4. Figure 1 below depicts a typical message as it appears on the network Data link layer header Network layer header X layer header Session layer header Presentation layer header Application layer header Data link layer trailer Message Bits that actually appear on the network Figure 1: A typical message on a network i. Layer X appends a header into the message in Figure 1. What is the role of Layer X? (2 marks) ii As shown in Figure 1, the message is appended with a header at every layer, Surely it would be more efficient to have just a single header at the front of each message with all the control in it than all these separate headers. Why is this not done