Federation is a feature that enables organizations that have deployed Communications Server to communicate easily and securely across the public Internet. As long as both organizations have deployed an Access Edge Server, federation can be used to view presence and exchange IMs.
Organizations can also use federation to participate in web conferences with each other or have audio and video conversations with one another. Similar to the way email has become a standard means of communication, federation for rich collaboration capabilities has emerged as a standard way to conduct business across organizations.
Federation is not limited to organizations with only Lync Server, but can also be used with IBM Sametime or Cisco Unified ...