MPLS labels are supposed to be locally unique because that makes them simple to assign (no need to coordinate the label values between MPLS switches). Globally unique MPLS labels would just destroy the whole concept.

http://blog.ioshints.info/2012/07/could-mpls-over-ip-replace-vxlan-or.html

Maybe a cheeky email to the authors of the RFC could stir an answer?

Particularly I like the idea of being able to have a stretched network without the need for full MPLS. Although I thought MPLS was purely L3 so I’m not sure how it how it would benefit L2?

Subscribed for follow up comments

“Further, the MPLS would only run on the hypervisor softswitches, and would not require any MPLS support on the physical hardware in the data center.”

Clarified your point for me. So I’m not a VMWare guy (yet) but isn’t it true that most hypervisor switches are strictly layer 2? If that’s the case, Im not sure you can implement what you are referring to. It seems that you are suggesting that the hypervisor switch become the ‘PE’ in a standard MPLS environment. Now, I will say at this point that most of my MPLS experience is carrier related so I could be off but bear with me. At some point in the path, you need to tell the device(s) how to get into a certain VRF right? This is done in most cases by handing off an interface (or sub-interface) to a customer (a server in your case I believe) and defining something like this on the interface ‘ip vrf forwarding ‘. Those interfaces you define that on, are in my experience layer 3 interfaces. Which in most cases (as far as I know) you don’t talk layer 3 until you get to a physical switch (from the hypervisor northbound). And when you do, that layer 3 interface is generally shared for many hosts which would sort of defeat the purpose wouldnt it? You could technically trunk with sub interfaces, but Im not sure what that would buy you.

Layer 2 VPNS in MPLS make sense for the virtual data center, but Im not sure how they could be applied ‘gracefully’ without fully extending MPLS into the DC.

Hope we are on the same page now. Again, Im no VMWare expert so I could be wrong. I suppose it depends entirely on what you want to do and what features you want to support. I think the end point though is that I think the DC switches will need to support MPLS for this to work since VRFs are a layer 3 concept.

What do you think?

Richard, I guess my viewpoint is that MPLS is a proven, understood technology. Rather than re-inventing something new, why not re-use something that already exists?

Jon, the presence of a label stack does not, in my humble opinion, render the solution redundant. Based on my understanding, we could use MPLS VPNs to provide either Layer 2 *or* Layer 3 service inside the VPNs, and by encapsulating MPLS in IP we eliminate the need for data center operators to rip/replace/upgrade all their equipment to support MPLS. Of course, as I mentioned, I’m not a MPLS/networking expert, so perhaps there’s a key consideration that I’m overlooking.