Q. What is networking? What are various types of
networking?
In summary, all networks must have the following:-
·
A resources to
share (resource)
·
A pathway to
transfer data (transmission medium)
·
A set of rules
governing how to communicate (protocols)
Need for networking:-
File Sharing:-
Networks serve as an effective means to share the files with different
uses.
Example- In an organization one file can be shared by
the different departments if it is placed on network systems.
Peripheral Sharing:-
Some compute devices are very expensive.
Example- laser printer and large hard disks are quite
costly. Network enables to share these
costly devices.
Fast Communication:-
It is possible that the mail from one place to another could take
several day. But through networking
manages can be sent speedily.
High Reliability:-
Networking provides high reliability by using alternate sources of
supply.
Example:- All
files could be copied on two or three machines, so that if one of them is
unavailable due to hardware or any other failure, the other copies could be
used for applications such as military, banking, air traffic control and many
other applications this is of great importance.
Fax Facilities:-
Compute can have fax systems integrated with networking. This allow them to send pictures along with
the text.
Thus the newspaper reports can be prepared and sent
over the world at a very high speed by composing and publishing them from
different centers.
Backups:- As
all data is stored on a sever, backing up critical data becomes a simple
process.
Types of Networking
Local Area Network (LAN) :- One of the major benefits of implementation
of LAN is sharing expensive resources such as storage devices, printers
etc. This is achieved through providing
servers on the LAN. It is dedicated
computer that controls one or more resources.
Three major categories of services used in LANs are-
·
File Server
·
Printer Server
·
Modem Server
In networking file server is used to share storage
space for files.
Similarly printer server is used to handle printing
woks of all workstation connected in the network.
In LAN environment also modem is required to get
connected to other network or simply to used a telephone.
Metropolitan Area Network (MAN):- A metropolitan area network (MAN) is designed
to extend over an entire city. It may be
a single network such as a cable television network, or it may be a means of
connecting a number of LANs into a larger network so that resources may be
share LAN to LAN as well as device-to-device.
For example, A company can use a MAN to connect the LANs in all its
officer throughout a city.
A MAN may be wholly owned and operated by a private
company, or it may be a service provided by a public company such as local
telephone company. Many telephone
companies provide a popular MAN service called switch Multi-Megabit Data
Services (SMDS).
Wide Area Network (WAN):- Wide are networks connect computes and
smaller network to large networks over greater geographic areas, including
different continents. These computers
may be linked by means of cables, optical fibers or satellites.
To access the networks, the users use a modem which is
a device that allows computers to communicate over telephone lines.
The largest wide area network is the internet, a
collection of networks linking millions of computer users on every continent.
Transmission Channel for WAN:- for transmission in a WAN, three types of
channels are used. These are-
·
Radio wave
Transmission
·
Microwave
Transmission
·
Communication
Satellites
Hardware Requirements for WAN:- There are mainly four H/W devices which are
required to establish linkage between geographically separated computers these
are-
·
Bridges
·
Routers
·
Gateways
·
X.25 Standard
Interface
Q:- What are various topologies are used for
networking? Explain with their advantages and disadvantages.
·
Ans:- The term topology refers to
the way a network is level out, either physically or logically. Two or more devices connect to a link, two o
more links form a topology. The topology
of a network is the geometric representation of the relationship of all the
links and linking devices to each other.
There are five basic topologies possible: Mesh, Star, Tree, Bus and
Ring.
Mesh:- 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. A fully connected mesh network therefore has
n(n-1)/2 physical channels to link n devices.
A mesh offers several advantages over other network
topologies. First, the use of dedicated
links guarantees that each connection can carry its own data load, thus
eliminating the traffic problems that can occur when links must be shared by
multiple deices. Second, a mesh topology
is robust if one link becomes unusable, it does not effect the entire
system. Another advantage is privacy or
security when every message sent travels along dedicated lie, only the intended
recipient sees it.
The main disadvantage of a mash are related to the
amount of cabling and the number of I/O ports required first, because every
device must be connected to ever other device, installation and reconfiguration
are difficult. Second, the sheer bulk of
the wiring can be greater than the available space (in walls, ceilings, or
floors) can accommodate for these reasons a mesh topology is usually
implemented in a limited fashion.
Star:- 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 each other. Unlike a mesh topology, a star topology, a
star topology does not allow direct traffic between devices. The controller acts as an exchange if one
device the data to the controller, which then relays the data to other
connected.
A star topology is less expensive than a mesh
topology. In a star, each device needs
only one link and one I/O ports to connect it to any number of others. This factor also makes it easy to install and
reconfigure. For less cabling needs to e
housed, and additions, moves and deletions involve only one connection: between
that device and the hub.
Other advantages include robustness if one link fails,
only that link is affected. All other
links remain active. As long as the hub
is working, it can be used to monitor link problems.
However, although a star requires for less cable than
a mesh,. Each node must be linked to a central hub. For this reason more cabling is required in a
star than in some other topologies (such as tree, ring or bus).
Tree Topology:-
It is a network in which computers are interconnected tree structure.
To transfer information from node 4 to node 6. information goes to node 2 then root then
node 1 finally to node 6.
Advantage:- A
tree structure facilities functional grouping.
For example- one branch may contain all the general ledger terminals,
another branch may have all the accounts receivable terminals and so on if one
branch stops functioning, the other branches in a tree network will not be
affected.
§ It is easy to add new nodes or branches to it.
Disadvantage:-
Data movement through this network can be slow.
Bus Topology:-
In this topology, all devices on network are connected to a single
continuous cable called a bus.
Transmission from any station travels the length of the bus in both
directions and can be received by all other stations. The destination device, on identifying the
address on the data packet copies the data on to its disk and fees the line.
if computer 1 wants to communicate with 4 then it
first checks whether the communication line is free. When the line becomes free it transmits the
message addressed to 4 on it. As the
message travels on the line, each computer checks whether it is addressed to
it. In this case when is find its
“address” in the message it accept it sends the acknowledgement to 1 and frees
the line.
Advantages:-
The main advantage of this method is the reduction in physical lines.
§ A wide range of equipment can be attached to the LAN
without any problem.
§ A new node can be added to the LAN without disturbing
the network and other nodes.
§ Low cabling cost because of short cable length to be
used.
§ Not requiring that every computer be cp and running in
order for the network to function.
Disadvantages:-
In this topology, fault detection is very difficult because the network
is not centralized in any particular node.
This means that detection of a fault may have to be performed from many
points in the network.
§ Only one message can travel at a time.
§ When a message from two nodes comes on the line, a
collision occurs. The chances of collision
taking place are always there.
§ Low reliability.
A break or short circuit in the cable an holt the whole network.
Ring Topology:-
The ring is a circular topology, each device connects directly to the
ring. The ring topology is also called a
loop in this case, each node is connected to the only two neighboring nodes.
A ring may be unidirectional or bi-directional. In a unidirectional ring, data moves in one
direction. Only, whereas in a
bi-directional ring data may move in both directions, but one direction at a
time.
The data is accepted from one of the neighboring node
and is transmitted onward to another.
Example- if E receives data from A it examines whether
it is addressed to itself. If it is,
then E uses it else it passes the message to D.
Advantages:-
Short cable length. This means
that fewer connections will be needed, which will in turn increase network
reliability.
§ As thee is only one able connecting each node to its
immediate neighbors, it is not necessary to allocate space in the building for
wiring closets.
§ It is very simple to install.
Disadvantages:-
There may be large communication delays as the number of nodes
increases.
§ Each node on the ring must handle the data being
transferred by other nodes.
§ If one node fails to handle the transfer of data then
whole of network fails.
§ It is difficult to diagnose faults. We have to check each and every node to know
which node is faulty.
§ It is not possible to shut down a small selection of
the ring while keeping the majority of its working normally.
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