Is there a possibility to use any other two OSI model layers' middle positions? What is the basic concept of switching of packets with MPLS on layer 2.5 of OSI Reference model?
Why is MPLS label added between layer 2 header and layer 3 header of OSI model and not between headers of layer 3 and 4 of OSI model?
Is that a practical problem you are asking about (then please add further details) or rather a hypothetical question?– Zac67 ♦Mar 15 at 8:28
MPLS is a layer-2 protocol. However, no layer-1 carries MPLS directly, so it gets tacked on to various other layer-2 protocols. (hence "layer-2.5") Adding it after a layer-3 header would make no sense as the entire point was to eliminate the overhead of IP routing.