One of the biggest Microsoft Teams telephony news items from Microsoft Ignite, Microsoft partners will be offering Survivable Branch Appliances for Microsoft Teams.
These appliances allow telephony to keep working via a PSTN connection to the Survivable Branch Appliance even if the internet/Office 365 connectivity is down.
It works with a new Teams mode called Teams Offline mode.
On the SBC is a VM which runs Microsoft software to continue to run telephony. In the future, Microsoft hopes to add P2P VoIP call to the offline/survivability mode.
Ribbon will be rolling out SBA support for Teams in SBC 1000 & SBC 2000 9.0.x release, in concert with Microsoft making it generally available for Teams. AudioCodes will also be providing Teams Survivable Branch Appliances.