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
71
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.
72
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.
73
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.
74
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.
75
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.
76
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.
77
Which protocol is primarily used for distributing labels in a Multiprotocol Label Switching (MPLS) network?
Answer:
LDP
The Label Distribution Protocol (LDP) is used by Label Switch Routers (LSRs) to exchange label mapping information. This allows the routers to build a Label Forwarding Information Base (LFIB) to forward packets based on labels rather than IP addresses, facilitating high-speed switching and traffic engineering.
78
What does the 'ACK' flag in a TCP header indicate?
Answer:
That the acknowledgment field in the header is valid and contains the next expected sequence number.
In TCP, the ACK flag is set in almost every packet after the initial SYN. When this bit is set to 1, it means the 32-bit 'Acknowledgment Number' field contains the sequence number that the sender of the ACK is expecting to receive next, effectively confirming that all prior data has been received correctly.
79
Which of the following is true about 'Multiplexing' in the Transport Layer?
Answer:
It allows multiple applications to use the network simultaneously through the use of port numbers.
Multiplexing at the Transport Layer (TCP/UDP) allows a single host with a single IP address to support many concurrent applications. By using unique port numbers for each connection, the transport layer can 'demultiplex' incoming data and deliver it to the correct application process.
80
What is the 'MTU' (Maximum Transmission Unit)?
Answer:
The largest size of a protocol data unit (PDU) that can be communicated in a single network layer transaction.
The MTU is the maximum size (in bytes) of a packet or frame that can be sent over a specific physical medium. For standard Ethernet, the MTU is typically 1500 bytes. If a packet is larger than the MTU of a link it needs to cross, it must be fragmented (in IPv4) or dropped (in IPv6).