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
151
What is the purpose of 'Subnetting'?
Answer:
To divide a large network into smaller, more manageable logical segments.
Subnetting allows a network administrator to divide a single large block of IP addresses (like a Class B network) into several smaller networks. This helps reduce broadcast traffic, improves security by isolating network segments, and allows for more efficient use of the assigned IP address space.
152
What is the 'Diameter' of a network in graph theory terms?
Answer:
The maximum number of edges on the shortest path between any two nodes.
In network topology analysis, the diameter is the longest of all shortest paths between any two nodes. A smaller diameter generally implies that the network can communicate more efficiently, as the 'worst-case' distance between any two points is minimized.
153
Which of the following describes the 'Silly Window Syndrome' in TCP?
Answer:
Small increments in window space lead to the transmission of very small data segments.
Silly Window Syndrome occurs when either the sender or the receiver forces the transmission of very small segments (e.g., 1 byte of data in a 40-byte header). This is highly inefficient. It is usually mitigated by Nagle's algorithm on the sender side and Clark's solution on the receiver side, which prevents the receiver from advertising a tiny window.
154
Which mechanism is used in HTTP/2 to allow the server to send resources to the client before the client requests them?
Answer:
Server Push
HTTP/2 Server Push allows a server to speculatively send resources (like CSS or JavaScript files) that it anticipates the client will need. This reduces the number of round trips required to render a page, as the client doesn't have to wait to parse the HTML before requesting secondary assets.
155
What is the 'Three-Way Handshake' in TCP?
Answer:
SYN, SYN-ACK, ACK
The three-way handshake is the process used to establish a TCP connection. The client sends a SYN (Synchronize) packet, the server responds with a SYN-ACK (Synchronize-Acknowledgment), and the client completes the process with an ACK (Acknowledgment). This ensures both sides are ready and have synchronized their initial sequence numbers.
156
In the context of congestion control, what does 'ECN' (Explicit Congestion Notification) allow routers to do?
Answer:
Mark packets to signal congestion to the end hosts without dropping them.
ECN is an extension to the Internet Protocol and TCP that allows end-to-end notification of network congestion without dropping packets. Routers that support ECN can set bits in the IP header to indicate congestion. The receiver then echoes this back to the sender in an ACK, allowing the sender to reduce its transmission rate before packet loss actually occurs.
157
What does the 'Multipath TCP' (MPTCP) extension allow a single connection to do?
Answer:
Transmit data across multiple network paths (e.g., WiFi and LTE) simultaneously.
Multipath TCP (MPTCP) is an effort to allow a single TCP connection to spread its traffic across multiple interfaces or paths. This provides better resource utilization, increased throughput, and improved resilience. For instance, a smartphone could use both its cellular data and WiFi connections simultaneously to download a single file.
158
What is the 'Slow Start' threshold (ssthresh) used for in TCP?
Answer:
To determine when to switch from Slow Start to Congestion Avoidance.
In TCP congestion control, the sender starts in the Slow Start phase, doubling the congestion window every RTT. Once the window size reaches the ssthresh (Slow Start Threshold), the sender switches to the Congestion Avoidance phase, where the window grows linearly to avoid overwhelming the network.
159
How does the QUIC protocol handle the 'Head-of-Line Blocking' issue found in TCP?
Answer:
By implementing multiple independent streams within a single connection over UDP.
In TCP, if one packet is lost, all subsequent packets in the buffer are held up until the lost packet is retransmitted (Head-of-Line Blocking). QUIC runs over UDP and supports multiple streams within one connection. If a packet in one stream is lost, it only affects that specific stream, allowing other streams to continue processing data without delay.
160
What is the primary goal of the 'Nagle's Algorithm'?
Answer:
To reduce the number of small packets sent over the network by buffering them.
Nagle's algorithm is used to improve the efficiency of TCP/IP networks by reducing the number of very small packets (like those containing only one character from a telnet session). It works by delaying the sending of small segments until they can be combined into a larger segment or until an ACK is received for previous data.