3. Main frame-level architectures

Frame-level architectures group together all techniques in which it is necessary to go back to the frame level to find the information needed to route or switch the frame. In this architecture we find the various transfer techniques, essentially of the switched type, i.e. setting up a path in the network using references to move the frame forward. These technologies are ATM, frame relay, Ethernet and MPLS. We'll see that MPLS is a rather special case, classified as level 2 or 3 and sometimes put at level 2.5. But to be truly correct with regard to standardization, MPLS is classified as a level 2 architecture.

Figure 6 shows a frame-level architecture.

In this architecture, it is necessary to go up to frame level in the intermediate transfer nodes, but not...