Mobile users encounter various mobile application scenarios that require special planning. For example, a user might start using a mobile application while not in work by connecting via a 3G network, then switch to the corporate Wi-Fi network when arriving at work, and then switching back to 3G when leaving the building. The environment needs to support such network transitions and guarantee a consistent user experience. This section describes the infrastructure requirements that are needed to support mobile applications and automatic discovery of mobility resources.

Supporting the scenario outlined in the paragraph above can only be accomplished if the client stays connected with a single entity. This entity is the Reverse Proxy, regardless of whether the client is internally connected or connected via 3G/Internet.

Note: The Discover URL (LYNCDISCOVERYINTERNAL) must point to the Front End Pool Web Service Virtual IP (VIPs) addresses.
Note: The Front End Server Internal Mobility URL must point to the Reverse Proxy external IP address.
Note: The Front End Server External Web Service URL must point to the Reverse Proxy external IP address.
Note: Although mobile applications can also connect to other Lync Server 2013 services, the requirement to send all mobile application web requests to the same external web FQDN applies only to the Lync Server 2013 Mobility Service. Other mobility services do not require this configuration.
Note: However, both the internal Mobility Service URL and the external Mobility Service URL are associated with the external Web Services FQDN.
Note: The internal Web Service (running on port 443) does not offer mobility services, as the diagram above is showing.