Bit length of a link is defined as the number of bits that can be present in the link at an instant when a stream of bits fully occupies the link. Bit Length, B = R*t, where R is the data rate and t is the propagation delay (t=d/V where d is the length of the link and V is the velocity of propagation in the link.). If the bit length of a link is much larger than the frame length, efficiency (utilisation) of the system is reduced. Define the parameter a as the ratio of propagation time to transmission time. a) Show that a =bit length of the link / frame size. b) Define the utilisation, U, of the link as throughput divided by the data rate. Show that; 11Ua=+ c) From the above expression it can be observed that when a increases the utilisation of the link decreases. Using appropriate diagrams, explain the process of sending a frame on a link with a<1 and a>1. Consider for each case when the first bit reach the receiver where is the last bit of the stream. Use the above explanation to show how utilisation decreases with increasing a. d) Now consider a ring network using IEEE 802.5 Token Ring protocol. Consider the 2 cases a<1 and a>1 and explain the process of sending a frame on the ring for these 2 cases. Consider for each case when the first bit reach the receiver where is the last bit of the stream. e) Slotted ring is a method used by long distance rings to increase the utilisation. Slotted ring allows multiple users to communicate at the same time. Using the answer to part d) explain why it is only suitable for long distance rings. f) Consider a ring of length 20 km with a data rate of 200 Mbps and 1000 stations/repeaters, each of which introduces a 1-bit delay. Each slot contains room for one 3-byte source address, 3-byte destination address, 156 bytes of data and 2 byte control data. How many users can simultaneously transmit on this ring? Assume propagation speed in the ring is 2x108 ms-1. What is the maximum data utilisation (ratio of data bits to all bits) of this ring?