You are here: CSP Developer’s Guide: Common Channel Signaling > 2 Introduction to SS7 > SS7 Card Synchronization
Overview
The Excel platform attempts to synchronize SS7 cards following all fault conditions except the removal of the card. When synchronization is complete, redundancy is re-established and the host receives a CCS Redundancy Report message.
All configuration and query API messages (except CCS Redundancy Query) are blocked during the synchronization process. Depending on the specific configuration and the amount of traffic being handled, synchronization of the SS7 cards can take a significant amount of time.
Synchronization can be suspended by the host during high traffic periods to avoid the system slow-down incurred by sending a CCS Redundancy Configure message with the Options field value 0x01 (Suspend Synchronization).
The SS7 card in the Active state resets and returns to service as an independent card and redundancy is disabled. Only the SS7 card in the Active state continues to process calls. The other card can be reconfigured as an independent card or redundancy during slow traffic periods.
Important! In a switchover, if PPL Configuration Byte 0x32 for ISUP SPRC component (0x13) is disabled, the host sends no circuit reset message to the network and no purge message is sent to the host. Disabling causes the host to respond to calls that are in a setup state as though they are in an unknown state.
During an SS7 card switchover, the Excel platform maintains connections for those channels that were connected prior to the switchover. Therefore, answered calls remain active. Calls in the process of setup are torn down. The Excel platform informs the host of all in-service channel states using the DS0 Status Change (0x42) message which sends switchover purge code 0x18. Purging is done over all the channels which have no active calls (incoming or outgoing). Some of them will be idle and some will be in an intermittent state. Purging will bring those channels into a known idle state. See the API Reference, DS0 Status Change (0x42) message, for more information about purge code 0x18.
Along with the purge code sent to the host, a Circuit Reset (RSC) message is sent to the network. When a Release Complete (RLC) message is received by the SS7 card, the channel is brought back into service.