Need to implement OpenSER as a front-end to Asterisk:
1. to act as Registrar for SIP devices typically behind NAT
2. to act as SIP Proxy without an RTP Proxy implementation
2a. redirect calls to the Asterisk environment assigned to the SIP device. Asterisk will be configured with the same SIP user/pass and will route calls within the appropriate dialplan context
2b. send incoming calls from Asterisk to the SIP device.
2c. send outgoing calls from Asterisk to PSTN gateways (via SIP)
2d. send incoming calls from PSTN gateways to the appropriate Asterisk environment (via SIP)
3. No Billing/CDR features required
4. Failover requirements to be discussed.
Network / Service configuration is described in diagram.jpg