The seven layers of the internet. Specifically, computer systems framework used to communicate over a network. This is referred to as the OSI(Open System Interconnection) Model. The OSI model is really just a concept, first implemented by the majority of Computer companies in the 1980s. It's not a tangible protocol. It doesn't have any functions, or . It just helps us better understand the processes occurring.
Typically (as you can also see in the picture above), the OSI model is presented and read in descending order, but for general understanding purposes, I will start from the first(bottom) layer.
Physical (Layer 1): As the name states, these are the physical connections that connect devices. Think, internet cables, wireless connections, etc.
Data Link (Layer 2): This layer connects and disconnects any connection between two nodes. This layer communicates using bits. There are two sub-layers within this, LLC(Logical Link Control and MAC (Media Access Control). The former controls the flow and order of frames, error checks, and identifies network protocols. The latter, uses MAC Addresses(which can be considered as a node ID), to send and receive data between devices.
Network (Layer 3): This is where you unplug and plug in the router, and become your household's savior. This layer handles switches and routing, using logical (non-physical) routes to transmit data. Basically, it uses addressing to route packets to its destination.
Transport (Layer 4): This layer handles data transfer between systems and/or hosts. Now that it has data, and needs to transfer, how much data needs to be sent? When and where, etc.
Session(Layer 5): Establishes communication channels for two computers and/or network devices to speak with one another. This is a prime example of perfect communication skills. A computer starts a session, waits until data is transferred, and when done, the conversation ends.
Presentation(Layer 6): Helps translate the network data to a form that application itself can understand, and vice versa.
Application (Layer 7): Information here is received by end-users where software such as web-browsers,FTP, helps display that incoming data to users.
These are just basic definitions for the OSI model. There are many(and I mean MANY) sources out there that delves deep into each layer. Although still widely used, much of the modern internet is based on the TCP/IP model.
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