Planning for Federation and Public IM

Lync Online enables users to communicate with other users from external organizations that also use Lync or Office Communications Server by way of federation. In addition, Lync Online users can communicate with Skype users via public IM federation. By default, both of these services are turned off for new Lync Online deployments. However, making use of these services is as simple as logging on to the Office 365 portal and enabling the features. Since up to a day or so is required before activation after these services are enabled, Lync Online administrators should plan ahead and enable the services several days before the Lync Online users need to begin using them.

From a planning perspective, one additional consideration is the policy the organization will adopt with regard to communication with external organizations. Lync Online provides support for maintaining either a whitelist of organizations that the users will be allowed to communicate with, or a blacklist of organizations that the users will not be allowed to communicate with. These lists are configured by entering the SIP domains of the organizations that will be either allowed or blocked; therefore, this configuration will dictate the level of maintenance that will be required on the part of the Lync Online administrators to support the federation policy of the organization.

Using a blacklist results in a more open policy that should be adopted by organizations that are less concerned about which external organizations their users are communicating with, and it requires less maintenance for that very reason. On the other hand, organizations that prefer to maintain tight control of communication with external organizations need to use the whitelist approach. This of course results in a higher level of maintenance to uphold the policy, particularly if there are many SIP domains to which the organization would like to communicate. This is because the Lync administrators need to first determine the SIP domain for any organization that will be allowed for federation, and then add each SIP domain to the whitelist. Further, the external organization also needs to be configured for federation with the Lync Online organization, and depending on whether that organization has an open or closed federation policy, it might be necessary for the Lync administrators on both sides to communicate the required information before configuring federation.