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This draft is a work item of the Layer 3 Virtual Private Networks Working Group of the IETF.
Title : BGP/MPLS IP VPNs
Author(s) : E. Rosen
Filename : draft-ietf-l3vpn-rfc2547bis-01.txt
Pages : 47
Date : 2003-9-15
This document describes a method by which a Service Provider may use
an IP backbone to provide VPNs (Virtual Private Networks) for its
customers. This method uses a 'peer model', in which the customers'
edge routers ('CE routers') send their routes to the Service
Provider's edge routers ('PE routers'). BGP is then used by the
Service Provider to exchange the routes of a particular VPN among the
PE routers that are attached to that VPN. This is done in a way
which ensures that routes from different VPNs remain distinct and
separate, even if two VPNs have an overlapping address space. The PE
routers distribute, to the CE routers in a particular VPN, the routes
from other the CE routers in that VPN. The CE routers do not peer
with each other, hence there is no 'overlay' visible to the VPN's
routing algorithm.
Each route within a VPN is assigned an MPLS label; when BGP
distributes a VPN route, it also distributes an MPLS label for that
route. Before a customer data packet travels across the Service
Provider's backbone, it is encapsulated with the MPLS label that
corresponds, in the customer's VPN, to the route that is the best
match to the packet's destination address. This MPLS packet is
further encapsulated (e.g., with another MPLS label, or with an IP or
GRE tunnel header) so that it gets tunneled across the backbone to
the proper PE router. Thus the backbone core routers do not need to
know the VPN routes.
The primary goal of this method is to support the case in which a
client obtains IP backbone services from a Service Provider or
Service Providers with which it maintains contractual relationships.
The client may be an enterprise, a group of enterprises which need an
extranet, an Internet Service Provider, an application service
provider, another VPN Service Provider which uses this same method to
offer VPNs to clients of its own, etc. The method makes it very
simple for the client to use the backbone services. It is also very
scalable and flexible for the Service Provider, and allows the
Service Provider to add value.
This document obsoletes RFC 2547.
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