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

Consider the following statements.

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

GATE CSE 2015 Set 3

Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection?

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

GATE CSE 2015 Set 1

Identify the correct order in which a server process must invoke the function calls accept, bind, listen, and recv according to UNIX socket APL

GATE CSE 2015 Set 2

Which one of the following socket API functions converts an unconnected active TCP socket into a passive socket?

GATE CSE 2014 Set 2

The transport layer protocols used for real time multimedia, file transfer, DNS and email, respectively are

GATE CSE 2013

Which of the following transport layer protocols is used to support electronic mail?

GATE CSE 2012

What is the maximum size of data that the application layer can pass on to the TCP layer below?

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

Packets of the same session may be routed through different paths in

GATE CSE 2005

Which of the following functionalities must be implemented by a transport protocol over and above the network protocol?

GATE CSE 2003

Marks 2

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 _________

GATE CSE 2024 Set 2

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?

GATE CSE 2023

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 _____________.

GATE CSE 2022

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 ___________.

GATE CSE 2022

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?

GATE CSE 2021 Set 1

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 ______

GATE CSE 2021 Set 1

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?

GATE CSE 2021 Set 1

Consider a TCP connection between a client and a server with the following specifications: the round trip time is 6 ms, the size of the receiver advertised window is 50 KB, slow start threshold at the client is 32 KB, and the maximum segment size is 2 KB. The connection is established at time t = 0. Assume that there are no timeouts and errors during transmission.
Then the size of the congestion window (in KB) at time t + 60 ms after all acknowledgements are processed is ______.

GATE CSE 2020

Match the following

Field	Length in bits
P. UDP Header’s Port Number	I. 48
Q. Ethernet MAC Address	II. 8
R. IPv6 Next Header	III. 32
S. TCP Header’s Sequence Number	IV. 16

Consider the following statements regarding the slow start phase of the $$TCP$$ congestion control algorithm. Note that $$cwnd$$ stands for the $$TCP$$ congestion window and $$MSS$$ denotes the Maximum Segment Size.

$$(i)$$ $$\,\,\,\,\,\,\,\,\,\,\,$$ 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?

Consider an $$IP$$ packet with a length of $$4,500$$ bytes that includes a $$20$$-byte $$IPv$$$$4$$ header and a $$40$$-byte $$TCP$$ header. The packet is forwarded to an $$IPv4$$ router that supports a Maximum Transmission Unit $$(MTU)$$ of $$600$$ bytes. Assume that the length of the $$IP$$ header in all the outgoing fragments of this packet is $$20$$ bytes. Assume that the fragmentation offset value stored in the first fragment is $$0.$$

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

For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 megabyte and the maximum output rate is 20 megabytes per second. Tokens arrive at a rate to sustain output at a rate of 10 megabytes per second. The token bucket is currently full and the machine needs to send 12 megabytes of data. The minimum time required to transmit the data is __________ seconds.

GATE CSE 2016 Set 1

Assume that the bandwidth for a TCP connection is 1048560 bits/sec. Let $$\alpha $$ be the value of RTT in milliseconds(rounded off to the nearest integer) after which the TCP window scale option is needed. Let $$\beta $$ be the maximum possible window size the window scale option. Then the values of $$\alpha $$ and $$\beta $$ are

GATE CSE 2015 Set 2

Let the size of congestion window of a TCP connection be 32 KB when a timeout occurs. The round trip time of the connection is 100 msec and the maximum segment size used is 2 KB. The time taken (in msec) by the TCP connection to get back to 32 KB congestion window is __________.

GATE CSE 2014 Set 1

Consider an instance of TCP’s Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of the slow start phase is 2 MSS and the threshold at the start of the first transmission is 8 MSS. Assume that a timeout occurs during the fifth transmission. Find the congestion window size at the end of the tenth transmission.

GATE CSE 2012

While opening a TCP connection, the initial sequence number is to be derived using a time-of-day (ToD) clock that keeps running even when the host is down. The low order 32 bits of the counter of the ToD clock is to be used for the initial sequence numbers. The clock counter increments once per millisecond. The maximum packet lifetime is given to be 64s.

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?

GATE CSE 2009

A computer on a 10 Mbps network is regulated by a token bucket. The token bucket is filled at a rate of 2 Mbps. It is initially filled to capacity with 16 Megabits. What is the maximum duration for which the computer can transmit at the full 10 Mbps?

A client process P needs to make a TCP connection to a server process S. Consider the following situation: the server process S executes a socket( ), a bind( ) and a listen( ) system call in that order, following which it is preempted. Subsequently, the client process P executes a socket( ) system call followed by connect( ) system call to connect to the server process S. The server process has not executed any accept( ) system call. Which one of the following events could take place?

In the slow start phase of the TCP congestion control algorithm, the size of the congestion window

Suppose that the maximum transmit window size for a TCP connection is 12000 bytes. Each packet consists of 2000 bytes. At some point of time, the connection is slow start phase with a current transmit window of 4000 bytes. Subsequently, the transmitter receiver two acknowledgments. Assume that no packet are lost and there are no time-outs. What is the maximum possible value of the current transmit window?

A : 1000 bytes
B : 100 bytes
C : 1000 bytes

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.

A : 1000 bytes
B : 100 bytes
C : 1000 bytes

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).

What is the rate at which application data is transferred to host H_C? Ignore errors, acknowledgements, and other overheads.

A TCP message consisting of 2100 bytes is passed to IP for delivery across two networks. The first network can carry a maximum payload of 1200 bytes per frame and the second network can carry a maximum payload of 400 bytes per frame, excluding network overhead. Assume that IP overhead per packet is 20 bytes. What is the total IP overhead in the second network for this transmission?