Layered protocol

General We can only develop on the operating system, do not require yourself to realize the various layers of the network. That is, in addition to the application layer, many things of the underlying include physical layers, etc. are hardware vendors and operating system manufacturers to package, and the details are not seen to us, so it is shielded. It means that this is this.

The operating system only provides development interface for developers. You can not know how the computer network implements data transmission, but you can use the development interface provided by the operating system to implement the data transfer function you want.

Layered protocol

As for the so-called service, it is also a detail of this layer package (shield) to achieve the interface (service).

For example, the data link layer and the network layer; the functionality implemented by the network layer must use the data link function of the data link layer. For the data link layer, a data link service is provided for the network layer.

image point is:

Data link layer tells the network layer, I will give you a data link service, you don't have to manage how to help you build a data link, put data Transfer to the destination. You only need to fill the data into the place I specified (buffer), I will send you to the destination.

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