Consider the following scenario:
- You deploy the Enterprise Voice feature in a Microsoft Lync Server 2013 environment.
- You configure the IP private branch exchange (PBX) gateway to fork an incoming public switched telephone network (PSTN) call to an IP telephone and a Lync client.
- You configure two users (user A and user B) in the environment.
- User A makes a PSTN call to user B. Then, the IP telephone and Lync client of user B are ringing.
- User B answers the call by using the IP telephone.
This issue occurs because Mediation Server deals with the SIP reason header incorrectly, and then generates a missed call notification.