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7 layer OSI Model

The Transport Layer

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Then there are several other servers designed for use within an office or within a community, in which case the port on which these servers listen is decided by the designer and is advertised to the users/clients. For example in my office we have a server called the Beacon server which listens to request on port 14007 and replies by feeding back a GUI. The concept of ports is an important entity of the transport layer. We have already discussed the application, presentation and session layer, the actual user data comes from the application layer and is wrapped up by the presentation and session layer to complete the user part of the packet.

So let's get it clear, packet is the whole or the end product and the packet comprises of the user part, the transport layer information, the network layer information, the link layer information and the physical layer information. The user part comprises of the application layer information (mostly the user data), the presentation layer information (to facilitate comprehension on the other end) and the session layer information (to ensure the right information goes to the right session). I would like to consider the transport layer, network layer, link layer and physical layer as the machine part because it does not contain any user data. One thing transport, network and link layer have in common is that they all have an addressing schema.

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