Microsoft Lync Server Enterprise Edition - software assurance - 1 server

Microsoft Lync Server provides complete presence, instant messaging, conferencing and enterprise voice capabilities through a single, easy-to-use interface that is consistent across PC, browser, and mobile device. You can architect your deployment for high availability using data center resiliency and survivable branch appliances. Administrators benefit from a single, consistent management infrastructure, capabilities to increase availability, and interoperability with existing systems.