The restart procedure is used to return calls to the Null state or the interface to an idle condition. The procedure is usually invoked when the other side of the interface does not respond to other call control messages or a failure has occurred (e.g. following a data link failure, when a backup D-channel can be used, or following the expiry of timerT308 due to the absence of response to a clearing message). It may also be initiated as a result of local failure, maintenance action or mis-operation.
NOTES
1 Layer 3 procedures and resources associated with those data links with SAPI = "0000 000" should be initialized by the restart procedures.
2. The call reference flag of the global call reference applies to restart procedures. In the case when both sides of the interface initiate simultaneous restart requests, they shall be handled independently. In the case when the same channel(s) or interface(s) are specified, they shall not be considered free for reuse until all the relevant restart procedures are completed.
When
a) both the user and the network are aware of the configuration of the interface; and,
b) the interface is a basic access(Recommendation I.431 [27]) where a point-to-point configuration exists; or
c) the interface is a primary rate access (Recommendation I.430 [46]);
then the user and the network shall implement the procedures of 5.5. In all other cases, the procedures of 5.5 are optional.