Download Explain the term simplex, half-duplex and full

Explain the term simplex, half-duplex and full-duplex used in communication dialog
mode.
Simplex
In simplex operation, a network cable or communications channel can only
send information in one direction; it's a “one-way street”. A good example would
be your keyboard to your CPU. The CPU never needs to send characters to the
keyboard but the keyboard always sends characters to the CPU. In many cases,
Computers almost always send characters to printers, but printers usually never send
characters to computers (there are exceptions, some printers do talk back). Simplex
requires only one lane (in the case of serial).
Half-Duplex
Technologies that employ half-duplex operation are capable of sending
information in both directions between two nodes, but only one direction or the
other can be utilized at a time. This is a fairly common mode of operation
when there is only a single network medium (cable, radio frequency and so
forth) between devices. The only advantage that Half-Duplex would have is the
single lane or single track is cheaper then the double lane or double track.
For example, in conventional Ethernet networks, any device can transmit, but
only one may do so at a time.
Full-Duplex
In full-duplex operation, a connection between two devices is capable of
sending data in both directions simultaneously. Full-duplex channels can be
constructed either as a pair of simplex links (as described above) or using one
channel designed to permit bidirectional simultaneous transmissions. A full-
duplex link can only connect two devices, so many such links are required if
multiple devices are to be connected together.
Explain the term analog and digital signal.
An analog signal is a continuous signal that contains time-varying quantities. Unlike a digital signal, which
has a discrete value at each sampling point, an analog signal has constant fluctuations. The public
dial-up service supports analogue signals. Analogue signals are what we encounter
every day of our life. Speech is an analogue signal, and varies in amplitude (volume),
frequency (pitch), and phase.
The three main characteristics of analogue signals are,

Amplitude
This is the strength of the signal. It can be expressed a number of different ways (as
volts, decibels). The higher the amplitude, the stronger (louder) the signal.
Frequency
This is the rate of change the signal undergoes every second, expressed in Hertz (Hz),
or cycles per second.
Phase
This is the rate at which the signal changes its relationship to time, expressed as
degrees. One complete cycle of a wave begins at a certain point, and continues till the
same point is reached again. Phase shift occurs when the cycle does not complete, and
a new cycle begins before the previous one has fully completed.
Digital Signals
A digital signal refers to an electrical signal that is converted into a pattern of bits. Unlike an analog signal,
which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at
each sampling point. Digital signals are the language of modern day computers. Digital
signals comprise only two states. These are expressed as ON or OFF, 1 or 0
respectively. Examples of devices having TWO states in the home are,


Light Switches: Either ON or OFF
Doors: Either OPEN or CLOSED
Explain the term Bandwidth, Data Terminal Equipment (DTE), and Data circuitterminating equipment (DCE).
Bandwidth
describes
the
maximum data
transfer
rate
of
a network or Internet connection. It measures how much data can be sent over a
specific connection in a given amount of time. For example, a gigabit Ethernet
connection has a bandwidth of 1,000 Mbps, (125 megabytes per second). An
Internet connection viacable modem may provide 25 Mbps of bandwidth.
While bandwidth is used to describe network speeds, it does not measure how
fast bits of data move from one location to another. Since data packets travel over
electronic or fiber-optic cables, the speed of each bit transferred is negligible.
Instead, bandwidth measures how much data can flow through a specific
connection at one time.
When visualizing bandwidth, it may help to think of a network connection as a tube
and each bit of data as a grain of sand. If you pour a large amount of sand into a
skinny tube, it will take a long time for the sand to flow through it. If you pour the
same amount of sand through a wide tube, the sand will finish flowing through the
tube much faster. Similarly, a download will finish much faster when you have a
high-bandwidth connection rather than a low-bandwidth connection.
Bandwidth also refers to a range of frequencies used to transmit a signal. This type
of bandwidth is measured in hertz and is often referenced in signal processing
applications.
What is your understanding about the term CODEC and MODEM using suitable example?
COder/DECoder) A hardware circuit that performs analog-to-digital conversion (ADC) and/or digitalto-analog (DAC) conversion. When a digital device receives analog signals from a microphone, VHS tape
or other analog source, the ADC converts them to digital audio samples and video frames. Generally, the
results are further compressed to save bandwidth
(COmpressor/DECompressor) Software and/or hardware that compresses digital audio and video data
in order to reduce file size. Compressed files can be transmitted faster and stored in less space. For
example, a song on a CD can be reduced to 10% of its original file size using MP3 compression (see MP3).
The size of a movie/video file is dramatically reduced using various compression techniques
Short for modulator-demodulator. A modem is a device orprogram that enables a computer to transmit data over, for
example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over
telephone lines is transmitted in the form ofanalog waves. A modem converts between these two forms.
Examples of modems include a standard fax/phone modem, a cable modem or a DSL
modem or even a satellite modem. All modems perform what is called modulation to encode
your data into the line signal and demodulation to decode it from the line signal. The term
MODEM is short for Modulator/Demodulator.
Explain the term multiplexer and concentrator with at least one similarity and
dissimilarity.
multiplexer - A communications device that multiplexes (combines) several signals for
transmission over a single medium. A demultiplexer completes the process by separating
multiplexed signals from a transmission line. Frequently a multiplexer and demultiplexer are
combined into a single device capable of processing both outgoing and incoming signals. A
multiplexer is sometimes called a mux.
concentrator - A type of multiplexor that combines multiple channels onto a single transmission
medium in such a way that all the individual channels can be simultaneously active. For
example, ISPs use concentrators to combine their dial-up modem connections onto faster T-1 lines that
connect to the Internet.
Concentrators are also used in local-area networks (LANs) to combine transmissions from a cluster
of nodes. In this case, the concentrator is often called a hub or MAU.
A concentrator is a device which carries multiplexed data packets similar to multiplexer with only
difference that it offers storage capability while multiplexer does not
The main difference is in the way input & output relationship is defined. A Mux is hardware
device the input & output are directly related to data rate. In concentrator the low speed input
channel can share a small no of high speed channel at its output via software control
Explain serial and parallel transmission with suitable diagram
Digital data transmission can occur in two basic modes: serial or parallel. Data
within a computer system is transmitted via parallel mode on buses with the
width of the parallel bus matched to the word size of the computer system.
Data between computer systems is usually transmitted in bit serial mode.
Consequently, it is necessary to make a parallel-to-serial conversion at a
computer interface when sending data from a computer system into a network
and a serial-to-parallel conversion at a computer interface when receiving
information from a network. The type of transmission mode used may also
depend upon distance and required data rate.
Parallel Transmission
In parallel transmission, multiple bits (usually 8 bits or a byte/character) are
sent simultaneously on different channels (wires, frequency channels) within the
same cable, or radio path, and synchronized to a clock. Parallel devices have a
wider data bus than serial devices and can therefore transfer data in words of
one or more bytes at a time. As a result, there is a speedup in parallel
transmission bit rate over serial transmission bit rate. However, this speedup is
a tradeoff versus cost since multiple wires cost more than a single wire, and as
a parallel cable gets longer, the synchronization timing between multiple
channels becomes more sensitive to distance. The timing for parallel
transmission is provided by a constant clocking signal sent over a separate wire
within the parallel cable; thus parallel transmission is considered synchronous.
Serial Transmission
In serial transmission, bits are sent sequentially on the same channel (wire)
which reduces costs for wire but also slows the speed of transmission. Also, for
serial transmission, some overhead time is needed since bits must be
assembled and sent as a unit and then disassembled at the receiver.
Serial transmission can be either synchronous or asynchronous. In
synchronous transmission, groups of bits are combined into frames and frames
are sent continuously with or without data to be transmitted. In asynchronous
transmission, groups of bits are sent as independent units with start/stop flags
and no data link synchronization, to allow for arbitrary size gaps between
frames. However, start/stop bits maintain physical bit level synchronization
once detected.
Explain the term synchronous and asynchronous transmission
The term synchronous is used to describe a continuous and consistent timed transfer of data blocks.
Synchronous data transmission is a data transfer method in which a continuous stream of data
signals is accompanied by timing signals (generated by an electronic clock) to ensure that the
transmitter and the receiver are in step (synchronized) with one another. The data is sent in blocks
(called frames or packets) spaced by fixed time intervals.
Synchronous transmission modes are used when large amounts of data must be transferred very
quickly from one location to the other
asynchronous transmission works in spurts and must insert a start bit before each data character
and a stop bit at its termination to inform the receiver where it begins and ends.
The term asynchronous is used to describe the process where transmitted data is encoded with start
and stop bits, specifying the beginning and end of each character.
Explain the term ‘Hub’ and outline at least two major characteristics of it.
This is a hardware device that is used to connect multiple computers together on a
network. It is a central connection for all the computers in a network, which is
usually Ethernet-based. Information sent to the hub can flow to any other
computer on the network. If you need to connect more than two computers
together, a hub will allow you to do so.
Characteristics
- A HUB is a device for connecting multiple ethernet
devices together & making them act as single
- It does not manage any network traffic
- It is just a BROADCAST device
Explain the term ‘Switch’ and outline at least two major characteristics of it.
A network switch is a small hardware device that joins multiple computers together within one local
area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI
model.
Network switches appear nearly identical to network hubs, but a switch generally contains more
intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of
inspecting data packets as they are received, determining the source and destination device of each
packet, and forwarding them appropriately. By delivering messages only to the connected device
intended, a network switch conserves network bandwidth and offers generally better performance
than a hub.
Characteristics
- reduces the number of collision domains
- connects LAN segments
- increases the number of collision domains
- filters data before forwarding it to its destination on the network
What is Network Address Translation (NAT) and what is its role in a network?
NAT allows an Internet Protocol (IP) network to maintain public IP addresses separately from private
IP addresses. NAT is a popular technology for Internet connection sharing. It is also sometimes used
in server load balancing applications on corporate networks.
In it's most common configuration, NAT maps all of the private IP addresses on a home network to the
single IP address supplied by an Internet Service Provider (ISP). This allows computers on the home LAN to
share a single Internet connection. Additionally, it enhances home network security by limiting the
access of external computers into the home IP network space.
Role:
- NAT is a very important aspect of firewall security. It conserves the number of public
addresses used within an organization, and it allows for stricter control of access to
resources on both sides of the firewall.
- NAT can be used to allow selective access to the outside of the network, too.
Workstations or other computers requiring special access outside the network can
be assigned specific external IPs using NAT, allowing them to communicate with
computers and applications that require a unique public IP address. Again, the
firewall acts as the intermediary, and can control the session in both directions,
restricting port access and protocols.
Write two advantages and two disadvantages of ISDN network services.


Abbreviation of integrated services digital network, an international communications standard for sending
voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of
64 Kbps (64,000 bits per second).
There are two types of ISDN:
Basic Rate Interface (BRI) -- consists of two 64-Kbps B-channels and one D-channel for transmitting control
information.
Primary Rate Interface (PRI) -- consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one Dchannel (Europe).
ISDN Disadvantages

The disadvantage of ISDN lines is that it is very costly than the other typical telephone system.

ISDN requires specialized digital devices just like Telephone Company.
ISDN Advantages
ISDN takes only 2 seconds to launch a connection while other modems take 30 to 60 second for
establishment.
The basic advantage of ISDN is to facilitate the user with multiple digital channels. These channels can
operate concurrently through the same one copper wire pair.
Explain the term ‘Frame relay’, its characteristics, and application with suitable diagram.
Frame relay is a data link network protocol designed to transfer data on Wide Area Networks
(WANs). Frame relay works over fiber optic or ISDN lines. The protocol offers low latency and to
reduce overhead, does perform any error correction, which is instead handled by other components of
the network.
Frame relay has traditionally provided a cost-effective way for telecommunications companies to
transmit data over long distances.
Explain your understanding about VoIP and Video over IP?
VoIP is a technology that allows telephone calls to be made over computer networks like the
Internet. VoIP converts analog voice signals into digital data packets and supports real-time, two-way
transmission of conversations using Internet Protocol (IP).
VoIP calls can be made on the Internet using a VoIP service provider and standard computer audio
systems. Alternatively, some service providers support VoIP through ordinary telephones that use
special adapters to connect to a home computer network.
VoIP offers a substantial cost savings over traditional long distance telephone calls. The main
disadvantage of VoIP is a greater potential for dropped calls and degraded voice quality when the
underlying network links are under heavy load.
Wired & wireless communication diagram
WI-FI & WI-MAX
Wi-Fi wireless fidelity is the technology that allows you to connect to the internet at fast speed
without using wires. It allows user to create their own LAN & conduct wireless data transmission
between different network elements. Wi-Fi operates at 2.4 Ghz & 5.8 Ghz & each access point
can cover about 100 m radius.
WI-Fi Applications:
Healthcare:
- Lab administration
- People with disabilities
- Point of care testing
- Controlling patient data
Education:
- More efficient learning methods
- Ideal for campus wide coverage
Retail:
- Mobile scanners
- Direct inventory mgmt.
Manufacturing:
- Product Management
- Field based data collection
Advantages:
- Mobility
- Ease of installation
- Cost
- Flexibility
- Speed
- Roaming
- Use unlicensed part of radio spectrum
Disadvantage
- Limited range
- Degradation in performance
- Interference
Wi-Max
Stands for worldwide interoperability for microwave access. The 2 driving forces of modern
internet are broadband & wireless. The wimax standard combines the two delivering high speed
broadband internet access over wireless connection. Wimax is next generation of wifi or wirless
technology that will connect internet at faster speed & much longer ranges than current wirelss
tehnology
Features:
- Scalability
- Quality of service
- Range
- Coverage
Benefits of Wi-max
- Speed: Faster than broadband service
- Wireless: easier to extend suburban & rural areas
- Broad coverage: Much wider coverage than Wi-Fi
Disadvantages:
- Lack of quality
- Epxensive network
- Bad weather
- Power consuming
Benefits to customers:
- Range of technology & service level choice for both fixed & wireless broadband
operators
- Rapidly declining fixed broadband prices
VSAT Characteristics & technology
1.) It possesses the ability of digital treatment and transmission for multiple signals including
voice, data and television conference. When transmitting voice, data and television
conference, data compression technology has been widely adopted.
2.) Flexible multi-access mode. The transmission line from primary station to remote small
station is called outbound or outroute while the transmission link from small station to
primary station is called inbound or inroute.
3.) Network management system is more and more perfect.
4.) Abundant network topological structure. Network topological structure of VSAT has three
kinds which are star-shaped, meshed and composite. Star-shaped structure mainly applied in
data communication must have primary station. Meshed structure mainly applied in voice
communication doesn’t have primary station. And composite structure with more complex
network management and channel control is available for large website comprehensively
transferring multiple sets of information. The selection of network topological structure is
mainly based on business demand.
5.) Compared with other communication ways, VAST system possess the characteristic that
communication link cost is not relevant to the distance, thus it is particularly applied to
remote areas.
6.) VSAT system expansion is easier. Use scope and transmission ability of VSAT can be
expanded as long as the number of small station is increased and the bandwidth of uplink
carrier and downlink carrier is adjusted according to the demand.
What is virtualization? What are its different execution environments? How does it operate over
storage, network, OS servers and application layers? What is cloud computing? Give at least five
comparative note of cloud computing with traditional computing?
Network virtualization is a method of combining the available resources in a network by
splitting up the available bandwidth into channels, each of which is independent from the
others, and each of which can be assigned (or reassigned) to a particular server or device in real
time. Each channel is independently secured. Every subscriber has shared access to all the
resources on the network from a single computer.
Network management can be a tedious and time-consuming business for a human
administrator. Network virtualization is intended to improve productivity, efficiency, and job
satisfaction of the administrator by performing many of these tasks automatically, thereby
disguising the true complexity of the network. Files, images, programs, and folders can be
centrally managed from a single physical site. Storage media such as hard drives and tape drives
can be easily added or reassigned. Storage space can be shared or reallocated among the
servers.
Network virtualization is intended to optimize network speed, reliability, flexibility, scalability,
and security. Network virtualization is said to be especially effective in networks that
experience sudden, large, and unforeseen surges in usage.
Packet switching & circuit switching
 Packet
circuit
Category of protocols
Name(layer)
Importance Names of protocols What it does
ethernet, SLIP, PPP,
Allows messages to be packaged and
Hardware(link)
Essential Token Ring,
sent between physical locations.
ARCnet
Manages movement of messages and
Package
reports errors. It uses message
Essential IP, ICMP
management(network)
protocols and software to manage this
process. (includes routing)
Communicates between layers to
Inter layer
allow one layer to get information to
Essential ARP
communication
support another layer. This includes
broadcasting
Controls the management of service
between computers. Based on values
Service
Critical
TCP, UDP
in TCP and UDP messages a server
control(transport)
knows what service is being
requested.
DNS provides address to name
Application and user
translation for locations and network
Important DNS, RPC
support
cards. RPC allows remote computer to
perform functions on other computers.
RARP, BOOTP,
DHCP, IGMP,
Enhances network management and
Network Management Advanced
SNMP,RIP, OSPF, increases functionality
BGP, CIDR
FTP, TFTP, SMTP,
Utility(Application)
Useful
Telnet, NFS, ping, Provides direct services to the user.
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