WHY THE ETHERNET IS CALLED A MULTIPLE ACCESS PROTOCOL?




5.1 Suppose the information content of a packet is the bit pattern 1111 1011 1001 1100 and an even parity scheme is being used. What would the value of the field containing the parity bits be for the case of a two-dimensional parity scheme? Your answer should be such that a minimum-length checksum field is used.
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5.2 Refer to the Cyclic Redundancy Check (CRC) codes discussed in the textbook and follow the conventions used in the textbook. Consider the 5-bit generator, G=10011, and suppose that D has the value 1010101011. What is the value of R? Show the process how you obtain the solution.

5.3 Consider two nodes A and B uses the slotted ALOHA protocol to contend for a channel. Suppose node pA and pB are A and B’s retransmission probabilities. Provide a formula for node A’s average throughput. What is the total efficiency of the protocol with these two nodes?

5.4 A disadvantage of the content of approach for LANs, such as CSMA/CD, is the capacity wasted due to multiple stations attempting to access the channel at the same time. Suppose that time is divided into discrete slots, with each of N stations attempting to transmit with probability p during each slot. What fraction of slots is wasted due to multiple simultaneous transmission attempts?

5.5 In CSMA/CD, after the 4th collision, what is the probability that a node chooses k=4? The result k=4 corresponds to a delay of how many seconds on a 10 Mbps Ethernet?

5.6 Why is an ARP query sent within a broadcast frame? Why is an ARP response sent within a frame with a specific destination MAC address?

5.7 Why the Ethernet is called a multiple access protocol? Why it is referred to as an unreliable and connectionless approach?

Chapter 6 [30 points]

6.1 What are the services that can be provided using IEEE 802.11?

6.2 What are the differences between the infrastructure mode and the ad-hoc mode in wireless networks?

6.3 Why are acknowledgements used in 802.11 but not in a wired Ethernet?

6.4 Suppose the IEEE 802.11 RTS and CTS frames were as long as the standard DATA and ACK frames. Would there be any advantages to using the CTS and RTS frames? Why or why not?

6.5 What is the difference between a permanent address and a care-of address? Who assigns a care-of address?
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