Computer Science/IT MCQs
Topic Notes: Computer Science/IT
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
41
What is 'NAT Traversal' and why is it necessary?
Answer:
Methods for establishing connections between hosts behind different NAT devices (e.g., in P2P).
Network Address Translation (NAT) often prevents incoming connections from reaching hosts inside a private network. NAT Traversal techniques, such as STUN, TURN, or Hole Punching, are used by applications like VoIP and P2P file sharing to establish direct communication between two hosts even if both are behind NAT routers.
42
Which BGP attribute is used to prevent routing loops within an Autonomous System (AS)?
Answer:
AS_PATH
The AS_PATH attribute is a mandatory transitive attribute that lists the autonomous systems through which the routing information has passed. When a BGP speaker receives a route, it checks the AS_PATH; if its own AS number is already in the list, it rejects the route to prevent a routing loop.
43
Which of the following is a characteristic of 'Anycast' routing?
Answer:
A packet is delivered to the 'nearest' node among a group of nodes sharing the same address.
Anycast is a network addressing and routing methodology where a single destination address is shared by multiple devices. The routing protocol delivers the packet to the topologically 'closest' node. This is widely used in CDN (Content Delivery Networks) and DNS (Domain Name System) to reduce latency and provide load balancing.
44
What is the function of the 'Flow Label' field in the IPv6 header?
Answer:
To enable per-flow handling by routers for real-time traffic or Quality of Service (QoS).
The 20-bit Flow Label field in IPv6 is used to tag sequences of packets that require special handling by routers, such as non-default quality of service or real-time service. It allows routers to efficiently identify a 'flow' without having to deep-packet inspect transport-layer headers (like TCP/UDP ports).
45
What is the 'Maximum Segment Lifetime' (MSL) in TCP?
Answer:
The time a host waits in the TIME_WAIT state to ensure late segments are discarded.
MSL is the maximum time a TCP segment is expected to exist in the network system. TCP waits for 2 times the MSL (2MSL) in the TIME_WAIT state after closing a connection. This ensures that any delayed segments from the old connection are not misidentified as part of a new connection using the same ports.
46
What is the primary function of the 'Spanning Tree Protocol' (STP)?
Answer:
To prevent switching loops in Ethernet networks with redundant paths.
STP (IEEE 802.1D) is a Link Layer protocol that ensures a loop-free topology for Ethernet networks. It detects redundant paths and logically blocks certain ports to prevent broadcast storms, while maintaining the ability to unblock those paths if a primary link fails.
47
What is the difference between a 'Hub' and a 'Switch'?
Answer:
A hub broadcasts data to all ports, whereas a switch sends data only to the specific destination port.
A hub is a physical layer device that simply repeats incoming signals to all of its ports, creating a single collision domain. A switch is a data link layer device that learns MAC addresses and uses them to intelligently forward frames only to the intended recipient, creating separate collision domains for each port.
48
What is 'Cubic' in the context of Linux networking?
Answer:
The default TCP congestion control algorithm that uses a cubic function for window growth.
TCP CUBIC is a congestion control algorithm that is the default in many Linux kernels. Unlike traditional Reno which uses linear window growth, CUBIC uses a cubic function to scale the congestion window based on the time since the last congestion event. This makes it more efficient and fair on high-bandwidth, high-latency networks (long fat pipes).
49
What is the 'Exposed Node Problem' in wireless networks?
Answer:
A node that is prevented from sending to a destination because of an unrelated neighbor's transmission.
The exposed node problem occurs when a node is near a transmitter but not the receiver. Because the node senses the medium as busy, it refrains from sending its own data to a different recipient, even though its transmission would not actually interfere with the ongoing communication. This leads to inefficient use of the wireless spectrum.
50
What is the 'Application Layer' in the TCP/IP model equivalent to in the OSI model?
Answer:
Application, Presentation, and Session layers
The original TCP/IP model combined several functions into one 'Application' layer. In the more granular 7-layer OSI model, these functions are separated into the Session (dialogue control), Presentation (data formatting/encryption), and Application (network services for software) layers.