Intel SIU520 SS7 Transferring the Circuit Group, Re-synchronization of Circuit State Information

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

conc_id on the host (conc_id is set when the RSI link was started, optionally by rsicmd). This message will only be received by the application if the RSI link is con- figured with the conc_id set to the application’s module ID.

At the same time, the affected SIU (if it can), will issue an API_MSG_SIU_STATUS message with status value 30 (decimal) indicating a host link failure on the specified host ID. This message is sent to the host configured to receive management messages (host 0 by default).

There are two failure modes that can cause loss of communication:

■Complete failure of one SIU in a dual-resilient pair

■Partial TCP/IP failure causing loss of communication between the host and one SIU of the pair via the TCP/IP LAN

From the application’s point of view, there is no difference in these cases since the RSI link fails in either case. From a system point of view, the main difference is that in the second case, the inter-SIU communication may still be functioning.

If the affected SIU loses communication with all of its hosts, it automatically deactivates all SS7 signaling links, preventing any messages from being processed by any remaining active circuit groups.

Transferring the Circuit Group

If any of the circuit groups terminating on the host are currently active on the affected SIU, the host application must transfer control of each affected circuit group from the failed SIU (the primary SIU) to the remaining SIU (the secondary SIU). Transferring a circuit group normally involves deactivating the group on the controlling SIU then reactivating it on the other. However, since the host is unable to communicate with the failed SIU, the application is only required to send an API_MSG_COMMAND message to the secondary SIU with cmd_type of 8 (activate circuit group) for each affected group.

The activate circuit group command should be issued with a request for a response and the application should not send any call processing or circuit management commands until the response (acknowledgement) has been received from the secondary SIU.

The SIU processes single commands in sequence;

therefore, if an activate command is received while a previous command is executing, the response will be received with a non-zero status (in this case, a value

of 4 indicating “equipment busy”). The application should reattempt the activate command on receipt of a response indicating “busy”.

Since the failure may affect SIUA and SIUB, the host may choose to wait for a period of time following notification of the failure to determine if communication with the other unit remains stable. The circuit groups may then be transferred after this timeout if the communication to the secondary unit remains active.

Re-synchronization of Circuit State Information

Once the circuit group activation(s) are acknowledged from the secondary SIU, the application needs to resynchronize the circuit state information based on the application’s knowledge of the current circuit state. This is achieved by sending three CGSC requests to the secondary SIU.

Circuits that were in a call set-up state or idle (i.e., any circuit that was not in the steady state “speech” or “answered” state) should be RESET. Circuits that were in the speech stage of an incoming call should be forced to INCOMING ACTIVE; circuits that were in the speech state of an outgoing call should be forced to OUTGOING ACTIVE. The forcing of the circuit state to either INCOMING ACTIVE or OUTOING ACTIVE is achieved using the CGSC Request API message, with ptype set to 14 (decimal) for INCOMING ACTIVE and 15 (decimal) for OUTGOING ACTIVE.

Calls that were in outgoing set-up prior to the transfer should be re-attempted following successful completion of the transfer. The application should be able to re-attempt a failed outgoing call attempt, as this may occur under normal operating conditions. The originating switch will automatically reattempt calls that were in incoming set-up. When these commands are acknowledged, the application may resume normal

call activity.

Note: The TUP protocol does not currently support forcing of circuit states to INCOMING ACTIVE or OUTGOING ACTIVE, this step should therefore be omitted. No additional signaling should be exchanged for TUP calls that were in the answered state following the transfer. In this case, OUTGOING ACTIVE calls should be released (at the appropriate time) with a circuit reset.

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Contents Application Note Intel CommunicationsTable of Contents Table of Figures Abstract SIU Circuit-switched API OperationManagement Interface Transaction-based API OperationSIU Connected to Adjacent Node with Two Links in Link Set Failure of SS7 LinksLink Failure of RoutesFailure of Signaling Interface Unit Failure of Power SupplyRouting Architectures of a Dual-resilient SIU System Connection to a Single Adjacent Signaling PointConnection to an Adjacent Mated STP Pair Compares the advantages and disadvantages of these methods SS7 Dual SIU Architecture for Circuit-Switched ApplicationsMTP1-3 Circuit Group Active Inactive MTP1-3 Siua Siub Dual SIU Architecture for Transaction-based ApplicationsSS7 Failure of Application Failure of IP SubnetworkSIU520 HostInter-SIU Link over Crossed E-1/T-1 Cable Hardware RequirementsChanges to the config.txt Parameter File System ConfigurationConfiguring the Inter-SIU Link Circuit Group Configuration Routing ConfigurationExample Configuration For Siua Connecting a Host to Two SIUsFor Siub GCTsetinstance Communicating with Both Siua and SiubGCTgetinstance Transferring Control of a Circuit Group between SIUsRe-synchronization of Circuit State Information Transferring the Circuit GroupTransferring Control Back Recovery of the Failed UnitCircuit Group Conflict If an SIU fails do I need to take any action? How can I tell if an SIU fails?What happens if an inter-SIU SS7 link fails? What happens if the Ethernet interfaces fail on an SIU?Route Ten Parsippany, NJ Phone

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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