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The Reference Model is a conceptual framework for understanding how computers communicate. The OSI model defines seven different layers of communication rules. Each layer of the OSI model has its own means of communication or protocol. The OSI model is used as a reference when explaining how data passed over the network moves through each layer. Each of the seven layers has specific responsibilities and logically interfaces to the layer above or below it. Each layer in the OSI model provides a different service needed for communication across an IP network and physical media. The top three layers often are called the “upper layers” since they deal primarily with application data. The lower layers deal primarily with getting packets to their destination. Many refer to these layers as infrastructure. 

Questions:

1. For this discussion, compare and contrast two layers of the Open Systems Interconnection (OSI) Reference Model, including the protocols that run on each layer.

2. What was the reason that IPv6 was introduced?  Why do you think many organizations are not upgrading their network solely to IPv6 and run that protocol instead of running IPv4?  

3. What is the purpose of subnetting when using IPv4 addressing?  What role does subnet mask play in subnetting of IPv4?