MPLS - what OSI layer

[tonycarr]

I'm trying to study about MPLS and having difficultly trying to possition it with the OSI reference model. Does anyone have any views on this?

As it switches based on tags, is this a layer 2 function.?

It creates the FIB from IP addresses, so is this part a layer 3 funtion ?

What about layer 4 and above, I feel that it is performing some higher layer functions as well ?

Any ideas welcome....

[ccoleman]

Tony,

MPLS is similiar to the placement of ATM in the OSI layer. MPLS functions at Layer 2 and a 1/2. Granted, MPLS interacts with higher layers of the OSI model but not directly. Even the creation of the FIB is not directly performed by MPLS but by CEF. The only place in a packet trace that you would see a MPLS reference would be between the layer 2 and layer 3 headers. MBGP prepends RD information to the IP networks being distributed but is still a function of MBGP.

Hope this helps.

CC