1.1 A network protocol can be defined as an established set of rules that determine how data is transmitted between different devices in the same network. Discuss the two principal functions of a network protocol. [6 marks] 1.2 The Open Systems Interconnect (OSI) reference model is a seven-layer conceptual framework that describes networking or telecommunications systems, each layer with its own function. Network professionals visualise their networks through the OSI lenses, which helps them manage problems and plan their networks for optimisation. Provide guidelines on how a network engineer can effectively use the OSI model's seven layers to optimise a computer/telecommunications network. [10 marks] 1.3 Explain how data is transmitted from one node to another in a computer / or telecommunications network. [6 marks] 1.4 Describe the three elements from which a single optical fiber is constructed. [3 marks]