During migration from Skype for Business/Lync/OCS to IM and Presence Service, Microsoft Lync and Microsoft Office Communicator users should maintain the same identity, which is their Uniform Resource Identity (URI). Maintaining the same identity during migration has the following benefits:

• It allows for the user’s availability state to be continually monitored by existing followers because the user’s identity does not change.

• It also allows for much simpler migration of a user’s contact lists because the contact lists can be directly imported from the Microsoft server to IM and Presence Service.

IM and Presence Service URIs are composed by joining the Cisco Unified Communications Manager user ID with the IM and Presence Service domain as follows:

<userid>@<domain>

If users are manually added through the Cisco Unified Communications Manager user interface or through the Cisco Unified Communications Manager Bulk Administration Tool (BAT), you must ensure that the user ID that you specified when you created the user matches the user portion of the user’s Microsoft server URI. For example, if the Microsoft user's URI is bobjones@foo.com, you should create the CUCM user with a user ID of bobjones.

If Cisco Unified Communications Manager is configured to synchronize users from Active Directory, you must ensure that the Active Directory field that is used to map to the Cisco Unified Communications Manager user ID matches the user portion of the Microsoft server URI. Note the following:

• Cisco Unified Communications Manager maps to userID from a limited number of Active Directory fields, the most common of which is sAMAccountName.

• If Cisco Unified Communications Manager maps userID to sAMAccountName, the Microsoft server URI for the migrating users must also match the format <sAMAccountName>@<domain>.

• If the sAMAccountName of Bob Jones is bjones, the Microsoft server URI must be bjones@cisco.com.

• If any Microsoft server URIs do not match the format <sAMAccountName>@<domain>, you can modify the URIs for each batch of Microsoft server users before you migrate that batch to IM and Presence Service.

The partitioned intradomain federation integration between the IM and Presence Service and Skype for Business/Lync/OCS is designed to provide basic communication between users during a phased migration from a Microsoft server to IM and Presence Service.

However, partitioned intradomain federation integration introduces a performance overhead. Because of this, IM and Presence Service can support a maximum of 130,000 SIP intradomain federation contacts per server. To ensure that this federated contact threshold is not exceeded on any IM and Presence Service node during migration of users from the Microsoft server to IM and Presence Service, a detailed user migration plan may be required.

You can use the following calculation to get an estimate of the maximum number of IM and Presence Service users that can be supported without breaking the above federated contact threshold:

Max Supported Users = 130,000 / Average Contact List Size.

Based on this calculation, the following table gives an indication of the maximum number of IM and Presence Service users that can be supported without breaking the 130,000 federated contact threshold.

You require a detailed user migration plan if the number of users to be provisioned on any IM and Presence Service node within your deployment exceeds the relevant limit above. Contact your Cisco Support representative to begin the process of defining a detailed migration plan.

Notes

1. The values for the maximum number of supported users in the table above are based on worst-case figures; that is, in the case where all contacts are federated.

   With proper migration planning, the full complement of users can be deployed on an IM and Presence Service node in a phased manner, without breaking the 130,000 federated contact threshold.

2. When high availability is enabled, each IM and Presence Service node must be able to handle the load associated with all users within the IM and Presence Service 2-node subcluster because, in the event of a node failure, the second node in the cluster services all users on its own. Therefore, the limit per node must be halved.

3. If you are unsure about the average contact list size within your Microsoft server deployment, assume it to be worst-case (200 contacts) when you are deciding whether a migration plan is required.

4. The values for the maximum number of supported users in the table above assume the Cisco supported virtual platform based on the IM and Presence Service OVA template for 5000 users. The equivalent numbers for the 1000 user OVA are detailed below.

Cisco provides a number of tools to allow bulk migration of users from Skype for Business/Lync/OCS to IM and Presence Service. To allow you to plan your migration, it is important to be aware of the time required for each tool to run when you are migrating a large number of users. This section describes the expected run time for each of those tools.

Note	If you have a mixed deployment of both Lync and OCS servers, you must run the tools on the Lync users and then run the tools again on the OCS users.