CHAP: 1- INTRODUCTION TO NETWORKING

Q1: What is a network?

Ans: A network is a set of devices (often referred to as nodes) connected by communication

links. A node can be a computer, printer, or any other device capable of sending and/or

receiving data generated by other nodes on the network.

Q2: What is the definition of a computer network?

Ans: A computer network is a group of computer systems that are linked together through

communication channels to facilitate communication and resource-sharing among a wide

range of users.

Q3: What are the uses of Computer Network?

Ans:

Uses of Computer Networks:

● Users can share resources and communicate.

● File sharing.

● Hardware sharing (Printers, CD-ROM drives and hard drive).

● Program sharing.

● Multiplayer gaming.

Q4: What are the components of a computer network?

Ans: a) Servers

b) Clients,

c) Transmission Media,

d) Shared data,

e) Shared printers and other peripherals,

f) Network Interface Card,

g) Network Operating System,

h) Hub,

i) Switch,

j) Router,

k) LAN Cable.

Q5: Discuss the definitions of

a) Hub

b) Repeater

c) Switch

d) Bridges

e) Routers f) Gateway

g) Modem

(These are the network devices).

Ans:

a) Hub: A hub works in the physical layer of the OSI model. It is basically a nonintelligent

device, and has no decision making capability. What a hub basically does is take the input

data from one of the ports and broadcast the information to all the other ports connected to

the network.

b) Repeater: A repeater is an electronic device that receives a signal, regenerates it and

retransmits at a higher level or with a higher power. A repeater also works in the Physical

layer. The repeaters are used in places where amplification of input signals is necessary.

Repeaters are used within a network to extend the length of communication.

c) Switch: A switch is an intelligent device that works in the data link layer. The term

intelligence refers to the decision making capacity of the switch. Switches operate at both

the physical layer and the data link layer. Since it works in the data link layer, it has

knowledge of the MAC addresses of the ports in the network.

d) Bridges: Bridges are used to connect similar network segments that are using similar

communication standards. A bridge filters the data traffic at a network boundary. Bridges

operate at both the physical layer and the MAC sublayer of the Data link layer. Bridges

inspect incoming traffic and decide whether to forward or discard it.

e) Routers: Routers are networking devices used to extend or segment networks by

forwarding packets from one logical network to another. Routers are most often used in

large internetworks that use the TCP/IP protocol suite connecting TCP/IP hosts and local

area networks (LANs) to the internet using dedicated leased lines. Routers work at the

network layer to move packets between networks using their logical addresses i.e the IP

addresses of the destination hosts on the network.

f) Gateway: A gateway is an internetworking device used to connect networks that use

different networking protocols. A gateway is necessary when there are different

technologies implemented by the different LAN’s which are to be connected together.

g) Modem: The device that converts digital signals into analog signals and analog signals

to digital signals is called modem. The word modem stands for modulation and

demodulation. The process of converting digital signals to analog signals is called

modulation. The process of converting analog signals to digital signals is called

demodulation. Modem are used with computers to transfer data from one computer to

another computer through telephonic lines.

Q6: What is network topology? What network topologies are there in

a computer network?

Ans: Network topology refers to the layout of a network and how different nodes in a

network are connected to each other and how they communicate.

Following are the five most common network topologies:

● Bus topology,

● Ring topology,

● Star topology,

● Mesh topology,

● Tree topology.

Q7:.Discuss the definitions of:

a) Bus topology

b) Ring topology

c) Star topology

d) Mesh topology

e) Tree topology

Ans: a) Bus topology: In this topology, all the nodes are connected to a single cable

(called bus), by the help of interface connectors. This central cable is the backbone of the

network and is known as Bus. Bus networks are relatively used for small networks. It is good

for LAN.

( Fig 1.1: Bus topology)

b) Ring topology: In a ring topology, all the nodes are connected in a closed loop. Message

travels around the ring, with each node reading those messages addressed to it.

( Fig 1.2:Ring topology)

c) Star topology: In a star network devices are connected to a central computer, called a hub.

Nodes communicate across the network by passing data through the hub.

( Fig 1.3:Star topology)

d) Mesh topology: In a mesh topology, every device has a dedicated point-to-point link to

every other device in the network. The term dedicated means that the link carries traffic only

between the two devices it connects.

(Fig 1.4:Mesh topology)

e) Tree topology: This is a hybrid topology that combines characteristics of linear bus and

star topologies. In a tree network, groups of star-configured networks are connected to a linear

bus backbone cable.

(Fig 1.5:Tree topology)

Q8: Which topology is used by the Ethernet systems?

Ans: Bus topology.

Q9: What are the basic differences between connection oriented and

connectionless service?

Ans: If connectionless service is offered, packets are inserted into the network individually

and routed independently. No advanced setup is needed. In this context, the packets are

frequently called datagrams and the network is called a Datagram network. If a connection-

oriented service is used, a path from the source router all the way to the destination router must

be established before any data packets can be sent. This connection is called VC (Virtual

circuit) and the network is called Virtual-circuit network.

After the end of the transmission, the connection is released, which in turn removes the virtual

circuit.

Q10: Compare Virtual-circuit and Datagram networks.

Ans:

Q11: Discuss the OSI reference model.

Ans:

(Fig 1.7:The OSI reference model)

Q12: Explain the key functions of all the layers of the OSI model.

Ans: i) Physical Layer:

The physical layer of the OSI model defines the electrical and mechanical

specifications used in networking including transmission distances, the various types of media

available and electrical issues.

This layer is concerned with transmitting raw bits over a communication channel.

ii)The Data Link Layer:

a) The main task of the data link layer is to transform the raw input data into data frames and

transmit the frames sequentially.

b) It takes care of the flow control i.e a fast transmitter should not drown a slow receiver of

data.

c) This layer also controls the access to the shared channel.

iii) The Network Layer:

a) The main task of the network layer is to determine how packets are routed from source to

destination.

iv) The Transport Layer:

a) The basic function of the transport layer is to accept data from above it, split it up into

smaller units, pass these to the network layer, and ensure that all the pieces arrive correctly at

the other end.

b) Error recovery is done in the layer.

v) The Session Layer:

a) The session layer allows users on different machines to establish sessions between

them.

b) Session layer, establishes ,manages and terminates sessions between applications.

vi)Presentation Layer:

a) The presentation layer is concerned with the syntax and semantics of the information

transmitted.

b) The presentation layer manages these data structures and allows higher-level data

structures to be defined and exchanged through the network with a standard encoding format.

vii)The Application Layer:

a)Application layer defines the communications services used by the user's applications to

transmit data over the network.

b)This layer defines application protocols such as FTP, Email clients, Web browsers,

Telnet etc.

Q13: Compare TCP/IP and OSI model.

Ans: a) TCP/IP has 4 layers whereas the OSI model has 7 layers.

b) TCP/IP model is based on standard protocols around which the Internet has developed. It is

a communication protocol, which allows connection of hosts over a network whereas OSI is a

generic, protocol independent standard, acting as a communication gateway between the

network and the end user.

c) In the TCP/IP model the transport layer does not guarantee delivery of packets. Still the

TCP/IP model is more reliable, on the other hand, In OSI model the transport layer guarantees

the delivery of packets.

d) In the TCP/IP, transport Layer is both Connection Oriented and Connection less Whereas

In the OSI, transport Layer is Connection Oriented.

e) In the TCP/IP, network Layer is Connection less, on the other hand, In OSI, Network Layer

is both Connection Oriented and Connection less.

Q14: Discuss TCP/IP model.

Ans: The TCP/IP protocol suite consists of four layers: host-to-network

(or link

layer),internet layer, transport layer and application layer.

The Link Layer: This layer specifies details of how data is physically sent through the

network, including how bits are electrically signaled by hardware devices that interface

directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper

wire. This layer acts as an interface between hosts and transmission links.

The Internet Layer: This layer packages data into different independent IP datagrams, which

contain source and destination address information that is used to forward the datagrams

between hosts and across networks. They may even arrive in a completely different order in

the destination than how they were sent from the host,in which case it is the job of higher

layers to rearrange them, if in-order delivery is desired. This internet layer defines an official

packet format protocol called IP(Internet Protocol),and a companion protocol called

ICMP(Internet Control Message Protocol)that helps it function.

The Transport Layer: The layer above the internet layer in the TCP/IP model is usually

called the transport layer. It is designed to allow entities on the source and destination hosts to

carry on a conversion. Two end-to-end transport protocols have been defined here.

The Application Layer: Application layer defines the communications services used by the

user's applications to transmit data over the network.

Introduction To Networking

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Introduction To Networking

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