PSTN Inbound (Originating Customer) Failover Routing
When the Peeredge Switch receives a SIP Invite from an upstream PSTN Service Provider in the Dallas data center, the switch matches an Originating Customer Trunk Group based on the called party number in the SIP Invite. The Softswitch then builds a list of all active trunk members configured in this Trunk Group for Dallas and then forwards the SIP Invite to the trunk member (i.e. SBC/PBX) based on the configured Call Distribution.
If there are no active trunk members in Dallas or no responses from the active trunk members in Dallas, the Softswitch forwards the SIP Invite to the Ashburn Softswitch, which builds a list of all active trunk members configured for Ashburn. The Ashburn Softswitch then forwards the SIP Invite based on the configured Call Distribution. The same call failover routing behavior occurs if the SIP Invite is first received in the Ashburn data center. An active trunk member is any customer SBC/PBX that responds to SIP Option messages. If SIP Option messages (Trunk Monitoring) are not configured on the Originating Customer Trunk Group, then all trunk members in the trunk group are considered active.
PSTN Outbound (Terminating Customer) Failover Routing
When the Peeredge Switch receives a SIP Invite from a customer in the Dallas data center, it matches a Terminating Customer Trunk Group based on the customer’s SBC/PBX IP Address, Port, and Protocol (UDP, TCP, TLS). If no match is found, the Softswitch responds with a SIP 401 with a WWW-Authenticate header to allow for SIP Registration-based authentication. Once authenticated, the Softswitch routes the SIP Invite to all configured PSTN Provider Trunk Groups configured in Dallas.
In the unlikely event that all configured PSTN Provider Trunk Groups configured in Dallas are down, the SIP Invite is forwarded to the Ashburn datacenter, and the Ashburn Softswitch routes the SIP Invite to all configured PSTN Provider Trunk Groups configured in Ashburn. The same call failover routing behavior occurs if the SIP Invite is first received in the Ashburn data center.