NETWORK • a Network is a Group of Devices (Nodes)

8/14/2019 NETWORK a Network is a Group of Devices (Nodes)

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NETWORK


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ESSENTIAL OF NETWORKS:

(1) Terminals (Computers)

(2) Softwares

(3) Hardware Peripherals


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(i) Dumb Terminal:

A combination of keyboard and monitor that has no local

computing power, used to input/output information to or from a

remote controlling computer.

(ii) Smart Terminal

A terminal that has its own processing section for little

computing not for programming. It is also connected to

controlling computers for the programming and major tasks.


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(iii) lntelligent Terminal:

A terminal which has its own processing section,

limited storage capacity and itself a

programmable as well as independently performs

major tasks but it has not secondary disk storagecapacity (Normally). It is also not able to perform

complex & sharing process and for these, it

depends on the remote controlling computer.


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TYPES OF NETWORK

Network can be divided into two manner.

(1) According to Range

(2) According to Topology (Mapping)


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(1) ACCORDINGTO RANGE:

It has also three types - (i) Peer-to-Peer Network

(ii) Local Area Network (LAN)

(iii) Wide Area Network (WAN) (2) ACCORDING TO TOPOLOGIES

It has also the following types -

(i) Bus Network (ii) Ring Network (iii) Star Network (iv) Mesh Network


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CONNECTIVITY DEVICES

NETWORK TYPES : ACCORDING TO RANGE

(1) Peer-To-Peer Network:

A peer-to-peer is a network in which two or more

nodes can communicate with each other directly,

without the need for any intermediary devices.Each node in a peer-to-peer network can be a

client and a server simultaneously. All

computers (nodes) in a network are capable of

accessing data, software and other networkresources directly.


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In other words, it is a very small network for a limited

space like small office / institution. In which all the

intelligent terminals are used. There is no dedicated fileserver is used but networking is only for communication

or sharing drives, files and printers etc.


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Benefits :-

1. Peer-to-peer network are relatively easy to

implement and operate.

2. Peer-to-peer network is also inexpensive to operate.

Uses :

Peer-to-peer networking has two primary uses are:-

1. It is ideally suited for small organization with a limited

budget for information technologies and limited need

for information sharing.

2. Workgroups within larger organization can also use

this methodology for a tighter sharing of information

within a particular group.


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(2) LAN (Local AreaNetwork):

A local area network links the devices in a singleoffice, building or campus.

A LAN can be as simple as two PCs and aprinter in ones home office, or it can bethroughout a company and include voice, soundand video peripherals.

At present, LAN - size is restricted to a few

kilometers.


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In brief, we can say that LAN is a digital

communication system in which the large

numbers of computers are inter-

connected with their associated peripherals by

cables, within a particular geographical area.

LANs allow resource sharing between personal

computers or workstations. The resources

means hardware (eg. a printer), software (eg. an

application program), or data.


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A common example of a LAN is a work

group of job related computers, for

example, engineering workstations or

accounting PCs.

One of the computers is given a

large - capacity disk drive and becomes a

server to the other clients. Software is

stored on this central server and used asneeded by the whole group.


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In addition size, LANs stand apart from other types of networks by

their transmission media and topology.

In LAN use achieve upto 100 Mbps data transmission speed.

However, since all the equipment is located within a single

establishment, LANs are normally installed and maintained by the

organization. Hence they are also refered to as Private Data

Networks.

There are two quite different types of LAN : wired LANs and wireless

LANs. As the name simply, wired LANs utilised (fixed) wiring such as

twisted pair or coaxial cable - as the transmission medium, while

wireless LAN utilised Radio or light waves. Examples of LANs are -

ETHERNET By Xerox Corporation. OMININET BY CORVUS

SYSTEM.

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(3) WAN (Wide Area Network):

A Wide Area Network is a network that connects users across

large distances, often crossing the geographical boundaries of

cities or states.


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DIFFERENCE BETWEEN


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DIFFERENCE BETWEEN

LAN & WAN The range of LAN is very limited (i.e. 1 km)

and it may be increased by using repeaters.

Instead of WAN is unlimited (i.e. world wide).

The communication medium in LAN Is private

(i.e. owned by the user) while a WAN is a

public system (i.e. hired by the user).


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In LAN the data transmission cost is

negligible but in WAN it is very much

because medium is hired. In LAN the terminals are connected

physically (i.e. by coaxial or fiber-optic

cables) but in WAN Network is formed bytelephone lines, Microwave and satellite

links.


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Types of Network Terminal

SERVER

CLIENT


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SERVER

In Networking any computer which

serves its all available facilities to all

other computers of a Network (likeaccess of files. Communication,

printing etc) is termed as SERVER.


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CLIENT

A Client may be a PC or a workstation

on a network

using services

provided by the network server.


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NETWORK TYPES

ACCORDING TO TOPOLOGIES

(MAPPINGS) Bus Network

Ring Network

Star Network

Mesh Network


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Bus Network

In networking, a method of connections of

computers that allows all network nodes toreceive the same message through the

network cable at the same time.


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Advantage of Bus Network

Short cable length and simple wiring layout.Because there is a single common data path

connecting all nodes, the bus topology allows a

very short cable length to be used.

Additional nodes can be connected to an

existing bus network at any point along its

length.


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Disadvantages of the Bus Network:

In most LANs based on a bus, control of

the network is not centralized in any

particular node. This means that detection

of a fault may be performed from many

points in the network. If a node is faulty on a bus. It must be

rectified at the point where the node is

connected to the network. Once the faulthas been located. The node can simply be

removed.


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Ring Network:

In this type of network, there is a closed loop or circleis formed in which each node in the network is

connected to the next and message move in one

direction around the system.

When a message arrives at a node, the nodeexamines the address information in the message. If

the address matches the nodes address, the

message is accepted, otherwise the node regenerates

the signal and places the message back on thenetwork for the next node in the system. It is this

regeneration that allows a ring network to cover much

greater distances than star and bus network.


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Advantages of the Ring Network:

The amount of cabling involved in a ring topology iscomparable to that of bus and is small relative to thatof star. This means that less connection will beneeded, which will in turn increase network reliability.

Since there is only one cable connecting each node toits immediate neighbours, it is not necessary toallocate space in the building for wiring closets.

Optical fiber offers the possibility of very high speedtransmission, Because traffic on a ring travel in onedirection, it is easy to use optical fiber as medium of

transmission.

Di d t f Ri N t k


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Disadvantages of Ring Network:

The transmission of data on a ring goes through every

connected node on the ring before returning to thesender. If one node fails to pass through itself, theentire network has failed and no traffic can flow untilthe defective node has been removed from the ring.

The fact that failure of one node will effect all othershas serious implication for fault diagnosis.

For a very big ring network it is not possible to shutdown a small section of the ring while keeping themajority of it working normally while rectifying the

problem at some node.


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STAR NETWORK


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STAR NETWORK

In this type of network the computers areconnected in the form of a star. In which atthe center of the star is a wiring hub orconcentrator and the nodes are arranged

around the central point representing thepoints of the star.

Each node is directly connected to the

hub so due to this failure of any node doesnot restricts the complete network but it isvery costly system because each computerhas separate wiring.


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Advantages of the Star Network:

The star topology has a number ofconcentration points i.e. at the central node.These provide easy access for service ofreconfiguration of the network.

Connection points in any network are inherentlyprone to failure. If one node goes off (fail) theentire system will not be affected and only that

node can be removed. The fact that the central node is connected

directly to every other node in the networkmeans that faults are easily detected and

isolated.


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Mesh Network:

A mesh network has point-to-point

connections between every device in the

network. Each device requires an interface forevery other device on the network, mesh

topologies are not usually considered

practically.


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Advantages of Mesh Network:

It has very much fault tolerance capacity.

In case of a media failure the signal can

be bypassed through the other roots.

We can use this network as any other kind

of network.


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Disadvantages of Mesh Network:

Installation is very difficult.

Very much expensive network.

ADVANTAGES OF NETWORKS


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ADVANTAGES OF NETWORKS

(i) Security/EncapsulationA system can limit the kinds of interactions

that a user can have with the entire system. For

example, a bank can allow an user access to his own

account through an automated teller machine (ATM)

but not to banks entire database.

(ii) Distributed Databases:

A single system need not have storage capacity forentire database. So we can use different computer to

store database. For example, the World Wide Web

gives access to information that is actually stored

anywhere on the Internet.

(iii) Fast Problem Solving:


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( ) g

Multiple computers working on segments of a problemconcurrently can solve the problem faster than a singleworking alone.

(iv) Secuirty through Redundancy:

Multiple computers running the same program at the sametime provide security through redundancy. For example, in

the space shuttle, three computers run the same programso that if one develops a hardware error, the other two canoverride it.

(v) Collaborative Processing:

Both multiple computers and multiple user may interact on atask. For example, in a chatroom action of one person arevisible to and affect all the others.


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NETWORK • a Network is a Group of Devices (Nodes)