The Peeredge Switch supports:
load balance (similar to round robin)
failover (primary/secondary, etc.)
weighted distribution for PSTN Inbound (Customer Originating) calls
46 Labs typically recommends an evenly weighted (i.e. 50/50, 33/33/33, etc.) distribution. A weighted distribution attempts to contact all active customer SBCs/PBXs before returning a SIP 503 Service Unavailable to the upstream PSTN provider.
When using load balance distribution, a SIP 503 Service Unavailable is sent to the upstream PSTN provider if there is no response from the first customer SBC/PBX contacted.