When the media servers are collocated with the major branch offices, there is a possibility to have only one backup media server located at the Lotus Sametime Unified Telephony cluster nodes. This is called N + 1 redundancy, since there is one redundant media server for N branch offices. N + 1 media server survivability can be achieved for both, geographically collocated and separated Lotus Sametime Unified Voice Clusters. In normal operation, the media servers at all branches are operational and handle all the media server traffic from the Lotus Sametime Unified Telephony. Load balancing is achieved by assigning each branch office its own rate area.
In N+1 redundancy, N represents the number of primary media servers. These are the media servers that are first in the list of media servers in a destination of media servers. If N is greater than 1, an origin destination must be created to create a specific media server for a specific branch office. This is equal to the number of offices (branch + main) that have a local media server.
In case of failure, the following takes place depending on the failure type:
Node failure: When a Lotus Sametime Unified Telephony node fails, the other node takes over. The MGCP signaling manager on the partner node still uses media servers in the same manner as before the failure.
Media server failure: When a branch's media server fails, the Lotus Sametime Unified Telephony detects this event and the branch starts using the centralized backup media server. The other branches continue to use their own media servers.
Branch failure: When an entire branch fails, the other branches continue to use their own media servers and are unaffected by the failure.
WAN failure: When the WAN connection with a particular branch fails, the other branches are unaffected by the failure.
Parent topic: Survivability Overview
Media Server Survivability with 1+1 Redundancy