In the 1980s, the European-dominated International Standards Organization (ISO), began to develop its Open Systems Interconnection networking suite. OSI has two major components: an abstract model of networking (the Basic Reference Model, or seven-layer model), and a set of concrete protocols. The standard documents that describe OSI are for sale and not currently available online.
This is the creative description of the whole thing: Taken from http://www.lewistech.com/rlewis/Resources/james.aspx
The OSI model describes the flow of data in a network, from the lowest layer (the physical connections) up to the layer containing the user's applications. Data going to and from the network is passed layer to layer. Each layer is able to communicate with the layer immediately above it and the layer immediately below it. This way, each layer is written as an efficient, streamlined software component. When a layer receives a packet of information, it checks the destination address, and if its own address is not there, it passes the packet to the next layer.
When two computers communicate on a network, the software at each layer on one computer assumes it is communicating with the same layer on the other computer. For example, the Transport layer of one computer communicates with the Transport layer on the other computer. The Transport layer on the first computer has no regard for how the communication actually passes through the lower layers of the first computer, across the physical media, and then up through the lower layers of the second computer.
The OSI Reference Model includes seven layers:
| Number | Name | 7 | Application | 6 | Presentation | 5 | Session | 4 | Transport | 3 | Network | 2 | Data-Link | 1 | Physical (the lowest layer)
James Bond meets Number One on the 7th floor of the spy headquarters building. Number One gives Bond a secret message that must get through to the British Embassy across town. Bond proceeds to the 6th floor where the message is translated into an intermediary language, encrypted and miniaturized. Bond takes the stairs to the 5th floor where Security checks the message to be sure it is all there and puts some checkpoints in the message so his counterpart at the US end can be sure he's got the whole message. On the 4th floor the message is analyzed to see if it can be combined with some other small messages that need to go to the embassy end. Also if the message was very large it might be broken into several small packages so other spies can take it and have it reassembled on the other end. The 3rd floor personnel check the address on the message and determine who the addressee is and advising Bond of the fastest route to the Embassy. On the 2nd floor the message is put into a special courier pouch(packet). It contains the message, the sender and destination ID. It also warns the recipient if other pieces are still coming. Bond proceeds to the 1st floor where Q has prepared the Aston Martin for the trip to the Embassy.
Bond departs for the US Embassy with the secret packet in hand. On the other end the process is reversed. Bond proceeds from floor to floor where the message is decoded. The British Ambassador is very grateful the message got through safely. "Bond, please tell Number One I'll be glad to meet him for dinner tonight".
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