+----------+ +----------+ +-----------+ |Sensor or | | ESRP | | PSAP | |Aggregator| | | | | +----+-----+ +---+------+ +----+------+ | | | Sensors | | trigger | | emergency | | alert | | | | | | | | | SIP MESSAGE w/CAP | | | (including service URN, | | such as urn:service:sos) | |------------------>| | | | | | ESRP performs | | emergency alert | | routing | | | MESSAGE with CAP | | | (including identity info) | | |----------------------------->| | | | | | PSAP | | processes | | emergency | | alert | | SIP 200 (OK) | | |<-----------------------------| | | | | SIP 200 (OK) | | |<------------------| | | | | | | |