Bus Data communications Q’s
1. 3 criteria that a network manager should apply when choosing
the type of media to use in a new network installation.
 The distance the media can carry the signal.
 The amount of data and speed needed for transmission.
2. Difference between LAN and WAN.
3.
4.
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LAN - An individual network usually spans a single geographical
area providing services and applications to people within a
common organizational structure, such as a single business,
campus or region. A LAN is usually administered by a single
organization.
WAN - When a company or organization having locations that
are separated by large geographical distances, it may be
necessary to use a TSP to interconnect the LANs at the different
locations. These networks that connect LANs in geographically
separated locations are referred to as Wide Area Networks
(WANs). WANs use specifically designed network devices to
make the interconnections between LANs.
Why is security important on a network?
To prevent unauthorized access to them. Protecting the
information contained within the packets being transmitted
over the network and the information stored on network
attached devices.
What are the advantages of the process of ‘segmenting data’
for sending over a network?
By sending smaller individual pieces from source to destination,
many different conversations can be interleaved on the
network. The process used to interleave the pieces of separate
conversations together on the network is called multiplexing.
Segmentation can increase the reliability of network
communications. The separate pieces of each message need
not travel the same pathway across the network from source to
destination. If part of the message fails to make it to the
destination, only the missing parts need to be retransmitted.
5. What is meant buy ‘encapsulation’? At which layer of the OSI
model does it occur.
Data encapsulation refers to sending data where the data is
augmented with successive layers of control information before
transmission across a network.
6. List the layers of the OSI reference model, stating the function
of each layer.
 Application - Provides a set of interfaces for applications
to access network services
• Presentation - Handles data formatting for network
communications
• Session - Ensures ongoing communication across a network
• Transport - Responsible for creating and maintaining endto-end connection.
 Network - Responsible for network traffic control
• Data-link - Provides control of the physical layer and Data
detects and corrects errors
• Physical - Transforms bits into electromagnetic signals
7. What are the differences between serial and parallel
communications?
 Serial communication is the process of sending data one
bit at a time sequentially over a communication channel.
 Parallel communication can transmit multiple binary digits
simultaneously.
The key difference between a parallel and serial
communication channel is the number of electrical
conductors used to convey bits, a parallel channel has more
than one conductor.
8. Explain ‘simplex’, half-duplex’ and ‘full-duplex’.
 Simplex - Data travels in one direction only:
unidirectional. Simple communications protocols Used in
broadcast networks e.g. CCTV
 Half-duplex - Data transfer is in both directions:
bidirectional. Communication is not simultaneous,
therefore each end on the link must wait for their turn to
transmit e.g. taxi
 Full-duplex - Data transfer is bidirectional and
simultaneous. Most modern systems are full duplex as
there is a significant speed advantage.
9. How does data compression work?
Data compression is the process of using less bits to represent
the object. Two categories of compression: lossy and lossless
• Lossy compression - removes information from the original
data that is deemed unnecessary and is most commonly used
on multimedia data
• Lossless compression - uses statistics to reduce the amount of
data needed to represent the information and is typically used
on more critical data.
10.
If the bandwidth of a network line 100Mb/s would you
expect the throughput to more or less? Why?
???
11.
How do we measure delay on a network?
End-to-end delay measures the delay from the source to the
receiver, in terms of the length of time it takes a packet to be
transmitted from the sender across the network to the
receiver. A related metric is the round-trip time, RTT, which is
the length of time it takes a packet to be transmitted by the
sender to the receiver and acknowledgement of receipt
received back by the sender.
12.
Briefly outline the different types of noise found on
networking media.
 Thermal: happens regardless of whether there is signal or
not and is present in every electronic system that is above
absolute zero (0 kelvin), TV static is partially due to
thermal noise.
 Crosstalk: this is where transmission in one circuit or
channel causes undesirable effects in another circuit or
channel.
 Impulse: this is also called popcorn noise, it involves
sudden jumps in voltages on a network and can cause
modems to become desynchronised. It is typically caused
by faulty electrical equipment close to the network
cabling or faulty cabling on the network.
13.
Outline the construction of unshielded twisted pair (UTP)
cable.
14.
Why is optical fibre cable used in long distance
communications in preference to copper cable?
In fibre optic transmission the light (optical signal) that is
generated travels down the fibre cable as it cannot escape
and ricochets off the walls of the fibre cable all the way
to its destination. Optical fibre cable has a high distance of
about 1-100,000 metres compared to coppers short distance of
around 1-100 metres. Fibre cable is immune to EMI, RFI and
Electrical hazards.
15.
What is the purpose of the operating system on a router?
Where is it stored?
Operating Systems manage the software and hardware
resources of a computing device. PC operating systems
(Windows 8, Linux and OS X) perform technical functions that
enable:
 Use of a mouse.
 View output.
 Enter and store user created content.
The Operating system is stored on the hard disk and when
the computer is powered on it loads into RAM.
16.
Give 3 examples of intermediary devices on a network,
and briefly state the function of each.
 Switch - Layer 2, full duplex, uses MAC address lookup to
retransmit on correct port, sends data frames across
network.
 Router - Layer 3, sends data packets between networks,
core routers backbone of internet. (Typically, the default
gateway of the network.)
 Hubs - Layer 1, half duplex, broadcasts across all ports (no
MAC address information), less reliable, worse bandwidth
than a switch.
17.
What configuration files are maintained on a switch?
???
18.
What is the purpose of the console port on a router?
Allows configuration commands to be entered via terminal
emulation for setting up switch/router.
• When performing an initial configuration.
• When networking services fail, and remote access is not
possible.
19.
What passwords can be configured on a router?
 Console (User Verification).
 Privileged mode (secret for encrypted).
 Vty for remote access.
20.
What network information does an end device need to
be able to communicate on the network to which it is
connected?
Each end device on a network must be configured with an IP
address and a subnet mask is also necessary.
21.
What are the differences between a normal LAN switch
and a Multi-Layer switch?
Normal LAN switch - Layer 2, full duplex, uses MAC address
lookup to retransmit on correct port, sends data frames across
network.
Multilayer Switch - Layer 3, essentially a router that can switch,
more expensive and complicated to configure
22.
In networking what is the differences between a logical
topology and a physical topology?
Physical topology - identifies the physical placement of the
various components of a network, including device location and
cable installation.
Logical topology - illustrates how data flows within a network,
regardless of its physical design.
23.
Why is a physical star topology preferred to a physical bus
topology?
Bus topology has a single point of failure so is bad for a large
office network. Star topology is more secure than bus network
and is easier to detect faults on the network.
24.
Briefly outline ethernet.
 One of the most widely used LAN technologies.
 Operates in the data link layer and the physical layer
 Family of networking technologies that are defined in the
IEEE 802.2 and 802.3 standards
25.
What are the responsibilities of the MAC sublayer?
The MAC sublayer is responsible for Data encapsulation and
Media access control.
26.
What is meant by the term ‘media access control’?
Responsible for the placement of frames on the media and the
removal of frames from the media.