ISUP:Circuit group functions

The SS7 protocol offers some circuit group actions which affect more than one circuit at the same time. Amongst those actions are RESET, BLOCK and UNBLOCK.

To understand how these work, the end-user must first know that a group is defined by a mutual agreement between two peer ISUP nodes about which circuits are part of which group. It also means that there is no ‘group ID’ or a similar concept that is carried over to SS7 MSUs. When the ISUP layer receives a group command, it has to calculate which circuits are to be affected according to the configuration it has and three parameters from the received command (current CIC, range value and the status bit field).

In every group event, the “range and status” IE indicates which circuits are affected by the command. Since the command is also received on a specific circuit, the layer calculates which circuits are affected starting from that circuit. (Please refer to the IE definition here.) Please also note that certain third-party models of SS7 hardware require group functions to be sent on the CIC of the first circuit in a circuit group and will simply ignore group commands that are not addressed that way.

NOTE: For better interoperability with other equipment, you should always send group commands on the first circuit of a circuit group and fill the range (and/or status bit field) accordingly.