half-duplex mode, both the devices can send and receive the
data and also can utilize the entire bandwidth of the
communication channel during the transmission of data.

Disadvantage of Half-Duplex mode:

o In half-duplex mode, when one device is sending the data,
then another has to wait, this causes the delay in sending the
data at the right time.

FULL-DUPLEX MODE

o In Full duplex mode, the communication is bi-directional, i.e.,

the data flow in both the directions.
o Both the stations can send and receive the message simultaneously.
o Full-duplex mode has two simplex channels. One channel has
traffic moving in one direction, and another channel has traffic
flowing in the opposite direction.
o The Full-duplex mode is the fastest mode of communication between
devices.
o The most common example of the full-duplex mode is a
Telephone network. When two people are communicating
with each other by a telephone line, both can talk and listen at
the same time.
Advantage of Full-duplex mode:
o Both the stations can send and receive the data at the same time.

Disadvantage of Full-duplex mode:

o If there is no dedicated path exists between the devices, then the
capacity of the communication channel is divided into two
parts.
COMPARISON - SIMPLEX, HALF-DUPLEX AND FULL-DUPLEX MODE

BASIS FOR SIMPLE HALF- FULL-

COMPARISO X DUPLEX DUPLEX
N MODE MODE MODE
Direction of Communication Communication Communicatio
communicatio is unidirectional. is bidirectional, n is
n but one at a bidirectional.
time.
Send/Receive A device can Both the Both the
only send the devices can devices can
data but cannot send and send and
receive it or it receive the receive the
can only receive data, but one at data
the data but a time. simultaneously
cannot send it. .
Example Radio, Walkie-Talkie Telephon
Keyboard, and e
monitor. network.

3.Explain in detail about OSI model

o OSI stands for Open System Interconnection.
o It is a reference model that describes how information from a software
application in one computer moves through a physical medium to the software
application in another computer.
o OSI consists of seven layers, and each layer performs a particular network
function.
o OSI model was developed by the International Organization for Standardization
(ISO) in 1984, and it is now considered as an architectural model for the inter-
computer communications.
o OSI model divides the whole task into seven smaller and manageable tasks.
Each layer is assigned a particular task.
o Each layer is self-contained, so that task assigned to each layer can be performed
independently.

ORGANIZATION OF THE OSI LAYERS

FUNCTIONS OF THE OSI LAYERS
1. PHYSICAL LAYER

The physical layer coordinates the functions required to transmit a bit stream
over a physical medium.
The physical layer is concerned with the following functions:
 Physical characteristics of interfaces and media - The physical layer
defines the characteristics of the interface between the devices and the
transmission medium.
 Representation of bits - To transmit the stream of bits, it must be encoded to
signals. The physical layer defines the type of encoding.
 Signals: It determines the type of the signal used for transmitting the
information.
 Data Rate or Transmission rate - The number of bits sent each second –is also
defined by the physical layer.
 Synchronization of bits - The sender and receiver must be synchronized at
the bit level. Their clocks must be synchronized.
 Line Configuration - In a point-to-point configuration, two devices are
connected together through a dedicated link. In a multipoint configuration, a link
is shared between several devices.
 Physical Topology - The physical topology defines how devices are connected
to make a network. Devices can be connected using a mesh, bus, star or ring
topology.

 Transmission Mode - The physical layer also defines the direction of

transmission between two devices: simplex, half-duplex or full-duplex.

2. DATA LINK LAYER

It is responsible for transmitting frames from one node to the next node. The
other responsibilities of this layer are
 Framing - Divides the stream of bits received into data units called frames.
 Physical addressing – If frames are to be distributed to different systems on the
network , data link layer adds a header to the frame to define the sender and
receiver.
 Flow control- If the rate at which the data are absorbed by the receiver is
less than the rate produced in the sender ,the Data link layer imposes a flow ctrl
mechanism.
 Error control- Used for detecting and retransmitting damaged or lost frames
and to prevent duplication of frames. This is achieved through a trailer added at
the end of the frame.
 Medium Access control -Used to determine which device has control over the
link at any given time.
3. NETWORK LAYER

This layer is responsible for the delivery of packets from source to

destination.
It determines the best path to move data from source to the destination
based on the network conditions, the priority of service, and other factors.
The other responsibilities of this layer are
 Logical addressing - If a packet passes the network boundary, we need another
addressing system for source and destination called logical address. This
addressing is used to identify the device on the internet.
 Routing – Routing is the major component of the network layer, and it
determines the best optimal path out of the multiple paths from source to the
destination.

4. TRANSPORT LAYER

It is responsible for Process to Process delivery. That is responsible for source-

to- destination (end-to-end) delivery of the entire message, It also ensures
whether the message arrives in order or not.
The other responsibilities of this layer are
 Port addressing / Service Point addressing - The header includes an address
called port address / service point address. This layer gets the entire message to
the correct process on that computer.
 Segmentation and reassembly - The message is divided into segments and
each segment is assigned a sequence number. These numbers are arranged
correctly on the arrival side by this layer.
 Connection control - This can either be connectionless or connection
oriented.
 The connectionless treats each segment as an individual packet and delivers to
the destination.
 The connection-oriented makes connection on the destination side before the
delivery. After the delivery the termination will be terminated.
 Flow control - The transport layer also responsible for flow
control but it is performed end-to-end rather than across a single link.
 Error Control - Error control is performed end-to-end rather than across
the single link..

5. SESSION LAYER

This layer establishes, manages and terminates connections between

applications. The other responsibilities of this layer are
 Dialog control - Session layer acts as a dialog controller that creates a dialog
between two processes or we can say that it allows the communication between
two processes which can be either half-duplex or full-duplex.
 Synchronization- Session layer adds some checkpoints when transmitting the
data in a sequence. If some error occurs in the middle of the transmission of
 data, then the transmission will take place again from the checkpoint. This
process is known as Synchronization and recovery.
6. PRESENTATION LAYER

It is concerned with the syntax and semantics of information exchanged

between two systems.
The other responsibilities of this layer are
 Translation – Different computers use different encoding system, this layer is
responsible for interoperability between these different encoding methods. It
will change the message into some common format.
 Encryption and decryption-It means that sender transforms the original
information to another form and sends the resulting message over the n/w. and
vice versa.
 Compression and expansion-Compression reduces the number of bits
contained in the information particularly in text, audio and video.

7. APPLICATION LAYER
This layer enables the user to access the network. It handles issues such as
network transparency, resource allocation, etc. This allows the user to log on to
remote user.
The other responsibilities of this layer are
 FTAM (File Transfer, Access, Management) - Allows user to access files in
a remote host.
 Mail services - Provides email forwarding and storage.
 Directory services - Provides database sources to access information about
various sources and objects.

5.Explain TCP/IP ?
 The TCP/IP architecture is also called as Internet architecture.
 It is developed by the US Defense Advanced Research Project Agency
(DARPA) for its packet switched network (ARPANET).
 TCP/IP is a protocol suite used in the Internet today.
 It is a 4-layer model. The layers of TCP/IP are

1. Application layer
2. Transport Layer (TCP/UDP)
3. Internet Layer
4. Network Interface Layer
APPLICATION LAYER
 An application layer incorporates the function of top three OSI
layers. An application layer is the topmost layer in the TCP/IP
model.
 It is responsible for handling high-level protocols, issues of
representation.
 This layer allows the user to interact with the application.
 When one application layer protocol wants to communicate
with another application layer, it forwards its data to the transport
layer.
 Protocols such as FTP, HTTP, SMTP, POP3, etc running in the
application layer provides service to other program running on top
of application layer

TRANSPORT LAYER
 The transport layer is responsible for the reliability, flow control,
and correction of data which is being sent over the network.
  The two protocols used in the transport layer are User Datagram
protocol and Transmission control protocol.
o UDP – UDP provides connectionless service and end-to-
end delivery of transmission. It is an unreliable protocol
as it discovers the errors but not specify the error.
o TCP – TCP provides a full transport layer services to
applications. TCP is a reliable protocol as it detects the
error and retransmits the damaged frames.

INTERNET LAYER
 The internet layer is the second layer of the TCP/IP model.
 An internet layer is also known as the network layer.
 The main responsibility of the internet layer is to send the
packets from any network, and they arrive at the destination
irrespective of the route they take.
 Internet layer handle the transfer of information across multiple
networks through router and gateway .
 IP protocol is used in this layer, and it is the most significant
part of the entire TCP/IP suite.

NETWORK INTERFACE LAYER

 The network interface layer is the lowest layer of the TCP/IP model.
 This layer is the combination of the Physical layer and Data Link
layer defined in the OSI reference model.
 It defines how the data should be sent physically through the network.
 This layer is mainly responsible for the transmission of the data
between two devices on the same network.
 The functions carried out by this layer are encapsulating the IP
datagram into frames transmitted by the network and mapping of
IP addresses into physical addresses.
 The protocols used by this layer are Ethernet, token ring, FDDI,
X.25, frame relay.

COMPARISON - OSI MODEL AND TCP/IP MODEL

 S.No OSI MODEL TCP/IP MODEL
1 Defined before advent of Defined after the advent of Internet.
internet
2 Service interface and protocols Service interface and protocols were
are clearly distinguished before not clearly distinguished before
3 Internetworking not supported TCP/IP supports Internet working

4 Strict layering Loosely layered

5 Protocol independent standard Protocol Dependant standard

6 Less Credible More Credible

7 All packets are reliably TCP reliably delivers packets, IP

delivered does not reliably deliver packets

6.Explain in detail about design issues in the network layer?

Network layer is majorly focused on getting packets from the source to the
destination, routing error handling and congestion control.
Before learning about design issues in the network layer, let’s learn about it’s
various functions.
 Addressing:
Maintains the address at the frame header of both source and destination and
performs addressing to detect various devices in network.
 Packeting:
This is performed by Internet Protocol. The network layer converts the packets
from its upper layer.
 Routing:
It is the most important functionality. The network layer chooses the most
relevant and best path for the data transmission from source to destination.
 Inter-networking:
It works to deliver a logical connection across multiple devices.
Network layer design issues:
The network layer comes with some design issues they are described as follows:

1. Store and Forward packet switching:

The host sends the packet to the nearest router. This packet is stored
there until it has fully arrived once the link is fully processed by
verifying the checksum then it is forwarded to the next router till it
reaches the destination. This mechanism is called “Store and Forward
packet switching.”

2. Services provided to Transport Layer:

Through the network/transport layer interface, the network layer
transfers it’s services to the transport layer. These services are described
below.
But before providing these services to the transfer layer following goals
must be kept in mind :-

 Offering services must not depend on router technology.

 The transport layer needs to be protected from the type, number and topology of
the available router.
 The network addresses for the transport layer should use uniform numbering
pattern also at LAN and WAN connections.
Based on the connections there are 2 types of services provided :
 Connectionless – The routing and insertion of packets into subnet is done
individually. No added setup is required.
 Connection-Oriented – Subnet must offer reliable service and all the packets
must be transmitted over a single route.
3. Implementation of Connectionless Service:
Packet are termed as “datagrams” and corresponding subnet as “datagram
subnets”. When the message size that has to be transmitted is 4 times the size of
the packet, then the network layer divides into 4 packets and transmits each
packet to router via. a few protocol.Each data packet has destination address and
is routed independently irrespective of the packets.
4. Implementation of Connection Oriented service:
To use a connection-oriented service, first we establishes a connection, use it
 and then release it. In connection-oriented services, the data packets are
delivered to the receiver in the same order in which they have been sent by the
sender.
It can be done in either two ways :
 Circuit Switched Connection – A dedicated physical path or a circuit is
established between the communicating nodes and then data stream is
transferred.
 Virtual Circuit Switched Connection – The data stream is transferred over a
packet switched network, in such a way that it seems to the user that there is a
dedicated path from the sender to the receiver. A virtual path is established here.
While, other connections may also be using the same path.

7.Explain internetwork?
INTERNETWORK

o An internetwork is defined as two or more computer network LANs or WAN.

o An Internetwork can be formed by joining two or more individual networks
by means of various devices such as routers, gateways and bridges.
o An interconnection between public, private, commercial,
industrial, or government computer networks can also be
defined as internetworking.
o Types of Internetwork

Extranet Intranet
An extranet is used for
An intranet belongs to an
information sharing. The
organization which is
access to the extranet is
only accessible by
restricted to only those
the organization's
users who have login
employee or members.
credentials. An extranet
The main aim of the
is the lowest level of
intranet is to share the
internetworking. It can be
information and
categorized as MAN,
resources among the
WAN or other computer
organization employees.
networks. An extranet
An intranet provides the
cannot have a single
facility to work in groups
LAN, atleast it must
and for teleconferences.
have one connection to
the external network.

Internetworking is combined of 2 words, inter and networking which

implies an association between totally different nodes or segments. This
connection area unit is established through intercessor devices akin to routers or
gateway. The first term for associate degree internetwork was catenet.
To enable communication, every individual network node or phase is
designed with a similar protocol or communication logic, that is Transfer
Control Protocol (TCP) or Internet Protocol (IP). Once a network communicates
with another network having constant communication procedures, it’s called
Internetworking. Internetworking was designed to resolve the matter of
delivering a packet of information through many links.
There is a minute difference between extending the network and
Internetworking. Merely exploitation of either a switch or a hub to attach 2 local
area networks is an extension of LAN whereas connecting them via the router is
an associate degree example of Internetworking. Internetworking is enforced in
Layer three (Network Layer) of the OSI-ISO model. The foremost notable
example of internetworking is that the Internet.
There is chiefly 3 units of Internetworking:
1. Extranet
2. Intranet
3. Internet
1. Extranet – It’s a network of internetwork that’s restricted in scope to one
organization or entity however that additionally has restricted connections to the
networks of one or a lot of different sometimes, however not essential. It’s the
very lowest level of Internetworking, usually enforced in an exceedingly
personal area. Associate degree extranet may additionally be classified as a
Man, WAN, or different form of network however it cannot encompass one
 local area network i.e. it should have a minimum of one reference to associate
degree external network.
2. Intranet – This associate degree computer network could be a set of
interconnected networks, which exploits the Internet Protocol and uses IP-based
tools akin to web browsers and FTP tools, that’s underneath the management of
one body entity. That body entity closes the computer network to the remainder
of the planet and permits solely specific users. Most typically, this network is
the internal network of a corporation or different enterprise. An outsized
computer network can usually have its own internet server to supply users with
browseable data.
3. Internet – A selected Internetworking, consisting of a worldwide interconnection
of governmental, academic, public, and personal networks based mostly upon
the Advanced analysis comes Agency Network (ARPANET) developed by
ARPA of the U.S. Department of Defense additionally home to the World Wide
Web (WWW) and cited as the ‘Internet’ to differentiate from all different
generic Internetworks. Participants within the web, or their service suppliers, use
IP Addresses obtained from address registries that manage assignments.

8.Difference between Connection-oriented and Connection-less Services?

Both Connection-oriented service and Connection-less service are used for the
connection establishment between two or more two devices. These types of
services are offered by the network layer.
Connection-oriented service is related to the telephone system. It includes
connection establishment and connection termination. In a connection-oriented
service, the Handshake method is used to establish the connection between
sender and receiver.

Connection-less service is related to the postal system. It does not include any
connection establishment and connection termination. Connection-less Service
does not give a guarantee of reliability. In this, Packets do not follow the same
path to reach their destination.
Difference between Connection-oriented and Connection-less Services:
Connection-oriented Connection-less
S.NO Service Service

Connection-oriented Connection-less
service is related to the service is related to
1. telephone system. the postal system.

Connection-oriented Connection-less
service is preferred by Service is preferred
long and steady by bursty
2. communication. communication.

Connection-less
Connection-oriented Service is not
3. Service is necessary. compulsory.

Connection-less
Connection-oriented Service is not
4. Service is feasible. feasible.

In connection-oriented In connection-less
Service, Congestion is Service, Congestion
5. not possible. is possible.

Connection-less
Connection-oriented Service does not give
Service gives the a guarantee of
6. guarantee of reliability. reliability.

7. In connection-oriented In connection-less
Service, Packets Service, Packets do
 Connection-oriented Connection-less
S.NO Service Service

not follow the same

follow the same route. route.

Connection-oriented Connection-less
services require a Service requires a
bandwidth of a high bandwidth of low
8. range. range.

Ex: TCP
(Transmission Control Ex: UDP (User
9. Protocol) Datagram Protocol)

Connection-oriented Connection-less
requires authentication. Service does not
require
10. authentication.

9.Write a note on ICMP?

ICMP

o ICMP stands for Internet Control Message Protocol.

o The ICMP is a network layer protocol used by hosts and routers to send the
notifications of IP datagram problems back to the sender.

o ICMP uses echo test/reply to check whether the destination is reachable and
responding.

o ICMP handles both control and error messages, but its main function is to report
the error but not to correct them.

o An IP datagram contains the addresses of both source and destination, but it

does not know the address of the previous router through which it has been
passed. Due to this reason, ICMP can only send the messages to the source, but
not to the immediate routers.
o ICMP protocol communicates the error messages to the sender. ICMP messages
cause the errors to be returned back to the user processes.

o ICMP messages are transmitted within IP datagram.

The Format of an ICMP message

o The first field specifies the type of the message.

o The second field specifies the reason for a particular message type.

o The checksum field covers the entire ICMP message.

10.Difference Between IPv4 and IPv6:

fIPv4 IPv6

IPv4 has a 32-bit address

length IPv6 has a 128-bit address length

It Supports Manual and

DHCP address It supports Auto and renumbering
configuration address configuration

In IPv4 end to end,

connection integrity is In IPv6 end to end, connection
Unachievable integrity is Achievable

Address space of IPv6 is quite

It can generate large it can produce
9 38
4.29×10 address space 3.4×10 address space
fIPv4 IPv6

The Security feature is IPSEC is an inbuilt security

dependent on application feature in the IPv6 protocol

Address representation of Address Representation of IPv6 is

IPv4 is in decimal in hexadecimal

Fragmentation performed In IPv6 fragmentation performed

by Sender and forwarding only by the sender
routers

In IPv4 Packet flow In IPv6 packet flow identification

identification is not are Available and uses the flow
available label field in the header

In IPv4 checksum field is In IPv6 checksum field is not

available available

In IPv6 multicast and any cast

It has broadcast Message message transmission scheme is
Transmission Scheme available

In IPv4 Encryption and In IPv6 Encryption and

Authentication facility not Authentication are provided
provided

IPv4 has a header of 20-60 IPv6 has header of 40 bytes fixed

bytes.