Computer Knowledge

Computer Networks

2,461 Questions

Computer networks involve the architecture, protocols, and security measures used for digital communication. This collection covers OSI model layers, IP addressing, data transmission, and cryptographic standards. These concepts are vital for the computer knowledge sections of banking and government exams.

OSI model layersNetwork protocolsIP subnet maskingData encryption standardsServer configurationsNetwork commands

Computer Networks Questions

Multiple choice

An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it: 245.248.128.0/20. The ISP wants to give half of this chunk of addresses to Organization A, and a quarter to Organization B, while retaining the remaining with itself. Which of the following is a valid allocation of address to A and B?

  1. 245.248.136.0/21 and 245.248.128.0/22

  2. 245.248.128.0/21 and 245.248.128.0/22

  3. 245.248.132.0/22 and 245.248.132.0/21

  4. 245.248.136.0/24 and 245.248.132.0/21
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since half of 4096 host addresses must be given to organization A, we can set 12th bit to 1 and include that bit into network part of organization A, so the valid allocation of addresses to A is 245.248.136.0/21 Now for organization B, 12th bit is set to '0' but since we need only half of 2048 addresses, 13th bit can be set to '0' and include that bit into network part of organization B so the valid allocation of addresses to B is 245.248.128.0/22

Multiple choice

The transport layer protocols used for real-time multimedia, file transfer, DNS and email respectively are

  1. TCP, UDP, UDP and TCP

  2. UDP, TCP, TCP and UDP

  3. UDP, TCP, UDP and TCP

  4. TCP, UDP, TCP and UDP
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Real-time multimedia needs connectionless service, so underlying transport layer protocol used is UDP. File transfer runs over TCP protocol with port no. 21. DNS runs over UDP protocol within port no. 53. Email needs SMTP protocol which runs over TCP protocol within port no. 25.

Multiple choice

Which of the following addressing modes are suitable for program relocation at run time?

  1. Absolute addressing
  2. Based addressing
  3. Relative addressing
  4. Indirect addressing

  1. 1 and 4

  2. 1 and 2

  3. 2 and 3

  4. 1, 2 and 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Program relocation at run time transfers complete block to some memory locations. This require as base address and block should be relatively addressed through this base address. This require both based addressing and relative addressing mode.

Multiple choice

Which of the following functionalities must be implemented by a transport protocol over and above the network protocol?

  1. Recovery from packet losses

  2. Detection of duplicate packets

  3. Packet delivery in the correct order

  4. End to end connectivity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transport protocols are mainly for providing end to end connections by making sockets. Recovery from packet loss & delivery in correct order, duplication is checked by Data link layer.

Multiple choice

Which of the following assertions is FALSE about the Internet Protocol (IP)?

  1. It is possible for a computer to have multiple IP addresses

  2. IP packets from the same source to the same destination can take different routes in the network

  3. IP ensures that a packet is discarded if it is unable to reach its destination within a given number of hops

  4. The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Internet protocol ensures that a packet is forwarded if it is unable to reach its destination within a given no. of hops. One computer can have multiple IP addresses also packets having same source & destination can take different routes. Source doesn't decide where to route the packet, but it is decided by the routing tables at intermediate routers.

Multiple choice

Host A is sending data to host B over a full duplex link. A and B are using the sliding window protocol for flow control. The send and receive window sizes are 5 packets each. Data packets (sent only from A to B) are all 1000 bytes long and the transmission time for such a packet is 50 micro second. Acknowledgement packets (sent only from B to A) are very small and require negligible transmission time. The propagation delay over the link is 200 micro second. What is the maximum achievable throughput in this communication?

  1. 7.69 × 106 bps

  2. 11.11 × 106 bps

  3. 12.33 × 106 bps

  4. 15.00 x 106 bps
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Data packet size = 1000 byte        Number of packets = 5        Total data = 5000        Transmission time = 50 micro second/packet        Propagation delay = 200 micro second        So for 5 packets = 50 * 5 = 250 micro second        Total time for 5 packets = 250 + 200 = 450 micro second        Rate = Data/time = 5000*1000000/450 = 11.11*1000000 bps

Multiple choice

Consider the diagram shown below where a number of LANs are connected by (transparent) bridges. In order to avoid packets looping through circuits in the graph, the bridges organize themselves in a spanning tree. First, the root bridge is identified as the bridge with the least serial number. Next, the root sends out (one or more) data units to enable the setting up of the spanning tree of shortest paths from the root bridge to each bridge. Each bridge identifies a port (the root port) through which it will forward frames to the root bridge. Port conflicts are always resolved in favour of the port with the lower index value. When there is a possibility of multiple bridges forwarding to the same LAN (but not through the root port), ties are broken as follows: bridges closest to the root get preference and between such bridges, the one with the lowest serial number is preferred.

Consider the correct spanning tree for the previous question. Let host H1 send out a broadcast ping packet. Which of the following options represents the correct forwarding table on B3?

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Multiple choice

While opening a TCP connection, the initial sequence number is to be derived using a time-of-day (ToD) clock that keeps running even when the host is down. The low order 32 bits of the counter of the ToD clock is to be used for the initial sequence numbers. The clock counter increments once per millisecond. The maximum packet lifetime is given to be 64s. Which one of the choices given below is closest to the minimum permissible rate at which sequence numbers used for packets of a connection can increase?

  1. 0.015/s

  2. 0.064/s

  3. 0.135/s

  4. 0.327/s
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation