Tuesday, April 10, 2012

MPLS Laeyer 3 VPNs


  • VPNs:
    • Customers can connect geographically divers sites across the provider's network
  • Traditionally VPN were based on IPsec(layer-3) or TLS(laery-2)
  • These 2 were slow & having less features.
  • By using MPLS we will overcome these problems.
  •  With Layer-3 VPNs the service provider participate in the customer's Layer-3 routing.
    • Service provider's PE router  connect with CE router with L3 protocols
  • Layer 2 VPNs: Provider connect the customer site with layer 2 technologies like ATM, Frame-relay or ethernet.
  • MPLS Layer 3 VPNs:
    • Combines the logic of MPLS tunnels with layer 3 routing information
    •  PE routers learn customer routes from Customer Edge(CE) routers.
    • PE routers advertise customer routes to other PEs via multi-protocol BGP.
    • No need to know about the customer route in the middle of the SP network.
    • BGP next-hops point to MPLS tunnels
      • ex: loopbacks of PE routers
    • MPLS L3 VPNs have 2 basic components
      • Seperation of customer routing information
        • to do this VRF (Virtual Routing & Forwarding) used.
        • VRF used on PE routers to keep track on customer routes on per interface basis.
      • Exchange of customer routing information.
        • to do this MP-BGP is used over the MPLS network.
        • Traffice is label switched towards the BGP next-hops.
    • The idea of MPLS VPN is 
      • establishing a full-mesh of dynamic MPLS LSRs between PE routers.
      • using these PE routers for tunneling VPN packets across the network core.