tailieunhanh - Signaling System No.7 Protocol Architecture And Sevices part 25

Additional Call Processing Messages In addition to messages presented in the chapter, many other messages are used in various contexts for call processing. | Additional Call Processing Messages In addition to messages presented in the chapter many other messages are used in various contexts for call processing. Some of the additional messages are used to support supplementary services while others indicate specific network actions. Appendix B ISUP Messages ANSI UK ETSI ITU-T includes a complete list of all ISUP messages their binary encoding and a brief description. Maintenance Messages and Procedures ISUP provides an entire category of messages that are commonly categorized as maintenance messages. Until now this chapter has focused on the call processing aspect of ISUP. This section discusses those messages that are used for diagnostics maintenance and the manipulation of ISUP facilities outside of the normal call processing realm. The exchange can autonomously generate some maintenance messages such as blocking BLO and Continuity Check Request CCR in response to an event or invoked manually by maintenance personnel. The collective set of messages described here helps to maintain trunk facilities and the integrity of user traffic. When necessary trunks can be blocked from user traffic tested and reset to a state of sanity. The following sections illustrate how ISUP maintenance is used to accomplish these tasks Circuit Ranges Circuit States Circuit Validation Continuity Blocking and Unblocking Circuits Circuit Reset Circuit Ranges ISUP maintenance messages apply to the CIC that is designated in the ISUP message. However many messages can be applied to a range of CICs. These messages are referred to as group messages. Since ISUP trunk circuits are usually multiplexed together on digital spans an action must often be applied to a larger group of circuits such as the entire span. If a span is removed from service or brought into service ISUP messages are sent to update the status of each of the span s circuits. If multiple spans are involved and individual messages were sent for each circuit a flood of messages would .