1) Choose ONE topic from the following two options Topic One: The open system interconnection model (OSI) is a network conceptual model, and this model is divided into seven layers from top to bottom: application layer, presentation layer, session layer, transport layer, network layer, data link layer and physical layer. Please answer the following questions in your thesis: Explain the main functions of these seven layers and their roles played in the network system.(20 marks) The two important protocols adopted by the Internet is TCP/IP. Please explain the basic principles of TCP/IP.(20 marks) The working principles of routing on the Internet. Explain why a message can be delivered across the Internet.(20 marks)