INTRODUCTION TO INTERNET PART :- 1
COMPUTER
NETWORKING
A computer network is a digital telecommunications
network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections (data links) between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi.
Network computer devices that originate, route and
terminate the data are called network nodes. Nodes
are generally identified by network addresses, and can include hosts such
as personal computers, phones, and servers, as well as networking hardware such as routers and switches. Two such devices can be said
to be networked together when one device is able to exchange information with
the other device, whether or not they have a direct connection to each other.
In most cases, application-specific communications protocols are layered (i.e. carried as payload) over other more general communications protocols. This
formidable collection of information
technology requires
skilled network management to keep it all running reliably.
Computer networks support an enormous number
of applications and services such
as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers, printers, and fax
machines, and use of email and instant messaging applications as well as many others. Computer networks
differ in the transmission medium used to carry their signals, communications
protocols to organize
network traffic, the network's size, topology, traffic control mechanism and organizational intent. The best-known
computer network is the Internet.
Types
of Network Topology
Network Topology is the
schematic description of a network arrangement, connecting various nodes(sender
and receiver) through lines of connection.
BUS
Topology
Bus topology is a
network type in which every computer and network device is connected to single
cable. When it has exactly two endpoints, then it is called Linear Bus
topology.
Features of Bus Topology
1.
It transmits data only in one direction.
2.
Every device is connected to a single cable
Advantages of Bus Topology
1.
It is cost effective.
2.
Cable required is least compared to other network topology.
3.
Used in small networks.
4.
It is easy to understand.
5.
Easy to expand joining two cables together.
Disadvantages of Bus Topology
1.
Cables fails then whole network fails.
2.
If network traffic is heavy or nodes are more the performance of
the network decreases.
3.
Cable has a limited length.
4.
It is slower than the ring topology.
RING Topology
It is called ring
topology because it forms a ring as each computer is connected to another
computer, with the last one connected to the first. Exactly two neighbours for
each device.
Features of Ring Topology
1.
A number of repeaters are used for Ring topology with large
number of nodes, because if someone wants to send some data to the last node in
the ring topology with 100 nodes, then the data will have to pass through 99
nodes to reach the 100th node. Hence to prevent data loss repeaters are used in
the network.
2.
The transmission is unidirectional, but it can be made
bidirectional by having 2 connections between each Network Node, it is
called Dual Ring Topology.
3.
In Dual Ring Topology, two ring networks are formed, and data
flow is in opposite direction in them. Also, if one ring fails, the second ring
can act as a backup, to keep the network up.
4.
Data is transferred in a sequential manner that is bit by bit.
Data transmitted, has to pass through each node of the network, till the
destination node.
Advantages of Ring Topology
1.
Transmitting network is not affected by high traffic or by
adding more nodes, as only the nodes having tokens can transmit data.
2.
Cheap to install and expand
Disadvantages of Ring Topology
1.
Troubleshooting is difficult in ring topology.
2.
Adding or deleting the computers disturbs the network activity.
3.
Failure of one computer disturbs the whole network.
STAR Topology
In this type of topology all the computers are connected to a
single hub through a cable. This hub is the central node and all others nodes
are connected to the central node.
Features of Star Topology
1.
Every node has its own
dedicated connection to the hub.
2.
Hub acts as a repeater
for data flow.
3.
Can be used with twisted
pair, Optical Fibre or coaxial cable.
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 because all the nodes depend on the hub.
4.
Performance is based on
the hub that is it depends on its capacity.
MESH Topology
It is a point-to-point connection to other nodes or devices. All
the network nodes are connected to each other. Mesh has
n(n-1)/2
physical
channels to link n
devices.
There are two techniques to transmit data over the Mesh
topology, they are :
1.
Routing
2.
Flooding
MESH Topology: Routing
In routing, the nodes have a routing logic, as per the network
requirements. Like routing logic to direct the data to reach the destination
using the shortest distance. Or, routing logic which has information about the
broken links, and it avoids those node etc. We can even have routing logic, to
re-configure the failed nodes.
MESH Topology: Flooding
In flooding, the same data is transmitted to all the network
nodes, hence no routing logic is required. The network is robust, and the its
very unlikely to lose the data. But it leads to unwanted load over the network.
Types of Mesh Topology
1.
Partial Mesh Topology
: In this topology some of the
systems are connected in the same fashion as mesh topology but some devices are
only connected to two or three devices.
2.
Full Mesh Topology
: Each and every nodes or devices
are connected to each other.
Features of Mesh Topology
1.
Fully connected.
2.
Robust.
3.
Not flexible.
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.
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.
Features of Tree Topology
1.
Ideal if workstations
are located in groups.
2.
Used in Wide Area
Network.
Advantages of Tree Topology
1.
Extension of bus and star
topologies.
2.
Expansion of nodes is
possible and easy.
3.
Easily managed and
maintained.
4.
Error detection is
easily done.
Disadvantages of Tree Topology
1.
Heavily cabled.
2.
Costly.
3.
If more nodes are added
maintenance is difficult.
4.
Central hub fails,
network fails.
HYBRID Topology
It is two different types of topologies which is a mixture of
two or more topologies. For example if in an office in one department ring
topology is used and in another star topology is used, connecting these
topologies will result in Hybrid Topology (ring topology and star topology).
Features of Hybrid Topology
1.
It is a combination of
two or topologies
2.
Inherits the advantages
and disadvantages of the topologies included
Advantages of Hybrid Topology
1.
Reliable as Error
detecting and trouble shooting is easy.
2.
Effective.
3.
Scalable as size can be
increased easily.
4.
Flexible.
Disadvantages of Hybrid Topology
1.
Complex in design.
2.
Costly.
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