DCC MODULE 4 PPT .pptx

SEMESTER : 4th
SUBJECT : DATA COMMUNICATION AND COMPUTER
NETWORK.
CHAPTER : Network topologies and network devices.
TOPIC : Network topology: introduction ,defination , types of
topology (i) ring (ii) bus (iii)star (iv)mesh (v)tree
(vi)hybrid.
Network connecting device: hub, switch ,router
,repeater ,bridge ,gateway, modern, wireless
infrastructure components.
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Content:
Network topologies.
Types of topology: bus, star, ring, mesh, tree, hybrid.
Network connecting devices: hub, switch, router,
repeater, bridge, gateway, modern, wireless
infrastructure components.

Network topologies: A network topology is the physical
and logical arrangement of nodes and connections in a
network. Nodes usually include devices such as switches,
routers and software with switch and router features. Network
topologies are often represented as a graph.
Network topologies describe the arrangement of networks
and the relative location of traffic flows.
Network geometry can be defined as the physical
topology and the logical topology. Physical – The physical
network topology refers to the actual connections (wires,
cables, etc.) of how the network is arranged. Setup,
maintenance, and provisioning tasks require insight into the
physical network.
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Logical – The logical network topology is a higher-level idea of how the
network is set up, including which nodes connect to each other and in which
ways, as well as how data is transmitted through the network. Logical network
topology includes any virtual and cloud resources.

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Physical Topology Logical Topology
Depicts physical layout of network.
Depicts logistics of network concerned with
transmission of data.
The layout can be modified based on needs.
There is no interference and manipulation involved
here.
It can be arranged in star, ring, mesh and bus
topologies.
It exists in bus and ring topologies.
This has major impact on cost, scalability and
bandwidth capacity of network based on selection
and availability of devices.
This has major impact on speed and delivery of data
packets. It also handles flow control and ordered
delivery of data packets.
It is actual route concerned with transmission. It is a high level representation of data flow.
Physical connection of the network. Data path followed of the network.

ARMIET/IT/SEM-6/DMBI 6
• Defination: The way of connecting the computers in a network is
called as topology.
•The topology of a network is the geometric representation of the relationship
of all the linking devices in a network.
•Network topology is defined as “the physical interconnection between
various elements on computer network, such as links and nodes.”
Types of topologies:
•Bus topology
•Ring topology
•Star topology
•Mesh topology
•Tree topology
•Hybrid topology

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Bus topology: The bus network topology is also referred to as
horizontal topology. This topology is very common among local area
networks. In this network, every computer is linked to a single connection
line or cable through an interface. Thus each computer can directly
communicate with other computer or device in the network.
Each work station or node has a particular address, and to access a specific
node, a user just needs to know its address.
Advantages
•The advantages of the tree network topology are as follows −
•Simple control of traffic flow
•Failure of a node does not influence the network.
•Disadvantages
•The disadvantages of the tree network topology are as follows −
•If the transmission channel fails, the entire network fails.
•It is complicated to isolate faults to any one particular component tied into
the bus.
•Because of the back of the concentration points, the problem resolution is
challenging.

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Ring topology: A ring topology is a network configuration where device
connections create a circular data path. Each networked device is connected to
two others, like points on a circle. Together, devices in a ring topology are called
a ring network.
In a ring network, packets of data travel from one device to the next until they
reach their destination. Most ring topologies allow packets to travel only in one
direction, called a unidirectional ring network. Others permit data to move in
either direction, called bidirectional.
The major disadvantage of a ring topology is that if any individual connection in
the ring is broken, the entire network is affected.
Advantages of a ring topology
•All data flows in one direction, reducing the chance of packet collisions.
•A network server is not needed to control network connectivity between each
workstation.
•Data can transfer between workstations at high speeds.
•Additional workstations can be added without impacting performance of the
network.

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Disadvantages of a ring topology
•All data being transferred over the network must pass through each
workstation on the network, which can make it slower than a star
topology.
•The entire network will be impacted if one workstation shuts
down.
•The hardware needed to connect each workstation to the network
is more expensive than Ethernet cards and hubs/switches.

Star topology: A star topology, sometimes known as a star network, is a
network topology in which each device is connected to a central hub. It is one
of the most prevalent computer network configurations, and it's by far the
most popular Network Topology. In this network arrangement, all devices
linked to a central network device are displayed as a star.
Applications of Star Topology
•In networking, star topology can be used a variety of places. You can find its
uses all around yourself due to its easy availability and cheap Star Topology
Equipment. However, some uses of star topology are as follows:
•Most computer labs in educational institutions utilise this design to connect
nodes in the lab.
•Our home networks are clearly configured in this Network Topology.
•Another use of star topology is the banking sector, where all banking users
are connected with each other with the help of this Type of Topology.

Advantages of Star Topology
•It is very reliable – if one cable or device fails then all the others will
still work
•It is high-performing as no data collisions can occur
•Less expensive because each device only need one I/O port and
wishes to be connected with hub with one link.
•Easier to put in
•Robust in nature
•Easy fault detection because the link are often easily identified.
•No disruptions to the network when connecting or removing
devices.
•Each device requires just one port i.e. to attach to the hub.
•If N devices are connected to every other in star, then the amount of
cables required to attach them is N. So, it’s easy to line up.
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Disadvantages of Star Topology
Requires more cable than a linear bus .
If the connecting network device (network switch) fails, nodes
attached are disabled and can’t participate in network
communication.
More expensive than linear bus topology due to the value of the
connecting devices (network switches)
If hub goes down everything goes down, none of the devices can
work without hub.
Hub requires more resources and regular maintenance because it’s
the central system of star .
Extra hardware is required (hubs or switches) which adds to cost
Performance is predicated on the one concentrator i.e. hub

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Mesh topology:A mesh topology is a network setup where each computer and
network device is interconnected with one another. This topology setup allows
for most transmissions to be distributed even if one of the connections goes
down. It is a topology commonly used for wireless networks. Below is a visual
example of a simple computer setup on a network using a mesh topology.
Advantages of a mesh topology
•Manages high amounts of traffic, because multiple devices can transmit data
simultaneously.
•A failure of one device does not cause a break in the network or transmission
of data.
•Adding additional devices does not disrupt data transmission between other
devices.
Disadvantages of a mesh topology
•The cost to implement is higher than other network topologies, making it a
less desirable option.
•Building and maintaining the topology is difficult and time consuming.
•The chance of redundant connections is high, which adds to the high costs
and potential for reduced efficiency.

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Hybrid topology: A hybrid topology is a type of network
topology that uses two or more differing network topologies.
These topologies can include a mix of bus topology, mesh
topology, ring topology, star topology, and tree topology.
The choice to use a hybrid topology over a standard topology
depends on the needs of a business, school, or the users. The
number of computers, their location, and desired network
performance are all factors in the decision.
Types of hybrid topologies
There are various types of hybrid topologies that integrate
many basic topologies to make a new form of topology on the
basis of the requirements. These topologies are hierarchical
network topology, Star wire Ring network topology, and star
wired bus topology.
1. Star-Ring hybrid topology
2. 2. Star-Bus hybrid topology

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1. Star-Ring hybrid topology
The star topology and ring topology are used to create the structure of a star
topology. Through a ring topology, two or more-star topologies are linked
with the help of a wired connection.
2. Star-Bus hybrid topology
A star-based bus topology is constructed by combining the two kinds of
topologies that are star topology and bus topology. The bus topology allows
two or more-star topologies to be linked to each other through wire
connection.

Advantages of Hybrid Topology
•Flexible: Hybrid Topology is the most flexible network topology as
it can be changed and assembled using different structures of
topology
•Used for a vast network: Hybrid topology was introduced to
overcome the shortcoming of other topologies i.e. they were not
able to fulfill the need for a vast network connection
•Reliable to use: Hybrid topology is a reliable and trustworthy
network connection structure as even when one node fails to work
it doesn’t shut down the whole system
•Any topology can be combined to make a new network
•Scalable: There is no fixed combination of topology networks to be
used in hybrid topology. A person or institute according to their
requirement can use any topology network to make a new network.

Disadvantages of Hybrid Topology:
•Design is very complex: Making a hybrid network takes lots of effort from
the network technicians of topologies as the design of networks is very
complex. Network processing also becomes very complex due to the complex
structure of topology.
•Costly: Hybrid topology requires a huge amount of resources and capital to
build up a network. These resources are costly and delicate to use. Once
damaged it must be bought back again to establish a better network thus
making it costlier than others.
•Difficult to install: Installation of such a vast and complex network is a
very difficult task. The cable network, as well as nodes, must be set
systematically. The workers must be skilled to install such a huge network
connection structure.
•Hardware requirements are more: The hardware used in the hybrid
topologies is more in number. The nodes cable and structure of the topology
make it difficult to install and multiple nodes require multiple cables for
establishing a connection.
•Cable failures: Sometimes due to cable failure of the main backbone cable
the other connected topologies that function with its help affect the entire
network.

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Network connecting device: Network devices, also known as networking
hardware, are physical devices that allow hardware on a computer network to
communicate and interact with one another. For example Repeater, Hub, Bridge,
Switch, Routers, Gateway, modem.
Hub – A hub is a basically multi-port repeater. A hub connects multiple wires
coming from different branches.
Repeater - the repeaters are used in places where amplification of input signal
is necessary.
Routers – A router is a device like a switch that routes data packets based on
their IP addresses. The router is mainly a Network Layer device.
Gateway – A gateway, as the name suggests, is a passage to connect two
networks that may work upon different networking models.

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Bridge – It is also known as the bridging router is a device that
combines features of both bridge and router.

Hub – A hub is a basically multi-port repeater. A hub connects multiple wires
coming from different branches, for example, the connector in star topology which
connects different stations. Hubs cannot filter data, so data packets are sent to all
connected devices. In other words, the collision domain of all hosts connected
through Hub remains one. Also, they do not have the intelligence to find out the
best path for data packets which leads to inefficiencies and wastage.
Types of Hub :
Active Hub:- These are the hubs that have their power supply and can clean, boost,
and relay the signal along with the network. It serves both as a repeater as well as a
wiring center. These are used to extend the maximum distance between nodes.
Passive Hub:- These are the hubs that collect wiring from nodes and power supply
from the active hub. These hubs relay signals onto the network without cleaning and
boosting them and can’t be used to extend the distance between nodes.
Intelligent Hub:- It works like an active hub and includes remote management
capabilities. They also provide flexible data rates to network devices. It also enables
an administrator to monitor the traffic passing through the hub and to configure
each port in the hub.

.
advantages of Hubs:
➨It can extend total distance of the network.
➨It does not affect performance of the network seriously.
➨It is cheaper.
➨It can connect different media types.
disadvantages of Hubs:
➨It does not have mechanisms such as collision detection and
retransmission of packets.
➨It does not operate in full duplex mode.
➨It can not connect different network architectures such as token ring and
ethernet etc.
➨It can not filter information i.e. it passes packets to all the connected
segments.
➨It does not have mechanism to reduce the network traffic.

Switch – A switch is a multiport bridge with a buffer and a design that can
boost its efficiency(a large number of ports imply less traffic) and performance. A
switch is a data link layer device. The switch can perform error checking before
forwarding data, which makes it very efficient as it does not forward packets that
have errors and forward good packets selectively to the correct port only. In other
words, the switch divides the collision domain of hosts, but the broadcast
domain remains the same.
Types of Switch
1. Managed switches: These switches offer advanced configuration options such
as VLANs, QoS, and link aggregation. They are suitable for larger, more
complex networks and allow for centralized management.
2. Unmanaged switches: These switches have a simple plug-and-play design and
do not offer advanced configuration options. They are suitable for small
networks or for use as an expansion to a larger network.
3. Smart switches: These switches have features similar to managed switches but
are typically easier to set up and manage. They are suitable for small- to
medium-sized networks.

1. Layer 2 switches: These switches operate at the Data Link layer of the OSI model
and are responsible for forwarding data between devices on the same network
segment.
2. Layer 3 switches: These switches operate at the Network layer of the OSI model and
can route data between different network segments. They are more advanced than
Layer 2 switches and are often used in larger, more complex networks.
3. PoE switches: These switches have Power over Ethernet capabilities, which allows
them to supply power to network devices over the same cable that carries data.
4. Gigabit switches: These switches support Gigabit Ethernet speeds, which are faster
than traditional Ethernet speeds.
5. Rack-mounted switches: These switches are designed to be mounted in a server
rack and are suitable for use in data centers or other large networks.

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Routers – A router is a device like a switch that routes data packets
based on their IP addresses. The router is mainly a Network Layer device.
Routers normally connect LANs and WANs and have a dynamically
updating routing table based on which they make decisions on routing
the data packets. The router divides the broadcast domains of hosts
connected through it.

Bridge : It is also known as the bridging router is a device that
combines features of both bridge and router. It can work either at
the data link layer or a network layer. Working as a router, it is
capable of routing packets across networks and working as the
bridge, it is capable of filtering local area network traffic.

Types of Bridges:
Transparent Bridge:
It is also known as the “Learning Bridges“. Transparent bridge has not
visibility to other installed stations or terminals over the computer network.
It does not need to reconfigure the station because it is either added or
deleted from the entire network. Main aim of the transparent bridge is
getting to block or forwarding the data packets depend on the MAC address.
It is getting more popularity while using in the networking.
Translational Bridge:
Translational bridge plays the role for converting the one networking system
to another type of system. This type of bridge allows to translate the fetched
data. With the help of translational bridge, two different types of networks
like as token ring and Ethernet network can be attached. It has a ability to
remove or add the any field and information from frame when it is required.

Source-Route Bridge:
Source-route bridge is introduced by IBM for using the Token ring networks.
It allows to embed the all frame routes into one frame, and then this bridge
takes the precise decisions that how the frame is forwarding with using of the
network. In this technique, two same network segments can be linked to data
link layer.
Special frames are discovered by the host, it is known as the “Discovery
Frame“, and it spreads them over the entire network. Source-route Bridge
helps to prevent the looping problems.
Remote Type Bridge:
Remote Bridge allows to make connection two networks at different locations
with using of WAN link like as MODEM or Leased Line. Its speed can be
varied depend on the local and wide area links. This bridge has internal buffer
that helps to hold the data grabbed from LAN network, and then it is getting

Repeater – A repeater operates at the physical layer. Its job is to regenerate the signal
over the same network before the signal becomes too weak or corrupted to extend the
length to which the signal can be transmitted over the same network. An important point
to be noted about repeaters is that they do not amplify the signal. When the signal
becomes weak, they copy it bit by bit and regenerate it at its star topology connectors
connecting if original strength. It is a 2-port device.
Advantages of the repeater:
•Repeaters can extend a network's total distance.
•A repeater is simple to connect.
•Repeaters do not seriously affect network performance.
•It is cost-effective.
•Certain repeaters can connect networks using different physical media.
•It has the ability to boost or strengthen the digital to retransmit.
•Some reporters can connect networks using various physical media

ARMIET/IT/SEM-6/DMBI
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Disadvantages of the repeater:
•Repeater are unable to reduce network traffic.
•Limitation in the number of repeaters.
•It cannot connect difference network architectures.
•It does not segment the network.
•Repeaters do not separate the device in the collision domain.
•Most of the repeaters on a network produce noise on the wire and increase the
possibility of packet collisions.
•A device that is separated only by a repeater is part of the same collision
domain.

Gateway :
A gateway is a network node that forms a passage between two networks operating
with different transmission protocols. The most common type of gateways, the
network gateway operates at layer 3, i.e. network layer of the OSI (open systems
interconnection) model. However, depending upon the functionality, a gateway can
operate at any of the seven layers of OSI model. It acts as the entry – exit point for a
network since all traffic that flows across the networks should pass through the
gateway. Only the internal traffic between the nodes of a LAN does not pass through
the gateway.
Features of Gateways
Gateway is located at the boundary of a network and manages all data that inflows or
outflows from that network.
It forms a passage between two different networks operating with different
transmission protocols.
A gateway operates as a protocol converter, providing compatibility between the
different protocols used in the two different networks.

Types of Gateways
•On basis of direction of data flow, gateways are broadly divided into two
categories −
•Unidirectional Gateways − They allow data to flow in only one direction.
Changes made in the source node are replicated in the destination node, but
not vice versa. They can be used as archiving tools.
•Bidirectional Gateways − They allow data to flow in both directions. They
can be used as synchronization tools.
ADVANTAGES OF GATEWAYS:
- Used to expand the network.
- Gateway is a server so it provides some security.
- We can connect two different types of networks.
- Protocol conversion is done.
- Effectively handles the traffic problems.
- And also establishes connections between internal network and external
network.

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DISADVANTAGES OF GATEWAY:
- Not an intelligent device. So noise prevention is not done.
- Never filter out the data
- Some what costly
- Protocol conversion is done so transmission rate is slower.
- Some what hard to handle.

Modem:
A modem converts data to a signal so it can be easily sent and received over a phone
line, cable, or satellite connection. For transmission over an analog telephone line—
which was once the most popular way to access the internet—the modem converts
data between analog and digital formats in real time for two-way network
communication. In the case of the high-speed digital modems popular today, the
signal is much simpler and doesn't require the analog-to-digital conversion.
Directional Capacity:
Half Duplex Modems: A point to a point system where more than two parties are
connected is called a duplex system. A half-duplex modem allows one-directional
transmission at a time. Carrier is detected through modem lines and the information
is given as signals to the digital interface of the communication system. There is only
one carrier frequency and the data will be transmitted only in one direction at a time.
The modem does not allow DTE transmissions and this will happen only if a
particular signal is passed.
Full Duplex Modems: Full duplex modem allows transmission from both directions
simultaneously. The two carriers are in line one is incoming and another one is
outgoing. The modems have a switch to transfer between half-duplex and full-duplex
systems. The performance of full-duplex is better when compared with half-duplex.
The wired connections can be used in full-duplex modems and they are two-wire
modems and four-wire modems. These types come under line connection as well.

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Transmission Types
Synchronized Modem: Synchronized transmission is a full-duplex type
transmission. Data is sent in the form of blocks or frames. Synchronization is a
compulsory communication need between the sender and receiver. In order to
send a large amount of data synchronized modems are more efficient and more
reliable. It is working with the help of clock signals and can handle continuous
stream of data bits. For transmission and reception, separate data bits are used.
Asynchronized Modem: Asynchronized modem is a half-duplex type modem
in which data is sent in the form of bytes or characters. The transmission using
this type of modem does not require synchronization. This type of modem is
able to handle data bytes with stop and start bytes. Only one byte or a character
flows at a time. The start and stop bit add two bits to the character sent. The
quality of the service offered is good.

ifference between Bridge and Repeater:
ifference between Bridge and Repeater:

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Thank you

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