Hardware Blocking
Hardware blocking is a condition for preventing use of an SS7 inter-machine trunk circuit - that is, a voice timeslot in an E1 or T1 digital transmission facility.
ITU Q.764 Section 2.8.2 and Q.763 Section 3.13 describe maintenance oriented blocking and hardware failure oriented blocking. Maintenance oriented blocking is an controlled and intentional circuit block put in effect by command. Hardware failure oriented blocking is the normally uncontrolled and unintentional blocking of a circuit resulting from some failure of a system or a component of a system. Local Hardware BlockingIn ss7boost, a circuit is hardware blocked for one or more of four causes. Those causes are:
Each circuit has four status fields associated with it, one field for each of the hardware blocking causes listed above. All four status fields must be cleared for the circuit to be hardware unblocked. A method must be devised for sending either a CGB/CGU with a Circuit Group Supervision Message indicator of "hardware failure" (ref. Q.763 Section 3.13), or a BLO/BLA when a circuit becomes hardware blocked or unblocked respectively. It remains to be decided if ss7boost will optionally send CGB/CGU with hardware failure indications, or always send BLO/BLA for both hardware and maintenance blocking conditions. Current thinking leans toward the latter method. With five blocking reasons (four hardware and one maintenance) is it necessary or desirable to send a blocking message each time one of the conditions is set? Or should only one blocking message be sent on the occurrence of the first condition and the unblock sent when all blocking conditions are cleared? If the latter method is chosen then there will need to be a state machine developed and a state variable maintained in the CDR for circuit. Remote Hardware BlockingOnly the CGB/CGU carries the Circuit Group Supervision Message field. So only when a node is capable of sending such messages with the `hardware failure oriented value in the CG Supervision Message field will ss7boost be able to set/clear the rhb bit in the CDR entry for a circuit. If a node does not send the CGB/CGU then there will be no distinct indication of remote hardware blocking. If the node only sends BLO/BLA then the remote maintenance block bit for a circuit will be set/cleared. CLI --ckt-report changesThe ss7boost_cli program ckt-report function will be enhanced to report the four hardware blocking status of each circuit in a report. Development Plan
Created by: mike last modification: Thursday 30 of August, 2007 [19:54:48 UTC] by mike |
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