External user access to audio/video (A/V) sessions, application sharing, and conferencing.Remote user access for instant messaging (IM).Federation using automatic DNS discovery of partners.TLS connections between client and server.
Lync Server 2010 uses certificates for the following purposes: Microsoft Lync Server 2010 communications software requires a public key infrastructure (PKI) to support TLS and mutual TLS (MTLS) connections.
