COMPUTER NETWORK
2 MARKS AND ANSWERS
UNIT 1
1.What
are the three criteria necessary for an effective and efficient network?
The most important criteria are performance,
reliability and security. Performance of the network depends on number of
users, type of transmission medium,the capabilities of the connected h/w and
the efficiency of the s/w.Reliability is measured by frequency of failure, the
time it takes a link to recover from the failure and the network’s robustness
in a catastrophe.Security issues include protecting data from unauthorized
access and viruses.
2.Group
the OSI layers by function.
The seven layers of the OSI model belonging
to three subgroups.network support layers: Consisting of Physical, data link
and network layers and theydeal with the physical aspects of moving data from
one device to another.User support layers: Consists of Session, presentation
and application layers and theyallow interoperability among unrelated software
systems.The transport layer ensures end-to-end reliable data transmission
3. What are the features provided by layering?
It decomposes the problem of building a
network into more manageablecomponents. Rather than implementing a monolithic
piece of software that doeseverything implement several layers, each of which
solves one part of theproblem.
It provides more modular design. To add some
new service, it is enough tomodify the functionality at one layer, reusing the
functions provided at all theother layers.
4. What are the two interfaces provided by
protocols?
Service
interface Peer interface
Service
interface-defines the operations that local objects can perform on the
protocol. Peer interface-defines the form and meaning of messages exchanged
between protocol peers to implement the communication service.
5.what is LAN?
A LAN is a common name used to describe a
group of devices that share a geographic location. LAN is limited to single
building or campus.
6. What is flow Control?
Flow control refers to a set of procedures
used to restrict the amount of data. The sender can send before waiting for
acknowledgment.
7. Define Error detection and correction.
Error Detection:
Data can be corrupted during transmission. It is called as an error. For
reliable communication, the receiver must find out the errors occurred in the
data which iscalled as error detection.
Error Correction:
It is the mechanism to correct the errors and it can be handled in 2
ways.
a) When an error is discovered, the receiver can have the sender
retransmit the entire data unit.
8. What is the use of two dimensional parity in error
detection?
Two-dimensional
parity check increases the likelihood of detecting burst errors. It is used to
detect errors occurred in more than one bits.
9. What are the issues in data link layer?
The data link layer has a number of specific
functions it can carry out. These functions include
a) Providing a well-defined service interface to
the network layer.
b) Dealing with transmission errors.
c) Regulating the flow of data so that slow
receivers are not swamped by fast senders.
10.
What are the ways to address the framing problem?
The
framing problem can be addressed by the following protocols: Byte-Oriented
Protocols(PPP)
Bit-Oriented
Protocols(HDLC)
Clock-Based
Framing(SONET)
11.What
are the responsibilities of data link layer?
Specific responsibilities of data link layer
include the following.
a) Framing
b) Physical addressing
c) Flow control
d) Error control
e) Access control
12. Mention the types of errors.
There are 2 types
of errors
a) Single-bit error.
b) Burst-bit error.
13. Define the following terms.
Single
bit error: The term single
bit error means that only one bit of a given data unit (such as byte
character/data unit or packet) is changed from 1 to 0 or from 0 to 1.
Burst error: Means that 2 or more bits in the data
unit have changed from 1 to 0 from 0 to 1.
14.
What is redundancy?
It is the error detecting mechanism, which
means a shorter group of bits or extra bits may be appended at the destination
of each unit.
15.What
is the purpose of hamming code?
A hamming code can be designed to correct
burst errors of certain lengths. So the simple strategy used by the hamming
code to correct single bit errors must be redesigned to be applicable for
multiple bit correction.
16.what
si mean by error control?
Error control is a method that can be used to
recover the corrupted data whenever possible.These are two basic types of error
control which are backward error control and forward error control.
17.
what is OSI?
A standard that specifies a conceptual model
called Open systems Interconnection network interface model, which breaks
networked communications into seven layers:
Application,Presentation,Session,Transport ,Network,Data link,Physical.
UNIT 2
1. What
are the responsibilities of Network Layer?
The Network Layer is responsible for the
source-to-destination delivery of packet possibly across multiple networks
(links).
a. Logical Addressing b. Routing.
2. What
is DHCP?
The Dynamic Host Configuration Protocol has
been derived to provide dynamic configuration. DHCP is also needed when a host
moves from network to network or is connected and disconnected from a network.
3.
Define ICMP?
Internet
Control Message Protocol is a collection of error messages that are sent back
to the source host whenever a router or host is unable to process an IP
datagram successfully.
4. What
is the need of internetwork?
To
exchange data between networks, they need to be connected to make an
Internetwork.
5. What
are the types of class full addressing?
The types are Class A, Class B, Class C,
Class D, Class E
6. What
do you mean by ARP?
ARP stands for Address resolution protocol,
maps an IP address to a MAC address
7. What
do you mean by RARP?
RARP stands for
Reverse Address resolution protocol, maps an MAC address to a IP address.
MAC sub layer resolves the contention for the
shared media. It contains synchronization, flag, flow and error control
specifications necessary to move information from one place to another, as well
as the physical address of the next station to receive and route a packet.\
9.
Define the term medium access control mechanism
The protocaol that determines who can
transmit on a broadcast channel are called medium access control(MAC)
protocaol. The MAC protocols are implemented in the Mac sublayer which is the
lower sublayer of the data link layer.
10.what
is bridge?
Bridge is a hardware networking device used
to connect two LANs. A bridge operates at data link layer of the OSI reference
model.
11.what
is a repeater?
Repeater is a hardware device used to
strengthen signals being transmitted on a networks.
12.define
router
A network layer device that connects networks
with different physical media and translates between different network
architecture.
13.what
is a switch?
A switch is a networking device that manages
networked connections between devices on a star networks.
14.what
is mean by Ethernet?
Ethernet is a networking technology developed
in 1970 which is governed by the IEEE 802.3 specification.
15.Advantages
of Ethernet
1.Inexpensive 2.Easy to install 3.Supports
various writing technologies.
UNIT 3
1.what
is routing?
Routing is a process of selecting paths in a
network through which network traffic is sent.
2.what
is the purpose of address resolution protocol(ARP)?
ARP is a dynamic mapping method that finds a
physical address for a given a logical address. i.e mapping IP address to
physical address.
3.define
an internetwork
A collection of interconnected netwoek is
called an internetwork.
4.state
the duties of network layer
1.Responsible for
the source to destinatination delivery of a packet. 2.Logical addressing
3.Routing
5.What
is multicasting?
Delivery of information to a group of
destinations simultaneously using the most efficient strategy to deliver the
messages over each link of the network only once.
1.reverse path
multicasting 2.reverse path broad casting
6.what
is multicast? What is the motivation for developing multicast?
Multicasting means delivering the same packet
simultaneously to a group of clients. Motivation for developing multicast is
that there are applications that wants to send a packet to more than one
destination hosts.
7.define
subnetting
Subnetting is a technique that allows a
network administrator to divide one physical network into smaller logical
networks and thus, control the flow of traffic for security or efficience
reasons.
8.mention
any four applications of multicasting
1.Broad casts of
audio and video 2.videoconferencing
3.Shared
Applications.
4.IGMP
is used by multicast routers to keep track of membership in a multicast group.
9.Describe
the process of routing packets
Routing is the act of moving information
across an internetwork from a source to a destination.
10.what
are the some routing algorithm types?
Static, dynamic, flat, hierarchical, host-
intelligent,router- intelligent,in tradomain ,interdomain,link state and
distance vector.
11.what
is a benefit of DHCP
1.simplicity:clients
need to manual configuration.
2.Mobility
and hosts:Hosts may move between networks without reconfiguring.
3.Mobility of network:Possible for internet service providers to
reconfigure customers address transparently.
4.Save
address space if individual clients are not always active.
12.What
are the services offered by network layer?
1.logical addressing 2.Routing.
13.what
are datagrams?
Packets in the IP layer are called datagrams.
13.
what is IP addressing?
An IP address is a numerical label assigned
to each divide in a computer network that uses internet protocol for
communication.
Two important
functions at IP address 1.Host identification
2.Location
addressing
14.How
can the routing be classified?
The routing can be classified as,
2) Non-adaptive routing.
15.what
are the salient features of IPv6?
Salient
features are :
1.Efficient and
hierarchical addressing and routing infrastructures. 2.IPv6 networks provide
auto configuration capabilities.
3.Better support
for QOS. 4.Large Address space.
5.
stateless and stateful address congiguration.
UNIT 4
1.what
are the fields on which the UDP checksum is calculated? Why?
UDP ckecksum includes a pseudoheader, the UDP
header and the data coming from the applicationlayer.
2.what
are the advantages of using UDP over TCP?
Does not include the overhead needed to
detect and maintain connection oriented semantics.
2.what
is TCP?
TCP provides a connection oriented,reliable
byte stream service.The connection oriented means the two applications using
TCP must establish a TCP connection with each other before they can exchange
data.
3.Define
congestion
When too many packets rushing to a node or a
part of network, the network performance degrades so this situation is called
as congestion.
4.list
the flag used in TCP header?
TCP header contains six flags. They are
URG,ACK,PSH,RST,SYN,FIN
5.Give
the approaches to improve the QOS..
Fine grained approaches , which provide QOS
to individual applications or flows. Integrated services , a QOS architecture
developed in the IETE and often associated with RSVP.
6.what
do you mean by QOS?
Quality of Service is used in some
organizations to help provide an optimal end user experience for audio and
video communications.Qos is most commonly used on networks where bandwidth is
limited:with a large number of network packets competing for a relatively small
amount of available bandwidth.
7. what
is multiplexing?
The job of gathering data chunks at the
sourcs host from different sockets, encapsulating each data chunks with header
information to create segments, and passing the segments bto the network layer
is called multiplexing.
8.what
is the demultiplexing?
The job of delivering the data in a transport
layer segment to the correct socket is called demultiplexing.
9.what
is RTT?
RTT is an acronym for Round Trip Time: it is
a measure of the time it takes for a packet to travel from a computer , across
a network to another computer, and back.
10.what
is the segment?
Transport layer protocols send data as a
sequence of packets.In TCP/IP these packets are called segments.
11.
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.
12.
list the services of end to end services.
1.Guarantee
message delivery.
2.Delivery messages
in the same order they are sent. 3.Deliver at most one copy of each message.
4.Support arbitrarily large message.
5.Support
synchronization.
13.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.
14.What
are the functions of transport layer?
1.Breaks messages
into packets. 2.connection control 3.addressing
4.Provide
reliability
15.what
are the types of QOS tools?
Classification
Congestion management Congestion avoidance Shaping/policing
Link efficiency
16.List
some ways to deal with congestion
1.packet
elimination 2.Flow control 3.Buffer allocation 4.Choke packets
When two or more
nodes would simultaneously try to tranmit packets to one node there is a high
probability that the number of packets would exceed the packet handling
capacity of the network and lead to congestion.
18.Explain
the three types of addresses in TCP/IP?
Three
types of addresses are used by systems using the TCP/IP protocol: the physical
address, the internetwork address (IP address), and the port address
19.
What are the flow characteristics related to QOS?
The flow characteristics related to QOS are
· `Reliability
· Delay
· Jitter
· Bandwidth
20.
What are the techniques to improve QOS?
The techniques to improve QOS are
· Scheduling
· Traffic shaping
· Resource reservation
· Admission control
21.
Define Socket address
The combination of IP address and port
address is called Socket address
22.
What are the two types of protocols used in Transport layer?
The two types of protocols used in Transport
layer are
· TCP
· UDP
23.Define
Throughput.
It is defines as a number of packets passing
through the network in a unit of time
24.Define
UDP
User
datagram protocol is a Unreliable, connectionless protocol, used along with the
IP protocol
25.What
is the need of port numbers?
Port numbers are used as a addressing
mechanism in transport layer
26. What are the types of port numbers used in
transport layer?
· Well-known port
· Registered port
· Dynamic port
27. Why TCP services are called Stream delivery
services?
TCP
allows the sending process to deliver data as a stream of bytes and the
receiving process to deliver data as a stream of bytes. so it is called as
stream of bytes.
It is the variation in delay for packets
belonging to same flow .
29.
Compare connectionless service & connection oriented service
In connection
less service there is no connection between transmitter & receiver Ex:
TCP
In connection
oriented service there is a connection between transmitter & receiver
Ex: UDP
30. What
is Unicast & Multicast communication?
Unicast
communication is one
source sending a packet to one destination. Multicast communication is
one source sending a packet to multiple destinations.
UNIT 5
1.define
the 2 types of user agents in the electronic mail system
Command driven:It normally accepts a one character command from the
keyboard to perform its task.
GUI based:They contain GUI components that allow the user to interact
with the software by using both the keyword and mouse.
2.What
is DNS?
DNS is a client/server application that identifies each host on the
internet with a unique user friendly name,
3. what
is the purpose of inverse domain?
The
inverse domain is used to map an address to a name.
4.what
is SMTP?
Simple Mail Tranfer Protocol is a standard and reliable host to host
mail transport protocol that operates over the TCP port 25.
5.State
the Purpose of SNMP
The primary purpose of SNMP is to allow the network administrator to monitor
and configure devices on the network, remotely via the network. These
configuration and monitoring capabilities are collectively referred to as
management.
6.What
is the Domain name system responsible for?
The Domain name system converts domain names (of the form www.vtubooks.com)
into ip numbers.
7. what
are the four main properties of of HTTP?
1.Global Uniform
Resource Identifier 2.Request response exchange. 3.Statelessness.
4.Resource
metadata
The
connection between sending mail.
9.What
is virtual terminal?
A virtual terminal is a data structure maintained by either the
application software or a local terminal.
10.what
are the basic functions of email?
Composition,Transfer,Reporting,Displaying,Disposition.
11.Define
www?
It is an internet application that allows users to wiew web pages and
move from one web page to another.
12.
what is the web browser?
Web browser is a software program that interprets and displays the
contents of HTML web pages.
13.What
is URL?
A string identifier that identifies a page on
the world wide web.
14.
what do you mean by TELNET?
TELNET
is used to connect remote computers and issue commands on those computers.
15What
are the responsibilities of Application Layer?
The
Application Layer enables the user, whether human or software, to access the
network. It provides user interfaces and support for services such as e-mail,
shared database management and other types of distributed information services
o
Network virtual Terminal
o File transfer,
access and Management (FTAM) o Mail services
o
Directory Services
16.
Write down the three types of WWW documents.
The documents in the WWW can be grouped into
three broad categories: static, dynamic and active.
A)
Static:
Fixed-content documents that are created and
stored in a server.
B)
Dynamic: Created by web server whenever a browser
requests the document.
C)
Active:
A program to be run at the client side
17. What is Fully Qualified Domain Name?
If a label is terminated by a null string is
called a Fully Qualified Domain Name.
18.
What is Generic Domains?
Generic
domain define registered hosts according to their generic behaviour. Each node
in the tree defines a domain, which is an index to the domain name space
database Eg. com – Commercial organizations
edu - Educational
institutions gov - Government institutions
The
TCP/IP protocol that supports electronic mail on the internet is called Simple
Mail Transfer Protocol (SMTP). It is a system for sending messages to other
computer users based on email addresses.
20.What
do you mean by File transfer protocol?
It is a standard mechanism provided by the
internet for copying a file from one host to
another
21. What are the two types of connections in FTP?
The two types of
connections in FTP are
· Control connection
· Open connection
22. Define HTTP.
It is
used mainly to access data on the World Wide Web. The protocol transfer data in
the form of plaintext, hypertext, audio, video and so on
23. What are the types of messages in HTTP
transaction?
The types of
messages in HTTP transaction are
· Request messages
· Response messages
24. What are the parts of a browser?
The parts of a browser are
· A controller
· A client program
· Interpreter
25. Name the four aspects of security.
· Privacy
· Authentication
· Integrity
· Non-repudiation
26.What
is POP?
Post Office Protocol, version3 (POP3) and Internet Mail Access Protocol
version4 (IMAP4) are protocol used by a mail server in conjunction with SMTP to
receive and hold mail for hosts.
27.What
is the function of SMTP?
The TCP/IP protocol supports electronic mail
on the Internet is called Simple Mail Transfer (SMTP). It is a system for
sending messages to other computer users based on email addresses. SMTP
provides mail exchange between users on the same or different computers.
28.How
does MIME enhance SMTP?
MIME is a supplementary protocol that allows
non-ASCII data to be sent through SMTP. MIME transforms non-ASCII data at the
sender site to NVT ASCII data and deliverers it to the
client SMTP to be sent through the Internet.
The server SMTP at the receiving side receives the NVT ASCII data and delivers
it to MIME to be transform feed back to the original data.
29.Why
is an application such as POP needed for electronic messaging?
Workstations interact with the SMTP host,
which receives the mail on behalf of every host in the organization, to
retrieve messages by using a client-server protocol such as Post Office
Protocol, version 3(POP3). Although POP3 is used to download messages from the
server, the SMTP client still needed on the desktop to forward messages from
the workstation user to its SMTP mail server.
16 MARKS WITH ANSWERS
UNIT 1
1.
Explain
ISO/OSI reference model. Physical layer
Data
link layer Network layer Transport layer Session layer Presentation layer
Application layer
2. Explain the topologies of the network. Mesh
topology
Star topology
Tree
topology
Bus topology
Ring topology
3. Explain the
categories of networks. Local Area Network(LAN) Metropolitan Area Network(MAN)
Wide Area Network(WAN)
4. Explain error
detection and error correction techniques. Types of errors
Single
bit error Burst error Error detection
Vertical
redundancy check(VRC) Longitudinal redundancy check(LRC) Cyclic redundancy
check(CRC) Checksum
Error correction
Single-bit error correction Hamming code
Burst error correction
5.
Explain
error control mechanism. Stop and wait ARQ
Sliding
window ARQ Go back-n Selective-reject
6. Explain the flow control mechanism Stop and
wait
Sliding window.
UNIT II
1. Explain about
Ethernet. Access method :CSMA/CD Addressing
Electrical
specification Frame format Implementation:
10 base 5 :Thick Ethernet
10 base 2 :Thin Ethernet
10 base T :Twisted-pair Ethernet
1 base 5 :Star LAN
2.Explain detail
about IEEE 802.3 MAC sublayer
Frame format Frame
length
Ethernet
specifications Manchester encoding
Binary exponential
Backoff algorithm Ethernet performance
3.Exlain detail
about Bluetooth Bluetooth architecture
Radio layer
Baseband layer Frame format
L2CAP
Hidden
Station Problem
3.Explain about
IPv4 address Classful addressing
Special ip
addressing Classless addressing Header format
IP fragmentation
Optons
Subnetting
a network
4.Explain about
Address resolution protocol Packet format
Encapsulation Proxy
ARP
5.Explain about
RARP Frame Format of RARP Encapsulation
6.Explain about
Internet Control Message Protocol Message types
Message format
Error Reporting
Echo Request and
reply Timestamp request and reply
Address
mask request and reply message.
UNIT III
1. Explain IP
addressing method. Internetwork protocol (IP) Datagram
Addressing
Classes
Dotted decimal notation
A sample internet
3. Define routing & explain distance vector
routing and link state routing. Distance vector routing
Sharing
information Routing table Creating the table Updating the table Updating
algorithm Link state routing Information sharing Packet cost
Link state packet
Getting
information about neighbors Initialization
Link state database
4. Define bridge and explain the type of
bridges.
Bridges
Types of bridges
Simple bridge
Multiport bridge
Transparent bridge
5. Explain subnetting Subnetting
Three
levels of hierarchy Masking
Masks
without subnetting Masks with subnetting
Finding
the subnetwork address Boundary level masking Non-boundary level masking
6. Write short notes about repeaters, routers and gateways. Repeaters
Routers
Routing
concepts Least-cost routing Non adaptive routing Adaptive routing Packet
lifetime Gateways
7.Explain detail
about Global internet BGP
Comparison
between RIP and OSPF
8.Explain multicast
routing DVMRP
PIM
UNIT IV
1. Explain the
duties of transport layer. End to end delivery
Addressing
Reliable delivery
Error control Sequence control Loss control Duplication control Flow control
Multiplexing
3.
Explain UDP & TCP.
User Datagram Protocol(UDP) Source port address Destination port address
Total length
Checksum
Transmission
Control Protocol(TCP) Source port address
Destination
port address Sequence number
Acknowledgement number
Header length
Reserved
Control
Window size
Check sum
Urgent pointer
Options and padding
4. Explain about congestion control.
Congestion avoidance
BECN
FECN Four situations Discarding
- Explain
about Congestion Avoidance DECbit scheme RED
- 6.Expplain
detail about QoS Policing
Iintegrated service Traffic Shaping Admission
Control RSVP
Differentiated Serviices/Qos
UNIT V
1.
Explain the functions of SMTP.
System for sending
messages to other computer users based on e-mail addresses. SMTP provides mail
exchange between users on the same
or different
computers. User Agent
Mail
Transfer Agent
Multipurpose Internet Mail Extensions
Post
Office Protocol
2. Write
short notes on FTP.
Transfer a file
from one system to another. TCP connections
Basic
model of FTP
3.
Explain
about
HTTP. HTTP
transactions HTTP messages
URL
4.
Explain
the WWW in detail. Hypertext & Hypermedia Browser Architecture Categories
of Web Documents HTML
CGI Java
5.Explain about
Electronic mail Email addressing
Message Headers
Formatted email
Functions of email
User agent and message
transfer agent Simple mail Transfer protocol Multipurpose internet mail
extensions Post Office Protocol(POP)
IMAP
6.Explain detail
about Domain Name System Components of DNS
DNS in the internet
Name space
Domain
name Space
Resolution
Message
format
Resource
records
Name
servers
LDAP
Dynamic
domain name system(DDNS)
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