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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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