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
81
In OSPF, what is the purpose of an 'Area Border Router' (ABR)?
Answer:
To connect one or more OSPF areas to the backbone area (Area 0).
An Area Border Router (ABR) is a router located on the border between OSPF areas. It maintains separate link-state databases for each area it belongs to and summarizes routing information from one area to another, specifically connecting non-backbone areas to the mandatory backbone area (Area 0).
82
In cellular networks, what is a 'Handoff' (or Handover)?
Answer:
The process of transferring an active call or data session from one base station to another as the user moves.
Handoff is a critical feature of mobile networks. As a mobile device moves out of the range of one cell tower and into another, the network must switch the connection to the new tower without interrupting the call or data session. 'Hard handoffs' involve a brief disconnect, while 'soft handoffs' (common in CDMA) connect to the new tower before disconnecting from the old one.
83
What is 'Baseband' transmission?
Answer:
Using the entire bandwidth of the medium to send a single digital signal.
Baseband transmission uses the entire capacity of the communication medium to transmit a single data signal at a time. It is commonly used in LANs (like Ethernet). In contrast, broadband (or passband) transmission divides the medium into multiple frequency channels to carry different signals at the same time.
84
In the context of network security, what is a 'Sybil Attack'?
Answer:
An attacker creates many fake identities to gain disproportionate influence in a peer-to-peer network.
A Sybil attack occurs when a single malicious actor creates multiple fake nodes or identities in a distributed system. This can be used to subvert reputation systems, rig elections, or disrupt routing in decentralized networks (like blockchains or DHTs) by controlling a large portion of the 'votes' or 'nodes'.
85
Which protocol is used by 'Ping' and 'Traceroute'?
Answer:
ICMP
The Internet Control Message Protocol (ICMP) is used by network devices to send error messages and operational information. Ping uses ICMP 'Echo Request' and 'Echo Reply' messages, while Traceroute often uses ICMP 'Time Exceeded' messages (generated when TTL reaches 0) to map the path to a destination.
86
In the context of Optical Fiber communication, what is 'Four-Wave Mixing' (FWM)?
Answer:
A nonlinear effect where the interaction of three wavelengths produces a fourth wavelength.
Four-Wave Mixing (FWM) is a third-order nonlinear effect in optical fibers. When three signals of different frequencies propagate through a fiber, they interact to generate new signals at frequencies that can overlap with existing channels, causing crosstalk and signal degradation, particularly in Wavelength Division Multiplexing (WDM) systems.
87
In Software Defined Networking (SDN), what is the primary role of the Southbound API?
Answer:
Communication between the SDN controller and the network forwarding devices.
The Southbound API is the interface used by the SDN controller to communicate with and program the underlying network switches and routers (forwarding plane). OpenFlow is the most well-known example of a Southbound API, enabling the separation of the control plane from the data plane.
88
What is the primary vulnerability addressed by 'DNSSEC'?
Answer:
DNS cache poisoning and man-in-the-middle attacks.
DNS Security Extensions (DNSSEC) add digital signatures to DNS records. This allows a DNS resolver to verify that the information received from the DNS server is authentic and has not been tampered with. It prevents attackers from redirecting users to malicious websites via cache poisoning.
89
In a Chord Distributed Hash Table (DHT), if there are $N$ nodes in the system, what is the average number of hops required to resolve a query?
Answer:
$O(\log N)$
Chord uses a finger table to maintain routing information for nodes at exponential distances around the identifier circle. This structure allows the system to resolve lookups by halving the distance to the target in each step, resulting in a lookup efficiency of $O(\log N)$ hops, which is highly scalable for large distributed systems.
90
Which of the following describes the 'Poisson distribution' relevance in network traffic modeling?
Answer:
It is used for modeling packet arrivals in traditional voice-centric networks.
While Poisson distributions were historically used to model telephone call arrivals (random and independent), they are often poor models for modern computer network traffic, which tends to be 'self-similar' or 'bursty'. However, the Poisson process remains a fundamental mathematical model for simple queuing theory in networking.