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
91
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.
92
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.
93
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.
94
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.
95
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).
96
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.
97
In wireless networking (802.11), what does the 'NAV' (Network Allocation Vector) represent?
Answer:
A virtual carrier sensing mechanism that tracks the remaining time the medium will be busy.
The Network Allocation Vector (NAV) is used in the CSMA/CA protocol for 802.11 wireless networks. It is a timer updated by information in the headers of frames sent by other stations. It allows a station to know how long the medium will be reserved for a transmission sequence (like an RTS/CTS exchange), even if the station cannot 'hear' the actual data transmission.
98
What is the function of 'Gratuitous ARP'?
Answer:
To update the ARP tables of other hosts when a host's IP or MAC address changes.
A Gratuitous ARP is an ARP Response that was not prompted by an ARP Request. It is broadcasted by a host to inform other hosts on the network about its IP-to-MAC mapping. This is commonly used for duplicate IP detection and for updating ARP caches on other devices when a cluster fails over or an interface is changed.
99
In the context of TCP Congestion Control, what is the specific purpose of the 'Fast Recovery' algorithm?
Answer:
To prevent the congestion window from dropping to 1 MSS after receiving three duplicate ACKs.
Fast Recovery is an optimization in TCP (specifically TCP Reno) that allows the sender to maintain a higher throughput after a packet loss is detected via triple duplicate ACKs. Instead of dropping the congestion window to 1 Maximum Segment Size (MSS) and entering Slow Start, it sets the window to a value related to the current threshold, assuming the network is still capable of delivering segments since ACKs are still arriving.
100
What is the purpose of the 'Pseudo-header' used in TCP and UDP checksum calculations?
Answer:
To protect against misrouted packets by including IP addresses and protocol information in the checksum.
The pseudo-header contains fields from the IP header (Source/Destination IP, Protocol, and Length). By including these in the transport-layer checksum, TCP and UDP can detect if a packet has been delivered to the wrong destination or has been corrupted in a way that the IP header alone might not catch.