TCP UDP Sockets and Congestion Control · Computer Networks · GATE CSE

TCP client P successfully establishes a connection to TCP server Q. Let $N_P$ denote the sequence number in the SYN sent from P to Q. Let $N_Q$ denote the acknowledgement number in the SYN ACK from Q to P. Which of the following statements is/are CORRECT?

Suppose two hosts are connected by a point-to-point link and they are configured to use Stop-end-Wait protocol for reliable data transfer. Identify in which one of the following scenarios, the utilization of the link is the lowest.

I. If the sequence number of a segment is m, then the sequence number of the subsequent segment is always m + 1.
II. If the estimated round trip time at any given point of time is t sec, the value of the retransmission timeout is always set to greater than or equal to t sec.
III. The size of the advertised window never changes during the course of the TCP connection.
IV. The number of unacknowledged bytes at the sender is always less than or equal to the advertised window

I. TCP connections are full duplex
II. TCP has no option for selective acknowledgment
III. TCP connections are message streams

Consider a TCP connection operating at a point of time with the congestion window of size 12 MSS (Maximum Segment Size), when a timeout occurs due to packet loss. Assuming that all the segments transmitted in the next two RTTs (Round Trip Time) are acknowledged correctly, the congestion window size (in MSS) during the third RTT will be _________

Suppose you are asked to design a new reliable byte-stream transport protocol like TCP. This protocol, named myTCP, runs over a 100 Mbps network with Round Trip Time of 150 milliseconds and the maximum segment lifetime of 2 minutes.

Which of the following is/are valid lengths of the Sequence Number field in the myTCP header?

Consider a 100 Mbps link between an earth station (sender) and a satellite (receiver) at an altitude of 2100 km. The signal propagates at a speed of 3 $$\times$$ 10⁸ m/s. The time taken (in milliseconds, rounded off to two decimal places) for the receiver to completely receive a packet of 1000 bytes transmitted by the sender is _____________.

Consider the data transfer using TCP over a 1 Gbps link. Assuming that the maximum segment lifetime (MSL) is set to 60 seconds, the minimum number of bits required for the sequence number field of the TCP header, to prevent the sequence number space from wrapping around during the MSL is ___________.

Consider two hosts P and Q connected through a router R. The maximum transfer unit (MTU) value of the link between P and R is 1500 bytes, and between R and Q is 820 bytes.

A TCP segment of size 1400 bytes was transferred from P to Q through R, with IP identification value as 0 × 1234. Assume that the IP header size is 20 bytes. Further, the packet is allowed to be fragmented i. e, Don't Fragment (DF) flag in the IP header is not set by P.

Which of the following statements is/are correct?

Consider the sliding window flow-control protocol operating between a sender and a receiver over a full-duplex error-free link. Assume the following:

1. The time taken for processing the data frame by the receiver is negligible.

2. The time taken for processing the acknowledgement frame by the sender is negligible.

3. The sender has infinite number of frames available for transmission.

4. The size of the data frame is 2,000 bits and the size of the acknowledgment frame is 10 bits.

5. The link data rate in each direction is 1 Mbps (= 10⁶ bits per second).

6. One way propagation delay of the link is 100 milliseconds.

The minimum value of the sender's window size in terms of the number of frames, (rounded to the nearest integer) needed to achieve a link utilization of 50% is ______

A TCP server application is programmed to listen on port number P on host S. A TCP client connected to the TCP server over the network.

Consider that while the TCP connection was active, the server machine S crashed are rebooted. Assume that the client does not use the TCP keepalive timer.

Which of the following behaviours is/are possible?

The fragmentation offset value stored in the third fragment is _______.

$$(i)$$ $$\,\,\,\,\,\,\,\,\,\,\,$$ The $$cwnd$$ increases by $$2$$ $$MSS$$ on every successful acknowledgment.
$$(ii)$$ $$\,\,\,\,\,\,\,\,\,$$ The $$cwnd$$ approximately doubles on every successful acknowledgement.
$$(iii)$$ $$\,\,\,\,\,\,\,$$ The $$cwnd$$ increases by $$1$$ $$MSS$$ every round trip time.
$$(iv)$$ $$\,\,\,\,\,\,\,\,\,$$ The $$cwnd$$ approximately doubles every round trip time.

Which one of the following is correct?

Which one of the choices given below is closest to the minimum permissible rate at which sequence numbers used for packets of a connection can increase?

Consider three IP networks A, B and C. Host H_A in networks A sends messages each containing 180 bytes of application data to a host H_C in network C. The TCP layer prefixes a 20 byte header to the message. This passes through an intermediate network B. the maximum packet size, including 20 byte IP header, in each network is:

The network A and B are connected through a 1 Mbps link, while B and C are connected by a 512 Kbps link (bps = bits per second).

Assuming that the packets are correctly delivered, how many bytes, including headers, are delivered to the IP layer at the destination for one application message, in the best case? Consider only data packets.

Consider three IP networks A, B and C. Host H_A in networks A sends messages each containing 180 bytes of application data to a host H_C in network C. The TCP layer prefixes a 20 byte header to the message. This passes through an intermediate network B. the maximum packet size, including 20 byte IP header, in each network is:

The network A and B are connected through a 1 Mbps link, while B and C are connected by a 512 Kbps link (bps = bits per second).