2. Network
A network is a collection of computers,
servers, mainframes, network devices,
peripherals, or other devices connected to
one another to allow the sharing of data. An
excellent example of a network is the
Internet, which connects millions of people all
over the world.
3. Types of Network
Communication Networks can be of
following 5 types:
Inter Network (Internet)
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Wireless.
4. Internet
The Internet is a worldwide collection of
networks that connects millions of
businesses, government agencies,
educational institutions, and individuals.
5. LAN
local area network (LAN) is a group of
computers and associated devices that share
a common communications line or wireless
link to a server. Typically, a LAN
encompasses computers and peripherals
connected to a server within a distinct
geographic area such as an office or a
commercial establishment.
6. MAN
A metropolitan area network (MAN) is a
computer network that interconnects users
with computer resources in a geographic area
or region larger than that covered by even a
large local area network (LAN) but smaller
than the area covered by a wide area network
(WAN).
7. WAN
A wide-area network (WAN) is any
telecommunications network or
computer network that extends over a large
geographical distance Typically,
a WAN consists of two or more local-area
networks (LANs). Computers connected to a
wide-area network are often connected
through public networks, such as the
telephone system.
8. wireless
A wireless network is a
computer network that uses wireless data
connections between network nodes.
9. Network Topology
Network topology is the layout of the
connections (links, nodes, etc.) of a
computer network. There are two main types
of topology. Network topologies may be
physical or logical. Physical topology means
the physical design of a network including the
devices, locations and cables.
10. Types:
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
It transmits data only in one direction.
Every device is connected to a single cable.
Advantages of Bus Topology
It is cost effective.
Cable required is least compared to other network topology.
Used in small networks.
It is easy to understand.
Easy to expand joining two cables together.
Disadvantages of Bus Topology
Cables fails then whole network fails.
If network traffic is heavy or nodes are more the performance of the network
decreases.
Cable has a limited length.
It is slower than the ring topology.
11. 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 neighbors for each device.
Features of Ring Topology:
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.
The transmission is unidirectional, but it can be made bidirectional by
having 2 connections between each Network Node, it is called Dual Ring
Topology.
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.
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.
12. Advantages of Ring Topology
Transmitting network is not affected by high
traffic or by adding more nodes, as only the
nodes having tokens can transmit data.
Cheap to install and expand
Disadvantages of Ring Topology
Troubleshooting is difficult in ring topology.
Adding or deleting the computers disturbs the
network activity.
Failure of one computer disturbs the whole
network.
13. 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
Every node has its own dedicated connection to
the hub.
Hub acts as a repeater for data flow.
Can be used with twisted pair, Optical Fiber or
coaxial cable.
14. Advantages of Star Topology
Fast performance with few nodes and low network
traffic.
Hub can be upgraded easily.
Easy to troubleshoot.
Easy to setup and modify.
Only that node is affected which has failed, rest of the
nodes can work smoothly.
Disadvantages of Star Topology
Cost of installation is high.
Expensive to use.
If the hub fails then the whole network is stopped
because all the nodes depend on the hub.
Performance is based on the hub that is it depends on
its capacity
15. MESH Topology
It is a point-to-point connection to other nodes or devices. All the network nodes
are connected to each other.
There are two techniques to transmit data over the Mesh topology, they are :
Routing
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
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.
Full Mesh Topology : Each and every nodes or devices are connected to each
other.
16. Features of Mesh Topology
Fully connected.
Robust.
Not flexible.
Advantages of Mesh Topology
Each connection can carry its own data load.
It is robust.
Fault is diagnosed easily.
Provides security and privacy.
Disadvantages of Mesh Topology
Installation and configuration is difficult.
Cabling cost is more.
Bulk wiring is required.
17. 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
Ideal if workstations are located in groups.
Used in Wide Area Network.
Advantages of Tree Topology
Extension of bus and star topologies.
Expansion of nodes is possible and easy.
Easily managed and maintained.
Error detection is easily done.
Disadvantages of Tree Topology
Heavily cabled.
Costly.
If more nodes are added maintenance is difficult.
Central hub fails, network fails.
18. 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
It is a combination of two or topologies
Inherits the advantages and disadvantages of the topologies
included
Advantages of Hybrid Topology
Reliable as Error detecting and trouble shooting is easy.
Effective.
Scalable as size can be increased easily.
Flexible.
Disadvantages of Hybrid Topology
Complex in design.
Costly.
19. Transmission Modes in Computer Networks
Transmission mode refers to the mechanism of transferring of
data between two devices connected over a network. It is also
called Communication Mode. These modes direct the direction
of flow of information. There are three types of transmission
modes. They are:
Simplex Mode
Half duplex Mode
Full duplex Mode
SIMPLEX Mode
In this type of transmission mode, data can be sent only in one
direction i.e. communication is unidirectional. We cannot send a
message back to the sender. Unidirectional communication is
done in Simplex Systems where we just need to send a
command/signal, and do not expect any response back.
Examples of simplex Mode are loudspeakers, television
broadcasting, television and remote, keyboard and monitor etc.
20. HALF DUPLEX Mode
Half-duplex data transmission means that data can be transmitted in both
directions on a signal carrier, but not at the same time.
For example, on a local area network using a technology that has half-
duplex transmission, one workstation can send data on the line and then
immediately receive data on the line from the same direction in which
data was just transmitted. Hence half-duplex transmission implies a
bidirectional line (one that can carry data in both directions) but data can
be sent in only one direction at a time.
Example of half duplex is a walkie- talkie in which message is sent one at
a time but messages are sent in both the directions.
FULL DUPLEX Mode
In full duplex system we can send data in both the directions as it is
bidirectional at the same time in other words, data can be sent in both
directions simultaneously.
Example of Full Duplex is a Telephone Network in which there is
communication between two persons by a telephone line, using which
both can talk and listen at the same time.
In full duplex system there can be two lines one for sending the data and
the other for receiving data.
21. Difference: Connection oriented and
Connectionless service
In connection oriented service authentication is
needed, while connectionless service does not
need any authentication.
Connection oriented protocol makes a connection
and checks whether message is received or not
and sends again if an error occurs, while
connectionless service protocol does not
guarantees a message delivery.
Connection oriented service is more reliable than
connectionless service.
Connection oriented service interface is stream
based and connectionless is message based.
22. A network protocol defines rules and
conventions for communication between
network devices. Network protocols include
mechanisms for devices to identify and make
connections with each other, as well as
formatting rules that specify how data is
packaged into sent and received messages.
Some protocols also support
message acknowledgment and data
compression designed for reliable and/or
high-performance network communication.
23. packet switching techniques to send and
receive messages in the form of packets —
messages subdivided into pieces that are
collected and reassembled at their
destination. Hundreds of different computer
network protocols have been developed, each
designed for specific purposes and
environments.
24. Internet Protocols:
The Internet Protocol (IP) family contains a set of related (and
among the most widely used) network protocols. Beside Internet
Protocol itself, higher-level protocols like TCP(Transmission
Control Protocol), UDP(User Datagram
Protocol), HTTP(Hypertext Transfer Protocol), and FTP(File
Transfer Protocol) all integrate with IP to provide additional
capabilities. Similarly, lower-level Internet Protocols
like ARP(Address Resolution Protocol) and ICMP(Internet
Control Message Protocol) also coexist with IP. In general,
higher-level protocols in the IP family interact more closely with
applications like web browsers, while lower-level protocols
interact with network adapters and other computer hardware.
Wireless Network Protocols:
Wi-Fi(wireless fidelity), Bluetooth, and LTE(Long Term
Evolution) are wireless networks have become commonplace.
25. A router is a networking device that forwards data
packets between computer networks.
26. Modem
A modem ( modulator-demodulator) is
a hardware device that converts data
between transmission media so that it can be
transmitted from computer to computer
(historically over telephone wires). The goal is
to produce a signal that can be transmitted
easily and decoded to reproduce the original
digital data.
27. A hub, also called a network hub, is a common
connection point for devices in a network. Hubs
are devices commonly used to
connect segments of a LAN. The hub contains
multiple ports. When a packet arrives at one port,
it is copied to the other ports so that all segments
of the LAN can see all packets.
What Hubs Do
Hubs and switches serve as a central connection
for all of your network equipment and handles a
data type known as frames. Frames carry your
data. When a frame is received, it is amplified and
then transmitted on to the port of the destination
PC.
28. Switch:
A switch is a device in a computer network that
connects other devices together. Multiple data cables
are plugged into a switch to enable communication
between different networked devices. Switches
manage the flow of data across a network by
transmitting a received network packet only to the one
or more devices for which the packet is intended. Each
networked device connected to a switch can be
identified by its network address, allowing the switch to
direct the flow of traffic maximizing the security and
efficiency of the network.MAC address is read.
29. A bridge is a type of computer network device
that provides interconnection with other bridge
networks that use the same protocol. Bridge
devices work at the data link layer.
bridging connects two separate networks as
if they were a single network.
There are four main types of network bridging
technologies: simple bridging, multiport
bridging, transparent bridging, and source
route bridging.
