What is the OSI Model?
The Open Systems Interconnection Model (OSI model) defines the components of a network connection in seven protocol layers. It is a conceptual framework which can be used to understand the components behind a network connection and is useful in understanding the types of DDoS attacks.
Each layer handle a specific job and communicates with the layers above and below itself. DDoS attacks target specific layers of a network connection; application layer attacks target layer 7 and protocol layer attacks target layers 3 and 4.