Building Fault-tolerant SS7 Systems Using the Intel® NetStructure™ SIU520 SS7 Signaling Gateway Application Note

Recovery of the Failed Unit

The host application is informed of recovery of the communication to the SIU with the same method used for notification of the failure. The RSI_MSG_LINK_ STATUS message in this case contains a status value of 1 (link to SIU recovered).

The host nominated to receive management indications (normally host 0) will also receive an API_MSG_SIU_STATUS message with status value 31 (decimal) indicating a host link has recovered to the specified host ID.

Transferring Control Back

Immediately following re-establishment of communication with the primary SIU, the application should send deactivate circuit group messages to this SIU to ensure that groups are only active on the secondary unit (this may be the case if the inter-SIU link had also failed). If the primary unit has recovered from a complete failure, no circuit groups will be active. This deactivate command will fail if the groups were not active and the application should ignore any acknowledgement of this command with a status value indicating processing failure. A “busy” response should cause the application to reattempt the deactivate.

When communication with the primary SIU has been re-established, the application should allow sufficient time to ensure that the communication is stable, thus avoiding repeatedly transferring circuits between units. After this time has expired, the application should transfer control of the affected circuit groups back to the original SIU.

This is achieved by deactivating the groups on the secondary SIU and re-activating the ones on the primary SIU. However, before the groups are deactivated, the circuits in that group should be maintenance blocked. (Using the Circuit Group Supervision Control API message). This does not affect any calls in progress, but will prevent these circuits from being selected for any new incoming calls. The application should also ensure that none of the affected circuits are selected for new outgoing calls.

When all existing calls are completed (all the circuits are therefore idle), the application should deactivate the circuit group by sending an API_MSG_COMMAND message with cmd_type of 9 to the secondary unit. When the acknowledgement that this command has been success- fully processed has been received, the groups should be activated on the primary unit by sending an API_MSG_COMMAND message with cmd_type of 8.

Once the acknowledgement of the activation has been received by the application, all affected circuits should be reset. This will force the circuits to a known (idle) state and remove the blocking status. When the reset is acknowledged from the terminating switch (by receipt of a circuit group supervision control confirmation message) the application may begin exchanging call traffic with the SIU.

Circuit Group Conflict

Both SIUs in a dual-resilient configuration periodically poll each other to determine which circuit groups are active on each unit. If a group is active on both units at the same time, an API_MSG_USER_EVENT message is issued by the unit that detects the conflict, indicating the group ID of the affected circuit group. The controlling application host should issue a deactivate command to the SIU that should not be controlling the circuit group and re-synchronize the circuits in the group (on the correct SIU) by issuing a reset.

The SIUs prevent this situation from arising by automatically sending a deactivate circuit group command to the other unit on receipt of the activate command. If the nature of the failure is such that inter-SIU communication is lost, it may be impossible for the SIU to issue the automatic deactivate command. Under this circumstance, when the failed SIU recovers, circuit groups may be active from the time before the initial failure. This situation is handled by the application sending a deactivate command for all of the previously active groups immediately following restoration of the communication with the SIU.

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Intel SIU520 SS7 manual Recovery of the Failed Unit, Transferring Control Back, Circuit Group Conflict
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SIU520 SS7 specifications

The Intel SIU520 SS7 is a significant advancement in the realm of telecommunications, specifically designed for seamless signaling in a wide array of telecommunication infrastructures. As a part of Intel's pioneering suite of products, the SIU520 plays a critical role in managing signaling for telephony systems that require efficient handling of SS7 protocols.

One of the main features of the SIU520 is its support for the SS7 signaling protocol, which is pivotal for the establishment and management of telephone calls over traditional circuit-switched networks. With its robust design, the SIU520 ensures reliability in signaling, contributing to the reduction of call set-up times and the minimization of errors, thus enhancing the overall quality of communication services.

The SIU520 incorporates advanced technologies such as high-speed data processing capabilities, allowing it to handle multiple signaling messages concurrently. This is particularly important in environments with high call volumes, where efficient processing can significantly affect the performance of telecommunication services. Furthermore, the architecture of the SIU520 is designed for scalability, enabling easy integration into existing infrastructures while accommodating future expansions as demand increases.

Another characteristic that sets the SIU520 apart is its support for various signaling types beyond standard SS7, including ISDN and SIP. This makes it a versatile tool for service providers aiming to offer diverse services, such as voice, video, and data communications. The SIU520 is also designed with a focus on interoperability, which ensures that it can effectively communicate with equipment from different manufacturers, thus providing flexibility in deployment.

In terms of security features, the SIU520 is architected to withstand common threats in the communication landscape. It employs encryption and authentication protocols to safeguard signaling traffic, ensuring that sensitive information remains protected during transmission.

In summary, the Intel SIU520 SS7 represents a robust and flexible signaling solution crucial for modern telecommunications. With its support for multiple protocols, high processing speeds, scalability, and secure communication capabilities, it stands as a testament to Intel's commitment to advancing telecommunication technologies and enhancing the efficiency and reliability of communication networks worldwide.
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