GATE ||Computer Network || OSI/ISO || PYQ ( 2010 to 2025)

In the following pairs of OSI protocol layer/sub-layer and its functionality, the INCORRECT pair is [GATE||2014|| Set 3 ||MCQ||1MARK]

A bit-stuffing based framing protocol uses an 8-bit delimiter pattern of 01111110. If the output bit-string after stuffing is 011111100101, then the input bit-string is: [GATE||2014|| Set 3||MCQ || 1-mark ]

Suppose that the stop-and-wait protocol is used on a link with a bit rate of 64 kilobits per second and 20 milliseconds propagation delay. Assume that the transmission time for the acknowledgment and the processing time at nodes are negligible. Then the minimum frame size in bytes to achieve a link utilization of at least 50% is: [GATE||2015|| Set 1 ||NAT||2MARK]

Consider a network connecting two systems located 8000 kilometers apart. The bandwidth of the network is 500 × 10⁶ bits per second. The propagation speed of the media is

4 × 10⁶ meters per second. It is needed to design a Go-Back-N sliding window protocol for this network. The average packet size is 10⁷ bits. The network is to be used to its full capacity. Assume that processing delays at nodes are negligible. Then, the minimum size in bits of the sequence number field has to be [GATE||2015||Set 3||NAT||2MARK]

Two hosts are connected via a packet switch with 10⁷ bits per second links. Each link has a propagation delay of 20 microseconds. The switch begins forwarding a packet 35 microseconds after it receives the same. If 10000 bits of data are to be transmitted between the two hosts using a packet size of 5000 bits, the time elapsed between the transmission of the first bit of data and the reception of the last bit of the data in microseconds is: [GATE||2015|| Set 3||NAT||2MARK]

A link has a transmission speed of 10⁶ bits/sec. It uses data packets of size 1000 bytes each. Assume that the acknowledgment has negligible transmission delay, and that its propagation delay is the same as the data propagation delay. Also assume that the processing delays at nodes are negligible. The efficiency of the stop-and-wait protocol in this setup is exactly 25%. The value of the one-way propagation delay (in milliseconds) is: [GATE||2015||Set 2|| NAT || 1-mark]

Consider two hosts X and Y connected by a single direct link of rate 10⁶ bits/sec. The distance between the two hosts is 10,000 km and the propagation speed along the link is 2×10⁸ m/sec.
Host X sends a file of 50,000 bytes as one large message to host Y continuously. Let the transmission and propagation delays be p milliseconds and q milliseconds, respectively.Then, the values of p and q are: [ GATE||2017||Set 2|| MCQ || 2-mark ]

Consider the following two statements:

• S1​: Destination MAC address of an ARP reply is a broadcast address.
• S2​: Destination MAC address of an ARP request is a broadcast address.

Which one of the following choices is correct? [ GATE||2021||SET1|| MCQ || 1-mark ]

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

• The time taken for processing the data frame by the receiver is negligible.
• The time taken for processing the acknowledgement frame by the sender is negligible.
• The sender has an infinite number of frames available for transmission.
• The size of the data frame is 2000 bits, and the size of the acknowledgement frame is 10 bits.
• The link data rate in each direction is 1 Mbps (= 10⁶ bits per second).
• 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||2021||SET1|| NAT || 2-mark ]

Assume that a 12-bit Hamming codeword consisting of 8-bit data and 4 check bits is transmitted. The data bits are denoted by d8,d7,d6,d5,d4,d3,d2,d1, and the check bits are given in the following tables:

Which one of the following choices gives the correct values of x and y? [GATE||2021 ||SET1||MCQ || 2-mark ]