In a deployment where branch survivability is not required, then users in branch locations may be connected to the server via a central SBC (Session Border Controller). This is similar to the remote user scenario, but the branch users are connected via an Enterprise WAN rather than via the public Internet.
If each branch location has its own subnet, then Lotus Sametime Unified Telephony based CAC (Call Admission Control) and Emergency Call Location Identification features may be used.
If there is no branch survivability provided, then the following redundancy considerations apply:
Lotus Sametime Unified Telephony cluster nodes are co-located in one data center (or geo-separated but in the same sub-net)
Parent topic: SBC (Session Border Controller)
If a High Availability SBC cluster is deployed, then failure of one SBC is transparent to the branch users.
If a non-redundant SBC is used, then failure of the SBC results in loss of service until the SBC is repaired.
Lotus Sametime Unified Telephony cluster are geo-separated in different data centers with different sub-nets
A data center outage requires the branch users register with the SBC in the other data center before they can originate or receive new calls. In this scenario the phones must be configured with DNS SRV or the IP addresses of the SBC's in both data centers and must register with the secondary SBC when connectivity to the primary SBC is lost.