Survivable and resilient real time communication architecture

An enhanced communication system providing multi-modal communication services with a resilient and survivable architecture, the system comprising:

• a plurality of function-specific servers;
• at least one branch office comprising a survivable branch appliance (SBA) configured to provide registration and routing services to clients associated with the branch office;
• and
• a first and a second data centers, each data center comprising:
• a user services server configured to provide presence, backup monitoring, and conferencing services;
• and
• at least one registrar cluster comprising a plurality of homogeneous servers configured to provide registration and routing services to clients associated with respective data centers, wherein
• backup registrar clusters in the second data center are assigned to primary registrar clusters in the first data center for data center survivability,
• clients are enabled to failover to an alternate registrar server within the same cluster in a transparent manner for cluster survivability, and
• user and call associated data are continuously replicated from a primary registrar cluster to a backup registrar cluster and an external backup data store such that the data is available upon one of:
• client failover and system restoration.

A computer-readable storage medium with instructions stored thereon for managing a resilient and survivable architecture of an enhanced communication system, the instructions comprising:

• registering clients with a registrar cluster in one of a data center and a branch office of the system to receive communication services from the system;
• providing data center survivability by assigning backup registrar clusters to primary registrar clusters at different data centers;
• providing cluster survivability by failing over clients to an alternate registrar server within the same cluster from their assigned home registrar in a transparent manner;
• providing call survivability by selecting one of:
• an alternate inter-cluster call path and a Public Switched Telephone Network (PSTN) call path;
• providing network survivability by enabling clients to discover a registrar cluster through one of:
• a Session Initiation Protocol (SIP) Dynamic Host Configuration Protocol (DHCP) discovery and a SIP multicast discovery;
• providing voicemail survivability in case of data network failure between a data center and a branch office by re-routing calls directed to voicemail to a messaging server at the data center over PSTN;
• and
• facilitating calls for users of the system, wherein at least one of the modalities of a call and a service associated with the call is restricted in response to one of:
• a data center outage and a data network outage.