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When the Peeredge SBC 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 Peeredge 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 platform 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.
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