Data Communication and Computer Networks MCQ - Functions of OSI and TCP/IP Layers

56 For which one of the following reasons does Internet Protocol (IP) use the time-to-live (TTL) field in the IP datagram header?

TTL field is used to Prevent packets from looping indefinitely.

57 Consider the following statements about the timeout value used in TCP.
(i) The timeout value is set to the RTT (Round Trip Time) measured during TCP connection establishment for the entire duration of the connection.
(ii) Appropriate RTT estimation algorithm is used to set the timeout value of a TCP connection.
(iii)Timeout value is set to twice the propagation delay from the sender to the receiver.
Which of the following choices hold?

(i) and (iii) are false, but (ii) is true.

58 Consider a TCP connection in a state where there are no outstanding ACKs. The sender sends two segments back to back. The sequence numbers of the first and second segments are 230 and 290 respectively. The first segment was lost, but the second segment was received correctly by the receiver.
Let X be the amount of data carried in the first segment (in bytes), and Y be the ACK number sent by the receiver. The values of X and Y (in that order) are

Data in 1st segment is from 230 to 289 (byte number) i.e. 60 bytes data.
As given 1st segment is lost so, TCP will send ACK for the next in-order segment receiver is expecting. So it will be for 230.

59 Which of the following system calls results in the sending of SYN packets?

Connect() is used on the client side, and assigns a free local port number to a socket. In case of a TCP socket, it causes an attempt to establish a new TCP connection.

60 The three way handshake for TCP connection establishment is shown below.

Which of the following statements are TRUE?
S1: Loss of SYN + ACK from the server will not establish a connection
S2: Loss of ACK from the client cannot establish the connection
S3: The server moves LISTEN → SYN_RCVD → SYN_SENT → ESTABLISHED in the state machine on no packet loss
S4: The server moves LISTEN → SYN_RCVD → ESTABLISHED in the state machine on packet loss.

S1 and S4 is true.