Obtain PKI certificates for the new servers and for the reverse proxy and new Edge Servers. You will need certificates for each computer running Office Communications Server 2007 R2. Certificates can be issued from an internal certificate authority (CA), or you can obtain the required certificates from a publicly trusted CA. Subject Alternate Name (SAN) certificates will be needed for some server roles and network interfaces. If you are planning on a single edge version after you transfer your users to Office Communications Server 2007 R2, then you may be able to reuse the existing certificates on the edge servers and proxy server. For details about certificate requirements, see Configure Certificates for Office Communications Serverin the Deploying Office Communications Server 2007 R2 Enterprise Edition documentation and the in the Deploying Office Communications Server 2007 R2 Standard Edition documentation.

If you intend to allow users who are homed on the Office Communications Server 2007 R2 pool to have external or remote access, you will need to prepare a complete set of security certificates to support Office Communications Server 2007 R2, Edge Server. For details, see Certificate Requirements for External User Accessin the Planning and Architecture documentation.