Data Link Layer
Q22.
A computer network uses polynomials over GF(2) for error checking with 8 bits as information bits and uses x^{3}+x+1 as the generator polynomial to generate the check bits. In this network, the message 01011011 is transmitted asQ23.
Frames of 1000 bits are sent over a 10^6 bps duplex link between two hosts. The propagation time is 25 ms. Frames are to be transmitted into this link to maximally pack them in transit (within the link). What is the minimum number of bits (I) that will be required to represent the sequence numbers distinctly? Assume that no time gap needs to be given between transmission of two frames.Q24.
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 _____.Q25.
The values of parameters for the Stop-and-Wait ARQ protocol are as given below: Bit rate of the transmission channel = 1Mbps Propagation delay from sender to receiver = 0.75 ms Time to process a frame = 0.25ms Number of bytes in the information frame =1980 Number of bytes in the acknowledge frame = 20 Number of overhead bytes in the information frame = 20 Assume that there are no transmission errors. Then the transmission efficiency ( expressed in percentage) of the Stop-and - Wait ARQ protocol for the above parameters is _________( correct to 2 decimal places)Q26.
Consider a binary code that consists of only four valid code words 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 areQ27.
An Ethernet frame that is less than the IEEE 802.3 minimum length of 64 octets is calledQ28.
In Ethernet CSMA/CD, the special bit sequence transmitted by media access management to handle collision is calledQ29.
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?Q30.
________ can detect burst error of length less than or equal to degree of the polynomial and detects burst errors that affect odd number of bits.