GATE||Computer Network||LAN||PYQ (2010 to 2025)

Consider a 128×10³ bits/second satellite communication link with one-way propagation delay of 150 milliseconds. Selective retransmission (repeat) protocol is used on this link to send data with a frame size of 1 kilobyte. Neglect the transmission time of acknowledgment. The minimum number of bits required for the sequence number field to achieve 100% utilization is ______. [GATE||2016|| Set 2 ||NAT || 2-mark]

Suppose we are transmitting frames between two nodes using Stop-and-Wait protocol.
The frame size is 3000 bits. The transmission rate of the channel is 2000 bps (bits per second) and the propagation delay between the two nodes is 100 milliseconds. Assume that the processing times at the source and destination are negligible. Also, assume that the size of the acknowledgment packet is negligible. Which ONE of the following most accurately gives the channel utilization for the above scenario in percentage? [GATE || 2025 ||SET2||MCQ || 2-mark ]

Consider an Ethernet segment with a transmission speed of 10⁸ bits/sec and a maximum segment length of 500 meters. If the maximum speed of propagation of the signal in the medium is 2×10⁸ meters/sec, then the minimum frame size (in bits) required for collision detection is __________. [GATE|| 2024 ||SET2||NAT || 2-mark ]

Node X has a TCP connection open to node Y. The packets from X to Y go through an intermediate IP router R. Ethernet switch S is the first switch on the network path between X and R. Consider a packet sent from X to Y over this connection.
Which of the following statements is/are TRUE about the destination IP and MAC addresses on this packet at the time it leaves X? [GATE || 2024 ||Set 2 ||MCQ || 1-mark ]

Consider a network using the pure ALOHA medium access control protocol, where each frame is of length 1,000 bits. The channel transmission rate is 1 Mbps (i.e., 10610^6106 bits per second). The aggregate number of transmissions across all the nodes (including new transmissions and retransmitted frames due to collisions) is modeled as a Poisson process with a rate of 1,000 frames per second. Throughput is defined as the average number of frames successfully transmitted per second. The throughput of the network (rounded to the nearest integer) is __________. [GATE||2021 Set 2 ||NAT||2MARKS]

Suppose that in an IP-over-Ethernet network, a machine X wishes to find the MAC address of another machine Y in its subnet. Which one of the following techniques can be used for this? [GATE|| 2019 MCQ || 2-mark]

Consider that 15 machines need to be connected in a LAN using 8-port Ethernet switches. Assume that these switches do not have any separate uplink ports. The minimum number of switches needed is _______. [GATE|| 2019 NAT || 2-mark]

Consider a simple communication system where multiple nodes are connected by a shared broadcast medium (like Ethernet or wireless).

The nodes in the system use the following carrier-sense based medium access protocol.

A node that receives a packet to transmit will carrier-sense the medium for 5 units of time.

If the node does not detect any other transmission in this duration, it starts transmitting its packet in the next time unit.

If the node detects another transmission, it waits until this other transmission finishes, and then begins to carrier-sense for 5 time units again.

Once they start to transmit, nodes do not perform any collision detection and continue transmission even if a collision occurs.

All transmissions last for 20 units of time.

Assume that the transmission signal travels at the speed of 10 meters per unit time in the medium.

Assume that the system has two nodes P and Q, located at a distance d meters from each other.

P starts transmitting a packet at time t=0 after successfully completing its carrier-sense phase. Node Q has a packet to transmit at time t=0 and begins to carrier-sense the medium.

The maximum distance d (in meters, rounded to the closest integer) that allows Q to successfully avoid a collision between its proposed transmission and P's ongoing transmission is _______. [GATE|| 2018 NAT || 2-mark]

Consider a binary code that consists of only four valid codewords as given below:
00000, 01011, 10101, 11110.

Let the minimum Hamming distance of the code be p and the maximum number of erroneous bits that can be corrected by the code be q. Then the values of p and q are: [GATE||2017|| Set 2|| MCQ || 2-mark ]

A computer network uses polynomials over GF(2) for error checking with 8 bits as information bits and uses x³+x+1 as the generator polynomial to generate the check bits. In this network, the message 01011011 is transmitted as: [ GATE||2017||Set 1 || MCQ || 2-mark]