An incoming PSTN call directly routed to the Teams user.

An outgoing call from a Teams user routed through Avaya SBC to an Avaya Aura® user.

An incoming PSTN call arriving at Avaya Aura® from Avaya SBC. Avaya Aura® uses EC500 and Call Coverage to forward the call a Teams user, and connects using the Avaya SBC direct routing capability.

A PSTN call routed to an Avaya Aura® user; the Avaya Aura® user does not accept the call; Avaya SBC redirects the call to a Teams user; mapping of the Avaya Aura® user to the Teams user is fetched from the organization’s LDAP Active Directory.

All SIP signaling elements like R-URI, Via, Route, R-R and Contact have FQDNs.

The Microsoft Phone System provides three FQDNs – primary, secondary and tertiary across three regions.

The Avaya SBC for a specific location reaches out to the location-specific DNS server and the FQDN resolves to the primary Microsoft Phone System of the location.

DNS-SRV returns A-records and resolves into the address of the primary, secondary, and tertiary Microsoft Phone Systems.

Avaya SBC REGISTERS to the primary Microsoft Phone System or next available healthy Microsoft Phone System and maintains the heartbeat using OPTIONS.

If the primary Microsoft Phone System is not in good operating condition or does not respond, Avaya SBC moves new calls to the next available Microsoft Phone System, and treats it as primary.