Types of Networks

 Personal area network, or PAN

is a computer network organized around an individual person within a single building

 Local area network, or LAN

is a group of computers and peripheral devices that share a common communications line or wireless link
to a server within a distinct geographic area.

 Metropolitan area network, or MAN

consists of a computer network across an entire city, college campus or small region.

 Wide area network, or WAN

occupies a very large area, such as an entire country or the entire world.

difference between full duplex and simplex transmission and full duplex

1. Simplex mode of transmission, the communication between sender and receiver occur only in one
direction. That means only the sender can transmit the data, and receiver can only receive the data

half duplex, both the sender and receiver can transmit the signal but, only one at a time

full duplex, the sender and receiver can transmit the signal simultaneously at the same time.

2. simplex mode of transmission, only one of the two devices on the link can transmit the signal, and
the other can only receive but can not send back the signal in reverse.

In a half duplex mode, both the devices connected on the link can transmit the signal but only one
device can transmit at a time.

In a full-duplex mode, both the device on the link can transmit simultaneously.

3. The performance of full duplex is better than half duplex and simplex because it better utilizes the
bandwidth, as compared to half duplex and simplex.
4. If we take the example of keyboard and monitor, it is observed that keyboard inputs the command and
monitor displays it, monitor never reply back to the keyboard; hence, it is an example of the simplex
transmission mode.

In a walkie-talkie, only one person can communicate at a time so; it represents an example of half
duplex mode of transmission.
 In a telephone, both the person on the either side of a telephone can communicate parallelly at the
same time; hence, it represents an example of a full-duplex mode of transmission.

Comparison chart

BASIS FOR
SIMPLEX HALF DUPLEX FULL DUPLEX
COMPARISON

Direction of Communication is Communication is two- Communication is two

Communication unidirectional. directional but, one at a directional and done
time. simultaneously.

Send/Receive A sender can send data A sender can send as A sender can send as well
but, can not receive. well as receive the data as receive the data
but one at a time. simultaneously.

Performance The half duplex and full The full duplex mode Full duplex has better
duplex yields better yields higher performance as it doubles
performance than the performance than half the utilization of
Simplex. duplex. bandwidth.

Example Keyboard and monitor. Walkie-Talkies. Telephone.

Different-types-of-computer-network-topologies and advantages and disadvantage

Network topology is the description of the arrangement of nodes (e.g. networking switches and routers)
and connections in a network

Topology defines the structure of the network of how all the components are interconnected to each
other.

Bus topology is a type of network topology in which all devices in the network are connected by one
central RJ-45 network cable or coaxial cable.
Advantages of Bus Topology :
 It is the easiest network topology for connecting peripherals or computers in a linear fashion.
 It works very efficiently well when there is a small network.
 The length of cable required is less than a star topology.
 It is easy to connect or remove devices in this network without affecting any other device.
 Very cost-effective as compared to other network topology i.e. mesh and star
 It is easy to understand topology.
 Easy to expand by joining the two cables together.
Disadvantages of Bus Topology :
 Bus topology is not great for large networks.
 Identification of problems becomes difficult if the whole network goes down.
 Troubleshooting individual device issues is very hard.
 Need terminators are required at both ends of the main cable.
 Additional devices slow the network down.
 If the main cable is damaged, the whole network fails or splits into two.
 Packet loss is high.
 This network topology is very slow as compared to other topologies.

Star topology is a network topology in which each network component is physically connected to a
central node such as a router, hub or switch.

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.
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.

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.

Advantages of Ring topology :

 data flows in one direction which reduces the chance of packet collisions.
 additional workstations can be added after without impacting performance of the network.
 Equal access to the resources.
 There is no need of server to control the connectivity among the nodes in the topology.
 It is cheap to install and expand.
 Minimum collision.
 Speed to transfer the data is very high in this type of topology.
 Due to the presence of token passing the performance of ring topology becomes better than bus
topology under heavy traffic.
 Easy to manage.
 Ring network is extremely orderly organized where every device has access to the token and
therefore the opportunity to transmit.
Disadvantages of Ring topology :
 Due to the Uni-directional Ring, a data packet (token) must have to pass through all the nodes.
 If one workstation shuts down, it affects whole network or if a node goes down entire network goes
down.
 It is slower in performance as compared to the bus topology
 It is Expensive.
 Addition and removal of any node during a network is difficult and may cause issue in network
activity.
 Difficult to troubleshoot the ring.
 In order for all the computer to communicate with each other, all computer must be turned on.
 Total dependence in on one cable.
 They were not Scalable.

Mesh topology is a type of network topology in which all devices in the network are interconnected.

Advantages of Mesh Topology :

 Failure during a single device won’t break the network.
 There is no traffic problem as there is a dedicated point to point links for every computer.
 Fault identification is straightforward.
 This topology provides multiple paths to succeed in the destination and tons of redundancy.
 It provides high privacy and security.
 Data transmission is more consistent because failure doesn’t disrupt its processes.
 Adding new devices won’t disrupt data transmissions.
 This topology has robust features to beat any situation.
 A mesh doesn’t have a centralized authority.
Disadvantages of Mesh Topology :
 It’s costly as compared to the opposite network topologies i.e. star, bus, point to point topology.
 Installation is extremely difficult in the mesh.
 Power requirement is higher as all the nodes will need to remain active all the time and share the
load.
 Complex process.
 The cost to implement mesh is above other selections.
 There is a high risk of redundant connections.
 Each node requires a further utility cost to think about.
 Maintenance needs are challenging with a mesh.

Hybrid Topology :
A hybrid topology is a type of network topology that uses two or more differing network topologies
Advantages of this topology : 
 This topology is very flexible.
 The size of the network can be easily expanded by adding new devices.
Problems with this topology :
 It is challenging to design the architecture of the Hybrid Network.
 Hubs used in this topology are very expensive.
 The infrastructure cost is very high as a hybrid network requires a lot of cabling and network
devices.

Difference between data element and signal element

A data element is the smallest entity that represent a piece of information; this is the bit. A signal
elements is the shortest unit (timewise) of a digital signal. In other words, data elements are what we
need to send; signal element are what we can send
Line Coding
Converts a sequence of bits to a digital signal using varying schemes.
Data Rate (Bit Rate)
Number of data elements (bits) sent in 1 second.

Signal Rate (Baud Rate)

Number of signal elements sent in 1 second. Measured in baud units. One goal in data communications is
to increase the data rate while decreasing the signal rate.
Factors Affecting Networking Performance
Physical Obstructions
Network Range & Distance between Devices
Wireless Network Interference
Signal Sharing
Network Usage & Load
Poorly Deployed Antennas
Local Environment Characteristics
Spectrum Channel Limitations
Signal Reflection
Wireless Signal Restriction

What are the propagation time and the transmission time for a 5-MB (megabyte) message (an
image) if the bandwidth of the network is 1 Mbps? Assume that the distance between the sender
and the receiver is 12,000 km and that light travels at 2.4 * 108 m/s.
Propagation time = (12000 * 1000) / (2.4 * 108 ) = 50 ms
Transmission time = (5000000 * 8) / 106 = 40 s

A sine wave is offset 1/6 cycle with respect to time 0 .what is phase in degrees and radians.
We know that 1 complete cycle is 360°. Therefore, 1/6 cycle is

The period of a signal is 100ms what is the frequency in khz

Data transmission, digital transmission, or digital communication is the transfer of data from one
point to another.
Advantages of digital transmission:

1. Immunity to transmission noise and interference.

2. Regenerative of the coded signal along the transmission path is possible.
3. Communication can be kept “private” and “secured” through the use of encryption.
4. It is possible to use a uniform format for different kinds of baseband signals.
5. It is possible to store the signal and process it further.
6. Digital signals are better suited for processing and multiplexing
7. Digital transmission systems are more immune to noise
8. Measurement and evaluation of digital signals is simpler.
9. It is possible to evaluate error performance of digital systems.

Disadvantages:

1. The required bandwidth is increased due to digital technology.

2. System Complexity is increased
3. In order to convert the analog signal to digital prior to transmission and then from digital to
analog receiver, we need to use the additional encoder and decoder circuit.
4. Synchronization is necessary for digital systems (between transmission and receiver clocks)
5. Digital transmission systems are not compatible to older analog transmission systems.

Why is turn passing a poor solution to the critical sections problem?

Turn passing is a poor solution as it will leave processes busy-waiting for their turn to run the critical
section

Interrupt disabling and enabling is a common approach to implementing mutual exclusion, what
are its advantages and disadvantages?
The simplicity of this approach is the main advantage, it can be implemented with 2 assembler
instructions. It can start cause problems when it is miss used, ie a process could turn off interrupts and
hog CPU and it will never be preempted. It also does not provide a secure system for user-land as process
can essentially never hand control back to the kernel.
A buffer overflow (or buffer overrun) occurs when the volume of data exceeds the storage capacity of
the memory buffer.

list and explain the factors that you would consider for a good web interface

Be mindful of contrast: Making sure there is simplicity and sufficient contrast between text and
background colors makes reading much easier.
Design for responsiveness: A website should always be adaptable to the screen it's being viewed on,
whether it's a 7-inch mobile phone or a 70-inch TV.
Experiment with design: Build exploration into the project's lead time to give yourself a chance to
discover new elements of design that can make your end product exceptionally unique and pleasurable to
use.
Focus on usability: Make sure users can use your site/app/program intuitively, even if they're visiting for
the first time.
Keep it consistent: Pick a design and stick with it throughout the project. Each page of the site should be
laid out the same way to avoid any confusion or frustration in the user's experience.
Keep relevance in mind: The interface should be conducive to an overall experience that is pleasant,
easy and informative.
Know your target user: It can be easy to let the overall goal get lost in the minutiae of the design
process but what you're designing is for the user and therefore should be user-focused.
Maintain branding: Your user should be able to identify your brand on every page of your site and new
users should be able to recognize your brand upon their first visit.
Make it easy on the eyes: Pay attention to the ease of readability through the layout. For example, keep
text edge-aligned, keep a limited color palette and choose a font that's easy to read.
Make it easy overall: Performing tasks should require minimal effort on the user's part and each page
should serve one main function.
Proofread: You'll want your finished product to be presented to your users free of any errors.
Provide logical next steps: Your UI design should allow users to intuitively figure out what to do next.
Remain predictable: Elements like buttons, pinch zoom and other interactive elements should function
as expected. Every element should have a meaningful function.
Use dynamic effects judiciously: User interaction is the goal, but over-using interactive elements can be
overwhelming. If they're not even super useful the user can be turned off from the whole thing. These
effects, rather, should be used to optimize the user's experience.

Applications of Communication & Computer Network

Information sharing describes the exchange of data between various organizations, people and
technologies.
Video conferencing is live, visual connection between two or more remote parties over the internet that
simulates a face-to-face meeting.
Resource Sharing making the collections of one library available to the patrons of. another library
efficiently and effectively.
Dynamic page displays different content for different users while retaining the same layout and design.
Such pages,
Instant messaging (IM) technology is a type of online chat allowing real-time text transmission over the
Internet or another computer network.

Explain the following terms

Transmission impairment occurs when the received signal is different from the transmitted signal.
Distortion is the act of altering something out of its original state 
Multiplexing is a method used by networks to consolidate multiple signals -- digital or analog -- into a
single composite signal that is transported over a common medium, such as a fiber optic cable or radio
wave
Attenuation refers to any reduction in the strength of a signal.
Packetizing is the partition of data into units for transmission in a packet-switching network

Data communications means the exchange of data between two devices via some form of transmission
medium such as a wire cable.

The effectiveness of a data communications system depends on four fundamentals

 
1. Delivery:
The system must deliver data to the correct destination. Data must be received by the intended device or
user and only by that device or user.
 
2. Accuracy:
The system must deliver the data accurately. Data that have been altered in transmission and left
uncorrected are unusable. 
 
3. Timeliness:
The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and
audio, timely delivery means delivering data as they are produced, in the same order that they are
produced, and without significant delay. This kind of delivery is called real-time transmission.
 
4. Jitter:
Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or
video packets. For example, let us assume that video packets are sent every 3D ms. If some of the packets
arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the result.
 

Electronic banking, Use of computers and telecommunications to enable banking transactions to be done

by telephone or computer rather than through human interaction.

Data rate depends on three factors, mention the factors that it depends on?
 The bandwidth available.
 The level of the signals we use.
 The quality of the channel (the level of noise)

Types of cables in networking

1. Coaxial Cable.
This system is rarely used. Installing a coaxial cable is complex. The cable can resist signal obstruction. A
plastic layer insulates the centre conductor and the braided metal.
2. Shielded Twisted Pair (STP) Cable
It is mostly used in business installations. It is suitable for areas with risk to the electrical current and
potential interference. Its external shield works as a ground. You can use the shielded twisted pair cable to
expand the distance between cables.
3. Fibre Optic Cable
It consists of several layers of protective materials that surround a centre glass core. Fibre optic cable
does not transmit electronic signals. Instead, it transmits light, removing the electrical obstruction
problem. It is suitable for areas with electrical interference. You can use it to connect networks between
buildings.
4. Unshielded Twisted Pair Cable
It is mostly used for computer networking and conventional telephone. It does not have internal shielding.
It is suitable for workgroups because of its good performance and flexibility. It has an outer insulating
jacket that protects the cable from damage or physical stress.
It is important to understand how the different types of networking cabling affect the other aspects of a
network.
Do you want to install a data cable in Perth home or commercial space? Powerlec offers any type of data
cabling in Perth. Contact us today on 08 9750 5203.