CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
OCTOBER15
ASSESSMENT_CODE MCA3050_OCTOBER15
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
18330
QUESTION_TEXT
What are the difference between Analog and Digital Network?
SCHEME OF
EVALUATION
Differences between Analog and Digital Networks:
[Any FIVE. TWO Marks Each. 2 Marks x 5 = 10 Marks]
1.Feature: Signal.
Analog Characteristics: Continuously variable in both amplitude and
frequency.
Digital Characteristics: Discrete signal represented as either changes in
voltage or changes in light levels.
2.Feature: Traffic Measurement.
Analog Characteristics: Hz (for example, a telephone channel is 4KHz).
Digital Characteristics: Bits per second (for example, a T-1 line carries
1.544 Mbps and an E-1 line transports 2.048 Mbps).
3.Feature: Bandwidth
Analog Characteristics: Low bandwidth (4KHz), which means low data
transmission rates because of limited channel bandwidth.
Digital Characteristics: High-bandwidth that can support high-speed
data and emerging applications that involve video and multimedia.
4.Feature: Network Capacity.
Analog Characteristics: Low; one conversation per telephone channel.
Digital Characteristics: High; multiplexers enable multiple conversations
to share a communication channel and hence to achieve greater
transaction efficiencies.
5.Feature: Network Manageability.
Analog Characteristics: Poor; a lot of labor is needed for network
maintenance and control because dumb analog devices do not provide
management information streams that allow the device to be remotely
managed.
Digital Characteristics: Good; smart devices produce alerts, alarms,
traffic statistics and performance measurements and technicians at a
Network Control Center (NCC) or Network Operations Center (NOC)
can remotely monitor and manage the various network elements.
6.Feature: Power requirements
Analog Characteristics: High because the signal contains a wide range of
frequencies and amplitudes.
Digital Characteristics: Low because only two discrete signals – the one
and the zero – needs to be transmitted.
7.Feature: Security
Analog Characteristics: Poor; when you tap into an analog circuit; you
hear the voice stream in its native form, and it is difficult to detect an
intrusion.
Digital Characteristics: Good; encryption can be used.
8.Feature: Error rates.
Analog Characteristics: High; 10 -5 bits (that is 1 in 100,000 bits) is
guaranteed to have an error.
Digital Characteristics: Low; with twisted-pair, 10 -7 bits (that is 1 in 10
million bits per second) will have an error, with satellite 10 -9 (that is 1
in 1 billion bits per second) will have an error, 10 -11 (that is 1 in 10
trillion bits per second) will have an error.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
18331
QUESTION_TEXT
Explain different Network Characteristics and Requirements.
SCHEME OF
EVALUATION
1.Using network characteristics, the subscriber can formulate specific
requirements to the network. For example, the user can claim the
following requirement: average transmission rate of his information
through the network must be no less than 2 Mbps. All QoS
characteristics for the transport services can be classified in one of the
following groups:
a.Performance
b.Reliability
c.Security
d.Provider-Only
The first three groups correspond to the transport service properties. The
fourth group combines QoS characteristics that are of interest only to the
service provider. (1 mark)
2.Performance: The main characteristics of network devices are – link
bandwidth and the performance of communication devices such as
switches and routers. These are the long term characteristics of network
resources of interest only to the service provider. Users, however are
interested in other performance characteristics which would allow them
to perform quantitative evaluations of the traffic rate and the quality of
its transmission. (2 marks)
3.Reliability: For describing service reliability, the following two
characteristics are often used: Percentage of the lost packet in the total
packet flow, and Service availability.
Both characteristics describe the reliability of the transport service from
the user’s view point. The difference between them is that they
characterize reliability at different time ranges. Packet lost characteristic
is defined as a ration of the number of lost packets to the total number of
transmitted packets. And for describing the reliability of individual
devices, there are such reliability characteristics as Mean Time Between
Failure (MTBF). In this relationship, another set of characteristics is
used for evaluating the reliability of complex systems.
Availability is the ration between the time period du. In this relationship,
another set of characteristics is used for evaluating the reliability of
complex systems.
Availability is the ration between the time period during which the
system or service remains usability and the overall time of system life.
Service availability represents a universal characteristic used by both end
users and service providers. Another characteristic used to evaluate
reliability of complex systems is fault tolerance. This is the system
capability of hiding failures of individual system components from users.
(3 marks)
4.Security: It is necessary to protect from unauthorized access all
resources within the internal LAN, including hardware, software and
data stored in the files and processed in RAM. To achieve this, it is
necessary to inspect all traffic incoming to the network from a public
network and to try to deny external access to any information that might
help intruders abuse confidential information resources. The most
frequently used protection tool of this type is the firewall. It represent
internetwork filters that check messages exchanged by all levels of
protocols and do not admit suspicious traffic into the protected network.
Information that is outside the limits or out of reach needs to be
protected. Usually, this information travels across provider network in
the of IP packets. Virtual Private Network (VPN) tools are most
frequently used for this purpose. (2 marks)
5.Provider-Only: These characteristics consider the main characteristic
service providers use when evaluating the efficiency of their networks.
These characteristics are often qualitative.
Extensibility is the possibility of relatively easily adding users, as well as
new network components; increasing the length of network segment
cables; and replacing the existing equipment with new devices, which
are more advanced and powerful. And scalability means the possibility
of greatly increasing the number of network nodes and link length
without degrading network performance. To ensure network scalability,
it is necessary to employ additional communications equipment and to
observe special rules for structuring the network. (2 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
18334
QUESTION_TEXT
Discuss various components of a basic DWDM system.
SCHEME OF
EVALUATION
1.DWDM MUX: Contains one WL converting transponder for each
WL signal is will carry.
2.An intermediate line amplifier it compensates the loss in optical
power while the signal travels along the fiber.
3.An intermediate optical terminal or optical Add-up MUX
4.A DWDM terminal DEmux:
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73695
QUESTION_TEXT
Explain the various fields present in LAP – D frame format.
SCHEME OF
EVALUATION
1. Flag: The flag field is a one-octet field that delimits.
2. Address: The address field is a two-octet field.
3. Control: The address field is a one or two octet field that
identifies the frame type.
4. Information: The information field is a variable size field with a
max of 260 octet comprising upper layer of information.
5. Frame Check Sequence: The FCS field is a two octet field.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125313
What is multiplexing? Explain the following multiplexing
i.
FDM
ii.
WDM
iii.
TDM
QUESTION_TEXT
Sharing the resources is knows as multiplexing (1 mark)
SCHEME OF
EVALUATION
i.
FDM: FDM is a method of sharing bandwidth of a
communication channel among multiple users by frequency
translating. (3 marks)
ii.
WDM: WDM is similar to FDM only difference is, it is
purposefully designed for fibre-optic cable. (3 marks)
iii.
TDM: TDM can be divided into 2 separate schemes:
Synchronous and Statistical. (3 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125317
QUESTION_TEXT
Define Proxy Server. Explain different types of Proxy.
1.
2.
3.
SCHEME OF
EVALUATION
4.
In computer networks, a proxy server is a server (a computer
system or an application) that acts as an intermediary for requests
from clients seeking resources from other servers. A client connects
to the proxy server, requesting some service, such as file,
connection, web page, or other resource available from a different
server. The proxy server evaluates the request as a way to simplify
and control their complexity. (2 marks)
Different types of proxy: Forward Proxy: Forward Proxies are
Proxies where the client server names the largest server to connect
to. Forward “roxies are able to retrieve from a wide range of
resources. (2 marks)
Open Proxy: An Open Proxy is a forwarding proxy server that is
accessible by any Internet user. (1 mark)
Reverse Proxy: A Reverse Proxy (or surrogate) is a proxy server
that appear to clients to be an ordinary server. Requests are
forwarded to one or more origin servers which handle the request.
The response is returned as if it came directly from the proxy server.
Reverse Proxies are installed in the neighborhood of one or more
web servers. All traffic coming from the Internet and with a
destination of one of the neighborhood’s web server goes through
the proxy server. The use of “reverse” originates its counterpart
“forward proxy” since the reverse proxy sits closer to the web server
and servers only a restricted set of websites. Figure below shows
different types of proxies: (5 marks)
(Diagram not required)