One of my readers is struggling with the aftermath of marketing gimmicks:
We will implement a new network soon, and we're discussing P-routers versus regular routers versus switches. I'm looking for arguments to go one way or the other.
The critical part is the functionality you need. Based on their intended use, some boxes tend to have low table sizes (you can’t pump a full BGP table into a ToR L3 switch even though it runs BGP unless you’re David Barroso – more about that in an upcoming Software Gone Wild podcast), or limited QoS, or no shaping, or…
You should always start with “what services do I want to offer”, continue with “how would I best implement them with the simplest possible design”, go down the path of “which functions do I need to make this design work” and finally “which boxes from which vendors fit my needs?”
As for MPLS, do keep in mind that very few L3 switches support MPLS, and even those that do tend to have a very limited number of MPLS labels (although QFX5100 does an excellent job squeezing 16K labels out of Trident-II chipset), which might or might not be a problem depending on what the outcome of the previous paragraph is.