The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Yakov,

 
> While we are busy arguing about whether MPLS is a separate 
> layer or not,
> please bear in mind that the whole concept of a layer assumes 
> (among other
> things) a single format for transport of the data from the 
> layer above.
> Since MPLS doesn't make such an assumption (as in some cases it uses
> the "shim" header, in other cases it uses the VCI/VPI, 
> etc...) one could
> conclude that perhaps MPLS doesn't fit into the traditional layering
> model at all.
> 
> Yakov.
> 


It seems that you have confused the "layer above" with the "layer below".
X over MPLS always requires a Shim header. It is the "layer below" or the
data-link layer that has different format.

-Shahram