Computer Network
Q41.
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 _____.Q42.
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)Q43.
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 areQ44.
An Ethernet frame that is less than the IEEE 802.3 minimum length of 64 octets is calledQ45.
In Ethernet CSMA/CD, the special bit sequence transmitted by media access management to handle collision is calledQ46.
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?Q47.
________ 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.Q48.
Consider a 128 \times 10^{3} 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 acknowledgement. The minimum number of bits required for the sequence number field to achieve 100% utilization is ________.Q49.
For the IEEE802.11 MAC protocol for wireless communication,which of the following statements is/are TRUE? I. At least three non-overlapping channels are available for transmissions. II. The RTS-CTS mechan is misused for collision detection. III. Unicast frames are ACKed.Q50.
In a token ring network the transmission speed is 10^7 bps and the propagation speed is 200 meters/\mu s. The 1-bit delay in this network is equivalent to: