SS7 Fault Conditions & Fault Recovery

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Overview

SS7 stack operations are based on at least one link in a link set on each card in the redundant pair. The stack operations are maintained through the following fault conditions:

• An SS7 card is:

• Removed (host receives Card Status Report message).

• Reset by either the Reset button or with the Reset Configuration message.

• Taken out of service either by the host with the Service State Configure message or by the CSP.

• Malfunctions and forces a reset.

• The redundancy link between the two SS7 cards is broken because:

• The I/O card(s) is removed.

• The card-to-card link on the bus is lost.

Fault Recovery

Important! The Stop button (on a given card) should always be pushed before removing that card from the system. The PPL Event Indications may not be generated if the SS7 card is pulled without first pressing the Stop button.

The table below shows the results and host action required in response to each fault scenario.

Event	Result	Host Notification	Action Required
SS7 card removed (Active)	- All answered calls are maintained on the remaining SS7 card. - Redundancy is disabled.	PPL Event Indication of Signaling link failure (MTP3 LSAC) * CCS Redundancy Report (Redundancy Status: 0x20 or 0x21) Alarm (Severity: 0x03, Entity: 0x02, Alarm Number: 0x0E) Card Status Report (Card Type: 0xFF)	1. Replace SS7 card. 2. Reconfigure redundancy. 3. Reconfigure signaling links on the replaced card (SS7 Signaling Link Configure). 4. Bring Links in service (Service State Configure)
SS7 card removed (Standby)	- All answered calls are maintained on the remaining SS7 card. - Redundancy is disabled.	Same as Above	Same as Above
SS7 card reset (Active)	- All answered calls are maintained on the remaining SS7 card. - The SS7 card that reset comes back in service with SS7 configuration maintained. - The CSP automatically synchronizes the SS7 cards and re-establishes redundancy.	PPL Event Indication of Signaling link failure (MTP3 LSAC) * CCS Redundancy Report (Redundancy Status: 0x29 or 0x30) Alarm (Severity: 0x03, Entity: 0x02 Alarm Number: 0x09) Card Status Report for I/O (Card State: 0x00) Card Status Report for SS7 (Card State: 0x00) CCS Redundancy Report (Redundancy Status: 0x03 or 0x04)	No action is required. To suspend synchronization, see Suspending Synchronization in this chapter.
SS7 card reset (Standby)	- All answered calls are maintained on the remaining SS7 card. - The SS7 card that reset comes back in service with SS7 configuration maintained. - The CSP automatically synchronizes the SS7 cards and re-establishes redundancy.	Same as Above	Same as Above
SS7 card taken out of service (Active)	- All answered calls are maintained on the remaining SS7 card. - Redundancy is disabled.	CCS Redundancy Report (Redundancy Status: 0x20 or 0x21) Card Status Report (Bit 3 of Card Status Byte is set)
SS7 card taken out of service (Standby)	- All answered calls are maintained on the remaining SS7 card. - Redundancy is disabled.	Same as Above	Same as Above
I/O is removed	- The active SS7 card currently processing calls remains in service and all calls are maintained. - The other SS7 card resets and redundancy is disabled.	CCS Redundancy Report (Redundancy Status: 0x22) Alarm (Severity: 0x03 Entity: 0x02 Alarm Number: 0x0E) Alarm (Severity: 0x03 Entity: 0x02 Alarm Number: 0x09) Card Status Report (Card Type: 0xFF)	1. Replace the I/O card. 2. Reconfigure redundancy. 3. Reconfigure signaling links on the replaced card (SS7 Signaling Link Configure). 4. Bring Links in service (Service State Configure)
Card-to-card link is broken	- The SS7 card in the Active state resets.	CCS Redundancy Report (Redundancy Status: 0x01 or 0x02) Alarm (Severity: 0x03, Entity: 0x02 Alarm Number: 0x09) Card Status Report for I/O (Card State: 0x00) Card Status Report for SS7 (Card State: 0x00) CCS Redundancy Report (Redundancy Status: 0x03 or 0x04)	Check I/O card. It has either faulted or been removed.