VPN Connectivity to Lync

Virtual Private Network (VPN) is a concept many users and organizations have been familiar with for years. The concept is that a remote user establishes a VPN connection to the office, and has full access to all internal services, which raises the question of why Lync Edge Server is required at all.

VPN works by encapsulating all traffic within a secured tunnel, but that tunnel generally includes a lot of overhead and additional latency. All of Lync’s SIP signaling traffic and A/V media traffic is already securely encrypted, so the additional VPN tunnel encapsulating the traffic is really redundant. This isn’t a huge problem for SIP signaling, but when two users try to establish an A/V call, that overhead, shown in Figure 31.11, can significantly impact the call quality.

Figure 31.11. VPN double encryption.

The Lync Edge Server provides the most optimal path for A/V calls for remote users. Any deployment leveraging audio or video features of Lync should not be relying on VPN to provide a way to connect calls for remote users.