Upon receiving a RESTART message, the recipient shall enter the Restart state associated to the global call reference and start timer T317; it shall then initiate the appropriate internal actions to return the specified channels to the idle condition and call references to the Null state. Upon completion of internal clearing, timer T317 shall be stopped and a RESTART ACKNOWLEDGE message transmitted to the originator, and the Null state entered.
Note 1 - If only a subset of the specified channels have been returned to the idle condition when timer T317 expires, a RESTART ACKNOWLEDGE message should be transmitted to the originator, containing a Channel identification information element indicating the channel(s) that have been returned to the idle condition.
If timer T317 expires prior to completion of internal clearing, an indication shall be sent to the maintenance entity(i.e. a primitive should be transmitted to the system management entity).
Even if all call references are in the Null state, and all channels are in the idle condition, the receiving entity shall transmit a RESTART ACKNOWLEDGE message to the originator upon receiving a RESTART message.
If the Restart indicator information element is coded as "all interfaces" then all calls on all interfaces associated with the D-channel shall be cleared. If the Restart indicator information element is coded as "all interfaces" and a Channel identification information element is included, the Channel identification information element is treated as described in 5.8.7.3.
If the Restart indicator information element is coded as "indicated channel" and the Channel indication information element is not included, then the procedures in 5.8.6.1 shall be followed.
If the Restart indicator information element is coded as "single interface" and that interface includes the D-channel then only those calls associated with the D-channel on that interface shall be cleared.
The receiving DSS1 protocol control entity for the global call reference shall indicate a restart request to only those DSS1 protocol control entities for specific call references which
a) are supported by the same Data Link Connection Endpoint Identifier (DLCI) (see Recommendation Q.920) as the DSS1 protocol control entity for the global call reference which received the RESTART message; and
b) correspond to the specified channel(s) or interface(s), or (if the D-channel was implicitly specified) are not associated with any channel, including calls in the call establishment phase for which a channel has not yet been allocated.
The following entities shall be released:
a) B and H channels established by Q.931 messages including channels used for packet access (case B) (consequently all virtual calls carried in the released channel(s) will be handled as described in 6.4.1);
b) user signalling bearer service connections.
c) other resources associated with acall reference, where specified in other DSS1 Recommendations.
Note 2 -Application to the Register procedures in Recommendation Q.932 requires further study.
The following entities shall not be released:
a) semi-permanent connections that a reestablished by man-machine commands;
b) calls associated with DSS1 protocol control entities supported by any DLCI other than one supporting the DSS1 protocol entity for the global call reference which received the RESTART message;
c) X.25 virtual calls and permanent virtual circuits using SAPI = 16;
d) TID and USID values established using terminal initialization procedures (see Annex A/Q.932).
If semi-permanent connections established by man-machine command are implicitly specified (by specifying "single interface or "all interfaces"), no action shall be taken on these channels, but a RESTART ACKNOWLEDGE message shall be returned containing the appropriate indications (i.e. "single interface" or "all interfaces").
If semi-permanent connections established by man-machine command are explicitly specified (by including a Channel identification information element in the RESTART message) no action shall betaken on these channels, and a STATUS message should be returned with cause No.82, identified channel does not exist, optionally indicating in the diagnostic field the channel(s) that could not be handled.