If the network does not support the call rearrangement procedures, it shall reject a RESUME message according to the error handling procedures of 5.8.3.2 a). For this purpose, the RESUME message would be deemed to be an unrecognized message.
If a received RESUME message cannot be actioned by the network (e.g. as a result of an unknown call identity a RESUME REJECT message shall be returned to the requesting user indicating one of the following causes:
a) No. 83 - A suspended call exists,but this call identity does not;
b) No. 85 - No call suspended; or
c) No. 86 - Call having the requested call identity has been cleared.
The call identity remains unknown. The call reference contained in the RESUME message is released by both the user and network side. Upon receipt of the RESUME REJECT message, the user shall stop timer T318 and enter the Null state.
If timer T307 expires the network shall initiate clearing of the network connection with cause No. 102, recovery on timer expiry; discard the call identity and release the reserved B-channel.
On release, the call identity can then be used for subsequent call suspension. If before the expiry of timer T307 the call is cleared by the remote user, the B-channel reservation is released but the call identity may be preserved by some networks along with a clearing cause (e.g. cause No. 16, normal call clearing).
If timer T318 expires, the user shall initiate call clearing in accordance with 5.3.2 f).