Lync Voice Mail Survivability (SA) with Exchange Unified Messaging
The SBA is aware of the centrally configured Exchange Unified Messaging component. Additional it is important to understand the process of Voice Mail Survivability. While the VoicemailReroutingConfiguration in Lync provides the SBA with an alternative path, rerouted via PSTN to the central Exchange UM site. The SBA is continuously check the SIP availability of the Exchange UM component, using the SIP OPTION based health checking. (Indeed, both SBA and non SBA Lync registrars act in the same way for all components, e.g. Exchange UM and other Gateway-SBC). Once the SIP OPTION command is sent, the sender expects an SIP 200 OK answer. Lync tries this health check several time even after it do NOT receive a 200 OK. As result of not receiving, the registrar will mark this target as DOWN and stop sending calls. Note: You can drill down this process, if you us OCSLogger and Snooper catching the OPTION and 200 OK communication directly on the SBA. Back to the Exchange UM, if Exchange ...