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
101
Which field in the IPv4 header is used to prevent packets from looping infinitely?
Answer:
Time to Live (TTL)
The TTL field is an 8-bit value that is decremented by every router that processes the packet. When the TTL reaches zero, the packet is discarded, and an ICMP 'Time Exceeded' message is usually sent to the source. This prevents packets from circulating indefinitely in the event of a routing loop.
102
What is 'Traffic Shaping'?
Answer:
Delaying some packets to bring them into compliance with a desired traffic profile.
Traffic shaping (also known as packet shaping) is a bandwidth management technique that delays certain types of packets to optimize or guarantee performance, improve latency, or increase usable bandwidth for some kinds of packets by delaying others. It is often used to ensure that a bursty connection doesn't exceed a committed rate.
103
What is 'Jitter' in network communications?
Answer:
The variation in packet arrival times (latency variance).
Jitter refers to the inconsistency in latency over time. In real-time applications like VoIP or video conferencing, high jitter can lead to choppy audio or distorted video because the receiver cannot smoothly reassemble the stream if packets arrive at highly irregular intervals.
104
Which layer of the OSI model does the 'TLS' (Transport Layer Security) protocol typically operate in, even though it's often used by applications?
Answer:
Transport Layer / Session Layer
TLS is designed to secure communications over the Transport Layer (TCP). In the OSI model, it is generally considered to span the Transport, Session, and Presentation layers. It provides encryption, authentication, and data integrity for application protocols like HTTP, SMTP, and FTP.
105
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.
106
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.
107
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.
108
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).
109
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.
110
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.