Freshers — Test 1

Correct Answer: A. A. Flow control
Explanation: Flow control is done to prevent the receiver from being overflowed with data. It is done using various open-loop (prevention) methods and closed-loop (recovery) methods.

Correct Answer: C. C. 20 and 60 bytes
Explanation: The size of the header can be 20 bytes at a minimum if there are no options and can go up to 60 bytes at maximum with 40 bytes in the options field. The header contains all the control information required to ensure ordered, error-free and reliable delivery of the segment.

Correct Answer: B. B. Three-way handshaking
Explanation: A three-way handshake allows both, the server and the client to choose their Initial Sequence Number and inform about it to the other party. This won’t be possible using the two-way handshake mechanism.

Correct Answer: D. D. Passive open
Explanation: This is the first step in the Three-Way Handshaking process and is started by the server. Then the Client picks an ISN (Initial Sequence Number) and synchronizes (shares) it with the Server requesting a connection. The Server acknowledges the clients ISN, and then picks an ISN and synchronizes it with the Client. At last, the Client acknowledges the servers ISN.

Correct Answer: A. A. Active open
Explanation: This is the second step in the Three-Way Handshaking process and is done by the client once it finds the open server and picks an ISN. The Server acknowledges the clients request, and then picks an ISN and synchronizes it with the Client. At last, the Client acknowledges the servers ISN.

Correct Answer: C. C. Simultaneous open
Explanation: In simultaneous open situation, two nodes send an SYN signal to each other and start a TCP connection. Here, both TCP nodes transmit a SYNC+ACK segment to each other and a connection is established between them. This doesn’t happen usually, because both sides have to know which port on the other side to send to.

Correct Answer: A. A. Sync flooding attack
Explanation: SYNC flooding attack is a form of Denial of Service attack. Due to the overflow of SYNC segments sent to the server, the victims are not able to request for a connection to the server, thus resulting in Denial of Service.

Correct Answer: D. D. Denial-of-service attack
Explanation: During SYNC flooding the system collapses and denies service to every request, making it a DoS attack. Some other DoS attacks are bandwidth flooding, connection flooding and UDP flooding.

Correct Answer: B. B. 16-bits and 16-bits
Explanation: All port addresses are of 16 bits and they specify the type of service being used by the network entity. For example, port 21 is used for FTP connections and port 25 is used for ICMP connections.

Correct Answer: D. D. Both sequence & acknowledgment number
Explanation: TCP header contains separate fields for sequence number and acknowledgment number. Comparing these values is what allows TCP to detect lost segments and in turn recover from that loss. After detecting the lost segments, the recovery may require retransmission of the lost segments of data.