Fault tolerance

[marca56]

• must support at least active-passive configuration
• should support active-active configuration [roadmap]

[ocarriles]

Routing design allows to stablish a routing policy to terminate a call. So backend failover/load balancing could be made: (https://github.com/RestComm/sbc/tree/master/application/src/main/java/org/restcomm/sbc/router) HA approach for the SBC itselft MUST be discussed