Computer Science - IT MCQs
Topic Notes: Computer Science - IT
<p>MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.</p>
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
171
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.
172
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.
173
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.
174
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.
175
What is 'Forward Error Correction' (FEC)?
Answer:
A technique where the sender adds redundant data so the receiver can correct errors without retransmission.
FEC is a signal processing technique where the sender includes extra (redundant) information in the message. This allows the receiver to detect and fix a certain number of bit errors caused by noise or interference on the transmission channel, reducing the need for time-consuming retransmissions.
176
In the BGP decision process, which attribute is checked first (highest priority)?
Answer:
Weight (Cisco specific) or Local Preference
The BGP path selection process follows a specific hierarchy. On Cisco routers, 'Weight' is checked first. In standard BGP implementations, 'Local Preference' is the first attribute evaluated. These attributes allow administrators to favor certain outbound paths over others before looking at path lengths or origin types.
177
Which of the following best describes 'VLAN Trunking' (802.1Q)?
Answer:
Connecting two switches and allowing traffic from multiple VLANs to pass over a single link.
VLAN Trunking allows multiple Virtual LANs to share a single physical connection between network devices (like switches). The 802.1Q standard adds a 'tag' to the Ethernet frame header to identify which VLAN the frame belongs to, ensuring the receiving switch can correctly route the traffic to the appropriate VLAN.
178
What is a 'Content-Addressable Memory' (CAM) table used for in a switch?
Answer:
To map MAC addresses to the physical ports on which they were seen.
A CAM table (often called a MAC address table) is used by high-speed switches to make forwarding decisions. When a frame arrives, the switch looks at the destination MAC address and checks the CAM table to determine which physical port that MAC address is associated with. If it's not in the table, the switch broadcasts the frame to all ports.
179
In the Context of RIP (Routing Information Protocol), what is 'Split Horizon'?
Answer:
A rule that prevents a router from advertising a route back out the same interface it learned it from.
Split Horizon is a loop-prevention mechanism in distance-vector routing protocols. It works by not sending routing information back to the source from which it was received. This prevents two routers from continuously bouncing incorrect routing information back and forth (counting to infinity).
180
In a Content Delivery Network (CDN), what is 'Edge Computing'?
Answer:
Running applications and processing data closer to the end-user at the network periphery.
Edge computing involves moving computation and data storage away from central data centers and closer to the 'edge' of the network—near the users. This reduces latency for applications like video streaming, gaming, and IoT by processing data locally rather than sending it back and forth to a distant cloud server.