6

Can someone explain to me what differences there are between MPLS and VPLS? Which one is the most efficient? Why?

I’ve read that the only difference is layer of technology: 2 (VPLS) vs 3 (MPLS). Does that mean that the routing table is managed on the local network?

Thanks in advance,

6

MPLS is a virtual "layer 3" network. The customer addresses packets by IP. The PE equipment have customer IPs and serve as customer routers. The MPLS admin needs to manage at least a little of the routing (unless there have been improvements since I last administered an MPLS network, I'd be interested to know if that is the case).

VPLS is a virtual "layer 2" network. The customer addresses packets by MAC. From the customer's point of view, the PE equipment behaves like a switch.

As for efficiency, both have their pros and cons.

EDIT: this was going to be a comment on @peter-green's answer but it got too long:

To elaborate on the router that needs to know both the customer's and the provider's networking: there are usually many of them, one at each point of entry from the customer network into the provider network. They are called PE routers (Provider Edge). Of course, one PE router can handle many entry points, for many clients. You could have one PE in, say, every US State capital, and each customer could have several offices in each city, all connected to that city's PE.

The MPLS PE will need to be configured with the IP addresses of the customers connected to it, at least the IPs connected directly. For the adresses on each customer site, it can either take a static route (which needs the provider to act for each site modification) or it can talk some routing protocol with the CPE (Customer Premise Equipment), which is a lot more complicated but which can let the client play with his on-site IPs without bothering the provider. The PE will learn the customer IPs connected to the other PE routers by talking MP-BGP with them.

The VPLS PE will need to know the customer's MAC addresses, but it will auto-detect them. If there are many MACs this could be a problem. As @peter-green notes, this also has a downside with Ethernet broadcasts in addition to the encapsulation overhead, but it has the upside of the provider not having to configure the customer IP addresses.

If this hasn't answered your questions, you'll have to specify more :)

  • Would I be right in assuming that the alternative of having the customer provide and administer the MPLS/IP gateway router is considered undesirable? – Peter Green May 20 '16 at 17:47
  • Having the customer administer the PE router is more or less impossible, since the PE router is common to all the clients connected to it and is connected to all the other PE routers that the provider has. The PE router admin can impact all the clients of the MPLS cloud. Of course, it would be perfectly possible to have a (web) interface for the clients where they can change the configurations of their own interfaces. One could give admin rights to the CPE router to let the client assign internal IPs, but I never had a client technical enough to do so :) – Law29 May 20 '16 at 22:48
2

As I understand it (having read a bit on this but not actually done it).

MPLS is a protocol for building large numbers of virtual links over a shared infrastructure. The system of layered labels allows the actual data switching process in the MPLS core to be very simple and hence fast. MPLS can carry various different protocols on top. Traffic belonging to different customers is kept separate by the MPLS labels, so it doesn't matter if different customers have overlapping IP or MAC address space.

You can run IP directly on MPLS, in that case there will need to be a router between each customer site and the provider network that is aware of both the MPLS system and the IP network it is connecting to. It can then establish routes over the MPLS links just as it would over any other underlying network. The downside is that you have one router that needs to know about both the provider's MPLS and the customer's IP routing and the customers IP subnet boundaries need to line up with their site boundaries.

VPLS is a protocol for building a virtual multipoint Ethernet network on top of a MPLS network (or alternatively an IP network). This is convenient, from your point of view it's like your provider gave you a big ethernet switch and plugged all your sites into it. However the convenience comes at a price, the encapsulation overhead is higher than straight IP over MPLS and any broadcasts you send into the VPLS network (and an Ethernet network will always have some broadcasts) will be immediately amplified .

  • Thank you for the explanation. I've an another question: If I make a traceroute from a computer based in network A to a computer based in network B, how many hops can I have? One or more? – Julien May 20 '16 at 21:32
  • @Julien The traceroute shows hops that decrement the TTL in packets. P routers certainly do not do that, but IIRC PE routers do (in IP over MPLS scenario. RUle of thumb is that if the equipment has an IP address in your address plan, then you will see it. For VPLS, you will not see anything except for the increase in transit time. – Law29 Jul 27 '16 at 11:47
  • Traceroute shows routers that process your IP packets. The "label switching routers" (aka P routers) are not IP routers and so don't show up in traceroute. With IP running direct on MPLS the "label edge routers" (aka PE routers) are IP routers and so show up in traceroute. With VPLS the label edge routers act as Ethernet bridges so they will now show up in traceroute. – Peter Green Jul 27 '16 at 12:13
0

MPLS 2.5 layer protocol between data link layer and network layer. Mpls enables the routers for label base switching using CEF table and ip routing table. It is known by its ebabled applications. Applications are L3VPNs, L2vpns, EoMPLS, AToMpls, FRoMPlS.

VPLS virtual Private LAN services technique used to extand LAN services over services provider network using the mpls application AToMpls (Any transfer over MPLS. VPLS use the pseudowires end to end and vsi/ vfi for creating a multipoint L2VPNs based on MAC addressing.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.