ZAMBIA CATHOLIC UNIVERSITY
Faculty of Business, Management and Finance
BIT: 123 Data Communication and Security
Study Material (Unit 1 and Unit 2)
INTRODUCTION TO COMPUTER NETWORKS
1. COMPUTER NETWORK
Computer network is network consists of two or more computers that are linked in order to
share resources (such as printers and CDs), exchange files, or allow electronic communications.
The computers on a network may be linked through cables, telephone lines, radio waves,
satellites, or infrared light beams.
A Compute network should ensure:
reliability of the data communication process, should c
security of the data.
performance by achieving higher throughput and smaller delay times.
2. FACTORS DRIVING THE ADOPTION OF NETWORKS
Wired or Wireless
When it comes to making a decision between a wired or wireless network, there are a couple
of factors that you should consider such as the number of computers you have in your business
and your personal preferences.
Wireless networking is a smart and affordable business IT solution especially since wireless
technology is getting cheaper and easier to configure. It also provides a safer and sleeker
environment for your office as you won’t have wires dangling all around. Plus, if you have
laptop users in your office, they can use it anywhere they want without having to worry about
connection problems.
Ethernet (wired connection) on the other hand could possibly offer you faster connection
speeds at a lower cost.
So, when you are considering wired or wireless network, it really depends on the size of your
business, number of workstation available and office layout. If you are not too sure which one
you need, our business IT service experts will be able to help you figure out which one is the
most suitable one for your organization.
Peer-to-Peer or Client-Server
Both network types connect the computers in your office and optimize your workflow by
allowing everyone to share files, data and resources.
A peer-to-peer (P2P) networking service means that the computers function as the client and
server. Each computer is directly connected to each other and you only need a router, modem
and cables to set up a P2P network.
In a Client-server network, all computers are connected to a central server that acts as the hub
of your business’ data. Applications and files are also available on the server and everyone can
use these resources at any time, provided they are authorized to access the information.
The main difference between the two is that P2P network relies on information provided by
the clients (users) and it could have other issues such as limited performance and security, and
can only carry a small number of users.
Although client-server networks are a little bit pricier, it allows for faster processes, more RAM
and storage space, all which plays an important part in ensuring the efficiency of your
organization.
Cost
Equipment and maintenance costs are often the first consideration in network design.
Fortunately, the cost of hubs, routers and switches are relatively low when compared to the
early days of networking. Other items that need to be taken into consideration when designing
a network include cabling and labor. For small offices, the cost of these may be negligible. On
the other hand, even small manufacturing or warehouse operations may require a significant
investment of time and cabling material to provide connections where they are needed.
Security
Securing a network from outside intrusion or data theft is a primary concern for many
companies. While it is possible to eliminate the expense of Ethernet cabling by opting for a
wireless network solution, Wi-Fi networking is the least secure method of sharing data and
connections. The encryption methods built into most commercial routers, Wireless Encryption
Protocol (WEP), Wireless Protected Access (WPA) and the more recent WPA2, can be cracked
by skilled hackers. Designing a network with hard-wired Ethernet connections eliminates the
risk of intrusion to only those with physical access to the network. Unfortunately, this risk
expands dramatically when the local network is connected to the Internet.
Outside Access
Internet access has become all but mandatory for most modern businesses. It's a good idea to
consider the type of Internet connection required and the amount and type of support you will
receive from your Internet service provider before designing the rest of your network. Some
ISPs will provide support and advice on connection speed requirements and security concerns
for commercial accounts before installation. Keep in mind that connecting your network to the
Internet exposes it, at some level, to attack from anywhere in the world. If you routinely send
and receive sensitive data to and from remote locations, consider a virtual private network for
additional security. When handling sensitive information on the internal network only, a
firewall device or software implementation may be appropriate.
Expansion
Planning for growth in the initial stages can save future expenditures. The price difference, for
example, between a 16-port switch and a 32-port switch can be negligible when compared to
the cost of purchasing a new switch to replace one that is too small. Most network devices are
designed to provide several years of service. Buying equipment with an eye to expansion may
delay the need for additional investment in equipment.
Support
In most cases, the simpler the network design, the less technical support you'll require for both
installation and maintenance. If you need a complex, high-speed network, consider the level of
technical assistance available locally. Many small businesses can't justify the cost of full-time
IT personnel. Designing a simple network that can be serviced quickly by local technicians
should be a primary consideration. If your business demands a complex network beyond the
capabilities of local service, design sufficient redundancy in critical network elements to ensure
a minimum level of service until repairs can be made.
3. BENEFITS OF COMPUTER NETWORK
a). Data Storage
Al the data of the respective organization will be stored in a remote server that can be accessed
in any given time. Each and every employee within an organization will be able to access
them.
And many computers are interconnected through a central server there is an increase in
capacity. If in case one of the employees happens to lose data, there won't be any problem in
retrieval since all the information are already stored inside the central server.
b). Connecting Computers
A single network can be used to connect limited number of computers interconnecting with
each other. Hence, all the computers do not need to have a ISP account, they can be functioned
under the network with single unit.
And depending on the location of workplace the type of network that needs to be deployed
changes. If the employees of an organization happen to work within it, a Local Area
Network (LAN) will be sufficient. Others who work from far sites, needs to be connected using
larger Wide Area Network (WAN). Internet is one type of network which spans globally.
c). Problem Solving
Computer networking makes it possible for people all around the world to troubleshoot and
solve problems in lesser amount of time. Their services include, business, education and
medical. For an example, the business can start a blog to attract customers in various places.
And all the medical expenses can be viewed for an emergency using a computer network.
d). Reliability
The information stored on the central server is considered to be reliable. If one PC happens to
lose the information, similar kind of data can be accessed using another computer. This ensures
that no interruptions occur to the working environment, thus leading to smooth functioning.
e). Flexibility
There are numerous reasons which contribute to the flexibility of computer networks. It
provides the opportunity for the user to explore the fundamental things.
And also, information sharing can be done through different approaches. If information needs
to be sent to different people simultaneously then emails can be used. Social networking sites
such as Facebook too has the capability to share information. Or else files can be uploaded to
cloud servers so that they are made accessible to various devices. Computer networks contain
various information sharing options that can be convenient to different individuals.
f). Security
Security and protection is already included with computer network. Thus it provides a better
security to sensitive and confidential information. Employees can benefit from sharing personal
information with each other coworkers without worrying of exposure to the intruders. Without
the prior approval of users, even other workers will not be able to view user's files. Hence, it
can overall lead to fraud reduction.
g). Collaboration
Collaboration is made easy using computer network especially for the corporate world.
Whether it is connecting teams, organizing social meetups or acquiring personal responses, all
these tasks can be done comfortably.
Apart from businesses, families can also use personal networks to organize picnics, share
pictures and videos or put on a shopping list all without exposing their security.
h) Cost
Even though computer network involves high amount of setup cost, there are indirect cost
reductions here. For an example the inexpensive networking software only needs to be installed
once and made available for all of the connected computers. Which means that there is no need
to purchase the software frequently for each and every user.
Plus, there are very a smaller number of file storage expenses since files are stored using a
central server.
i). Resource Sharing
Using computer networking, connected resources such as scanners, printers and photocopy
machines can be shared across multiple users. This is particularly important for large
organizations where they need to buy resources for each and every staff. By using a common
network, companies can make sure that the resources are made available to all the employees
those are working.
j). Information Sharing
Unlike earlier time, file sharing with another user can be done effortless using computer
network. Using cloud services such as google drive and drop box; users can upload files to a
cloud server such that it is made available to other people. At a given time, users can access
and download the required files even if they are in remote locations. Thus, saving more time
and effort.
4. DISADVANTAGES OF COMPUTER NETWORK
a). Robustness
The connected systems on a network entirely depend on the main server. In case if the server
breaks down, the system cannot be used anymore.
Not only will the main server, if the problem lies on the central server or the bridging device
the entire network be failing. That is the reason why most of the large organizations tend to
keep their central server as a powerful computer which makes the implementation and
maintenance easy.
b). Independence
Since networks are based on the centralized server, most of the decisions are made themselves.
This hinders the freedom of user who wants to use the computer as they desire.
Moreover, computer networking includes new procedures which makes the process easy. Thus,
there are more chances where users will be relying on computers even for basic tasks that
cannot be done by hand.
c). Malware Attack
Basically, due to their interactions, a virus can easily spread between computers in a network.
Even if one of the computers happens to get infected with malware, there are high chances of
them spreading to remaining computers.
Similar instances can happen if the central server becomes infected. All these can lead to file
corruption. For avoiding this, the network administrator should regularly scan for malwares.
d). Implementation
Al though computer networks are considered to be cost effective, it is certainly not when it is
implemented. Setting up a computer network can be expensive. It depends on the number of
systems connected. Additionally, there must be separate cables and equipment such as
switches, routers and hubs.
e). Security
Unlike standalone computers, a computer connected to a network possess many security risks.
Since there are large number of users using the network. For large networks such as WAN,
hackers can easily access the network using specialized tools developed for this purpose.
However, for preventing theft and other illegal activities, large organizations tend to use
various security tools such as firewall.
f). Productivity
One of the major problems of computer networking is that it can drastically decrease the
productivity of the company. When there is an internet access, employees can use it for other
purposes other than the office work. While this can help to relieve stress of employees, it can
contribute to higher percentage of productivity loss. Therefore, management must decide to
what extent they can allow the computer use.
g). Maintenance
For the proper functioning of a computer network, it requires regular maintenance. The
problem is this cannot be done with basic skills. It involves advanced configurations and
complicated installations. Therefore, a skilled network manager with experience needs to be
deployed.
h). Health Issues
Computer networking includes various entertainment options such as gaming. While gaming
works as a stress buster for many, playing for a long time can make the user addictive.
Gaming addiction in essence can cause many health issues both physical and mental. Some of
them are insomnia and obesity.
i). Accessibility
Even though most of the modern computers provide free access, there are still connectivity
issues in some countries. Particularly countries those are developing, people residing there
suffer from connectivity challenges. Unless these challenges are resolved, there is no assurance
of true global network.
j). Multitasking
Another advantage of computer network is that it allows multitasking. However not everyone
can take benefit of this. Most people who perform multitasking, tends to lose high level of
productivity. There are very few numbers of people who are able to perform multitasks without
losing productivity.
5. TYPES OF COMPUTER NETWORK
a). Personal Area Network (PAN)
The smallest and most basic type of network, a PAN is made up of a wireless modem, a
computer or two, phones, printers, tablets, etc., and revolves around one person in one building.
These types of networks are typically found in small offices or residences, and are managed by
one person or organization from a single device.
b). Local Area Network (LAN)
We’re confident that you’ve heard of these types of networks before – LANs are the most
frequently discussed networks, one of the most common, one of the most original and one of
the simplest types of networks. LANs connect groups of computers and low-voltage devices
together across short distances (within a building or between a group of two or three buildings
in close proximity to each other) to share information and resources. Enterprises typically
manage and maintain LANs.
Using routers, LANs can connect to wide area networks (WANs, explained below) to rapidly
and safely transfer data.
c). Wireless Local Area Network (WLAN)
Functioning like a LAN, WLANs make use of wireless network technology, such as Wi-Fi.
Typically seen in the same types of applications as LANs, these types of networks don’t require
that devices rely on physical cables to connect to the network.
d). Campus Area Network (CAN)
Larger than LANs, but smaller than metropolitan area networks (MANs, explained below),
these types of networks are typically seen in universities, large K-12 school districts or small
businesses. They can be spread across several buildings that are fairly close to each other so
users can share resources.
e). Metropolitan Area Network (MAN)
These types of networks are larger than LANs but smaller than WANs – and incorporate
elements from both types of networks. MANs span an entire geographic area (typically a town
or city, but sometimes a campus). Ownership and maintenance is handled by either a single
person or company (a local council, a large company, etc.).
f). Wide Area Network (WAN)
Slightly more complex than a LAN, a WAN connects computers together across longer
physical distances. This allows computers and low-voltage devices to be remotely connected
to each other over one large network to communicate even when they’re miles apart.
The Internet is the most basic example of a WAN, connecting all computers together around
the world. Because of a WAN’s vast reach, it is typically owned and maintained by multiple
administrators or the public.
g). Storage-Area Network (SAN)
As a dedicated high-speed network that connects shared pools of storage devices to several
servers, these types of networks don’t rely on a LAN or WAN. Instead, they move storage
resources away from the network and place them into their own high-performance network.
SANs can be accessed in the same fashion as a drive attached to a server. Types of storagearea networks include converged, virtual and unified SANs.
h). System-Area Network (also known as SAN)
This term is fairly new within the past two decades. It is used to explain a relatively local
network that is designed to provide high-speed connection in server-to-server applications
(cluster environments), storage area networks (called “SANs” as well) and processor-toprocessor applications. The computers connected on a SAN operate as a single system at very
high speeds.
i). Passive Optical Local Area Network (POLAN)
As an alternative to traditional switch-based Ethernet LANs, POLAN technology can be
integrated into structured cabling to overcome concerns about supporting traditional Ethernet
protocols and network applications such as Poe (Power over Ethernet). A point-to-multipoint
LAN architecture, POLAN uses optical splitters to split an optical signal from one strand of
single mode optical fiber into multiple signals to serve users and devices.
j). Enterprise Private Network (EPN)
These types of networks are built and owned by businesses that want to securely connect its
various locations to share computer resources.
k). Virtual Private Network (VPN)
By extending a private network across the Internet, a VPN lets its users send and receive data
as if their devices were connected to the private network – even if they’re not. Through a virtual
point-to-point connection, users can access a private network remotely.
6.ETHERNET
Ethernet is a technology that connects wired local area networks (LANs) and enables the device
to communicate with each other through a protocol which is the common network language.
This LAN is a network of computers and other electronic devices which covers a small area in
your places like in the office, house, room or building. Unlike LAN, wide area network (WAN)
covers much larger geographical areas. Furthermore, Ethernet is a protocol that controls the
processes on how the data is transmitted through LAN. It also indicates how the network
devices can transmit and format data packets so that the other network devices in the same area
network segment can be able to receive, process and recognize them.
Any other devices with access to a geographically localized network by the use of a cable such
as with wire rather than a wireless connection most likely use Ethernet whether at home, office
or a school setting. However, these physical cables have an only limited distance that they can
totally stretch and carry enough signals through their durability. This is the reason why there
are different types of Ethernet cables used to perform a particular task in a certain situation.
The following are the different types of Ethernet cables:
10Base2 – thin Ethernet
10Base 5 – thin Ethernet
10Base-T – Twisted-pair cable and can achieve a speed of 10 Mbps
100Base-FX- this makes possible in achieving a speed of 100 Mbps through multimode fiber
optic.
100Base-TX- similar to twisted-pair cable but with a 10 times greater speed.
1000Base-T- double twisted-pair cable of category 5 cables that allows a speed up to one
Gigabit per second.
1000Base-SX- this is based on multimode fiber optic that uses a short wavelength signal of
850 nanometers.
1000Base-LX – this is also based on multimode fiber optic but uses a long wavelength signal.
Ethernet Networks
The following are the different types of Ethernet networks:
Fast Ethernet
This is a type of Ethernet network that can transmit data at a rate of 100 Mbps through a twistedpair cable or fiber-optic cable. The data can be transferred from 10 Mbps to 100 Mbps with no
protocol translation or changes in the application and networking software.
Gigabit Ethernet
This is a type of Ethernet network that has the capability to transfer data at a rate of 1000 Mbps
based on a twisted-pair cable or fiber-optic cable. Among other types of Ethernet cable, this is
the most popular one.
Switch Ethernet
This is a piece of network equipment that is required for multiple network devices in a LAN.
In using this type of cable, a regular network cable shall be used instead of a crossover cable.
This Ethernet cable forwards the data from one device to another device with the same network.
Normally, this supports different data transfer rates. Ethernet is widely used as a network
technology due to the fact that the cost of such a network is not too high.[3]
Ethernet Origins
IEEE 802.3, which was defined by the Institute of Electrical and Electronics Engineers (IEEE),
introduced the standards or policies governing the use of Ethernet. During its launch in the
1980s, Ethernet technologies employed a single coaxial cable from which all devices in a local
area, identified by their media access control (MAC) addresses, and are connected to. This
early Ethernet model was called “10BASE5,” which users colloquially referred to as “thick
net.”
The issue with this antiquated setup is that when there’s a problem with one computer, the
whole network is affected. So-called “collisions” or what we now know as “network
congestion,” occur when devices “talk” with each other all at once. As such, communication
between devices should take place one after the other.
The arrival of twisted pair cabling and hubs and switches have eliminated this technical issue.
Individual connections now allow devices to transport data independently without relying on
the main cable. Thus, in the modern setup, problems on a particular port will not impact other
users on the network.
Another significant improvement is Ethernet’s reach. Back then, connections were limited to
100 meters from the switch to the device. However, today’s fiber-optic technology has
substantially extended the distance between endpoints.
7.How Ethernet Works
Ethernet lies in the lower layers of the Open Systems Interconnection (OSI) model. It facilitates
the operation of physical and data link layers. The OSI model, which is composed of seven
layers, illustrates how various communication protocols work together.
The OSI’s seven layers are:
Physical layer
Data link layer
Network layer
Transport layer
Session layer
Presentation layer
Application layer
The topmost layer is the application layer, which enables users to download and access data
from a browser or mail client. Users enter their queries through the application, which forwards
it to the next layer. The request comes in what’s called a “packet.” The packet contains data
about the destination web address and information about the sender. This information includes
the sender’s IP address, device version, and browser agent.
The packet is transmitted from the application layer until it reaches the bottom layer (now
called an “Ethernet frame”). The bottom or first layer is the one closest to your device. The
packet travels back and forth the OSI stack, being packed and unpacked in each layer for
checking.
7.ETHERNET ADVANTAGES AND DISADVANTAGES
Like any other technology, there is a good and a bad side to using Ethernet.
While Ethernet connection is faster than wireless, it is not mobile. A device designed to connect
to a network via cables or through Ethernet access can’t be quickly brought to another location,
such as from the office to an employee’s home. And unlike a wireless network, an Ethernet or
wired network is less flexible. You can’t easily add users to a wired network as you would to
a wireless one, especially if you don’t have the equipment (empty ports on routers and such)
and accessories (cables and the like) on hand.
But an Ethernet connection is more secure than a Wi-Fi connection. You can more easily
control who accesses an Ethernet network as opposed to a wireless one. That makes Ethernet
connections less prone to so-called “sniffing attacks.”
Ethernet access is also more stable than wireless access since radio frequencies don’t affect it.
Using specialized cables (e.g., Cat6) also allows Ethernet users to save on power consumption.
Ethernet networks, however, fall a bit on the pricey side to expand, not to mention timeconsuming. That’s because you’ll need more routers, switches, and meters and meters of wires.
You’ll also need to rewire all the devices, which takes a lot of time. Add to that the fact that
you’ll need professionals for network expansion as some wires may need to pass through walls
or floors.
Ethernet has been a widely used method of connecting computers. While its use may have been
superseded by the Internet, most organizations still rely on Ethernet for its security.
8.NETWORK TOPOLOGIES
Network topology
Network topology is the description of the arrangement of nodes (e.g., networking switches
and routers) and connections in a network, often represented as a graph.
No matter how identical two organizations are, no two networks are exactly alike. However,
many organizations are relying on well-established network topology models. Network
topologies outline how devices are connected together and how data is transmitted from one
node to another.
A logical network topology is a conceptual representation of how devices operate at particular
layers of abstraction. A physical topology details how devices are physically
connected. Logical and physical topologies can both be represented as visual diagrams.
A network topology map is a map that allows an administrator to see the physical network
layout of connected devices. Having the map of a network’s topology on hand is very useful
for understanding how devices connect to each other and the best techniques for
troubleshooting.
Types of network topology
There are many different types of topologies that enterprise networks have built on today and
in the past. Some of the network topologies we’re going to look at include bus topology, ring
topology, star topology, mesh topology, and hybrid topology.
What are the types of network topology?
Bus Topology Simple layout and cheap but vulnerable to failure and only suitable for low
traffic volumes. Not used for office networks today, but can still be found within some
consumer products.
Ring Topology Easy to manage and with a low risk of collision but reliant on all nodes being
powered up and in full working order. Rarely used today.
Star Topology All devices are connected to a central switch, which makes it easy to add new
nodes without rebooting all currently connected devices. This topology makes efficient use of
cable and is easy to administer. On the other hand, the health of the switch is vital. This
topology requires monitoring and maintenance. However, it is a commonly encountered
topology.
Tree Topology A hierarchical layout that links together groups of nodes. Creates parent-child
dependencies between root nodes and regular nodes. This layout can be vulnerable to failure if
a root node has a problem. This topology is complicated and difficult to manage and it uses a
lot of cable.
Mesh Topology Each node is connected to every other mode with a direct link. This topology
creates a very reliable network, but requires a large amount of cable and is difficult to
administer. Wi-Fi networks make this topology more feasible.
Hybrid Topology combines two or more of the standard topologies. This can be a good solution
to create quickly link together different existing networks into a unified system. Don’t confuse
the term “hybrid network topology” with “hybrid system” – a term that is applied to the
combination of onsite and cloud resources.
Bus Topology
Bus Topology Diagram
Pros:
Easy installation
Fewer cables required than Mesh and star topology
Good for small businesses
Low cost
Easy to manage and expand
Cons:
Backbone performance is critical
Easily congested on busy periods
Efficiency decreases rapidly with each added node
Data can only travel in one direction at any point in time
Bus topology is a network type where every device is connected to a single cable that runs from
one end of the network to the other. This type of network topology is often referred to as line
topology. In a bus topology, data is transmitted in one direction only. If the bus topology has
two endpoints, then it is referred to as a linear bus topology.
Smaller networks with this type of topology use a coaxial or RJ45 cable to link devices
together. However, the bus topology layout is outdated and you’re unlikely to encounter a
company using a bus topology today.
Advantages
Bus topologies were often used in smaller networks. One of the main reasons is that they keep
the layout simple. All devices are connected to a single cable so you don’t need to manage a
complex topological setup.
The layout also helped make bus topologies cost-effective because they can be run with a single
cable. In the event that more devices need to be added then you could simply join your cable
to another cable.
Disadvantages
However, relying on one cable does mean that bus topologies have a single point of failure. If
the cable fails then the entire network will go down. A cable failure would cost organizations
a lot of time while they attempt to resume service. Further to this, high network traffic would
decrease network performance because all the data travels through one cable.
This limitation makes bus topologies suitable only for smaller networks. The primary reason
is that the more network nodes you have, the slower your transmission speeds are going to be.
It is also worth noting that bus topologies are limited in the sense that they are half-duplex,
which means that data can’t be transmitted in two opposite directions simultaneously.
Ring Topology
Ring Topology Diagram
Pros:
Low incidence of collision
Low cost
Suitable for small businesses
Dual ring option provides continuity through redundancy
Cons:
One faulty node will bring the entire network down
Requires extensive preventative maintenance and monitoring
Performance declines rapidly with each additional node
Reorganizing the network requires a full system shutdown
In networks with ring topology, computers are connected to each other in a circular
format. Every device in the network will have two neighbors and no more or no less. Ring
topologies were commonly used in the past but you would be hard-pressed to find an enterprise
still using them today.
The first node is connected to the last node to link the loop together. As a consequence of being
laid out in this format packets need to travel through all network nodes on the way to their
destination.
Within this topology, one node is chosen to configure the network and monitor other devices.
Ring topologies are half-duplex but can also be made full-duplex. To make ring topologies fullduplex you would need to have two connections between network nodes to form a Dual Ring
Topology.
Dual Ring Topology
Dual Ring Topology Diagram
As mentioned above, if ring topologies are configured to be bidirectional then they are referred
to as dual ring topologies. Dual ring topologies provide each node with two connections, one
in each direction. Thus, data can flow in a clockwise or counterclockwise direction.
Advantages
With ring topologies, the risk of packet collisions is very low due to the use of token-based
protocols, which only allow one station to transmit data at a given time. This is compounded
by the fact that data can move through network nodes at high speeds which can be expanded
on when more nodes are added.
Dual ring topologies provided an extra layer of protection because they were more resistant to
failures. For instance, if a ring goes down within a node, then the other ring can step up and
back it up. Ring topologies were also low cost to install.
Disadvantages
One of the reasons why ring topologies were replaced is because they are very vulnerable to
failure. The failure of one node can take the entire network out of operation. This means that
ring topology networks need to be constantly managed to ensure that all network nodes are in
good health. However, even if the nodes were in good health your network could still be
knocked offline by a transmission line failure!
Ring topologies also raised scalability concerns. For instance, bandwidth is shared by all
devices within the network. In addition, the more devices that are added to a network the more
communication delay the network experiences. This means that the number of devices added
to a network topology needed to be monitored carefully to make sure that the network resources
weren’t stretched beyond their limit.
Making changes to a ring topology was also complicated because you need to shut down the
network to make changes to existing nodes or add new nodes. This is far from ideal as you’ll
need to factor in downtime every time you want to make a change to the topological structure!
Star Topology
Star Topology Diagram
Pros:
Easy to manage from one point – the switch
Easy to add and remove nodes
Durable
Low cable usage
Good for small businesses
Cons:
Requires specialist network hardware (the switch)
Makes the network reliant on the switch’s performance
A finite number of switch ports limits the network’s size
A star topology is a topology where every node in the network is connected to one central
switch. Every device in the network is directly connected to the switch and indirectly connected
to every other node. The relationship between these elements is that the central network hub is
a server and other devices are treated as clients. The central node has the responsibility of
managing data transmissions across the whole network and acts as a repeater. With star
topologies, computers are connected with a coaxial cable, twisted pair, or optical fiber cable.
Advantages
Star topologies are most commonly-used because you can manage the entire network from one
location: the central switch. As a consequence, if a node that isn’t the central node goes down
then the network will remain up. This gives star topologies a layer of protection against failures
that aren’t always present with other topology setups. Likewise, you can add new computers
without having to take the network offline like you would have to do with a ring topology.
In terms of physical network structure, star topologies require fewer cables than other topology
types. This makes them simple to set up and manage over the long-term. The simplicity of the
overall network design makes it much easier for administrators to run troubleshooting when
dealing with network performance faults.
Disadvantages
Though star topologies may be relatively safe from failure, if the central switch goes down then
the entire network will go down. As such, the administrator needs to manage the health of the
central node closely to make sure that it doesn’t go down. The performance of the network is
also tied to the central node’s configurations and performance. Star topologies are easy to
manage in most ways but they are far from cheap to set up and use.
Tree Topology
Tree Topology Diagram
Pros:
Blends bus and star topologies
Easy to manage
Easy to expand
Suitable for middle-sized businesses
Cons:
The network is dependent on the health of the root node
Requires networking expertise
Involves a lot of cable
Larger implementations require monitoring software
Can get expensive
As the name suggests, a tree topology network is a structure that is shaped like a tree with its
many branches. Tree topologies have a root node that is connected to another node hierarchy.
The hierarchy is parent-child where there is only one mutual connection between two
connected nodes. As a general rule, a tree topology needs to have three levels to the hierarchy
to be classified this way. This form of topology is used within Wide Area Networks to sustain
lots of spread-out devices.
Advantages
The main reason why tree topologies are used is to extend bus and star topologies. Under this
hierarchical format, it is easy to add more nodes to the network when your organization grows
in size. This format also lends itself well to finding errors and troubleshooting because you can
check for network performance issues systematically throughout the tree.
Disadvantages
The most significant weakness of tree topology is the root node. If the root node fails then all
of its subtrees become partitioned. There will still be partial connectivity within the network
amongst other devices such as the failed node’s parent.
Maintaining the network system is not simple either because the more nodes you add, the more
difficult it becomes to manage the network. Another disadvantage of a tree topology is the
number of cables you need. Cables are required to connect every device throughout the
hierarchy which makes the network layout more complex when compared to a simpler
topology.
Mesh Topology
Mesh Topology Diagram
Pros:
High speeds data transfers
Durable network that isn’t dependent on any one node
Very secure
Suitable for high-value networks for small to middle-sized networks
Easy to identify faulty equipment
Cons:
Requires a very large amount of cable
Can be difficult to secrete all the cable
Takes a long time to set up
Requires meticulous planning
There is a limit to the number of cables each computer can accommodate
A mesh topology is a point-to-point connection where nodes are interconnected. In this form
of topology, data is transmitted via two methods: routing and flooding. Routing is where nodes
use routing logic to work out the shortest distance to the packet’s destination. In contrast,
flooding is where data is sent to all nodes within the network. Flooding doesn’t require any
form of routing logic to work.
There are two forms of mesh topology: partial mesh topology and full mesh topology. With
partial mesh topology, most nodes are interconnected but there are a few which are only
connected to two or three other nodes. A full mesh topology is where every node is
interconnected.
Advantages
Mesh topologies are used first and foremost because they are reliable. The interconnectivity of
nodes makes them extremely resistant to failures. There is no single machine failure that could
bring down the entire network. The absence of a single point of failure is one of the reasons
why this is a popular topology choice. This setup is also secure from being compromised.
Disadvantages
However, mesh topologies are far from perfect. They require an immense amount of
configuration once they are deployed. The topological layout is more complex than many other
topologies and this is reflected by how long it takes to set up. You’ll need to accommodate a
whole host of new wiring which can add up to be quite expensive.
Hybrid Topology
Hybrid Topology Diagram
Pros:
Very flexible
Suitable for middle-sized and large organizations
Infinitely extendible
Adaptable to optimize equipment use
Cons:
Requires professional management
Needs monitoring software
Equipment costs are high
When a topology is composed of two or more different topologies it is referred to as a hybrid
topology. Hybrid topologies are most-commonly encountered in larger enterprises where
individual departments have network topologies that different from another topology in the
organization. Connecting these topologies together will result in a hybrid topology. As a
consequence, the capabilities and vulnerabilities depend on the types of topologies that are tied
together.
Advantages
There are many reasons why hybrid topologies are used but they all have one thing in
common: flexibility. There are few constraints on the network structure that a hybrid topology
cannot accommodate, and you can incorporate multiple topologies into one hybrid setup. As a
consequence, hybrid topologies are very scalable. The scalability of hybrid setups makes them
well-suited to larger networks.
Disadvantages
Unfortunately, hybrid topologies can be quite complex, depending on the topologies that you
decide to use. Each topology that is part of your hybrid topology will have to be managed
according to its unique network requirements. This makes administrators’ jobs more difficult
because they are going to have to attempt to manage multiple topologies rather than a single
one. In addition, setting up a hybrid topology can end up being quite costly.
9. HOW TO CHOOSE TOPOLOGY TO USE
There is a range of factors that you need to take into account when choosing which topology
to use. Before choosing a topology, you’ll want to closely consider the following:
Length of cable needed
Cable type
Cost
Scalability
First, you need to take into account the length of the cable you need to provide service to all
your network devices. A bus topology is the most lightweight in terms of cable needs. In this
sense, this would be the simplest topology to install and buy cables for. This ties into the second
factor, you need to consider the type of cable you’re going to use. Cable types range from
twister pairs to coaxial cables and optical fiber cables.
The cost of installing the topology is also very important. The more complex the topology you
choose is, the more you’ll need to pay in terms of resources and time to create that setup.
The final factor you’ll want to take into account is scalability. If you’re planning to
upscale your network infrastructure in the future you want to make sure that you use a network
that is easy to add devices to. A star topology network is ideal for this because you can add
network nodes with minimal disruption. This isn’t as simple within a ring network because you
will incur downtime if you add any nodes.