SS7 Redundancy
Dialogic continues to strive to make service availability to our users as much of the time as possible. To keep a very high reliability rate in the SS7 network, SS7 Redundancy or SS7 High Availability is available. SS7 Redundancy or SS7 High Availability utilizes two IMG 2020's that are configured into an active/standby redundant state. The Active server which is first configured is considered the primary SS7 server node and the standby is then configured as the Secondary SS7 server node.
An important element of the SS7 Redundancy approach utilized by the IMG 2020 is the Multi-Node EMS. Either a single or two Multi-Node EMS systems may be used. The active Multi-Node EMS monitors the status of the Primary and Secondary SS7 server nodes. In the event that the EMS detects a failure in the Primary SS7 server, the SS7 switchover which is described below will be initiated by the active EMS. When present, the redundant EMS provides another level of redundancy and will be able to take over the function of monitoring the SS7 server nodes in the event that the primary EMS fails. Setting up a redundant EMS will prevent the EMS itself from being a single point of failure in the event that the primary EMS fails. For more information, refer to the EMS Server - Installation and Setup and EMS Redundancy Configuration topics.
When SS7 redundancy is initially configured, all the functionality that is configured on the Primary SS7 server node is transferred and mirrored onto the secondary SS7 server node through RCOMM messaging. Any subsequent changes made to the SS7 configuration are mirrored to the Secondary SS7 server node as well. However, when configuring SS7 Redundancy, the SS7 links can be configured on the primary SS7 server node, the secondary SS7 server node, or any remote nodes (Not shown in diagram). These SS7 links load share the SS7 signaling traffic. Processing of the SS7 signaling is still handled by the primary SS7 server node but the SS7 messaging can be sent through any of the SS7 links configured regardless of which node the link is configured on. It is up to the Primary SS7 server node to determine which SS7 link the messaging is processed on.
If a failure occurs on the Primary SS7 server node which is also considered the active node, an SS7 switchover of the active state is automatically initiated. In this scenario, the Primary ss7 server node has failed and the active state has been transferred to the Secondary SS7 server node. At this point, the secondary node is considered the active node and all SS7 processing will continue on the Secondary/Active node. Being that the Primary node has failed, any SS7 links that are configured on the Primary node will also be lost and no SS7 signaling or data is processed through this node. Once the cause of the failure has been fixed, the Primary SS7 server node will re-configure itself and assume the role of the standby and the SS7 link will be added to the pool of available SS7 links. At this point, the Secondary SS7 server node is the active node and all SS7 processing is done on it. The Primary SS7 server node now assumes the role of the standby and is waiting for a failure to occur on the Secondary/Active SS7 server node to initiate another SS7 switchover. If however the administrator of the network wants the Primary SS7 server node to be the active SS7 server node, the administrator can initiate a manual switchover and all active functionality will be returned to the Primary SS7 server node as well as all standby functionality will be returned to the Standby SS7 server node.
SS7 Redundancy or SS7 High Availability utilizes more than one node to accomplish the SS7 Redundancy functionality. To be able to configure more than one node using the Web GUI application, the Multi-node feature must be employed. The Multi-node feature requires that a BDN EMS Software image to be configured and running on a Virtual Manager. In the Multi-node scenario, all messaging is processed by the BDN EMS Software before being sent to the IMG 2020 nodes. For information on how to set up and configure a Virtual Manager, refer to the Multi Node Installation topic.
The information below displays and describes the SS7 Primary/Active and SS7 Secondary/Standby nodes. It does not mention the remote node functionality that can also be configured. For information on configuring SS7 Redundancy or SS7 with remote SS7 nodes, refer to the Configure SS7 Redundant Nodes or Configure SS7 with Remote Node topics.
Diagram
The diagram below displays two IMG 2020's that are configured to utilize SS7 redundancy/high availability. Use the diagram below as reference for explanation in section above.
