Our company is interested in starting to look at VoIP to replace a legacy phone system that links 5 sites and approx. 450 users. Internally, we utilize Microsoft OCS/Exchange and would like to use these tools with the addition of voice for unified communications. In this scenario, do we just not buy the UC tools the VoIP vendors offer such as Shoretel’s Call Manager or Cisco Unified Personal Communicator? If so what makes the link to the VoIP system? Is there connector software that would be needed in its place? Is there pros/cons to this approach?