The OSI Model (Open Systems Interconnection Model) is an abstract framework used to describe the functions of a networking system. The OSI model characterizes computing functions into a universal set of rules and requirements in order to support interoperability between totally different merchandise and package. Important PointsThe combination of the IP address and the port number is named a socket. The socket is primarily a concept utilized in the transport layer of the internet protocol suite or session layer of the OSI model. The most important protocol at layer three (also referred to as the network layer) is the Internet Protocol or IP. IP is the standard for routing packets across interconnected networks--hence, the name net. MAC Addresses are a unique 48-bits hardware range of a laptop, which is embedded into a network card (known as Network Interface Card) throughout the time of production. mac address is employed by Media Access management (MAC) sublayer of Data-Link Layer. The sender & receiver's IP addresses are placed within the header by the network layer. Hence, the correct answer is A-II, B ? IV, C ? III, D ? I.