* MPLS nets that support Layer 2, 3 VPNs
Last time, we discussed the fact that we are beginning to see the emergence of private MPLS networks, typically within financial and government organizations. One of the strengths of these MPLS networks is their ability to support a variety of types of VPNs.
Last time, we discussed the fact that we are beginning to see the emergence of private MPLS networks, typically within financial and government organizations. One of the strengths of these MPLS networks is their ability to support a variety of types of VPNs.
MPLS networks support Layer 3 VPNs typically by using the IETF RFC 2547bis. This class of VPN transports traffic across the network by using MPLS tunnels and Multi-point BGP (MP-BGP) signaling.
Realizing the importance of Layer 2 VPNs, the IETF L2VPN working group has defined both encapsulation and label-distribution mechanisms that enable transporting a wide variety of protocols across an MPLS core network.
There are two common techniques for implementing Layer 2 VPNs within an MPLS network. One of these techniques, the Draft-Martini VPN, can support a wide range of encapsulations, including Ethernet, Frame Relay, ATM, HDLC, and PPP. However, a Draft-Martini VPN introduces an addition protocol into the network: Label Distribution Protocol (LDP), which is used to set up tunnels and distribute labels.
The second technique is referred to as a Draft-Kompella VPN. Through the use of Draft-Martini and other encapsulation techniques, a Draft-Kompella VPN supports a wide range of encapsulations. A Draft-Kompella VPN uses BGP, instead of LDP, for signaling. Since BGP is already used for routing across the MPLS core, this does not constitute introducing an additional protocol into the network.
A future newsletter will discuss the business value of MPLS’ traffic engineering capabilities.
