In some BGP multi-homed environments between networks, it is possible to achieve shorter convergence times by using certain features beyond traditional [RFC4271] BGP rules. One of these features is the so-called BGP advertise-external or best-external, so that Autonomous System Border Routers (ASBRs) also advertise the best externally received path, even though it may not result as the ultimate best path from the selection algorithm.
A label substitution policy in Junos OS provides resources to conserve and control labels in an inter-AS option B Autonomous System Border Router (ASBR) with local VRFs. It provides further instrumentation to be able to discern routes further than by its Route Targets (RTs) and determine a label action for them.
When extending MPLS L3VPNs across more than a single Autonomous System (ASs), multiple interconnect options may be used, as defined in [RFC4364], Section 10. All these options are well-known in the industry, each one with its pros and cons.