Category: Computer Networks Objective Questions

Computer Networks Multiple Choice Questions on “Packet Switching & Circuit Switching”.

1. A local telephone network is an example of a _______ network.
a) Packet switched
b) Circuit switched
c) Bit switched
d) Line switched

Answer: b
Clarification: Circuit switching is connection oriented switching technique, whereas in the case of packet switching, it is connectionless. Circuit switching is implemented in the Physical layer, whereas packet switching is implemented in the Network layer. Internet too is based on the concept of circuit switching.

2. Most packet switches use this principle ____________
a) Stop and wait
b) Store and forward
c) Store and wait
d) Stop and forward

Answer: b
Clarification: The packet switch will not transmit the first bit to outbound link until it receives the entire packet. If the entire packet is not received and the time-out period expires, the packet switch will inform the sender to resend the part of packet or the entire packet based on the algorithm being used.

3. If there are N routers from source to destination, the total end to end delay in sending packet P(L-> number of bits in the packet R-> transmission rate) is equal to ______________
a) N
b) (N*L)/R
c) (2N*L)/R
d) L/R

Answer: b
Clarification: The equation to find the end to end delay when no. of bits, transmission rate and no. of routers is given by (N*L)/R. The total end to end delay, that is, nodal delay is the sum of all, the processing delay, queuing delay, transmission delay and propagation delay.

4. What are the Methods to move data through a network of links and switches?
a) Packet switching and Line switching
b) Circuit switching and Line switching
c) Line switching and bit switching
d) Packet switching and Circuit switching

Answer: d
Clarification: Packet switching and Circuit switching are two different types of switching methods used to connect the multiple communicating devices with one another. Packet switching is used in conventional LAN systems and circuit switching is used in telephonic systems.

5. The required resources for communication between end systems are reserved for the duration of the session between end systems in ________ method.
a) Packet switching
b) Circuit switching
c) Line switching
d) Frequency switching

Answer: b
Clarification: In circuit switching, a physical path between the sender and receiver is established. This path is maintained until the connection is needed. Circuit switching is implemented in the Physical layer and is used in telephonic systems.

6. As the resources are reserved between two communicating end systems in circuit switching, ___________ is achieved.
a) authentication
b) guaranteed constant rate
c) reliability
d) store and forward

Answer: b
Clarification: Circuit switching is connection oriented and is always implemented in the physical layer. Once a path is set, all transmission occurs through the same path. It is used since the early times in telephonic systems.

7. In _________ systems, resources are allocated on demand.
a) packet switching
b) circuit switching
c) line switching
d) frequency switching

Answer: a
Clarification: In packet switching, the bits are received in out of order and need to be assembled at the receiver end, whereas in the case of Circuit switching, all the bits are received in order. All transmissions may not occur through the same path in case of packet switching.

8. Which of the following is not an application layer service?
a) Network virtual terminal
b) File transfer, access, and management
c) Mail service
d) Error control

Answer: d
Clarification: Application layer is the topmost layer in the OSI model. Network virtual terminal, mail service, file transfer, access and management are all services of the application layer. It uses protocols like HTTP, FTP, and DNS etc. to provide these services.

Computer Networks Multiple Choice Questions on “Telnet”.

1. Telnet protocol is used to establish a connection to __________
a) TCP port number 21
b) TCP port number 22
c) TCP port number 23
d) TCP port number 25

Answer: c
Clarification: TCP port 21 is used for FTP, TCP port 22 is used for SSH and TCP port 25 is used for SMTP. Telnet provides access to a command line interface on a remote computer using the TCP port number 23.

2. Which one of the following is not true?
a) telnet defines a network virtual terminal (NVT) standard
b) client programs interact with NVT
c) server translates NVT operations
d) client can transfer files using to remote server using NVT

Answer: d
Clarification: The client can use the NVT only to interact with the programs already present on the remote server, not to transfer files to it. To transfer files, an FTP connection has to be used.

3. All telnet operations are sent as ________
a) 4 bits
b) 8 bits
c) 16 bits
d) 32 bits

Answer: b
Clarification: Telnet provides a bi-directional, 8-bit byte oriented communications facility through which operations are sent as 8-bit bytes for the server to interpret.

4. AbsoluteTelnet is a telnet client for _______ Operating system.
a) windows
b) linux
c) mac
d) ubuntu

Answer: a
Clarification: AbsoluteTelnet was originally released in 1999. It was developed by Brian Pence of Celestial Software.

5. The decimal code of Interpret as Command (IAC) character is _______
a) 252
b) 253
c) 254
d) 255

Answer: d
Clarification: If we want that a character be interpreted by the client instead of server, we use the IAC character. If IAC is followed by any other code than IAC, the client interprets it as a character.

6. Which of the following is true for character mode operation of telnet implementation?
a) each character typed is sent by the client to the server
b) each character typed is discarded by the server
c) each character typed is aggregated into a word and then sent to the server
d) each character type is aggregated into a line and then sent to the server

Answer: a
Clarification: In character mode, each character that the user is typing is immediately sent to the server which then interprets it only after the complete operation command is received.

7. In which mode of telnet, the client echoes the character on the screen but does not send it until a whole line is completed?
a) default mode
c) character mode
c) server mode
d) command mode

Answer: a
Clarification: In the default mode, the client does not send each character typed by the user to the server, thus saving the amount of packet transmissions required for executing each operation. But the server has to remain idle until the client sends the completed line wasting a lot of time.

8. Which one of the following is not correct?
a) telnet is a general purpose client-server program
b) telnet lets user access an application on a remote computer
c) telnet can also be used for file transfer
d) telnet can be used for remote login

Answer: c
Clarification: File Transfer Protocol is used for file transfer. Telnet provides access to the command-line interface on a remote host.

Computer Networks Quiz on “Transition from IPV4 to IPV6”.

1. The main reason for transition from IPv4 to IPv6 is _________
a) Huge number of systems on the internet
b) Very low number of system on the internet
c) Providing standard address
d) To provide faster internet

Answer: a
Clarification: Due to huge number of systems on the internet and the lower number of available addresses on IPv4, transition from IPv4 to IPv6 needs to happen. IPv4 provides around 4 billion unique IP addresses whereas IPv6 provides over 340 undecillion unique IP addresses.

2. Which of the following is not a transition strategy?
a) Dual stack
b) Tunneling
c) Conversion
d) Header translation

Answer: c
Clarification: As IPv4 addresses are of 32 bits and IPv6 addresses are of 128 bits, it is not possible to convert IPv4 address to IPv6 address. So, Dual stack, tunneling and header translation are the three strategies which might help in the transition from IPv4 to IPv6.

3. To determine which version to use when sending a packet to a destination, the source host queries which of the following?
a) Dual stack
b) Domain Name Server
c) Header information
d) Transport layer

Answer: b
Clarification: Source host queries DNS to determine which version to use when sending a packet to a destination. The DNS contains both, the IPv4 and IPv6 addresses of the modern dual stack host servers.

4. The strategy used when two computers using IPv6 want to communicate with each other and the packet must pass through a region that uses IPv4 is ______________
a) Dual stack
b) Header translation
c) Conversion
d) Tunneling

Answer: d
Clarification: In tunneling, The IPv4 routers can form a tunnel in which at the sender’s side, the IPv6 datagram is encapsulated in to IPv4, and at the receiver’s side of the tunnel, the IPv4 packet is stripped and the IPv6 packet is sent to the receiver.

5. The correct format of packet in tunnel that uses IPv4 region is ________
i. IPv6 header
ii. Payload
iii. IPv4 header
a) iii-i-ii
b) iii-ii-i
c) i-ii-iii
d) i-iii-ii

Answer: a
Clarification: At the sender’s side, the IPv6 datagram is encapsulated in to IPv4 i.e. An IPv4 header is inserted on top of the IPv6 header, and then the packet is sent through the tunnel.

6. ___________ is necessary when the sender wants to use IPv6, but the receiver does not understand IPv6.
a) Dual stack
b) Header translation
c) Conversion
d) Tunneling

Answer: b
Clarification: Header translation is used when the sender wants to use IPv6, but the receiver does not understand IPv6. It is made possible through a Network Address Translation – Protocol Translation enabled device such as a gateway.

7. Header translation uses ___________ to translate an IPv6 address to an IPv4 address.
a) IP address
b) Physical address
c) Mapped address
d) MAC address

Answer: c
Clarification: A mapped IPv6 address contains the IPv4 address in its last 32-bits and is preceded by 16 1s and 80 0s. It can be used to translate an IPv6 address to an IPv4 address.

8. Which of the following is not a step in the Header translation procedure?
a) The IPv6 mapped address is changed to an IPv4 address by extracting the rightmost 32bits
b) The value of the IPv6 priority field is discarded
c) The type of service field in IPv4 is set to zero
d) The IPv6 flow label is considered

Answer: d
Clarification: In the header translation procedure, first the IPv6 mapped address is changed to an IPv4 address by extracting the rightmost 32bits, then the value of the IPv6 priority field is discarded, and finally the ToS field in the IPv4 header is set to zero. IPv6 flow label is ignored in the procedure.

Computer Networks Questions and Answers for Aptitude test on “Datagram Networks”.

1. Datagram switching is done at which layer of OSI model?
a) Network layer
b) Physical layer
c) Application layer
d) Transport layer

Answer: a
Clarification: Datagram switching is normally done at network layer. In datagram switching, the datagram stream need not be in order as each datagram can take different routes to the destination.

2. Packets in datagram switching are referred to as ________
a) Switches
b) Segments
c) Datagrams
d) Data-packets

Answer: c
Clarification: As the name suggests, in datagram switching packets are called as datagram. Each datagram/packet is treated as an individual entity and routed independently through the network.

3. Datagram networks mainly refers to _________
a) Connection oriented networks
b) Connection less networks
c) Telephone networks
d) Internetwork

Answer: b
Clarification: The switch does not keep the information about the connection state, hence it is connection less. There is no need for establishing a handshake to begin the transmission in such networks.

4. Datagrams are routed to their destinations with the help of ________
a) Switch table
b) Segments table
c) Datagram table
d) Routing table

Answer: c
Clarification: Routing table is used to route the packets to their destinations. The packet/datagram header contains the destination header for the whole journey to source to the destination through the routers.

5. The main contents of the routing table in datagram networks are ___________
a) Source and Destination address
b) Destination address and Output port
c) Source address and Output port
d) Input port and Output port

Answer: b
Clarification: Routing table contains destination address and output port to route the packets to their destinations. The port address specifies the particular application that the packet has to be forwarded to after it has reached the destination.

6. Which of the following remains same in the header of the packet in a datagram network during the entire journey of the packet?
a) Destination address
b) Source address
c) Checksum
d) Padding

Answer: a
Clarification: Destination address remains same in the header during the entire journey of the packet. There is no pre-decided route for the packets so each datagram/packet is treated as an individual entity and routed independently through the network.

7. Which of the following is true with respect to the delay in datagram networks?
a) Delay is greater than in a virtual circuit network
b) Each packet may experience a wait at a switch
c) Delay is not uniform for the packets of a message
d) All of the mentioned

Answer: d
Clarification: The delay of each packet in a datagram network is different as each packet might take a different route to the destination. The delay includes the propagation delay and the processing delay that is induced at each stop/switch that the packet encounters in its journey.

8. During datagram switching, the packets are placed in __________ to wait until the given transmission line becomes available.
a) Stack
b) Queue
c) Hash
d) Routing table

Answer: b
Clarification: When there are too many packets to be transmitted and the transmission line gets blocked while transmitting some packets, the remaining packets are stored in queue during delay and are served as first in first out. The delay is called as queuing delay.

9. The probability of the error in a transmitted block _________ with the length of the block
a) Remains same
b) Decreases
c) Increases
d) Is not proportional

Answer: c
Clarification: Probability of the error in a transmitted block increases with the length of the block. Hence, the blocks should be as short as possible for ideal transmission with low possibility of an error.

10. Which of the following is false with respect to the datagram networks?
a) Number of flows of packets are not limited
b) Packets may not be in order at the destination
c) Path is not reserved
d) Delay is the same for all packets in a flow

Answer: d
Clarification: The delay of each packet in a datagram network is different as each packet might take a different route to the destination. This happens because there is no pre-decided route for the packets.

Computer Networks Multiple Choice Questions on “Basics”.

1. The IETF standards documents are called ________
a) RFC
b) RCF
c) ID
d) DFC

Answer: a
Clarification: RFC stands for Request For Comments and they are documents that describe methods, behaviors, research, or innovations applicable to the working of the Internet.

2. In the layer hierarchy as the data packet moves from the upper to the lower layers, headers are ___________
a) Added
b) Removed
c) Rearranged
d) Modified

Answer: a
Clarification: Each layer adds its own header to the packet from the previous layer. For example, in the Internet layer, the IP header is added over the TCP header on the data packet that came from the transport layer.

3. The structure or format of data is called ___________
a) Syntax
b) Semantics
c) Struct
d) Formatting

Answer: a
Clarification: The structure and format of data are defined using syntax. Semantics defines how a particular pattern to be interpreted, and what action is to be taken based on that interpretation. In programming languages, syntax of the instructions plays a vital role in designing of the program.

4. Communication between a computer and a keyboard involves ______________ transmission.
a) Automatic
b) Half-duplex
c) Full-duplex
d) Simplex

Answer: d
Clarification: In simplex transmission, data flows in single direction which in this case refers to the data flowing from the keyboard to the computer. Another example would be of the mouse where the data flows from the mouse to the computer only.

5. The first Network was called ________
a) CNNET
b) NSFNET
c) ASAPNET
d) ARPANET

Answer: d
Clarification: ARPANET stands for Advanced Research Projects Agency Networks. It was the first network to be implemented which used the TCP/IP protocol in the year 1969.

6. A _______ is the physical path over which a message travels.
a) Path
b) Medium
c) Protocol
d) Route

Answer: b
Clarification: Messages travel from sender to receiver via a physical path called the medium using a set of methods/rules called protocol. Mediums can be guided (wired) or unguided (wireless).

7. Which organization has authority over interstate and international commerce in the communications field?
a) ITU-T
b) IEEE
c) FCC
d) ISOC

Answer: c
Clarification: FCC is the abbreviation for Federal Communications Commission. FCC is responsible for regulating all interstate communications originating or terminating in USA. It was founded in the year 1934.

8. Which of this is not a network edge device?
a) PC
b) Smartphones
c) Servers
d) Switch

Answer: d
Clarification: Network edge devices refer to host systems, which can host applications like web browser. A switch can’t operate as a host, but as a central device which can be used to manage network communication.

9. A _________ set of rules that governs data communication.
a) Protocols
b) Standards
c) RFCs
d) Servers

Answer: a
Clarification: In communications, a protocol refers to a set of rules and regulations that allow a network of nodes to transmit and receive information. Each layer in the network model has a protocol set, for example, the transport layer has TCP and UDP protocols.

10. Three or more devices share a link in ________ connection.
a) Unipoint
b) Multipoint
c) Point to point
d) Simplex

Answer: b
Clarification: A multipoint communication is established when three or many network nodes are connected to each other. Frame relay, Ethernet and ATM are some examples of multipoint connections.

Computer Networks Multiple Choice Questions on “Application Layer”.

1. Which is not a application layer protocol?
a) HTTP
b) SMTP
c) FTP
d) TCP

Answer: d
Clarification: TCP is transport layer protocol.

2. The packet of information at the application layer is called __________
a) Packet
b) Message
c) Segment
d) Frame

Answer: b
Clarification: For Application, Presentation and Session layers there is no data format for message. Message is message as such in these three layers. But when it comes to Transport, Network, Data and Physical layer they have data in format of segments, packets, frames and bits respectively.

3. Which one of the following is an architecture paradigms?
a) Peer to peer
b) Client-server
c) HTTP
d) Both Peer-to-Peer & Client-Server

Answer: d
Clarification: HTTP is a protocol.

4. Application developer has permission to decide the following on transport layer side
a) Transport layer protocol
b) Maximum buffer size
c) Both Transport layer protocol and Maximum buffer size
d) None of the mentioned

Answer: c
Clarification: Application layer provides the interface between applications and the network. So application developer can decide what transport layer to use and what should be its maximum buffer size.

5. Application layer offers _______ service.
a) End to end
b) Process to process
c) Both End to end and Process to process
d) None of the mentioned

Answer: a
Clarification: End to End service is provided in the application layer. Whereas process to process service is provided at the transport layer.

6. E-mail is _________
a) Loss-tolerant application
b) Bandwidth-sensitive application
c) Elastic application
d) None of the mentioned

Answer: c
Clarification: Because it can work with available throughput.

7. Pick the odd one out.
a) File transfer
b) File download
c) E-mail
d) Interactive games

Answer: d
Clarification: File transfer, File download and Email are services provided by the application layer and there are message and data oriented.

8. Which of the following is an application layer service?
a) Network virtual terminal
b) File transfer, access, and management
c) Mail service
d) All of the mentioned

Answer: d
Clarification: The services provided by the application layer are network virtual terminal, file transfer, access and management, mail services, directory services, various file and data operations.

9. To deliver a message to the correct application program running on a host, the _______ address must be consulted.
a) IP
b) MAC
c) Port
d) None of the mentioned

Answer: c
Clarification: IP address lets you know where the network is located. Whereas MAC address is a unique address for every device. Port address identifies a process or service you want to carry on.

10. Which is a time-sensitive service?
a) File transfer
b) File download
c) E-mail
d) Internet telephony

Answer: d
Clarification: Internet telephony is Loss-tolerant other applications are not.

11. Transport services available to applications in one or another form _________
a) Reliable data transfer
b) Timing
c) Security
d) All of the mentioned

Answer: d
Clarification: The transport services that are provided to application are reliable data transfer, security and timing. These are very important for proper end to end services.

12. Electronic mail uses which Application layer protocol?
a) SMTP
b) HTTP
c) FTP
d) SIP

Answer: a
Clarification: Email uses various protocols like SMTP, IMAP and POP. The most prominent one used in application layer is SMTP.