5.11. Circuit Group Blocking, Unblocking and Resetting

SS7 supports the block, unblock and reset maintenance operations at the circuit group level as well as on a per circuit basis. However, when the same operation must be performed on many circuits, sending a separate message for each individual circuit does not make efficient use of the signaling network bandwidth and may even overload some switches. Using circuit group maintenance messages is a better alternative in such cases.

The Global Call SS7 call control library will attempt to achieve this optimization transparently for the application. The application can invoke the gc_ResetLineDev( ) or gc_SetChanState( ) functions for individual circuits (line devices) but these circuit maintenance operations will be buffered by the library for a small amount of time, allowing more requests for other circuits within the same circuit group to be grouped with the original request and sent as one single circuit group maintenance message.

In addition, the application may elect to request circuit group maintenance operations directly on the groups through the gc_SetConfigData( ) function. This method is not recommended for general use because it is specific to the SS7 call control library. However, if for any reason the transparent mode described in the previous paragraph is not sufficient, the application has access to the full flexibility provided by the gc_SetConfigData( ) function. In such cases, the gc_SetConfigData( ) function can be called with a target type of GCTGT_CCLIB_SYSTEM and a target ID of GC_SS7_LIB. The target_datap parameter (of type GC_PARM_BLK) should be built using gc_util_insert_parm_ref( ) with a setID of S7SET_CCTGRP, a parmID of S7PARM_CCTGRP_STATE, and the value being the address of a S7PARM_CCTGRP_STATE_DATA structure. The S7PARM_CCTGRP_STATE_DATA structure contains the state field where the desired block, unblock, or reset operation is specified. The operation can be one of the following:

• S7_CCTGRP_STATE_MAINT_BLOCK - Put the circuits in a maintenance block state. In this state, active calls can continue, but new calls are not allowed.
• S7_CCTGRP_STATE_HW_BLOCK - Put the circuits in a hardware block state. In this state, active calls are disconnected and new calls are not allowed.
• S7_CCTGRP_STATE_MAINT_UNBLOCK - Undo a maintenance block operation.
• S7_CCTGRP_STATE_HW_UNBLOCK - Undo a hardware block operation.
• S7_CCTGRP_STATE_RESET - Reset the circuits, clearing any call and local maintenance or hardware block state.

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