Computer Networking questions from kerala PSC

1. Among the following IP Address classes, which one provides maximum of only 254 host addresses per network ID?
A.Class A
B.Class B
C.Class C
D.Class D
Ans is Class C
Explanation: For Class C The network id is 24 bits long and host id is 8 bits long
2^8-2=254 host address is maximum for class C.

2. Which device can use logical addressing system?
A.Hub
B.Switch
C.Router
D.
Ans is Router

3. You have an IP Address  of 172.16.13.5 with a 255.255.255.128 sub net mask . what is your class of address, subnet address and broadcast address?

( KERALA PSC SYSTEM ANALYST 2019)

A.Class A , Subnet 172.16.13.0, Broadcast address 172.16.13.127
B.Class B , Subnet 172.16.13.0, Broadcast address 172.16.13.127
C.Class B , Subnet 172.16.13.0, Broadcast address 172.16.13.255
D.Class B , Subnet 172.16.13.0, Broadcast address 172.16.255.255
Ans is Class B
Explanation:
class A:0-126
class B:128-191
class C:192-224
The above IP address 172.16.13.0 belongs to  Class B

To find Broadcast address
IP : 172.16.13.5
Subnet Mask:255.255.255.128
If subnet mask is 255 replace it with IP address
Then it will be 172.16.13.
For the last octect find difference of subnet mask and 256
256-128=128
then compare with last octect of IP address 5
here 128>5
so 128-1=127
there fore last octect is 127
Broadcast address will be 172.16.13.127

Routers are component of                   layer in OSI reference model

1. Physical Layer
2. Network Layer
3. Transport Layer
4. Data Link Layer

Ans : is Network Layer

No Of layers in OSI Refference model

1. Four
2. Five
3. Six
4. Seven
5. Ans is Seven

UGC NET 2018

Encrypt the message “HELLO MY DEARS” using Transposition cipher with

Key                        plain text 2 4 1 3

                            Cipher text 1 2 3 4

Split the message into 4 letters block key is 4

Then

HELL OMYD EARZ

Then as per key replace 2 to 1 ,4 to 2, 1 to 3, 3 to 4

Then it will be

ELHL MDOY AZER

Decrypt the message ‘WTAAD’ using the ceaser cipher with key=15

Ceaser cipher is shifting the message with key .

If it is encryption right shift with the key

If it is decryption left shif with the key .

Here it is decryption

Left shift of w with key 15 is H

For  T =E

A=L

A=O

Then ans will be HELLO

Bluetooth technology is the implementation of a protocol defined by the standard:

IEE 802.14

IDEA stands for:

Integrated Data Encryption Algorithm

Automatic repeat request error management mechanism is provided by:

A.      Logical link control sub layer

B.      Media Access Control sub layer

C.      Network interface Control Sub layer

D.      None of these

Which address is used in an internet employing the TCP/IP Protocols?

A.      Physical address and logical address

B.      Port address

C.      Specific Address

D.      All of the above

Multiplexing is used in:

A.      Packet Switching

B.      Circuit Switching

C.      Message Switching

D.      None of these

    Ans. Circuit Switching

Commercial use domain name will normally use the following suffix in their website address

Junior System Officer Milma 2017

A.      .net

B.      .com

C.      .gov

D.      .org

Ans: .com (option B)

A network with bandwidth of 10 Mbps can pass only an average of 1200 frames per minute with each frame carrying an average of 10,000 bits . What is the throughput of this network .

HSST(2018).

=(1200*10Mbps)/60

=1200*1000000

=1200000000/60=2000000=2Mbps

A system using NRZ-1 to transfer 10Mbps data. What is the average signal rate? HSST(2018).

A)      500 Kbaud

B)      1000 MHz

C)      500 MHz

D)     1000 Kbaud

Ans is 500 Kbaud

What is the minimum required bandwidth to send data at 1 Mbps rate to Manchester Encoding?

HSST(2018).

A)     10 Mhz

B)      2 MHz

C)      5 MHz

D)     1 MHz

Ans is 1 MHz

To send 3 bits data at a time at a bitrate of 3 Mbps with a carrier frequency of 10 MHz calculate the baud rate and bandwidth

A)      10 Mbaud and 10 MHz

B)      2 Mbaud and 2 MHz

C)      1 Mbaud and 8 MHz

D)     None of these

Eight channels each with 100 KHz bandwidth are to be multiplexed together . What is the minimum bandwidth of the link if there is a need for guard band of 10 KHz between channels to prevent interface ?

For 8 chnanel we need at least 7 guards bands

This means that the required bandwidth is atleast \100*8=800

7*10=70

800+70=870 KHz

The digital multiplexing technique for combining several low rate channels to high rate one

A)     TDM

B)      FDM

C)      CDM

D)     None of these

Ans is TDM (Time Division Multiplexing )

FDM (Frequency Division Multiplexing )

CDM (Code Division Multiplexing )

RG 59 category cables is used for

A)     Telephone

B)      LAN

C)      Cable TV Network

D)     None of These

Ans is Cable TV Network

The bit oriented protocol for communicate over point to point and multipoint link is

A)    HDLC

B)     Stop and wait protocol

C)     PPP

D)    PAD

HDLC is also an ISO STD developed from the synchronous Data Link Protocol standard proposed by IBM. HDLC NRM  also known as SDLC . HDLS is bit oriented protocol. For communication over point to point and multipoint

The service not provided by PPP is

A)     N/W Address configuration

B)      Authentication

C)      Flow Control

D)     None of these

Encryption is done at

A)     Presentation Layer

B)      Application Layer

C)      Session Layer

D)     Transport Layer

Ans is Presentation Layer

One channel carries all transmission simultaneously is

A)     TDMA

B)      CDMA

C)      FDMA

D)     PDMA

The IEEE standard for wifi is

A)     802.4

B)      802.1

C)      802.2

D)     802.11

An example for cell switched network is

A)     SONET

B)      ATM

C)      CPSR

D)     None of these

   GSM is a digital cellular phone system using

A)     TDMA AND PKT switching

B)      CDMS AND PKT switching

C)      TDMA AND FDMA

D)     FDMA AND CDMA

4.  HELO and PORT, respectively are commands from the protocoll:(ASSISTANT PROFESSOR - INFORMATION TECHNOLO0GY- TECHNICAL EDUCATION -ENGINEERING COLLEGES)

1. FT'P and HTI'P                                       
2. TELNet and POP3
3. HTTP and TELNET                                 
4. SMTP and FTP

Ans : SMTP and FTP 

Explanation:  

Simple Mail Transfer Protocol (SMTP) : It is an Internet standard used for transmitting email. Electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages. The client sends ‘HELO’ command to the SMTP server to identify itself and initiate the SMTP conversation.

File Transfer Protocol (FTP) : It is a network protocol used to transfer computer files between a client and server on a computer network. FTP communications use two port number values — one for commands (port 21 by default), and one for data transfer. This is where the PORT command comes into play. The PORT command is sent by an FTP client to establish a secondary connection (address and port) for data to travel over

5. 'Which of the following statements ieTRUE about CSMA/CD?

(ASSISTANT PROFESSOR - INFORMATION TECHNOLO0GY- TECHNICAL EDUCATION -ENGINEERING COLLEGES)

1. (   IEE802.ll wireless LAN runs CSMA/CD protocol
2.       Ethernet is not based on CSMA/CDprotocol
3.        CSMA/CD is not suitable for a high propagation delay network like satellite network
4.         There is no contention in a CSMA/CD network
5. Ans is 1.  (   IEE802.ll wireless LAN runs CSMA/CD protocol

SNMP Protocol is used for 

A.   Email

B.    Network Management

C.    Messaging

D.   File Transfer

Ans: Network Management

36. Communication between computers is always

A.   Serial

B.    Parallel

C.    Series parallel

D.   Direct

Ans: Serial

32. Which of the following is not a transmission medium 

A.   Coaxial cable

B.    Telephone lines

C.    Modem

D.   Microwave systems

Ans: Modem 

. ASCII Stands for (repeating question)

A.   American standard code for information interchange

B.    All purpose scientific code for information interchange

C.    American Security code for information interchange

D.   American Scientific code for information interchange

Ans:American Standard Code for Information Interchange(0-

24.Which  of the  following  TCP/lP  protocol is used for transferring files from one machine to another

A.   RARP

B.    ARP

C.    HTTP

D.   FTP

Ans:File Transfer Protocol (FTP)

File Transfer Protocol (FTP) is a standard Internet protocol for transmitting files between computers on the Internet over TCP/IP connections.

   22. A single packet on a data link is known as

A.   path

B.    frame

C.    group

D.   block

Ans:A single packet on a data link is known as Frame.

1,       Firefox, Opera, chrome, safari and Explorer are types of what’?
(A)     Web browser                                               (B)    Server
(C)     Client                                                         (D)    OS

 Ans: Web Browser

 In TCP a unique sequence number is assigned to each

A.   Byte

B.   Message

C.   Word 

D.   Segment 

Option A

A firewall is to be configured to allow hosts in a private network to freely open TCP connections and send packets on open connections. However, it will only allow external host to send packets on existing open TCP connections or connections that are being opened by internal hosts but not allow them to open TCP connections to host in the private network. To achieve this minimum capability of the firewall should be that of

A.            A combinauonal circuit

B.            Push down automaton with two stacks

C.           A finite automaton

D.          A pushdown automaton with one stacks

 

  HELO and PORT, respectively are commands from the protocol:

A.   FT'P and HTI'P                                       

B.   TELNet and POP3

C.   HTTP and TELNET                                 

D.   SMTP and FTP

 Answer : SMTP And FTP