OSPF Extensions to Support Traffic Engineering
To help provide traffic engineering and MPLS with information about network topology and loading, extensions have been added to the Junos OS implementation of OSPF. Specifically, OSPF generates opaque (link-state advertisements (LSAs), which carry traffic engineering parameters. The parameters are used to populate the traffic engineering database, which is used by the Constrained Shortest Path First (CSPF) algorithm to compute the paths that MPLS LSPs take. This path information is used by RSVP to set up LSPs and reserve bandwidth for them.
Configuring OSPF IGP Shortcuts
In OSPF, you can configure shortcuts, which allow OSPF to use an LSP as the next hop as if it were a logical interface from the ingress routing device to the egress routing device. The address specified on the to statement at the [edit protocols mpls label-switched-path lsp-path-name] hierarchy level must match the router ID of the egress routing device for the LSP to function as a direct link to the egress routing device and to be used as input to OSPF SPF calculations. When used in this way, LSPs are no different from Asynchronous Transfer Mode (ATM) and Frame Relay virtual circuits (VCs), except that LSPs carry only IPv4 traffic.
 | Note: Whenever possible, use OSPF IGP shortcuts instead of traffic engineering shortcuts. |
