Local Calls

Local VoIP Call Sequence of Events shows the sequence of events that occurs during a local VoIP call.

Local VoIP Call Sequence of Events

The following describes the sequence of events shown in Local VoIP Call Sequence of Events:

1. Phones A and B register with VoIP server - The Security Appliance builds a database of the accessible IP phones behind it by monitoring the outgoing VoIP registration requests. SonicOS translates between the phones’ private IP addresses and the Security Appliance’s public IP address. The VoIP server is unaware that the phones are behind a Security Appliance. It associates the same IP address for both phones, but different port numbers.
2. Phone A initiates a call to phone B by sending a request to the VoIP server - Even though they are behind the same Security Appliance, phone A does not know Phone B’s IP address. Phone A initiates a call to phone B using a phone number or alias.
3. VoIP Server validates the call request and sends the request to phone B - The VoIP server sends the call request to the Security Appliance’s public IP address. The Security Appliance then determines phone B’s private IP address.
4. Phone B rings and is answered - When phone B is answered, the Security Appliance translate its private IP information to use the Security Appliance’s public IP address for messages to the VoIP server.
5. VoIP Server returns phone B media IP information to phone A - Both the called and calling party information within the messages are translated by SonicOS back to the private addresses and ports for phone A and phone B.
6. Phone A and phone B directly exchange audio/video/data - The Security Appliance routes traffic directly between the two phones over the LAN. Directly connecting the two phones reduces the bandwidth requirements for transmitting data to the VoIP server and eliminates the need for the Security Appliance to perform address translation.