61. Discuss the concept of
redundancy in error detection.
Error detection uses the
concept of redundancy, which means adding extra bits for detecting errors at
the destination.
62. What are the three types
of redundancy checks used in data communications?
- Vertical Redundancy Check
(VRC)
- Longitudinal Redundancy Check
(LRC)
- Cyclic Redundancy Check (CRC)
63. How can the parity bit
detect a damaged data unit?
In parity check, (a redundant
bit) a parity bit is added to every data unit so that the total number of 1s is
even for even parity checking function (or odd for odd parity).
64. How can we use the
Hamming code to correct a burst error?
By rearranging the order of bit
transmission of the data units, the Hamming code can correct burst errors.
65. Briefly discuss Stop and
Wait method of flow control?
In Stop and Wait of flow
control, the sender sends one frame and waits for an acknowledgement before
sending the next frame.
66. In the Hamming code for
a data unit of m bits how do you compute the number of redundant bits ‘r’
needed?
In the Hamming code, for a data
unit of m bits, use the formula 2r > = m + r + 1 to determine r, the number
of redundant bits needed.
67. What are three popular
ARQ mechanisms?
- Stop and wait ARQ,
- Go – Back – N ARQ and
- Selective Report ARQ.
68. How does ARQ correct an
error?
Anytime an error is detected in
an exchange, a negative acknowledgment (NAK) is returned and the specified
frames are retransmitted.
69. What is the purpose of
the timer at the sender site in systems using ARQ?
The sender starts a timer when
it sends a frame. If an acknowledgment is not received within an allotted time
period, the sender assumes that the frame was lost or damaged and resends it.
70. What is damaged frame?
A damaged frame is recognizable
frame that does arrive, but some of the bits are in error (have been altered
during transmission)
71. What is HDLC?
HDLC is a bit oriented datalink
protocol designed to support both half-duplex and full duplex communication
over point to point and multiport link.
72. Give data transfer modes
of HDLC?
1. NRM – Normal Response Mode
2. ARM – Asynchronous Response
Mode
3. ABM - Asynchronous Balanced
Mode
73. How many types of frames
HDLC uses?
1. U-Frames
2. I-Frames
3. S-Frame
74. State phases involved in
the operation of HDLC?
1. Initialization
2. Data transfer
3. Disconnect
75. What is the meaning of
ACK frame?
ACK frame is an indication that
a station has received something from another.
76. What is CSMA?
Carrier Sense Multiple Access
is a protocol used to sense whether a medium is busy before attempting to
transmit.
77. Explain CSMA/CD
Carrier Sense Multiple Access
with collision detection is a protocol used to sense whether a medium is busy
before transmission but is has the ability to detect whether a transmission has
collided with another.
78. State advantage of
Ethernet?
1. Inexpensive
2. Easy to install
3. Supports various wiring
technologies
79. What is fast Ethernet?
It is the high speed version of
Ethernet that supports data transfer rates of 100 Mbps.
80. What is bit stuffing and
why it is needed in HDLC?
Bit stuffing is the process of
adding one extra 0 whenever there are five consecutive 1s in the data so that
the receiver does not mistake the data for a flag. Bit stuffing is needed to
handle data transparency.
81. What is a bridge?
Bridge is a hardware networking
device used to connect two LANs. A bridge operates at data link layer of the
OSI reference model.
82. What is a repeater?
Repeater is a hardware device
used to strengthen signals being transmitted on a networks.
83. Define router?
A network layer device that
connects networks with different physical media and translates between network
architectures.
84. State the functions of
bridge?
1. Frame filtering and
forwarding
2. Learning the address
3. Routing
85. List any two functions
which a bridge cannot perform?
- Bridge cannot determine most
efficient path.
- Traffic management function.
86. What is hub?
Networks require a central
location to bring media segment together. These central locations are called
hubs.
87. State important types of
hubs.
1. Passive hub
2. Active hub
3. Intelligent hub
88. Mention the function of
hub.
1. Facilitate adding/deleting
or moving work stations
2. Extend the length of network
3. It provides centralize management
services
4. Provides multiple
interfaces.
89. What is the main
function of gateway.
A gateway is a protocol
converter
90. A gateway operates at
which layer.
Gateway operates at all seven
layers of OSI model.
91. Which factors a gateway
handles?
Data rate, data size, data
format
92. What is meant by active
hub?
A central hub in a network that
retransmits the data it receives.
93. What is the function of
ACK timer?
ACK timer is used in flow
control protocols to determine when to send a separate acknowledgment in the
absence of outgoing frame.
94. What are the types of
bridges?
1. Transparent bridge
2. Source Routing bridge
Transparent bridge -
Transparent bridge keep a suitable of addresses in memory to determine where to
send data
Source
Routing bridge - Source Routing bridge requires the entire routing table to be
included in the transmission and do not route packet intelligently.
95. What are transreceivers?
Transreceivers are combination
of transmitter and receiver. Transreceivers are also called as medium
attachment unit (MAU)
96. What is the function of
NIC?
NIC is used to allow the
computer to communicate on the network. It supports transmitting, receiving and
controlling traffic with other computers on network.
97. Mention different random
access techniques?
1. ALOHA
2. CSMA
3. CSMA/CD
98. What is the function of
router?
Routers relay packets among
multiple interconnected networks. They route packets from one network to any
number of potential destination networks on an internet.
99. How does a router differ
from a bridge?
Routers provide links between
two separate but same type LANs and are most active at the network layer.
Whereas bridges utilize addressing protocols and can affect the flow control of
a single LAN; most active at the data link layer.
100. Identify the class and
default subnet mask of the IP address 217.65.10.7.
It belongs to class C.
Default subnet mask –
255.255.255.192
101. What are the fields
present in IP address?
Netid and Hostid.
Netid – portion of the ip
address that identifies the network.
Hostid – portion of the ip
address that identifies the host or router on the networks.
102. What is flow control?
How to keep a fast sender from
swamping a slow receiver with data is called flow control.
103. What are the functions
of transport layers?
The transport layer is
responsible for reliable data delivery. Functions of transport layer
i. Transport layer breaks
messages into packets
ii. It performs error recovery
if the lower layers are not adequately error free.
iii.Function of flow control if
not done adequately at the network layer.
iv.Function of multiplexing and
demultiplexing sessions together.
v. This layer can be
responsible for setting up and releasing connections across the
network.
104. What is segmentation?
When the size of the data unit
received from the upper layer is too long for the network layer datagrams or
datalink frame to handle, the transport protocol divides it in to smaller,
usuable blocks. The dividing process is called segmentation.
105. What is Transport
Control Protocol (TCP)?
The TCP/IP protocol that
provides application programs with access to a connection oriented
communication service. TCP offers reliable flow controlled delivery. More
important TCP accommodates changing conditions in the Internet by adapting its
retransmission scheme.
106. Define the term (i)
Host (ii) IP
a. Host : An end user’s
computer connection to a network. In an internet each computer is classified as
a host or a router.
b. IP: Internet Protocol that
defines both the format of packet used on a TCP/IP internet and the mechanism
for routing a packet to its destination.
107. What is UDP?
User Datagram Protocol is the
TCP/IP protocol that provides application program with connectionless
communication service.
108. What is the segment?
The unit of data transfer
between two devices using TCP is a segment.
109. What is a port?
Applications running on
different hosts communicate with TCP with the help of a concept called as
ports. A port is a 16 bit unique number allocated to a particular application.
110. What is Socket?
The communication structure
needed for socket programming is called socket.
A
port identifies a single application on a single computer.
Socket = IP address + Port
number
111. How TCP differ from the
sliding window protocols.
TCP differs from the sliding
window protocols in the following ways:
1. When using TCP, applications
treat the data sent and received as an arbitrary byte stream. The sending
- TCP module divides the byte
stream into a set of packets called segments, and sends individual segments
within an IP datagram.
- TCP decides where segment
boundaries start and end.
2. The TCP sliding window
operates at the byte level rather than the packet (or segment) level. The left
and right window edges are byte pointers.
3. Segment boundaries may
change at any time. TCP is free to retransmit two adjacent segments each
containing 200 bytes of data as a single segment of 400 byte.
4. The size of the send and
receive window change dynamically.
112. Explain how the TCP
provides the reliability?
A number of mechanisms provide
the reliability.
1. Checksum
2. Duplicate data detection
3. Retransmission
4. Sequencing
5. Timers
113. What is a datagram
socket?
A structure designed to be used
with connectionless protocols such as UDP.
114. What is congestion?
When load on network is greater
than its capacity, there is congestion of data packets. Congestion occurs
because routers and switches have queues or buffers.
115. Define the term Jitter.
Jitter is the variation in
delay for packets belonging to the same flow.
116. What is Configuration
management?
Configuration management (CM)
is a field of management that focuses on establishing and maintaining
consistency of a system or product's performance and its functional and
physical attributes with its requirements, design, and operational information
throughout its life.
117. What is Fault
management?
Fault management is the set of
functions that detect, isolate, and correct malfunctions in a
telecommunications network, compensate for environmental changes, and include
maintaining and examining error logs, accepting and acting on error detection
notifications, tracing and identifying faults, carrying out sequences of
diagnostics tests, correcting faults, reporting error conditions, and
localizing and tracing faults by examining and manipulating database
information.
118. What is Performance
management?
Performance management includes
activities that ensure that goals are consistently being met in an effective
and efficient manner. Performance management can focus on the performance of an
organization, a department, employee, or even the processes to build a product
or service, as well as many other areas.
119. What is Security
management?
Security Management is a broad
field of management related to asset management, physical security and human
resource safety functions. It entails the identification of an organization's
information assets and the development, documentation and implementation of
policies, standards, procedures and guidelines.
120. What is Accounting
management?
Accounting Management is the practical application of
management techniques to control and report on the financial health of the
organization. This involves the analysis, planning, implementation, and control
of programs designed to provide financial data reporting for managerial
decision making. This includes the maintenance of bank accounts, developing
financial statements, cash flow and financial performance analysis.
