Ask the Experts: What’s The Difference Between VLPS and MPLS?

Welcome to Ask the Experts, brought to you by In this video, Intelisys’ SVP Cloud Transformation Andrew Pryfogle talks about the difference between VPLS and MPLS technologies with Masergy’s Vice President for Global Technology Ray Watson. Find out more about global cloud networking platforms from Ray and the Masergy team here:

Andrew: Okay guys, welcome back to the studio for another Ask the Experts session. I’m joined here by Ray Watson, who’s the Vice President for Global Technology for Masergy. Ray, welcome man.
Ray: Welcome, it’s good to be here.
Andrew: All right. Good to have you. We’re talking about Advanced Data Networking here, and some of the trends around it and some of the technologies around it. Excited to get into your head. Thank you for contributing some time here as part of our faculty here at the University.
I want to talk with you about VPLS and MPLS. I wanted to get some layman’s terms from you on what’s the difference between these two WAN technologies. What are the use cases? Where does one fit better than the other? And perhaps, where do they even coexist? Speak to that real quick.
Ray: I’d be glad to. Andrew–of course, the textbook definition of the difference between VPLS, Virtual Private Land Service, and MPLS, Multiprotocol Label Switching, is that VPLS exists at Layer 2 of the OSI model, and MPLS exists at Layer 3 of the OSI model. But that’s just the textbook definition.
To put it to you in layman’s terms, the actual standard around Multiprotocol Label Switching, as defined in RFC4364 and 4762, the technology actually sits between those two layers and MPLS is the Layer 3 half and VPLS is the Layer 2 half. But what that really means to customers is that if they participate in a Multiprotocol Label Switching VPN at Layer 3 with their provider–which about 80% of global customers do that in some capacity today–what they’re doing is, they’re participating in routing with the carrier in the sense that either via BGP, Boarder Gateway Protocol, or IP, the customer tells the carrier what sub-nets each site represents, and the carrier propagates those at Layer 3 in a traditional IP VPN kind of way…
Andrew: Let me jump in there real quick. So you’re saying in MPLS, the customer basically gives the routing instructions to the carrier. The carrier has to design the network and the gear in the network to route appropriately. Is that fair?
Ray: 100 percent. There are certain characteristics that makes it an MPLS network: things like full meshing and quality of service, certainly being based on IP; but those are the characteristics of the Layer 3 MPLS side.
His bigger brother–or bigger cousin, you could think of it–is something called VPLS, which is Virtual Private Land Service. Confusingly enough, the “PLS” actually stands for something different in these two standards. But with VPLS, this all is happening at Layer 2.
The really simple way for folks in your community to think about this is–a gross oversimplification–is if you think of a customers’ wide area network where the cloud itself in the middle functions as a router, that’s a Layer 3 network. If the cloud in the middle itself functions as a switch, meaning it can do VLAN extensions, etc., that’s a Layer 2 network, or a VPLS network.
The big difference around the point that you just made about routing, is in the VPLS world, the customer does all their own routing. The carrier actually builds them out this Layer 2 network that is often associated with metro-type networks–but it also can be global–and the customer does their own routing. Specific to the analogy that you could use in the community–and again, I apologize if this is an oversimplification–but if you think in terms of Layer 3 MPLS versus Layer 2 VPLS, Layer 3 MPLS is really a Swiss Army knife. You have your cutting blade, you have some scissors, you have a finger nail cutter, you have a beer bottle opener, if you’re into that kind of thing. And there’s a lot of different functionalities that you can actually bring.
Whereas a VPLS network is really more like a scalpel. You have a very, very specific thing that you’re trying to accomplish. You have to be relatively an expert to do it. So one of the biggest differences between global MPLS and global VPLS networks is that typically the customers who buy Layer 2 network have in-house BGP expertise. Meaning that they have their own routing professionals that are inside their own networks.
Going to that Layer 3 versus Layer 2 analogy, one step further. If you think in terms of the Swiss Army knife versus the scalpel, many customers have said, “But I want both. What if I want to use that scalpel for the specific use case of replicating data from my New York to my London data center. But I really want that Swiss Army knife in order to connect all my branches.” The beautiful thing about the standards is, in many cases today, you can inter-operate them in a completely seamless way even over the same local loops. Even though this is sort of a classic religious-type discussion about Layer 2 versus Layer 3 and the pros versus cons, it’s not necessarily mutually exclusive.
Andrew: Interesting. That’s fascinating. Very cool. That’s really, really interesting. Let’s talk very briefly, if we could, give me a use case for each? What’s a use case for MPLS? What’s a use case for VPLS?
Ray: Sure. The classic example for an MPLS network is if you think in terms of an enterprise network. It has voice, video, some type of CRM system, multiple quality of service levels, and they need all types sites to talk directly to all other sites. Most customers actually have a need for fully mesh, especially with the growth of SIP, and Microsoft Link, and some of these technologies that are out there. But the predominate majority of their traffic actually going from site to either core data center or site to corporate, right? The beauty of MPLS is that full mesh capability.
Use case for Layer 2 would be if that same customer had four regional core data centers that they really wanted to keep on the same sub-net globally. Because remember with the Layer 2 they can control the sub-netting, and they can propagate it, and they can build it all over the world in order to provide extremely low latency, low jitter connectivity between these core sites. And more importantly, the customer then controls the sub-netting and the routing themselves. Anytime they need a new sub-net at one of those sites, they can bring it up as needed.
Andrew: Got it. Very cool, man. You’ve managed to take some very technical stuff and roll it down into simple terms, man. I appreciate that. Thank you.
Ray: Sure. My pleasure.
Andrew: Guys, that’s Ray Watson, he’s the Vice President of Global Technology for Masergy. One of the esteemed colleagues here for the faculty at the University.
Make sure you dig deep into the Masergy learning center, they’ve got great information there that can help you get smarter on the next generation of networks, how that’s driving even more cloud adoption. Good selling.