Coexistence with Teams

Microsoft provides several coexistence or upgrade modes to facilitate the transition to Teams. Think of it as a hiking trail with several starting points and different waypoints, with all trails leading to the same destination. Typically, larger companies using all the Skype for Business features (IM/presence/voice/conferencing) will need to start at the beginning of the path and cover all the waypoints. Smaller businesses may be able to skip one waypoint or another during their journey.

Regardless of where the journey begins, each upgrade mode requires a number of prerequisites:

• A fully functional Office 365 with the appropriate licenses for operating teams
• An active hybrid connection with Office 365 when using Skype for Business on-premises
• Skype for Business Server 2019 or Skype for Business Server 2015 with cumulative update (CU) 8

Temporary Islands Mode

Unfortunately, Islands mode does not mean a permanent tropical holiday where you can enjoy cold drinks. Instead, it is the default setting for companies that want to activate Teams. In this mode, all features and functions of Teams can be used, and it is therefore best suited for all Proof of Concept (PoC) testing.

However, Islands mode is not intended as a long-term solution because the end user is expected to use Skype for Business and Teams side by side. As the name suggests, teams in this mode are on an island: Teams and Skype for Business don't really know about each other's existence. Users can create content on the team channels, hold meetings, and chat with other users while using the Teams client.

This mode provides no actual coexistence with Skype for Business. For example, the presence status between the two clients cannot be synchronized. This might work in smaller companies, but it is certainly a problem for larger companies. Lessons to learn:

• Synchronizing presence data between Skype for Business and Teams is not possible. If a busy status is displayed in Teams, Skype for Business users do not see this status; instead, they only see the Skype for Business presence status.
• Messages from one-to-one conversations that users send in Islands mode are delivered according to the sending client. Therefore, if Eve tries to reach Adam via Skype for Business and Adam only runs Teams, Eve will receive notification of a "missed IM message."

Islands mode is therefore typically used for testing Teams and trying out its functions. In practice, companies should try to minimize the time spent in this mode and switch users to a coexistence mode, once available, to minimize negative effects on the user experience.

After a company has successfully tested a pilot installation of Teams, deployment for production use can begin. To ease the transition, users should be transferred to one of the upgrade or coexistence modes. Each of these modes provides predictable behavior when migrating from Skype for Business to Teams. In the next sections of this article, I assume that all Skype for Business workloads are in use.

Skype for Business Only

All users you switch to Skype for Business only mode will continue to be able to use Skype for Business in the usual way. Although this might not sound like too much fun, it does serve a useful purpose en route to Teams. If, for some reason, a group of users needs to stay with Skype for Business while the rest of the company starts using Teams, you can assign this mode to those users. These users will not be able to use Teams. However, and this is important, they will coexist with their colleagues who run Teams and who have been assigned a different coexistence mode. This coexistence mode ensures that the Skype for Business and Teams clients recognize each other and route instant messages and calls to the right application for the users.

If special business functions are required and some users need to stay with Skype for Business, this mode provides the necessary communication functions. Users in Skype for Business only mode can still participate in Teams meetings to which they are invited by internal or external users.