As with any Unified Communications product, Lync Server 2013 depends on a number of external systems to provide needed functionality. Active Directory and DNS provide vital infrastructure services, and server certificates are used to secure communications between systems. There are various network dependencies that come into play depending on Lync components and topology. The Office Web Apps Server is a new dependency that provides an enhanced conferencing experience. SQL is also an important part of the Lync ecosystem. Proper maintenance of the Lync SQL databases will help ensure smooth operation for the Lync Server 2013 environment.