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Understanding OpenFlow Traffic Steering Across MPLS Networks Using MPLS LSP Tunnel Cross-Connects

 

On MX Series devices that support OpenFlow, you can direct traffic from OpenFlow networks over MPLS networks by using logical tunnel interfaces and MPLS LSP tunnel cross-connects. Using logical tunnel interfaces, you can stitch an OpenFlow interface to an MPLS label-switched path (LSP), which enables you to direct traffic from the OpenFlow network onto the MPLS network. MPLS LSP tunnel cross-connects between interfaces and LSPs permit you to connect the OpenFlow network to a remote network by creating MPLS tunnels that use LSPs as the conduit.

The topology in Figure 1 illustrates an MPLS LSP tunnel cross-connect that connects two remote OpenFlow networks through an MPLS network. Circuit cross-connect (CCC) enables you to establish an LSP tunnel between the two domains, through which you can tunnel the traffic from one OpenFlow network across the MPLS network to the second OpenFlow network.

Figure 1: Connecting OpenFlow Networks Using MPLS LSP Tunnel Cross-Connects
 Connecting
OpenFlow Networks Using MPLS LSP Tunnel Cross-Connects

Router A and Router B are OpenFlow-enabled routers that have MPLS LSPs configured to route traffic across the MPLS network. LSP A-B routes traffic from Router A to Router B, and LSP B-A routes traffic from Router B to Router A.

Each router has an OpenFlow interface, ge-1, and an MPLS interface, ge-2. You can stitch the OpenFlow interface to the MPLS LSP by using two logical tunnel interfaces. You configure the first logical tunnel interface, lt-1, as a Layer 2 interface that participates in OpenFlow. The second logical tunnel interface, lt-2, uses CCC encapsulation. You configure lt-1 and lt-2 interfaces as peers, so that traffic entering one logical interface is automatically directed to the second logical interface.

On each router, MPLS LSP tunnel cross-connects are configured at the [edit protocols connections remote-interface-switch] hierarchy level. The cross-connects make an association between the CCC interface, lt-2, and the two LSPs, one for transmitting MPLS packets from the local device to the remote device and the other for receiving MPLS packets on the local device from the remote device.

For traffic flowing from Router A to Router B, the OpenFlow controller must install flow entries on Router A that direct the desired OpenFlow traffic from ge-1 as the OpenFlow ingress port to lt-1 as the output port. On Router B, the OpenFlow controller must install flow entries that direct the OpenFlow traffic from lt-1 as the OpenFlow ingress port to ge-1 as the output port. Similarly for traffic flowing from Router B to Router A, the OpenFlow controller must install flow entries on Router B that direct the desired OpenFlow traffic from ge-1 as the OpenFlow ingress port to lt-1 as the output port. On Router A, the OpenFlow controller must install flow entries that direct the OpenFlow traffic from lt-1 as the OpenFlow ingress port to ge-1 as the output port.