4.4. Deployment Modes

According to the system dimensioning and high-availability requirements, ABC SBC can be deployed in different modes:

4.4.1. Single Node Mode

In a single node mode, there is only one server processing the traffic and no backup server for failover in case of hardware or software failure. This mode is recommended for trial and testing purposes. The trial virtual image of the |SBC| is pre-configured in the single node mode.

4.4.2. High Available (HA) Pair Mode

HA pair ABC SBC installation is formed by two physically identical servers running in an active/hot-standby configuration. Only the active server processes signalling and media traffic. In case of any failure, the internal management system performs a failover where the originally standby machine becomes active. Switching the active and standby operation modes is also useful during the upgrades of the system.

Both the active and standby servers share virtual IP addresses (VIPs) and communicate with each other over the “Internal Management Interface” -IMI. Using Pacemaker the standby server can check the availability of the active server. Once the standby server determines that the active server is no longer available then the standby server will assume the role of active SBC and take over the VIPs used for receiving and sending the media and signalling messages.

Further, the active server replicates state information about running sessions to the standby machine. Thereby, after a failover the backup server will be able to continue processing already established calls and the failure of the server will not result in dropping of already established calls. Note however that calls are replicated after they are established and calls unanswered yet may be dropped. Also only signaling over connection-less transport protocols is certain to reach the Call Agents as transport protocol context gets lost during failover.

4.4.3. Cluster based solution

For very high traffic and performance requirements, ABC SBC instances (in a single or HA pair mode) can create a cluster. A SIP load balancer is put in front of these cluster nodes so as to distribute the SIP traffic to a particular ABC SBC instances.

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