MPLS and the OSI Reference Model

The OSI reference model consists of seven layers. Refer to Figure 2-4 for the OSI reference model.

Figure 2-4. OSI Reference Model

The bottom layer is Layer 1, or the physical layer, and the top layer is Layer 7, or the application layer. Whereas the physical layer concerns the cabling, mechanical, and electrical characteristics, Layer 2, the data link layer, is concerned with the formatting of the frames. Examples of the data link layer are Ethernet, PPP, HDLC, and Frame Relay. The significance of the data link layer is only on one link between two machines, but not beyond. This means that the data link layer ...

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