This document discusses different types of network hardware, transmission technologies, and topologies. It describes: - The two main transmission technologies are broadcast links which transmit to all devices, and point-to-point links which transmit between two devices. - Network topologies include star, tree, bus, mesh, and ring. Star topology uses a central hub. Tree uses a root node connected in a hierarchy. Bus uses a shared backbone. Mesh connects all devices directly. Ring connects devices in a loop. - Transmission modes are simplex (one-way), half-duplex (two-way but not simultaneous), and full-duplex (two-way simultaneous transmission).

1. 1.1 Network Hardware
Transmission Technology- Broadcast link and Point to point link
Broadly speaking, there are two types of transmission technology that are in widespread use:
• broadcast links and
• point-to-point links.
1. Unicast –
This type of information transfer is useful when there is
a participation of single sender and single recipient. So,
in short, you can term it as a one-to-one transmission.
For example, a device having IP address 10.1.2.0 in a
network wants to send the traffic stream(data packets)
to the device with IP address 20.12.4.2 in the other
network, then unicast comes into the picture. This is
the most common form of data transfer over the
networks.

2. 2. Broadcast –
Broadcasting transfer (one-to-all) techniques can be classified
into two types :
Limited Broadcasting –
Suppose you have to send stream of packets to all the devices
over the network that you reside, this broadcasting comes
handy. For this to achieve, it will append 255.255.255.255 (all
the 32 bits of IP address set to 1) called as Limited Broadcast
Address in the destination address of the datagram (packet)
header which is reserved for information transfer to all the
recipients from a single client (sender) over the network.
•Direct Broadcasting –
This is useful when a device in one network wants to transfer
packet stream to all the devices over the other network. This is
achieved by translating all the Host ID part bits of the
destination address to 1, referred as Direct Broadcast
Address in the datagram header for information transfer.

3. Multicast
A multicast is a transmission of data from a single source to multiple recipients. Multicasting is similar
to broadcasting, but only transmits information to specific users. It is used to efficiently
transmit streaming media and other types of data to multiple users at one time.
The simple way to send data to multiple users simultaneously is to transmit individual copies of the data to
each user. However, this is highly inefficient, since multiple copies of the same data are sent from the source
through one or more networks. Multicasting enables a single transmission to be split up among multiple
users, significantly reducing the required bandwidth.
Multicasts that take place over the Internet are known as IP multicasts, since they use the Internet protocol
(IP) to transmit data. IP multicasts create "multicast trees," which allow a single transmission to branch out to
individual users. These branches are created at Internet routers wherever necessary. For example, if five users
from five different countries requested access to the same stream, branches would be created close to the
original source. If five users from the same city requested access to the same stream, the branches would be
created close to users.
IP multicasting works by combining two other protocols with the Internet protocol. One is the Internet Group
Management Protocol (IGMP), which allows users or client systems use to request access to a stream. The
other is Protocol Independent Multicast (PIM), which is used by network routers to create multicast trees.
When a router receives a request to join a stream via IGMP, it uses PIM to route the data stream to the
appropriate system.
Multicasting has several different applications. It is commonly used for streaming media over the Internet,
such as live TV and Internet radio. It also supports video conferencing and webcasts. Multicasting can also be
used to send other types of data over the Internet, such as news, stock quotes, and even digital copies
of software. Whatever the application, multicasting helps reduce Internet bandwidth usage by providing an
efficient way of sending data to multiple users.

5. Point to Point Communication Link
The point-to-point scheme provides separate communication channels for each pair of computers. When
more than two computers need to communicate with one another, the number of connections grows very
quickly as number of computer increases.
Above figure illustrates that two computers need only one connection, three computers need three connections
and four computers need six connections.The total number of connection grows more rapidly than the total
number of computers,which becomes a very expensive option.

6. Figure shows a point- to-point connection for five computers located at two different locations, say, ground and
first floor of a building.
As there are five PCs, total ten connections will be required for
point-to-point connection. Out of these ten connections six are
passing through the same locution and thereby making point-to-
point connection an expensive one. Increasing the PC by one in
the above configuration at location 2 as shown in Figure will
increase the total number of connections to fifteen. Out ‘of these
connections eight connections will pass through the same area.

7. 1.2 Types of communication-simplex,half duplex ,full duplex (Transmission Modes )
Transmission mode means transferring of data between two devices. It is also known as communication mode. Buses and
networks are designed to allow communication to occur between individual devices that are interconnected. There are three
types of transmission mode:-
1. Simplex Mode –
In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can
transmit, the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one
direction.
Example: Keyboard and traditional monitors. The keyboard can only introduce input, the monitor can only give the output.

8. Half-Duplex Mode –
In half-duplex mode, each station can both transmit and
receive, but not at the same time. When one device is sending,
the other can only receive, and vice versa. The half-duplex
mode is used in cases where there is no need for
communication in both direction at the same time. The entire
capacity of the channel can be utilized for each direction.
Example: Walkie- talkie in which message is sent one at a time
and messages are sent in both the directions.
Channel capacity=Bandwidth * Propagation Delay

9. Full-Duplex Mode –
In full-duplex mode, both stations can transmit and receive
simultaneously. In full_duplex mode, signals going in one
direction share the capacity of the link with signals going in
other direction, this sharing can occur in two ways:
•Either the link must contain two physically separate
transmission paths, one for sending and other for receiving.
•Or the capacity is divided between signals travelling in both
directions.
Full-duplex mode is used when communication in both
direction is required all the time. The capacity of the channel,
however must be divided between the two directions.
Example: Telephone Network in which there is communication
between two persons by a telephone line, through which both
can talk and listen at the same time.
Channel Capacity=2* Bandwidth*propagation Delay

10. 1.3 Types of network topology-Bus,Star,Mesh,Ring,Tree

11. Star Topology
Star topology is the most popular network topology that is used in many business and home networks today.
A star topology is established with a central connection point called a hub node. The hub may be an actual
hub device or a network switch or a network router. Network devices generally connect to the hub with
Unshielded Twisted Pair (UTP) Ethernet cables also known as RJ45 cables. The main benefit of a star
network is that failure in any start network cable will only take down one computer’s network access but not
the entire LAN. However, if the hub node fails, the entire network will be down in a start network.

12. Tree Topology
The tree topology is also known as hierarchical topology . In a tree topology, a central ‘root’ node (top level
of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy with a
point-to-point physical link. The second level node may also have connected to one or more other nodes that
are one level down in the hierarchy with another point-to-point link. The top level node i.e root node is the
only node that has no other node above it in the hierarchy.
Multiple star networks can be connected with tree network where each hub node of a star network functions
as the node of a tree network.

13. Bus Topology
In a bus network, a common backbone is connected to all network devices. The high capacity bus backbone
(generally a single cable) functions as a shared communications medium and it joins networks and central
devices. If any network device wants to communicate with another network device within a bus network, the
device sends a broadcast message onto the backbone. All other devices will see the broadcast message but only
the desired recipient will accepts and process the message.
The performance of a bus network will be visual negatively if more than few dozen computers are connected to
this network. In addition, failure of the backbone cable will damage the whole network.

14. Mesh Topology
In a mesh network, every network device is connected to every other network device with a point-to-point
connection. This topology is mostly used in WAN and wireless networks. The route concept is introduced by
mesh topology and this topology is used by routers to determine the best path. Mesh network also provides
physical link redundancy in the event of a link failure. As each device is connected to all other devices in a
mesh network, this topology is the most expensive and difficult to maintain.
Two types of mesh topology are possible. If every device is connected to all other devices, it is called full
mesh. On the other hand, partial mesh also possible where some devices are connected to only indirectly to
others.

15. Ring Topology
In a ring network, every network device is connected to two neighbor devices with a point-to-point
connection for communication purpose. All devices in a ring network make a loop. If any cable or device is
fail, the loop will break and also break down the entire ring network. In the ring network, messages travel
through the loop in the same direction (effectively either clockwise or counterclockwise). FDDI, SONET or
Token Ring technology is used to implement a ring network. A Token is passed from one computer to another
which enables each computer to have equal access to the network.

16. 1.4 Introduction to LAN,MAN,WAN
Based on geographical spread, networks can be classified into the following three categories.
1. Local Area Network (LAN)
2. Metropolitan Area Network (MAN)
3. Wide area network (WAN)
Local Area Network (LAN)
1. Local area network is a group of computers connected
with each other in a small places such as school, hospital,
apartment etc.
2. LAN is secure because there is no outside connection
with the local area network thus the data which is shared
is safe on the local area network and can’t be accessed
outside.
3. LAN due to their small size are considerably faster, their
speed can range anywhere from 100 to 100Mbps.
4. LANs are not limited to wire connection, there is a new
evolution to the LANs that allows local area network to
work on a wireless connection.

17. Metropolitan Area Network (MAN)
MAN network covers larger area by connections LANs to
a larger network of computers. In Metropolitan area
network various Local area networks are connected with
each other through telephone lines. The size of the
Metropolitan area network is larger than LANs and smaller
than WANs(wide area networks), a MANs covers the
larger area of a city or town.

18. Wide area network (WAN)
Wide area network provides long distance transmission of
data. The size of the WAN is larger than LAN and MAN. A
WAN can cover country, continent or even a whole world.
Internet connection is an example of WAN. Other
examples of WAN are mobile broadband connections
such as 3G, 4G etc.

19. Advantages of WAN:
Centralized infrastructure: One of the main advantage of WAN is the that we do not need to maintain the backup
and store data on local system as everything is stored online on a data centre, from where we can access the
data through WAN.
Privacy: We can setup the WAN in such a way that it encrypts the data that we share online that way the data is
secure and minimises the risk of unauthorized access.
Increased Bandwidth: With the WAN we get to choose the bandwidth based on the need, a large organization can
have larger bandwidth that can carry large amount of data faster and efficiently.
Area: A WAN can cover a large area or even a whole world though internet connection thus we can connect with
the person in another country through WAN which is not possible is other type of computer networks.
Disadvantages of WAN:
Antivirus: Since our systems are connected with the large amount of systems, there is possibility that we may
unknowingly download the virus that can affect our system and become threat to our privacy and may lead to data
loss.
Expensive: Cost of installation is very high.
Issue resolution: Issue resolution takes time as the WAN covers large area, it is really difficult to pin point the
exact location where the issues raised and causing the problem.
Interconnection of Networks:
We have read LAN, MAN and WAN above, we also talked about internet. You can say that an internet is a
combination of LAN, MAN and WAN.

20. Communication Networks can be of following 5 types:
1.Local Area Network (LAN)
2.Metropolitan Area Network (MAN)
3.Wide Area Network (WAN)
4.Wireless
5.Inter Network (Internet)
Local Area Network (LAN)
It is also called LAN and designed for small physical areas such as an office, group of buildings or a factory. LANs are used
widely as it is easy to design and to troubleshoot. Personal computers and workstations are connected to each other
through LANs. We can use different types of topologies through LAN, these are Star, Ring, Bus, Tree etc.
LAN can be a simple network like connecting two computers, to share files and network among each other while it can
also be as complex as interconnecting an entire building.
LAN networks are also widely used to share resources like printers, shared hard-drive etc.

21. Characteristics of LAN
•LAN's are private networks, not subject to tariffs or other
regulatory controls.
•LAN's operate at relatively high speed when compared to the
typical WAN.
•There are different types of Media Access Control methods in
a LAN, the prominent ones are Ethernet, Token ring.
•It connects computers in a single building, block or campus,
i.e. they work in a restricted geographical area.
Applications of LAN
•One of the computer in a network can become a server
serving all the remaining computers called clients. Software can
be stored on the server and it can be used by the remaining
clients.
•Connecting Locally all the workstations in a building to let
them communicate with each other locally without any
internet access.
•Sharing common resources like printers etc are some common
applications of LAN.

22. Advantages of LAN
•Resource Sharing: Computer resources like printers, modems, DVD-ROM drives and hard disks can be shared with
the help of local area networks. This reduces cost and hardware purchases.
•Software Applications Sharing: It is cheaper to use same software over network instead of purchasing separate
licensed software for each client a network.
•Easy and Cheap Communication: Data and messages can easily be transferred over networked computers.
•Centralized Data: The data of all network users can be saved on hard disk of the server computer. This will help users
to use any workstation in a network to access their data. Because data is not stored on workstations locally.
•Data Security: Since, data is stored on server computer centrally, it will be easy to manage data at only one place
and the data will be more secure too.
•Internet Sharing: Local Area Network provides the facility to share a single internet connection among all the LAN
users. In Net Cafes, single internet connection sharing system keeps the internet expenses cheaper.