1. Give two motivations for using a protocol stack. 2. Consider a system with a 6 layer protocol stack. Layers 2 through 5 each add a 10 byte header. Layer 2 also adds a 4 byte footer. If a 52 byte message is generated at layer 6, what percentage of the bits transmitted over the physical media are overhead (headers and footers)? 3. If the unit exchanged at the data link level is called a frame and the unit exchanged at the network level is called a packet, do frames encapsulate packets or do packets encapsulate frames