BGP-LS is a new BGP address family that is intended to distribute IGP topology information to external servers such as Application Later Traffic Optimization (ALTO) or Path Computation Engines (PCE) servers. These external traffic engineering databases can then use this information when calculating optimal paths.
BGP-LS provides external ALTO and PCE servers with topology information for a multi-area or multi-level network. Through the use of one or two BGP-LS speakers per area or level, the external ALTO or PCE servers can receive full topology information for the entire network. The BGP-LS information can also be distributed through route reflectors supporting the BGP-LS to minimize the peering requirements.
Figure: Example BGP-LS network shows an example BGP-LS network.
