Q4: Consider a crossbar switch with four input and four output ports as shown in the figure below. (out of 10) Output 1 Output 2 Output 3-0 Output 4- 1 Number indicates output port Input 1 Input 2 Input 3 Input 4 a) Briefly explain why a crossbar switch outperforms a switch that is based on virtual memory and shared bus. b) Explain the term head of line (HOL) blocking and how it influences the performance of a crossbar swtch. 3 University of Bahrain College of Information Technology Department of Computer Engineering Computer Networks ITNE231 December 2020 c) Use the figure to give an example for a scenario in which NO HOL blocking occurs. To solve this you need to assign output port numbers to the first four packets in each input queue. And example is given for the first packet in the input queue 1. d) Use the figure to give an example for a scenario in which HOL blocking occurs. To solve this you need to assign output port numbers to the first four packets in each input queue. And example is given for the first packet in the input queue 1. e) Explain and suggest how the HOL blocking can be avoided